WADC TECHNICAL REPORT 59-681 FURTHER INVESTIGATIONS OF THE EFFECT OF PRIOR CREEP ON MECHANICAL PROPERTIES OF C1 10M TITANIUM WITH EMPHASIS ON THE BAUSCHINGER EFFECT Jeremy V. Gluck James W. Freeman The University of Michigan Research Institute September 1959 Materials Laboratory Contract No. AF 33(616)-3368 Supplement Nos. 3(58-1715) and S5(58-2202) Project No. 7360 Wright Air Development Center Air Research and Development Command United States Air Force Wright-Patterson Air Force Base, Ohio

FOR EWORD This report was prepared by the University of Michigan Research Institute under USAF Contract No. AF 33(616)-3368. This contract was conducted under Project 7360, "Materials Analysis and Evaluation Techniques,' Task 73604, "Fatigue and Creep of Materials. " The work was administered under the direction of the Materials Laboratory, Directorate of Laboratories, Wright Air Development Center, with Lt. W. H. Hill acting as project engineer. This report covers work conducted from January 1, 1958 to March 31, 1959. The research is identified in the records of the University of Michigan Research Institute as Project No. 2498.

ABSTRACT A study of the effect of prior creep at 6500 to 8000F on the short-time mechanical properties of C 1OM sheet showed property changes characteristic of the Bauschinger effect. After creep in tension, the tensile yield strength was increased and the compressive yield strength was decreased. Creep-exposure at 700~F was found to cause Bauschinger effects almost as large as those reported in the literature for cold-stretching. The magnitude of the effect depended to some extent on the direction of the applied stress with respect to the rolling direction of the sheet, possibly due to a Bauschinger effect present in the original sheet as well as preferred orientation effects. The time of creep-exposure also governed the extent of the effect. A study of variable strain paths indicated that there was no apparent difference between the effects of short-time plastic strain and creep strain in inducing a Bauschinger effect. However, for a given deformation, recovery effects caused a reduction in the effect as the creep time or temperature was increased. Periods of exposure at no load-at 700~F were found to be effective in removing the Bauschinger effect. The test material was also found to be subject to a structural instability during testing which accounted for increased strength and decreased ductility. The instability was a stress-activated breakdown of non-equilibrium beta to form a secondary alpha phase. Strain hardening during testing was at most a minor factor. PUBLICATION REVIEW This report has been reviewed and is approved. FOR THE COMMANDER: W. J. Trapp Chief, Strength and Dynamics Branch Metals and Ceramics Division Materials Laboratory WADC TR 59-681 iii

TABLE OF CONTENTS Page INTRODUCTION.......*..... I ~.... 1 TEST MATERIAL..................... 1 TEST SPECIMENS....................... 2 TEST EQUIPMENT AND PROCEDURES........... 2 RESULTS AND DISCUSSION............ ~..... 3 IDENTIFICATION OF THE BAUSCHINGER EFFECT IN CllOM.. *.................. l.... 4 MECHANISM OF THE BAUSCHINGER EFFECT........ 6 REMOVAL OF THE BAUSCHINGER EFFECT FROM ASPRODUCED HEAT A1172600............... 7 BAUSCHINGER EFFECTS INDUCED BY CREEP..... 9 EFFECT OF VARIABLE STRAIN PATHS ON MECHANICAL PROPERTIES AT ROOM TEMPERATURE.......... 11 Short-Time Strain Paths............... 12 Creep Strain Paths............... 13 Summary of Effects of Rapid and Creep Strain..... 14 DIRECTIONAL PROPERTIES OF C10OM SHEET......... 15 STRUCTURAL STUDIES OF C 1OM AND CORRELATION WITH MECHANICAL PROPERTIES.................. 18 CONCLUSIONS............ ~.......... 20 REFERENCES.......................... 21 WADC TR 59-681 iv

LIST OF TABLES Table Page 1. Comparison of Tension and Compression Properties at Room Temperature for Several Heats of C1IOM Titaniurn. 23 2. Effect of Unstressed Exposures on Selected Strength Ratios of C11OM (Heat A1172600)...... *.......24 3. Effect of Exposure to Short-Time Strain Paths on Room Temperature Mechanical Properties of C1IOM.. 25 4. Effect of Exposure to Creep Paths on Room Temperature Mechanical Properties of C11OM...............26 5. Effect of Specimen Orientation on Room Temperature Mechanical Properties of C1IOM after 10 hours Prior Creep-Exposure at 7000~F. 28. *. 6, Effect of Orientation and Exposure Conditions on Selected Strength Ratios of C11OM Titanium............... 29 7. Mechanical Properties of Metallographic Specimens...... 30 WADC TR 59-681 v

LIST OF ILLUSTRATIONS Figure Page 1. Sampling Procedure for Sheets of CIOM Titanium Alloy................... 31 2. Details of Test Specimens..... *.........~~ ~. 32 3. Tension and Compression Stress-Strain Curves at Room Temperature for Two Heats of C10OM —Specimens taken longitudinal to the sheet rolling direction....... 33 4. Effect of 10-hours Creep-Exposure on Relative Compressive Yield Strength of C110OM(Ti-8 Mn)...... *.... 34 5. Effect of 10-hours Creep Exposure on Compressive Yield Strength of CIIOM..................... 35 6. Effect of Prior Creep Time and Total Strain at 700~F on Room Temperature Compressive Yield Strength of C11OM 0.. 36 7. Effect of Exposure Time to Reach 1-Percent Total Plastic Strain at 700~F on Room Temperature Compressive Yield Strength of CIIOM.................. 37 8. Percent Change in Yield Strength of CLIOM from 10, 50, or 100-Hour Creep-Exposure at 7000F.......... 38 9. Effect of Short-Time Strain Paths on Room Temperature Properties of Cl1OM Exposed 100-hours at 700F...... 39 10. Effect of Post-Strain (Path 2) and 2nd Loading of Cyclic PostStrain (Path 4) on Room Temperature Yield Strength and Proportional Limit of CLIOM Exposed 100-hrs at 700~F... 40 11. Effect of Variable Creep Paths on Room Temperature Tension and Compression Properties of CO10M Exposed 100-hours at 700F' - 41 700F~ ~ ~. ~.....~................41 12. Effect of Stretching on Tensile and Compressive Yield Strengths of Commercially Pure Titanium at 0~ and 90~ to the Stretching Direction (Ref. 17).................. 43 13. Cutting Pattern and Identification Code for Orientation Studies of C 11OM Titaniurrj...................44 14. Effect of Specimen Orientation with Respect to Sheet Rolling Direction on Room Temperature Mechanical Properties of CllOM....................... 45 WADC TR 59-681 vi

LIST OF ILLUSTRATIONS (continued) Figure Page 15. Effect of 10-hours Unstressed Exposure at 700~F on Room Temperature Mechanical Properties of C1 10M Titanium at Various Orientations with Respect to the Sheet Rolling Direction. *............ 16, Effect of Exposure Conditions on Yield and Tensile Ratios of C IOM Titaniurr.............. *............ 47 17. Effect of Specimen Orientation with Respect to Sheet Rolling Direction on Room Temperature Mechanical Properties of CILOM After 10 Hours Prior Creep Exposure at 700~F.......... 48 18. Effect of Specimen Orientation on Loading Deformation of C 1OM at 700~F.... * 49 19. Effect of Specimen Orientation on Creep Strain Reached in 10 hours for C110M Creep Tested at 700~F............ * 50 20. Effect of 10-hrs. Exposure to Stress at 700~F on Tensile and Compressive Yield Strengths of C11OM Taken at Various Orientations with Respect to Sheet Rolling Direction...... 51 21, Effect of Plastic Deformation on Percentage Change in Room Temperature Mechanical Properties Following 10-hours Creep -Exposure at 700~F........... 52 22. CI 10M As Produced-Longitudinal Surface - Test Directions Indicated With Respect to Sheet Rolling Direction..~ ~..53 23. Optical and Electron Micrographs of C1IOM As-Produced (Transverse Sections.)................... 54 24-29. Electron Micrographs of C11OM Titanium (Transverse Sections). 55 30-33. Electron Micrographs of ClIOM Titanium (Transverse Section).. 56 WADC TR 59-681 vii

INTRODUCTION The effect of elevated temperature creep-exposure on the short-time mechanical properties of aircraft structual metals has been the subject of an investigation conducted at the University of Michigan for the past three years under the sponsorship of the Materials Laboratory, Wright Air Development Center, U. S. Air Force, under Contract AF 33(616)-3368. The materials studied included C1IOM titanium (Ref. 1), 2024-T86 aluminum (Ref. 2), 177PH stainless steel in the TH1050 condition (Ref. 3) and RH950 condition (R'ef. 4) and Ti-16-2. 5A1 titanium alloy (Ref. 5). The research has had the objective of accumulating the background information required to gain an insight into the basic principles governing creep damage to mechanical properties. Due to the absence of background information on this subject, systematic surveys of the effects of representative creep-exposures on both the room temperature properties and the properties at the exposure temperature have been necessary. The exposures have generally been conducted at three temperatures in the normally useful range of the material inquestion —-these temperatures were 6500, 700~ and 800~F in the case of CllOM. The exposure times were limited to 10, 50 or 100 hours, while the range of creep deformations studied was normally zero to 2 percent. For the CIIOM alloy it was previously shown (Ref. 1) that creep-exposure in tension tended to raise the short-time tensile yield strength and decrease the compressive yield strength —-a behavior consistent with the definition of the Bauschinger effect, "the phenomenon by which plastic deformation of a metal raises the yield strength in the direction of plastic flow and decreases the yield strength in the opposite direction." (Ref. 6) The present report extends the work of Reference 1 by detailed study of some aspects of the Bauschinger effect. In addition to re-evaluating previous data and surveying the theoretical basis for the Bauschinger effect, additional research was conducted on the effect of variable strain paths at 700~F, and the dependence of the effect on specimen orientation. Also included was a study of metallographic changes occurring during creep-exposure. TEST MATERIAL Eleven sheets of CI IOM titanium alloy in the annealed condition were received from the Rem-Cru Titanium Corporation in October of 1956. The material was all from Heat A 1172600. The sheets were 0. 064 inches thick by 30-36 inches wide by 60-90 inches long. The certified chemical analysis furnished by the producer follows: Element Percent (weight) Manganese 7.9 Carbon 0. 10 Nitrogen 0. 02 Hydrogen 0. 0093 "Manuscript released by authors October 15, 1959 for publication as a WADC Technical Report. " WADC TR 59-681 1

The manufacturer's reported properties for this material were the following: Ultimate Tensile Strength 149,400 psi Tensile Yield Strength 147,200 psi Elongation 15.0 percent Bend 3T TEST SPECIMENS Of the eleven sheets of C110M received, four were arbitrarily selected for providing test specimens. The longitudinal test specimens were chosen from among the first three sheets to provide a measure of the variation in properties between sheets and within individual sheets. The fourth sheet was used for studies of various specimen orientations and its sampling is discussed elsewhere (page 15 ). The longitudinal sampling procedure adopted was designed to permit economical utilization of the material. The sampling scheme for an individual sheet is illustrated in Figure 1. Each sheet was divided into one-inch wide strips running the length of the sheet. Over the 90-inch length of the sheet four sections or quarters of length were laid out. One end of the sheet was arbitrarily designated the "A" end and its subsections labeled AA and AB, while the other end was designated the "C" end and its subsections labeled CC and CD. Occasionally the AA samples were merely labeled A and the CC samples labeled C. The individual specimens were stamped with a number sequence designating the sheet number, section number, and the strip number. Thus, the specimen labeled ZCD-17T is a tensile specimen from the CD end of strip 17 from Sheet 2. The details of the test specimens used in this investigation are shown in Figure 2. All specimens for the tests of mechanical properties were designed so that they could be machined from the creep specimens following the desired exposure. For exposure to creep, the width of the gage section of the specimens was machined 0. 030 inches over the 0. 5 inch nominal width. This was machined off after creep exposure. This procedure permitted the measurement of the properties of the material itself unaffected by the particular edge effects, if any, associated with the exposure of the specimen. For ease in machining, jigs were constructed so that five or six specimens could be made concurrently. The blanks were milled to rough dimensions and the shoulder radii and gage sections were then ground to the finished dimensions TEST EQUIPMENT AND PROCEDURES Detailed discussion of the development of the test equipment and procedures has been previously given (Refs. 2 and 3) and will not be repeated in the present report. Wherever applicable, ASTM Recommend Practices were adhered to in test procedures. WADC TR 59-681 2

The creep-exposure tests were carried out in individual creep-testing machines with heating provided by a wire wound resistance furnace fitting over the specimen assembly. Strain measurements were accomplished using a modified Martens optical extensometer system. All creep-exposure specimens were placed in the hot furnace at about 50~F below the desired test temperature. The specimens were then brought up to temperature and distribution in a standard four-hour "hot load" period and then the stress was applied. Tensile and compression tests were conducted in a Baldwin-Southwark hydraulic tensile machine equipped with a strain pacer to give a strain rate of 0. 005 inches per inch per minute. A recording extensometer system employing a micro-former strain gage was used to give a continuous plot of the test results. The 0. 2-percent offset yield strength was determined for all tension and compression tests. A special compression testing fixture which included a loading ram and guide blocks to restrain lateral buckling of the specimen was used. Specimens prepared for optical or electron microscope examination were mounted in bakelite and wet ground on rotating laps using a series of silicon carbide papers through 600 mesh. Final polishing was carried out first with fine diamond compound and then on a Syntron vibratory polisher in an aqueous media of Linde "B" polishing compound. The polished samples were etched with "R" etch —composed of 13. 5 gm Benzalkonium Chloride, 35 ml Ethano', 40 ml Glycerine, and 25 ml Hydrofluoric acid (20%o) —by swabbing for 3-4 seconds. For electron microscope examination collodion replicas were made from the surface of the etched specimens. The replicas were shadowed with palladium to increase contrast and reveal surface contours. Polystyrene latex spheres of approximately 3400 A diameter were placed on the replicas prior to shadowing to indicate the angle and direction of shadowing and provide an internal standard for the measurement of magnification. The electron micrographs reproduced in this report are direct prints from the original negatives; consequently the polystyrene spheres appear black and the shadows appear white. Since the spheres are raised in the replica, a phase casting a shadow opposite to that cast by the latex spheres is in relief on the metal specimen; conversely, areas casting shadows in the same direction as cast by the latex spheres are depressions in the surface of the metal specimen and represent a phase that was attacked by the etchant. RESULTS AND DISCUSSION Data are reported which show that the original sheet stock exhibited the abnormal ratios of tensile to compressive yield strengths characteristic of the Bauschinger effect. The literature for the effect was reviewed from the viewpoint of the mechanism involved. Additional data are reported to show the introduction of the effect by prior creep. The directional properties of the sheet in relation to the Bauschinger effect were studied. A study was made of the relation of WADC TR 59-681 3

short time strain to creep strain by various paths in producing the effect. The report also includes the results of some structural studies made in relation to the general effects of prior creep on mechanical properties. IDENTIFICATION OF THE BAUSCHINGER EFFECT IN C 1OM The identification oi the Bauschinger effect present in the as-received annealed CI OM sheet (Heat A1172600) followed an inquiry into apparent discrepancies in the yield strengths. Preliminary data (Ref. 7 ) taken in the rolling direction indicated the compressive yield strength to be about 6075 percent of the tensile yield strength in the temperature range tested — room temperature to 800~F. These results drew comments from personnel at the Republic Aviation Corporation citing experience that tensile and compressive strengths of C1IOM tend to be approximately equal. (Ref. 8) Steps were then taken at the University to resolve this anomaly. The steps, partially reported in Reference 1, included a study of the compression test procedures and a reevaluation of the properties of the C 1O1M stock. In addition, arrangements were made with Republic Aviation to exchange different lots of CIOM sheet in order to provide independent checks of test procedures and also of the properties of the lot of C 1OM in question. A brief discussion of the results presented in Reference 1 follows. The University's compression test fixture and procedures were confirmed to be in substantial accord with accepted techniques (Refs. 9 and 10). These included the use of an averaging extensometer, off-set grooved guide blocks, and the use of a torque wrench in setting a consistent support force. Data taken on other materials with this equipment was found to agree with accepted results. Further tests were then run on the Cl1IOM stock using a support force more than ten times greater than normal. This was found to have only a slight effect on yield strength and ruled out premature buckling as a factor in producing low compressive yield strengths. Since the studies of the equipment and procedures failed to provide an answer to the yield strength discrepancy, attention was directed towards the test material itself. Examination of the data indicated that the lot of CllOM in question had a high ratio of tensile yield strength to ultimate tensile strength while the absolute value of the compressive yield strength, although slightly low, was comparable to values reported by other laboratories (Ref. 9). This indicated that the high tensile yield strength was also a contributor to the low ratio of the compressive yield strength to the tensile yield strength. Additional tension and compression tests were then run on C IOM sheet on hand from an earlier lot (Heat A5036) and on stock from Heat A50089 received from Republic Aviation in exchange for material from Heat A1172600. Comparative data from Republic Aviation was not received in time for inclusion in Reference 1. The results of room temperature tests conducted at the University and Republic Aviation (Ref. 11) on Heats A1172600 and A50089 are summarized in Table 1. Also included are some additional data from a Titanium Metallurgical Laboratory WADC TR 59-681 4

report (Ref. 9). Excellent agreement was obtained between the University and Republic Aviation on the tests of Heats A1172600 and A50089, thus confirming the original results obtained at the University and the reproducibility of the test procedures between the two laboratories. The only significant difference between the two laboratories was the consistently higher ductilities of the specimens tested at the University. If all the heats except Heat A1172600 are considered "normal" the data indicated that "normal" CIlOM exhibits a ratio of tensile yield strength to ultimate tensile strength of 0. 85-0. 90, while the compressive yield strength/ tensile yield strength ratio is about 1. 0-1. 05, ---- values consistent with Republic's initial comments. On the other hand, in material from Heat A1172600, the compressive yield strength/tensile yield strength ratio averaged only 0. 78, while the tensile yield strength /ultimate tensile strength ratio averaged 0. 97. These findings indicate thlat the as-received material from Heat A1172600 could be considered "abnormal". Reference to Table 1 indicates that while the abnormal material had a higher tensile strength and tensile yield strength than usual for the alloy, the main difference was a low compressive yield strength. A plot of tension-compression stress-strain curves for "normal" and "abnormal" C1IOM, Figure 3, shows a marked difference in the shape of the curve between the tension and compression portions for the "abnormal" material. The tension portion exhibited a sharp "knee' at a stress slightly below the yield strength i.e. the proportional limit was high, while the compression curve deviated from elastic behavior at a low stress and was gradually rounded. The shapes of the curves resemble those for a variety of materials cited in the literature as exhibiting the Bauschinger effect (Refs. 12-16). The relative values of the tensile and compressive yield strengths of the CIIOM from Heat A1172693 are also consistent with the previously cited definition of the effect. (see P. 1 ) On the basis of this evidence, it was concluded that the as-received C 1 OM stock from Heat A 1172600 (nominally hot rolled and annealed) was in a state of residual stress in tension in the rolling direction so as to exhibit a substantial Bauschinger effect when subsequently tested in tension and compression. The source of the residual stress in this material is uncertain. Waisman and Yen (Ref. 17) and Maykuth (Ref. 18) indicated that cold stretching or cold forming resulting in residual stresses can produce Bauschinger effects in titanium and its alloys. Other sources of residual stress are processing operations or treatments involving differential heating and cooling rates, joining operations, machining, grinding, etc. It is likely that the effect in the present material resulted from some final straightening or leveling operation. As will be discussed later, appreciable Bauschinger effects involving decreased compressive yield strength are caused by plastic strains of up to 3 percent. Whatever the cause of the residual stress, its presence in the as-produced material was previously unsuspected and resulted in the apparently anomolous values of yield strength. WADC TR 59-681 5

MECHANISM OF THE BAUSCHINGER EFFECT In the 78 years since Bauschinger (Ref. 19) first observed the effect given his name, numerous investigators have sought an explanation for the phenomenon. The relative success of these undertakings was succinctly stated by Wooley (Ref. 16) who said (writing in 1953), " There is no adequate (quantitative ) theory of the effect. " Qualitative explanations for the Bauschinger effect spring principally from the works of Heyn and of Masing (cited in the present report by reference to the reviews of Seitz(Ref. 20) and Barrett (Ref. 21). Essentially, these explanations depend on the action of residual microstresses produced due to differences in orientation between the non-isotropic grains of a polycrystalline material. Consider, for example, a cylindrical, polycrystalline bar with a load applied in tension. If some grains are oriented so that they have a high yield strength to the applied tensile load, while others are oriented with their weaker direction presented to the load, then when the load is removed, the latter grains are brought in to a compressive strain by tensile stresses in the former. The final state of the unloaded material then consists of an equilibrium between tensile and compressive stresses in many small regions. Upon reloading, the stress in those grains in residual compression must be raised first to zero and then to the tensile yield strength before flow can begin. As Barrett stated, "the material has been work hardened for stresses in this direction. " If, on the other hand, the material is subjected to a compressive stress after initial stressing in tension, the grains left in residual compression are already part way to their yield in compression and slight additional stresses will start plastic flow. Thus, the effective tensile yield strength of the aggregate is increased and the compressive yield strength is decreased. The converse would apply if the material is first subjected to compressive stress and then strained in tension. The residual stresses between grains, appearing after release of the load, were called Heyn stresses. Masing used the principle to explain the phenomenon of creep recovery in a polycrystalline material by means of the relaxation of Heyn stresses. Both Seitz and Barrett pointed out that such stress es could not be expected to appear in a homogeneously strained single crystal and therefore, according to this explanation, neither the Bauschinger effect nor creep recovery should be observed in a good single crystal. Seitz then refered to Sachs and Shoji's observation of the Bauschinger effect in single crystals of brass and explained it by a combination of the anisotropy of the metal and small inhomogeneties in plastic flow. Barrett mentioned a similar observation in single crystals of zinc and offered the view that the effects are due to stresses surrounding individual slip bands in single crystals or polycrystalline materials where relative displacement of the two sides of the slip band had occurred. Barrett also indicated that the Bauschinger effect may be produced after creep by the residual stresses left WADC TR 59-681 6

around slip bands, while if these stresses relax, an "aftereffect" is produced. Both Barrett (Ref. 21) and Corten and Elsesser (Ref. 14) referred to Zener's suggestion (Ref. 22) that the significant microscopic residual stress is a shearing stress in and around slip bands which generally traverse only part way through an individual crystal. This was apparently substantiated by observations in brass single crystals and cubically aligned polycrystalline copper. Corten and Elsesser (Ref. 14) also indicated that foreign elements in a lattice could influence the presence of microscopic residual stress and "residual atomic forces", i.e. forces generated between particles on the atomic level as a result of misfits in regions of disorder, through the action of lattice flaws in the initiation of new slip bands. A method for removing the Bauschinger effect was suggested by Elsesser, Sidebottom, and Chang (Ref. 13). They showed that it could be eliminated in inelastically deformed low carbon steel or alpha brass, while an increased elastic limit was retained, by the application of slightly elevated temperature treatments as the material was maintained at a high stress level. Studies (Ref. 15) made on structural members overstrained until inelastic deformation occurred in the most strained fibers (for the purpose of inducing favorable macroscopic residual stresses) showed that after unloading, 60-percent less residual stress was obtained than the theoretical amount. This loss was attributed to the Bauschinger effect, i. e. inelastic deformation on unloading acted to cancel out the desired macroscopic stress. In brass and low carbon steel the full theoretical stress was induced if the material was heated (aged) at low temperatures (180~ to 300~F) while the overstraining load was still applied. According to Corten and Elsesser (Ref. 14), aging under load removed the Bauschinger effect by reducing the "residual atomic forces" without materially affecting the macroscopic residual stresses. Experimental evidence indicated that the primary mechanism was a preferential rearrangement of copper and zinc atoms in brass and carbon and nitrogen atoms in steel by diffusion. Wooley (Ref.16) studied Bauschinger effects in several face-centered and body-centered cubic metals and after comparing the results with the theories of a number of authors, concluded that there was no adequate quantitative theory. For instance, Masing's theory was unsatisfactory for deformations above 1 percent; a theory proposed by Brandenburger (Ref. 24) could not account for experimental results with pure metals; while an earlier explanation by Wooley, based on exhaustion theory was inadequate. Calculations made by Wooley showed that the maximum Bauschinger strain produced by textural stresses, i.e. those arising from orientation differences, could not account for the total effect observed. Wooley then concluded that the effect was largely a property of individual grains and a semi-quantitative explanation was presented in terms of the rearrangement of dislocations by a work-hardening mechanism. REMOVAL OF THE BAUSCHINGER EFFECT FROM AS-PRODUCED HEAT A1172600 Examination of data from Reference I covering the effects of unstressed exposure on the mechanical properties of Heat A1172600 indicated that the Bauschinger effect could be materially reduced or eliminated from the as-produced material by suitable exposure to temperature. The following tabulation of yield strength ratios shows how 100 hours exposure at 800~F was instrumental in removing the Bauschinger effect while having only a small effect on the "normal" heats: WADC TR 59-681 7

Effect of Unstressed Exposure for 100 hours at 8000F on Selected Strength Ratios of CT I OM Titanium at Room Temperature Ratio: Tensile Y.S. Ratio: Compressive Y.S. Utimate T,. Tensile Y.S. Heat No. As Prod. 800"F- 1dhrs. As Prod. 8 00~F-100 hrs. A1172600 ("abnormal") 0.97 0.85 0.78 1. 13 A50089 ("normal") 0. 88 0. 77 1. 02 1. 05 A5036 ("normal") 0. 86 0. 84 1. 03 1. 09 Note: Calculated from data in Reference 1, p. 19. Specimens taken in the sheet rolling direction. Table 2 shows the effects of a number of different exposure temperatures and times on the room temperature strength ratios of Heat A1172600. These data indicate that exposure for 50 to 100 hours at 6500F was required to raise the room temperature compressive yield strength/tensile yield strength ratio to approximately 0. 90. At 700~F a four hour exposure, the pre-heat time in creep-exposure tests, raised the ratio to 0.95 while an exposure for 10 hours increased the ratio to 0.99, and the longer times at 700~F and 800~F caused further increases. Exposures for as long as 100 hours at 6500 and 700~F did not reduce the tensile-yield strength/ultimate tensile strength ratio of Heat A 1172600 below 0.92. The 800~F exposure, on the other hand, reduced this ratio to the range exhibited by "normal"material. The compressive yield strength/tensile yield strength ratio, however, then ranged from 1. 12 to 1. 14 —-slightly above "normal" behavior. In tests conducted at elevated temperatures somewhat similar results were obtained. (Table 2) Ten hours exposure at 700~F was the threshold condition for a significant increase in the compressive yield strength/tensile yield strength ratio, while the tensile yield strength/ultimate yield strength ratio showed a tendency to decrease with increased temperature and time of exposure. (Limited data at elevated temperatures (Ref. 9) showed that the compressive yield strength/ tensile yield strength ratio of "normal" CI OM was 1. 07 at 400~F and 1. 24 at 8000F). The results obtained with the present material, Heat A1172600, which contained an unknown amount of residual stress applied in an unknown manner, compare favorably with the simple case where the stress is produced by cold stretching in tension. For this case, information on stress relief procedures has been summarized by Maykuth (Ref. 18). Maykuth stated that for temperatures below 6000F, the exposure times needed to cause a significant reduction in residual stresses in CI lOM were impractically long. Although treatments of 15 minutes at 7000F were used, it was generally WADC TR 59-681 8

necessary to use higher temperatures for effective stress relief. For example, in material stretched 3 percent, a treatment of one hour at 825~F was effective in restoring the tensile and compressive yield strengths to their original values while after 2 percent pre-stretch, five minutes at 900~-1000~F reduced the tensile yield strength to the as-produced value. Some evidence also exists to indicate that treatments at 700~F, or above can cause a slight increase in the tensile yield strength of pre-stretched material as the result of precipitation hardening from the formation of omega phase. (Ref. 18) BAUSCHINGER EFFECTS INDUCED BY CREEP In the earlier part of the present investigation (Ref. 1) it was shown that specimens of CO1M subjected to creep in tension at either 6500 or 700~F exhibited an increased tensile yield strength and decreased compressive yield strength in short-time tests conducted either at room temperature or the creep temperature. In some cases, the deformation included short-time plastic loading strain while in other cases it consisted solely of creep strain. In any event, it was found that residual stresses after plastic strain at sufficiently low elevated temperatures can be of sufficient magnitude to cause Bauschinger effects. The very pronounced degree of the Bauschinger effects produced by creep exposure is shown by Figure 4 in which Maykuth's data for cold stretching C 11OM (Ref. 18) is compared with curves calculated from the data of Reference 1 for creep exposures of 10 hours at 650~, 700~ or 800~F. In Figure 4 the change in compression yield strength fromthe "recovered" value (exposure to temperature alone) is plotted against the total plastic strain obtained in the creep-exposure. This strain includes both short-time plastic loading strain and creep strain. Also included in Figure 4 is a table showing the effect of the 10 hours unstressed exposure on the compressive yield strength/ tensile yield strength ratio. As indicated previously, the four hour pre-heat time at 700~F was sufficient to almost completely remove the original Bauschirger effect. On the other hand, the four hour pre-heat time at 6500F did not result in appreciable recovery prior to loading. Assuming the absolute yield strength after the 10 hour exposure at 700~F to be the "normal"value for this heat, the data of Maykuth were used to calculate the effect of cold stretching on the compressive yield strength of "normal" Heat A1172600. This relationship is plotted in Figure 5 together with the absolute strength values previously obtained. The zero strain intercepts in this plot refer of course to the conditions of unstressed exposure. From Figures 4 and 5 it is readily seen that the plastic strain from a 700~F creep exposure can cause a loss in short-time compressive yield strength almost as severe as that produced by cold-stretching. In connection with this plot it should also be noted that the compressive yield strength after first decreasing rises as deformation is continued. This was observed both by Maykuth (Ref. 18) for C1IOM titanium and Waisman and Yen WADC TR 59-681 9

(Ref. 17) for commercially pure titanium, stainless steel, and several aluminum alloys. This effect is attributed to strain hardening which eventually counteracts and overcomes the influence of the microresidual stresses causing the original loss of strength. Of the materials mentioned above, the maximum loss in strength, about 42 percent from the base value, occurred in C1IOM cold stretched 2-3 percent. The loss became less severe as the amount of cold-stretching was increased above 3 percent. The extent of the creep-induced Bauschinger effect depends on the time and temperature at which the creep occurs and, possibly, the relative amounts of short-time strain and creep strain. Of course, in Heat A 1172600, the picture is complicated by the original Bauschinger effect in the as-produced material, This is brought out by Figure 4 which shows that a greater relative decrease in compressive yield strength with increased plastic strain occurred for the condition which had a greater amount of recovery prior to loading —-the 700~F exposure —-while the material exposed at 650OF showed a much smaller decrease. However, as Figure 5 shows, the material crept at 6500F had an appreciably lower compressive yield strength to begin with. The recovery in strength resulting from the unstressed exposure at 800F was reduced only to a limited extent by the creep at this temperature. The explanation for this behavior is not immediately evident. Among the factors that could have counteracted the Bauschinger effect are the following: 1. Strengthening from transformation of beta. (Confirmed to some extent by metallographic evidence. ) 2. Strain-aging. 3. Simultaneous recovery due to the higher creep temperature. 4. A possible transition in the mechanism of creep whereby the deformation processes governing the short-time room temperature strength may not be solely operative at the creep temperature. For example, the creep at 800~F could include a greater grain boundary contribution, thus lessening the tendency for the formation of residual stresses within the grains. Furthermore, it appears that in addition to the creep temperature and total strain, the creep time had an effect on the subsequent yield strengths of the material. Figure 6 is a plot of room temperature compressive yield strength after creep at 700~F versus total strain for creep times of 10, 50 and 100 hours. (Again it should be noted that the four hour pre-heat period resulted in almost complete recovery prior to the application of the creep load. ) The maximum loss in yield strength followed 10 hours creep at 700~F while the least effect followed 100 hours creep. A cross plot of these data for i-percent total strain is presented in Figure 7. On this plot the value indicated for 1-percent cold stretching was estimated from Maykuth's data. Also indicated on this plot is the amount of short-time strain making up the total strain of i-percent for the various creep WADC TR 59-681 10

times. This plot indicates that the longer the creep time, the less severe the loss of compressive strength, and incidentally, the smaller the fraction of short-time strain making up the total strain. To a lesser extent, the change in tensile yield strength was also governed by the creep time at 700 F. This is indicated in Figure 8, a plot of the relative changes at room temperature of both the tensile and compressive yield strength following 700~F creep. Figures 5 and 6 show that the shorter the exposure time to produce a given amount of creep at 700~F, the more pronounced is the subsequent Bauschinger effect. This time dependence suggests that recovery processes and/or metallurgical instabilities modify the deformation-dependent properties of the material. EFFECT OF VARIABLE STRAIN PATHS ON MECHANICAL PROPERTIES AT ROOM TEMPERATURE. The data discussed in the preceding sections on the effects of creep on mechanical properties were obtained from specimens which were maintained under constant load and temperature. If the load raised the stress above the proportional limit, rapid strain was introduced before creep occurred. The total plastic strain was composed of both rapid initial strain and creep strain mainly in the creep exposures at 650~ and 700~F because high stresses were required to induce creep. At 800~F the stresses were below the proportional limit in most cases. It will be recalled that the creep specimens exposed at the lower temperatures exhibited substantially greater Bauschinger effects than those exposed at 800~F. The question accordingly arose as to whether there was a difference in the effect of rapid strain and creep strain in so far as their effect on mechanical properties was concerned. Recovery during creep could be responsible for the reduced Bauschinger effect at the higher temperatures and longer exposure times. On the other hand, creep strain might not introduce a Bauschinger effect. Accordingly experiments were undertaken in which strain was introduced by various paths. The conditions were selected to provide information on the relative roles of creep and rapid strain in the influence of recovery. Exposure conditions of 100 hours at 700'F were selected. This permitted the introduction of 1 to 2 percent strain while keeping the loads below the proportional limit. Secondly, there was evidence that recovery occurred fairly rapidly at this temperature. Several conditions of strain and recovery were investigated. Short time strain was introduced at the begining and at the end of 100 hours at 700 ~F In addition, it was introduced at other time periods in order to vary the recovery conditions. Creep strains were also introduced under various conditions with and without accompanying short time strains. The influence of the exposure conditions on properties were measured by tension and compression tests at room temperature. The results are tabulated in Tables 3 and 4, and shown graphically by Figures 9, 10, and 11. In both the Tables and Figures diagrams of each path are included in order to facilitate understanding of the manner in which the exposure was conducted. WADC TR 59-681 11

In the path diagrams the abcissa is time and the ordinate is stress. The following -ode is used: -- = Exposure at no load. I = Loading I Uloadin Both loading and unloading are assumed I g= Unloading to be instantaneous. 4 = Specimen cooled under load (to minimize strain ijF~~~~~ ~~~recovery) = Creep The graphical presentation of the results relates the property changes to two base conditions. The intercepts of the curves on the zero strain axis are the properties after 100 hours exposure without stress at 700~F. This point of origin was used because the main intent is to study the effect of strain at 700~F. The graphs also show the properties for the original sheet without any exposure to indicate the combined effects of heating and strain. Proportional limit values for both tension and compression tests are included. Because the Bauschinger effect alters the complete stress-strain characteristics, it was felt that the proportional limit values in addition to 0. 2-percent offset yield strengths would help clarify the effects. Short-Time Strain Paths The results of the tests, Table 3 and Figure 9, show the following: 1. Strain introduced rapidly at the end of the 100 hours of exposure to 700~F (Paths 2 and 4) increased tensile yield strengths and proportional limits in comparison to the values resulting from exposure without any strain. At the same time the compressive yield strengths and proportional limits were reduced. These changes are characteristic of the Bauschinger effect. 2. When the rapid strain was introduced beofre exposure (Path 1) or partially before exposure and partly at 50 hours (Path 3) the compressive yield strengths and proportional limits were unchanged in comparison to material exposed without strain. 3. Ultimate tensile strengths increased about the same whether the strain was introduced before or after exposure to 700"F. This suggests that some other factor was involved in addition to the residual stresses which cause the Bauschinger effect. 4. Ductility values were not appreciably changed by short time strain under any of the conditions investigated. WADC TR 59-681 12

5. The changes in yield strengths and proportional limits were less when half of the strain was introduced after 50 hours of exposure and half at the end of the exposure period (Path 4) than when all the strain was introduced at the end of the exposure period (Path 2). Figure 10 shows that the changes were in proportion to the amount of plastic strain applied at the end of the exposure period. Apparently recovery from the influence of the strain introduced at 50 hours occurred during the subsequent 50 hours without stress. 6. It will be noted that about 0. 5 percent strain at the end of the exposure period reduced the compressive yield strength and proportional limit values to about the same level as those of the unexposed material. There was little further change in these values as the result of increasing the strain to 2 percent. 7. Table 3 shows that a small amount of recovery of plastic deformation occurred by "creep" when specimens were held at 7000F after the introduction of rapid plastic strain. This is a normal result of heating after straining. Creep Strain Paths Creep was introduced by several different paths (Paths 5, 5a, 6, 7, 8, 9 and 10) and the effects on room temperature mechanical properties measured (Table 4 and Figure 11. ) The results may be summarized as follows: 1. In all cases there was a substantial increase in ultimate strength, yield strength and proportional limit in tension. These were nearly proportional to the amount of strain. Ductility was also reduced in contrast to the short-time strain paths which did not change ductility. 2. Compressive yield strengths were practically unaffected by creep strain. Restricting the creep to the last 50 or 25 hours of exposure (Paths 6 and 9) resulted in some decrease. Holding at 7000F for the last 50 hours after the inducing creep for the first 50 hours (Path 7) resulted in some increase. 3. There was some decrease in compressive proportional limit for all cases except Path 7 where the specimens were held for the last 50 hours without stress. 4. In those cases where short time strain was introduced along with creep (Paths 5a, 10 and probably 8 and 9) the changes in tensile properties were not quite as marked as when creep alone was involved. These results indicate that creep at 700~F did not result in as marked a Bauschinger effect as did short-time strain at the end of the exposure period. In fact the main indication of a Bauschinger effect was the somewhat reduced compressive proportional limit and the increase in tensile yield strengths, while the compressive yield strengths were unchanged. The evidence for a time dependent strain-induced structural change increasing strengths in tension seems quite marked. Presumably if it were not for the weak Bauschinger effect from creep, the compressive strengths would also have been increased. WADC TR 59-681 13

Summary of Effects of Rapid and Creep Strain Plastic strain up to about 2 percent superimposed on the effects of holding C10OM samples at 700~F for 100 hours had certain effects on mechanical properties at room temperature. Both rapid and creep strains increased ultimate and yield strengths and proportional limits in tension. Rapid strain did not cause as much increase in ultimate strength as did creep strain. Rapidly applied strains did not alter ductility in tension while creep strain reduced it somewhat. These changes occurred whether or not recovery periods without stress were included in the paths. The possible exception to this generality was an apparent reduction in the magnitude of the changes when rapid strain was combined with creep strain. Compressive yield strengths were reduced by rapid strains applied at the end of 100 hours exposure to 7000F. Creep strains did not appreciably alter the compressive yield strengths except possibly for a slight reduction when the creep strain was introduced during the last 25 hours of exposure. Holding at 700~F without stress after creep resulted in increased compressive yield strength. Compressive proportional limits were reduced by rapid strain. Creep strains may have slightly reduced compressive proportional limits if there was no period of recovery without stress. About 0. 5 percent plastic strain applied rapidly at the end of the exposure period reduced the compressive yield strength and proportional limit to about the same values as for the original sheet. Larger strains caused little further change. The difference in the effects of creep strain or rapid strain on the ultimate strength and ductility indicates that there was a strain-activated structural change occurring during the creep-exposures. That is, creep strain was more effective than rapid strain. In addition, short time strain without the opportunity for recovery introduced a marked Bauschinger effect. On occasion this was superimposed on the effects of the strain-activated structural change. Furthermore, in the case of the compressive properties, the increased strength associated with the strain-activated structural change was offset by the Bauschinger effect introduced by creep. This resulted in little net change in the compressive properties rather than the increase to be expected from the structural change. Due to this factor there was an appreciable increase in the ratio of tensile yield strength to compressive yield strength after creep even though the compressive yield strength did not change. Only when there was opportunity for recovery after creep did the compressive properties increase in accordance with the structural change. It is evident from the data that the intensity of the Bauschinger effect was reduced for creep in 100 hours in comparison to short time strain. As the data cited in primary section indicated, creep at 6500 or 700"F introduces a marked Bauschinger effect. However, as the temperature and time period for creep is increased, the intensity of the effect is reduced and becomes negligible at sufficiently high temperatures and long times. For example, the effect of the time period was indicated in Figure 7. If creep can occur, there is certainly opportunity for stress relief. Thus when creep occurs under conditions where there is relatively little or no strain hardening resulting from the creep, simultaneous recovery should eliminate the Bauschinger effect. The data indicate that creep strains up to 2 5 percent in 100 hours at 700~F represent a condition where there is partial recovery from the creep-induced Bauschinger effect. WADC TR 59-681 14

Short-time strains involved in the Bauschinger effect noted for creep specimens exposed at lower test temperatures undoubtedly contributed to the Bauschinger effects. However, the data reported in this section indicate that the creep was also a contributing factor. DIRECTIONAL PROPERTIES OF CI 10M SHEET In the previous studies of C IOM the properties were determined on specimens taken from the sheet stock in the direction of rolling. It was established on the basis of the observed Bauschinger effect in the as-produced material that the residual stress causing the effect, although of an unknown amount and unknown direction of application, was in tension in the rolling direction. It should however be recognized that residual stresses have components at all angles to the direction of the plastic deformation producing the stress (Ref. 17). Furthermore, axial elongation of metals is accompanied by lateral contraction or an axial tensile stress has a lateral component in compression. Figure 12, taken from the data of Waisman and Yen (Ref. 17) shows that commercially pure titanium stretched and then tested laterally (90~) to the stretching direction exhibits increased compressive yield strength and decreased tensile yield strength, a behavior opposite to that of the same mateiial when tested in the stretching direction. The magnitude of the effect appears to be about the same for both testing directions. In addition to the superimposed directionality of residual stresses, a more common source of the directionality of mechanical properties in sheet materials arises from preferred orientations developed during rolling and possibly from phases occurring as stringers in the rolling direction. In recognition of these factors a study was carried out of the effect of orientation on mechanical properties of the C110M stock investigated. Specimen blanks from Heat A1172600 were cut from sheet stock at orientations of 30~, 45~, 60~, a'nd 90~ to rolling in the configuration illustrated in Figure 13. Testing was carried out at room temperature on material in the original condition and following stressed exposures at 700~F for 10 hours, a condition producing a large Bauschinger effect in longitudinal specimens. Tests at room temperature on as-produced sheet gave the results in Table 5 and Figure 14 for the effect of specimen orientation. There was no difference in the tensile or compressive yield strength at 30~ to the rolling direction. The tensile yield strength was higher than the compressive yield strength between 0~ and 30~ to the rolling direction. From 30~ to 90~ the compressive strength was higher. The maximum difference in both cases was of the order of 25, 000 to 30,000 psi. The compressive yield strength ranged from 110,000 to 162,000 psi while the tensile yield strength varied only about 10, 000 psi. In addition to the yield strengths, the other mechanical properties of the sheet exhibited a dependence on the orientation. A minimum in ultimate strength and a maximum in ductility occurred at approximately 45~ to rolling, while minimum WADC TR 59-681 15

ductility was observed at 60~ to rolling. As would be expected the tensile yield strength was much closer to the ultimate strength between 0" and 45~ than between 45" and 90~. Apparent maxima also occurred in the tensile and compressive modulus values, although these values should not be regarded as precise inasmuch as they were calculated from slopes of the stress-strain curves. The variations in properties with orientation are a consequence of both the Bauschinger effect and of preferred orientations developed during working of the material. This topic of preferred orientation has been thoroughly discussed by Barrett (Ref. 21) and Richards (Ref. 24) among others. The mechanical properties following 10 hours exposure without stress at 700~F, Table 5, are plotted in Figure 15. Comparison with Figure 14 shows that the stress relief afforded by this exposure resulted in an increase in the tensile or compresssive yield strength at those orientations where the original residual stress had caused a reduction in strength. Thus, the compressive yield strength was increased at the orientation of 0~ to 45~ to rolling and the tensile yield strength was increased in the 60-90~ orientations. In addition, the tensile yield strength increased in relation to the ultimate tensile strength in the 45-90~ orientations. The ultimate strength, ductility and relative modulii were little affected. The effects of the exposure on the ratio of tensile yield strength to ultimate tensile strength and compressive yield strength to tensile yield strength were calculated and are tabulated in Table 6 and plotted as a function of orientation in Figure 16, The ratio of compressive yield strength to tensile yield strength, a measure of the Bauschinger effect, varied, depending on orientation, from 0. 76 to 1.25 before exposure and 1. 01 to 1. 09 after exposure. The slightly higher yield strength ratio at the orientations of 45~-90~ to rolling is probably related to the preferred orientation of the sheet. The effects on mechanical properties of creep exposure for 10 hours at 700~F (Table 5) are presented graphically in Figure 17. In this figure the data are plotted both as functions of the creep deformation and the total plastic deformation. The data show that regardless of the specimen orientation, deformation of the material in tension had the following general effects on room temperature mechanical properties: The ultimate and tensile yield strengths increased; the tensile yield strength increased relative to the ultimate tensile strength; the compressive yield strength decreased; and the ductility decreased. The decrease in compressive yield strength at 0~ was in relation to material heated for 10 hours without stress. Hardness changes, however, were small and inconsistent. (Table 5) Both the deformation behavior and the magnitude of the changes in mechanical properties depended to some extent on the specimen orientation. Examination of the data in Table 5 indicates that extensive plastic deformation occurred during loading of several specimens taken from the sheet at 30~ or 45~ to the sheet rolling direction. In two cases, the deformation was so rapid and so great that it could only be estimated from the full scale travel of the extensometer system. This behavior is graphically shown in Figure 18, a plot of stress versus loading deformation. For comparison an average stress-strain curve for short-time tensile tests of WADC TR 59-681 16

longitudinal (0~ to rolling) specimens at 700~F is included in Figure 18. This figure shows that the specimens taken at intermediate orientations (30", 45~, 600) had appreciably greater loading deformations at a given stress than did the 0~ and 90~ specimens. Examination of the individual loading curves for these tests indicated that a lower proportional limit could account for this behavior. The creep behavior of these specimens is indicated in Figure 19, a plot of stress versus creep strain reached in 10 hours at 700~F. This plot shows that at a given stress the transverse (90~) specimens crept somewhat less than longitudinal (0~) specimens, while the specimens oriented at 30~, 45~, and 60~ crept a greater amount. Therefore, for a given amount of total plastic strain, the 0~ and 90~ specimens contained a higher proportion of creep strain than did the 30~, 45~, and 60~ specimens. In Figure 16, the ratio of compressive yield strength to tensile yield strength is plotted as a function of specimen orientation both for total plastic strains of 0. 5 and 1. 0 percent and for 1. 0 percent creep strain (Data tabulated in Table 6). The relative shape of the yield-strength-ratio curves with orientation is the same for all the deformation parameters, the curves being merely displaced towards lower values as the amount of deformation increased. As Figure 16 indicates, the yield strength ratio (a measure of the Bauschinger effect) is sensitive to the sheet orientation, being lowest for longitudinal (0~) specimens and highest for transverse (90~) specimens. A total plastic strain of 0.5 percent in 10 hours at 700~F resulted in ratios at 0~ as low as in the as-produced material. The yield strength ratio for transverse (90~) specimens after 0.5 percent total plastic strain in 10 hours was the same as that following the four hour pre-heat for the longitudinal condition. However, it should be recognized that an original Bauschinger effect was initially present in the transverse direction in the asproduced material and the relative decrease in yield ratio was similar for both specimen orientations. The absolute values of the tensile and compressive yield strengths as a function of total plastic strain are plotted for all orientations in Figure 20. For plastic strains of less than 2 percent, the longitudinal (0~) specimens had the lowest compressive yield strength while the transverse (90~) direction had the highest tensile yield strength. Another view of these results can be gained from an examination of Figure 21. This plot shows the percent change in mechanical properties with respect to the value for the unstressed exposure as a function of deformation. Thus, the effect of deformation can be evaluated independent of the variation in the initial properties resulting from preferred orientations in the sheet. The orientationapparently did not affect the relative increase in ultimate tensile strength with increased creep strain. The relative loss of ductility showed a variable, but possibly not significant dependence on the orientation. For instance, the apparently unchanged ductility of the 60~ specimen is not considered significant since a specimen tested to a large total strain was not available for this condition. The same reasoning is probably valid in explaining the curve for the transverse (90~) orientation. WADC TR 59-681 17

Specimen orientation does appear to be of some significance in the response of the room temperature yield strengths to prior plastic strain at 7000F. The longitudinal specimens (0~) had the greatest relative loss in compressive yield strength, while the effect in the transverse (90~) specimens was the least severe of any orientation for total strains up to 1. 5 percent. No data were available to indicate that the curve for the 90~ specimens would level off at greater strains as did the others. At a strain of 2 percent the increase in tensile yield strength ranged from about 5 to 12 percent, while the decrease in compressive yield ranged from approximately 15 to 29 percent. It appears, therefore, that the response of the ClIOM sheet material to prior creep in tension is manifested in an increased ultimate tensile strength and decreased ductility that tends to be fairly independent of the specimen orientation, while the changes in the yield strengths are somewhat orientation sensitive. A further factor is the gross microstructure of the material. Figure 22 is a photomicrograph of the longitudinal surface of the C11OM alloy showing how the alpha grains were strung out in the rolling direction. Indicated on the photograph are the relative orientations of the various specimens. This shows that in the 90~ direction of testing the vast majority of the alpha-beta interfaces are normal to the direction of creep and tensile testing while the opposite is the case for specimens taken in longitudinal (0~) direction. The gross difference in the grain boundary orientation with respect to the applied stress might account for some of the differences in behavior between these two orientations and the behavior of the intermediate orientations. STRUCTURAL STUDIES OF C1 IOM AND CORRELATION WITH MECHANICAL PR OPER TIES During the present investigation metallographic studies of CI OM were extended to include the use of the electron microscope. Previous studies, limited to optical examination at magnifications up to 1000x, were inconclusive, revealing no apparent structural changes that could be correlated with the mechanical properties following creep-exposure (Ref. 1). The more detailed study made possible by the electron microscope led to the discovery of a phase transformation in the hot rolled and annealed structure, probably the beta-to-omega-to-alpha transformation, apparently stress-activated at 700~F and time and temperature controlled at 800~F. Even then, an entirely clear cut correlation of structural changes with mechanical properties was not apparent. An optical micrograph at 500x and an electron micrograph at 3500x of the asproduced condition are presented in Figure 23. Representative electron micrographs at 8200x magnification are presented in Figures 24 through 33. In conjunction with Figure 22, the lower magnification pictures show that the asproduced condition consisted of somewhat variable-sized, elongated alpha grains in a beta matrix. Following creep-exposure for 100 hours at 650~F (Figure 25) or unstressed exposure for 10 hours at 700~F (Figure 26), no structural changes were apparent. However, a 10 hour creep exposure to a large deformation at 700~F (Figure 27) TWADC TR 59-681718 WADC TR 59-681

caused a slight roughening of the matrix indicating the initiation of the beta-toomega transformation. A specimen subjected to 100 hours unstressed exposure at 700~F also showed evidence of roughening (Figure 28), while a specimen crept for 100 hours at 700~F exhibited large amounts of a well-defined, rodlike precipitateprobably alpha (Figure 29). Lesser amounts of this precipitate were also observed in a specimen crept for 50 hours at 700~F. (The alpha phase resulting from this reaction will be termed secondary alpha to distinguish it from the much larger particles of original alpha. ) Exposure without stress at 800F for 10 hours (Figure 30) or 100 hours (Figure 32) resulted in the appearance of larger secondary alpha particles. Creepexposures at 800~F (Figures 31 and 33) did not appear to change significantly the relative amount and distribution of the secondary alpha although its size was perhaps increased over that produced by the unstressed exposures. However, the time of exposure at 8000F appeared to have a greater influence on the amount of secondary alpha produced than did the presence of stress. On the other hand, the precipitation at 700~F appeared to have been stress-activated. Although the photomicrographs reveal striking changes in the structure as a result of exposure, the change in the mechanical properties was, in most cases, relatively small. The room temperature mechanical properties of these specimens are summarized in Table 7. Interpretation of the data was rendered difficult by the necessity of accounting for the relative contributions of the creep-induced Bauschinger effect and the phase transformation. Hardness changes were limited to a range of 3-6 points Rockwell "C" and were generally consistent with the strengths. As discussed in the section on the influence of strain paths, the structural change probably accounts for the property changes which appeared to be stress-activated and time dependent. This discussion also pointed out that a Bauschinger effect induced by creep masked changes in compressive properties due to the structural changes. Also it contributed to the increases in the properties in tension. WADC TR 59-681 19

CONCLUSIONS Creep-exposure of Cl1OM sheet at 6500 or 700~F caused appreciable changes in the short-time tensile and compressive yield strengths characteristic of the Bauschinger effect. After creep in tension, the tensile yield strength was increased and the compressive yield strength was decreased. The Bauschinger effect after creep at 800~F was slight. A structural instability was found to occur during creep exposure at 700~ and 800~F, accounting for slightly increased strength and decreased ductility, although the possibility of strain hardening also exists. The magnitude of the Bauschinger effect induced by creep-exposure at 700~F approached the values given in the literature for cold-stretching. The investigation was complicated by the presence of a Bauschinger effect in the as-produced material. This was removed during the pre-heat period prior to creep testing at 700~ or 800~F but not at 650~F. Consequently, the additional effect of 6500F creep-exposure was not as great as would have been found if the tests had been conducted on stress-free material. Studies of variable strain-paths at 700 F indicated that there was no apparent difference between short-time plastic strain and long-time creep strain in inducing the Bauschinger effect. However, simultaneous recovery during creep caused the effect to be lessened for a given deformation as the creep time was increased. Unstressed exposure, generally at 700~F or above, was effective in removing the Bauschinger effect. A study of the effect of specimen orientation showed that the magnitude of the creep-induced Bauschinger effect depended to some extent on the orientation of the applied stress with respect to the sheet rolling direction. The deformation properties also exhibited a dependence on the orientation. The structural instability during testing was a stress-activated breakdown of non-equilibrium beta to form a secondary alpha phase. This was revealed by electron microscope studies. WADC TR 59 -681 20

REFERENCES 1. Gluck, J. V., Voorhees, H. R., and Freeman, J. W., "Effect of Prior Creep on Mechanical Properties of Aircraft Structural Metals, Part III. CLIOM Titanium Alloy" WADC Technical Report 57-150 Part III, January, 1958 2. Gluck, J. V., Voorhees, H. R., and Freeman, J. W., "Effect of Prior Creep on Mechanical Properties of Aircraft Structural Metals (2024-T86 Aluminum and 17-7PH Stainless)" WADC Technical Report 57-150, January, 1957 3. Gluck, J. V., Voorhees, H. R., and Freeman, J. W., "Effect of Prior Creep on Mechanical Properties of Aircraft Structural Metals, Part II, 17-7PH (TH 1050 Condition)." WADC Technical Report 57-150 Part II, November 1957 4. Gluck, J. V. and Freeman, J. W., "Effect of Prior Creep on Short-Time Mechanical Properties of 17-7PH Stainless Steel (RH 950 Condition Compared to TH 1050 Condition)" WADC Technical Report 59-339, March, 1959 5. Gluck, J. V. and Freeman, J. W., "Effect of Prior Creep on the Mechanical Properties of a High-Strength, Heat-Treatable Titanium Alloy, Ti-16V2.5AI" WADC Technical Report 59-454, March, 1959 6. Lyman, T. (editor) Metals Handbook, p. 2, American Society for Metals, Cleveland, Ohio (1948) 7. Gluck, J. V., Voorhees, H. R., and Freeman, J. W., "Sixth Progress Report to Materials Laboratory, Wright Air Development Center on Effect of Prior Creep on Mechanical Properties of Aircraft Structural Metals" (Contract AF 33(616)-3368) May 25, 1957 8. Letter from J. C. O'Brien, Republic Aviation Corp., Farmingdale, New York, Dated August 1, 1957 (Ref: 57-4582) 9. Hyler, W. S., "An Evaluation of Compression-Testing Techniques for Determining Elevated Temperature Properties of Titanium Sheet" Titanium Metallurgical Laboratory, Battelle Memorial Institute, TML Report No. 43 (June 8, 1956) 10. "Uniform Testing Procedures for Sheet Materials" Department of Defense Titanium Sheet Rolling Program. Defense Metals Information Center, Battelle Memorial Institute, DMIC Report No. 46D, September 12, 1958 11. Letter from R. F. Wichser, Republic Aviation Corp., Farmingdale, New York, dated May 6, 1958 12. Templin, R. L. and Sturm, R. G., "Some Stress-Strain Studies of Metals" Journal of the Aeronautical Sciences, p. 189. (March 1940) WADC TR 59-681 21

13. Elsesser, T. M., Sidebottom, 0. M., and Corten, H. T., "The Influence of Aging on the Bauschinger Effect in Inelastically Strained Beams" Trans. ASME, vol, 74, No. 8, pp. 1291-1296 (November 1952) 14. Corten, H. T. and Elsesser, T. M., "The Effect of Slightly Elevated Temperature Treatment in Microscopic and Submicroscopic Residual Stresses Induced by Small Inelastic Strains in Metals" Trans. ASME, vol. 74, No. 8, pp. 1297-1302 (November 1952) 15. Sidebottom, 0. M. and Chang, C-T., "Influence of the Bauschinger Effect in Inelastic Bending of Beams" Proceedings First U. S. Nat'l. Cnngress of Applied Mechanics, ASME, New York, 1952, pp. 631-639 16. Wooley, R. L., "The Bauschinger Effect In Some Face-Centered and Body-Centered Cubic Metals" Phil. Mag. Ser. 7, vol, 44, No. 353, pp. 597-618 (June 1953) 17. Waisman, J. L. and Yen, C. S., "Effect of Forming in Mechanical Properties", Proc, ASTM Pacific Coast Meeting, September 17-21, 1956, pp. 33-44 18. Maykuth, D. J., "Stress Relief, Annealing, and Reactions with Atmosphere of Titanium and Titanium Alloys", Paper Delivered at ASM Titanium Conference, Los Angeles, California, March 25-29, 1957; also issued as a Memorandum dated May 24, 1957 by Titanium Metallurgical Laboratory, (now Defense Metals Information Center), Battelle Memorial Institute, Columbus Ohio 19. Bauschinger, J., Ziviling, vol. 27, p. 289 (1881) 20. Seitz, F., Physics of Metals, pp. 145-149, McGraw-Hill Book Company, New York, 19t43 21. Barrett, C. S., Structure of Metals, pp. 359-60, 367, McGraw-Hill Book Company, New York, (Second Edition) 1952 22. Zener, C. in Symposium on the Cold Working of Metals, p. 180, American Society for Metals, Cleveland, 1949 —-- Elasticity and Anelasticity of Metals, pp. 145-146, University of Chicago Press, Chicago, 1948 23* Richards, T. LI., "Preferred Orientation of Non-Ferrous Metals", article in Progress in Metal Physics, vol. 1, Chalmers, B. (ed.), p. 281, Interscience Publishers, New York, 1949 24. Brandenburger, H., Schweiz. Arch. Angew. Wiss. Tech., vol. 13, p. 232, 268 (not consulted) WADC TR 59-681 22

0 1H3 TABLE 1 COMPARISON OF TENSION AND COMPRESSION PROPERTIES AT ROOM TEMPERATURE FOR SEVERAL HEATS OF C1 10M TITANIUM U-' Tension Propertied Compression Properties X*. 270 Offset Ratio: 0.2% Offset ~atio: ~ "^C71-~~~ ~Number Range/ Ultimate Strength Yield Strength Elongation Modulus, E Ten. Yield Number Yield Strength Modulus, E Com Yield ~~ Heat No. Data Source of Tests Average (1000 psi) (psi) (%) x 106 Ten. Ult. of Tests (1000 psi) (x 106psi) Ten. Yield A-1172600* U cd M 9 Range 144-152 139-147 20.5-24.0 15.8-16.9 -- 9 105-111 15.8-16.7 -- Average 146.2 142. 3 22.4 16.5 0.98 108. 1 16.2 0.76 A-1172600* R.A.C. 12 Range 144-149 135.5-145.5 13.5-17 15.0-15.7 -- 7 103.8-120.2 16.4-16.9 -- Average 146.7 140.3 15.5 15.3 0.96 112.8 16.7 0.80 A-50089** U of M 3 Range 127.8-130.5 114-115.2 24-26.8 14.7144.9 -- 3 115-117.3 15.3 -- Average 129.4 114.5 25.5 14.8 0.88 115.8 15.3 1.01 A-50089** R.A.C. 12 Range 131-133.8 113.6-119.1 16-19 14.3-15.0 -- 3 120.3-123.5 16.6-16.9 -- Average 132.0 117.2 17.0 14.7 0.89 121.9 16.7 1.04 NI A-5036*** U of M 2 Range 130-136 113-116 -- 14.4-15. 1 -- 2 116.5-119.5 15.7-16. 1 -- (OO^ ~Average 133 114.5 -- 14.8 0.86 118.0 15.9 1.03 A-32233-11 Boeing 3 Range -- 120.5-121.8 -- 16.0-16.4 -- 3 129.1-130.7 16.4-16.5 -- Average 133 121 1 -- 16.3 -- 130.0 16.5 1.07 A-40006-Me Boeing 3 Range -- 134.4-137.5 -- 15.5-16.0 -- 3 131.9-135.8 16. 1-16.6 -- Average 136.0 -- 15.7 -- 134.0 16.4 0.99 A-40006-MI Boeing 3 Range -- 136.2-137.9 -- 16. 1-16.6 -- 3 140.6-144 16.4-16.8 -- Average -- 1 3 1 -- 16.4 -- 142.0 16 7 1.03 Unknown Armour 3 Range -- 120.5-124.0 -- 15.6-16.0 -- 3 125. 1-128.1 16.3-16.6 -- Average -- 121.9 -- 15.8 -- 126.7 16.4 1.03 Data Sources: U. of M. -- University of Michigan R.A.C. -- Republic Aviation Corporation Boeing -- Boeing Atipane Corporation (Data from TML Report No. 43) Armour -- Armour Research Foundation (Data from TML Report No. 43) * Material tested for WADC TR 57-150 Pt III ** Material furnished by Republic Aviation for checking purposes. *** Material remaining from an earlier research project —reported in WADC TR 54-54 "A Study of Creep of Titanium and Two of Its Alloys" by J. V. Gluck and J. W. Freeman.

TABLE 2 EFFECT OF UNSTRESSED EXPOSURES ON SELECTED STRENGTH RATIOS OF C M (HEAT A117600)95 Exposure Conditions Test Temp. Ratio: Tensile Yield Ratio: Compressive Yield Temp(0F) Time (hrs) (~F) 4t Ultimate Tensile Te n Tensile Yield PART I As10-Produced Room 0.97 0.99 65050 Room 0.92 1.00 50 Room 0.95 0.88 100 Room 0.94 0.92 700 4** Room 0.93 0.95 10 Room 0.97 0.99 50 Room 0.92 1.00 100 Room 0.95 0.96 800 10 Room 0.91 1. 12 50 Room 0.89 1. 14 100 Room 0.85 1. 13 PART II As-Produced 650 0.87 0.64 650 10 650 0.84 0.64 50 650 0 0.85 0.63 100 650 0.87 0.68 As-Produced 700 0.88 0.61 700 10 700 085 0.85 50 700 0.83 0.80 100 700 0.77 0.92 As-Produced 800 0.91 0.66 800 10 800 0.797 0.88 50 800 0.74 1.03 100 800 0.81 0.75 * Note: Calculated from data in Ref. 1, Tables 2, 5, 6, 9, and 10. WADC TR 59-681 24

TABLE 3 EFFECT OF EXPOSURE TO SHORT-TIME STRAIN PATHS ON ROOM TEMPERATURE MECHANICAL PROPERTIES OF CIIOM Deformltion Room Tamprature Proprrtai After Expour ~Nominal~~~ ~Total Loading platic IiltImate ~ o.Ia^st Exposure Sequenc. (Elastic + Total Type of Tensile 0.2% Off.et Proportonl Elo tlon Modulu. ^ _Path _ D(.C4 SE me~lfl NoHa. Plastict)c Loading Creep Platic T.. Strength Yield Ll t Noa, None. Averge A.-produced - -...- Tenaile 146.211 142889 93600 22.4 31.3 16.5 Nona Ne.. Av..rge A.-produced - - - Comp. -- 108, 111 800 16. ~,No e. NOVA IA37A 00'F- I00 hr -.... Tensile 146500 140,000 111,000 9. 32.0 154 3Ar 7~00F.100 hr —...... Tenaile IS4,000 146.000 127,000 24.0 32.2 15.9 15,z5O 143,000 1U0. 3I 1,................................................................................................................... 700F- 100 hr -C.... Camp..- 134 000 1I 3A13 700*F00hr -- -- -- - Comp..- 132 000 0 - 2AB33 700'F-100br -- --... Comp. -- 36,500 10000 134,200 108,000 1I.3 ) Pr roai 0.05 3AZ~ A.~ At 700'F-91,000poi-Load- 0.94 0.30 -- 0.30 Unlod-Hold 100 hr -- -.0.04 0.26 Tensil 157,000 147,500 125.000 20.7 27.2 14 1.0 2C29 A.W At 700-F-96,000poi.-Load. 1.54 0.01. 0. 81. Unload-Hold 100 hr.....0, 077 Tensill 14,000 146,000 125.000 23.3 2.4 15.0,0 S 2CDZ9 A. At 700'F-97,000poi-Load- 2.35 I. 65.. 1.65. Unload-Hold lOOhr.. -0.01 1.64 Temie 162.000 151,500 134,000 ZIs 20.2 14...0S IC16 A. At 700F -91,000 p.-Laad- 1. 64 0.96 - 0.96. Unload-Hold 100hr.... 003 0.99 Comp..- 130,000 104000. ~1. 5 lA2 A. At 700*F-96,000 psi-Load- 1.90 1.21. I 1,21 D. Unload-Hold 100 hr.-...0.06 1. 5 Camp. -- 137,000 99.000.. 9 12 Pot-Stan 0 3C23 A. At 700'F-Hold 100hr. B. 91,000pai load-Coal under load 1. 14 0.41 -- 0.41 Tenile 172,000 160,000 120,00 2.3 22,8 10.1 1 0 2CD1o A, At 700*F-Hold 100hr6 B. 97,000psi load-Cool under load 1.70 0.98 -- 0.98 Toeaile 164,000 164,000 6000 20.0 0.0.6 1,5 ZCDI A. At 700-F-Hold 100hr6 B. 96,000 psi load-Cool under load 1.37 0,66 -. 0.66 Tensile 156,000 156,000 124,000 18,3 2I.0 14.7 4 15 1ABZZ A. At 700*F-Hold 100lhr B. 97,O000pi load-Cool under load 2.45 1.80 -- 1.80 Tenlle 159,000 1S9,000 133.000 22.0 32.1 14.7 - 0.0 2A3 3.At 700'F-Hold 100 hr$ B. 91,000psi load-Cool under load 1. 18 0.61 -. 0.61 Comp, -. 102,000 54,000 1. 5 IAB8 A, At 700-F-Hold 100hr6 B. 96,000pai load-Cool under load 2.65 1.92 -. 1.92 Comp... 104,01 56,000 1,6 3) Cyclic 0,5 2AB23 A, Al700'F-89,500 pai load 0.96 0.2 -. 0.28 Pr.striln B. Uoload-Hold 50hl~. -~ -0.02 0.26 C. 89,500 p.i load 0.1 0.12 -- 0.38 D. Unload-Hold50hr O.002 0,36 Tenille 152,500 144,000 122.130,000 22.0 36,0 155. 1.5 3A16 A. At 700*F-93,000psi load 1,17 0.40.. 0.40 B. Unload -Hold 50hri. --.0.02 0.38 C. 93.000 pa. load 0.81 0.16.- 0.54 D. Unload-Hold 506hr.0.05 0,49 Ta.i1l. 157,500 149,500 123.131,000 20,5 31.0 14.9 1.0 1C13 A, A.t 700F-94,O00pii load 2.17 1.53.- 1.53 B, Unload-Hold 50hr-. -- -0.04 1.49 C. 94,000p.i - load 1.12 0.22.. 1.71 D. Unload-hold 50 hr.. --.0,03 1.68 Tenalla 159,000 152,000 131,000 22,5 28,0 11,7 0.5 IA12 A.At 7000F-92.000p.i load 0.84 0.13.. 0.13 B. Unload-Hold 50hr..-.. -0.02 0.11 C. 92,000 pai load 0.83 0,15 -- 0.26 D. Unload-Hold 50hr..... -- 0.26 Camp... 129,000 99,000 ~.. 15,3 1.5 3AB19 A. At 700'F-94.000 p.1 load 1.97 1.27 -- 1.27 B. Unload-Hold 50 hr~ C. 9b,000pai load..... D. Unload-Hold 50hr. 0.96 0.25 -~ 1.52 Camp. -- 136,500 104,000...- 16,1 4) Cyclic 0.0 10C027 A Al 700'0-Hold 50hri Pofl-Strain 0. 89,500pai load 1.05 0.50.- 0.50 C. Unload-Hold 50hre.-.0.05.. 0.45 130.89,500pal load: 1.00 0.30 -. 0.75 E. Unloaded and aooled.. -,.... Tonail. 156,500 152,000 143,000 20,0 30,0 14,9 1.5 3C31 A. At 7000F-Hold 50hri B.9,.500ipai load 1.19 0,54.. 0,54 C. Unload-Hold 50. O - 13. 93,5001.1 load 0,66 0.23.- 0.77 E.Stop-Cool aaldr load -....... Tensie 15500 154,000 144,000 14,5 29,6 15,0 0.5 zCis A. At 700'F-Ibld 50hr6 B.92,000pai load 1.19 0.54.. 0.54 C. Unload-hold SOIlir.....0.02 0,02 D, 9L,000pii load 0.4 0.22.. 0.74 E. Unlo-dd and cooled.. -... 0.74 Comp... 109,700 75,000 ~-.. 16,1 1.5 IC122 A. At 7000'-Hold 50hr* -- B. 94,000 pai load 1,62 0.67.. 0.67 C. Unload-Iold 50ibr.-.. 0,67 D.196.000 psi load 1.10 0.40 -. 1.07 Camp. -. 117,.00 83,000.... 16.5 WADC TR 59-681 Z5

TABLE 4 EFFECT OF EXPOSURE TO CREEP PATHS ON ROOM TEMPERATURE MECHANICAL PROPERTIES OF CIIOM D~~fU-,.tiw' Roo-007 [tO-)-rtutr Propetties Alter Exposure Plastic IFttal ~ Tu7ti] Iypt of r[tiil, Strength Yield Litmit Elongation R. A. Modulus, E Path footrtmatittt Specitmtet Not. Liposot. S-tu- 17.i 1' Co ot, bt (Itso) ( psi) (psi) (% (, I0 6t 5) Creep 0.5 IC27 A. At 700l-1,000 pil totd 0.37 nil -- -- Only B. Creet 100 hr-(-tool -ttlvr lod -- -- 0.58 0. b8 ronsile 159,000 150,000 134,000 18.0 Z9.0 14.8 1.5 3AB6 A. At 7008.-ht.000 l>t load 0. St I -- -nB. C: r 1 0 IOh to-tol - i)o 1 -r lool -. -- 1.41 1.\41 F I16e l68,00 00 tst, 140,000 18.8 25.0 14.5 0.5 2AII A. At 70J'V-5-t,000 )o, load o. to — n / + B. Cret-t lOOhrt-Cool o-r- li-d.- -- 0. to Ot.) Cottp. --- 137,500 86,000 -- - 15.6 ( 1. 5 ICD16 A. At 700'F-t)8.000 [>ti lodd 0.48 tiIl B. Creep lOOhr-Cool to iitor load -- --,.it 7.35 Co-op. --- 178,000 87,000 -- -- 15.8 1.5 3CD-'5 A. At 700'5-t).000 i loaot 0.57 0.0o, 0, 0~ B. Creep lOOthr.Cool todor otad --.- 27 1'.77 Cootp. --- 137,000 90,000 -- -- 15.6 6) Post 0.5 3AB It A. At 70008'-Hold 50Ohri Creep B. b7.OO pot load 0.4" ot C. Creep 50hr~-Cool under load -- -. 0.47 0.47 lTcajilt 156,000 151,000 97,000 20.5 27.7 15.2 1.5 tAB12 A. At 700'-FHold 50hr. A B. 75.000 pSI load 0.70 0.01 -- 0.04 C. Creep'O trs-Cool under load -- -- 1.0i 1.08 1enile 163,300 158,000 116-141,000 20.0 34.2 15.5 0.5 1C- - A. At 7008 —t uld S h0r, — -ott- - - - --- B. 71,000,i load 0.57 nil C. Creep 50hr,-Cool und,-r load -. -- 0.59 0.59 Contp. --- 124,000 77,000 -- -- 15.9 1.5 2CDb A. At 700-'-Hotld 50hr. B. 75,000 p.t liad 0.59 0.09 -- 0.09 C. Creep 5Ohr.-Cool under load -- -. 0.75 0.84 Cttoop. --- 120,500 79.500 -- -. 15.7 7) Pre-Creep 0.5 2A22 A. At 700'i.-6-o.000 psi load 0.47 nil -- - B. Cree;p 50hr~-reto-, load --. 0.36 0.36 C. Hold 50hr.-no ~trea. -- -- -0.02 0.34 Tentile 157,000 146,000 131,000 21.0 37.0 15.2 1.5 3A6 A. At 7008F-71.000 p.i load 0.59 0.02 -- 0.02 B. Creep 50hri-remot,-e load -- 0.87 0.89 C. Hold 50hrs-no stress -- -- -0102 0.87 Tensile 168.500 153.000 126,000 17.3 25.6 15.5 / 0.5 IA25 A. At 7008. —63.000 psi load 0.56 nil B. Creep 50hra-renove load -- -- 0.56 0.56 ^ C, Hold 50hrs-no stress -- - -- 0.56 Comp. --- 142,500 108.000 -- -- 6.7 1.5 3ABZZ A. At 700'F-72.000 psi load 0.58 0.05 -- 0.05 B. Creep SOhri-remoove load -- -- 0.72 0.77 C. Hold 50hro-no stress -- -- -- 0.77 Comp. --- 136.500 100.000 -- -- 16.4 1.5 2CD8 A. At 700'F-71,000 psi load 0.57 0.04 -- 0.04 B. Creep 50hrt-remove load -- -- 1.07 1.11 C. Hold 50hr.-no stress --.. -0.08 1.03 Comp. --- 141,000 109.000 -- -- 16.3 8) Cyclic 0.5 2AB22 A. At 700'F-45.000 psi load 0.35 nil Creep B. Creep 50hrs-remove load -- -- 0.17 0.17 C. 45.000 p.i load 0.34 nil -- 0.17 D. Creep 50hrs-Cool under load -- -- 0.22 0.39 Tensile 158.500 146.000 125.000 16.8 29.8 15.S 1.5 3CD31 A. At 700'F-68.000 psi load 0.55 nil B. Creep 50hr.-remove load -- -- 0.71 0.71 C. 68.000 psi load 0.50 nil -- 0.71 D. Creep S0Ohr-Cool under load -- -- 1.69 2.40 Tensile 165.000 156.000 130.000 15.5 19.4 14.S 7 0.5 3CD2b A. At 700'F-45.000 pai load 0.30 nil /1/T B. Creep 50hra-rcmove load -- -- 0.21 0.21 fl/t C. 45.000 psi load 0.28 nil -- 0.21 _/ V j_ D. Creep 50hr.-Cool under load -- -- 0.19 0.40 Comp. --- 137,600 96.000 -- 1 6 1.5 ICDS4 A. At 7001F-68,000 psi load 0.56 0.06 -- 0.06 B. Creep 50hr.-remove load.. -- 0.58 0.64 C. 68.000 psi load 0.48 nil -- 0.64 D. Creep SOhr.-Cool under load -- -- 1.32 1.96 Comp. --- 132.500 90,000 -- -- 16.3 1.5 2C6 A. At 7001F-68.000 psi load 0.59 nil D. Creep SOhrt-remove load -- -- 0.56 0.56 C. 68.000 p.i load 0.50 nil -- 0.56 D. Creep SOhrs-Cool under load.- -- 1.12 1.68 Comp. --- 135.000 80.000 --. 16.5 9) Interrupted 0.5 IAB25 A. At 700'F-58,000 psi load 0.45 nil Creep B. Creep 25 hre-remove load -- - 0.17 0.17 C. Hold 50hrs.(bearm only).... -- 0.17 D. 58.000 psi load 0.46 nil -- 0.17 E. Creep ZShrs-Cool under load -- -- 0.23 0.40 Tenille 156,000 151.000 143,000 20.5 32.0 15.2 1.5 3CD23 A. At 7000Y-73.000 psi load 0.56 0.08 -- 0.08 B. Creep 25hre-remove load -- -- 0.40 0.48 C. Hold 50 hr. -- -.0.01 0.47 D. 73.000 psi load 0.60 0.06 -- 0.53 E. Creep 25hre-Cool under load -- -- 0.76 1.29 Tentile 167,000 161.000 150.000 19.5 27.5 15. 3 4 0.5 lA8 A. At 700'F-58,000 psi load 0.48 nil -- -- P t 1^B. Creep 25hrt-remoro e load -- -- 0.21 0.21 /Ii o C. Hold 50 hr. -- - -0.02 0.19 f I 8 0 D. 58.000 psi load 0.49 nil -- 0. 19 E. Crerp 25hre-Cool under load -- -- 0.35 0.54 Comp. --- 139.000 100,000 -- - 17.1 0.5 IC2 A. At 700'F-69,000 psi load 0-58 0.05 -- 0.05 B. Creep 25hro-remove load -- -- 0.27 0.32 C. Hold 50 hr. -- -- -0.07 0.25 D. 63,000 psi load 0,'t 0.07 -- 0.52 E. Creep 25 hr.-Cool under load -- -- 0.43 0.75 Comp. --- 126,000 82,000 -- -- 15.4 1.5 2CDII A. At 7001F-73,000 psi load 0.56 0.08 -- 0.08 B. Creep 25hr.-remoooe load -- -- 0.44 0.52 C. Hold 50hr. -- -- -- 0.52 D. 73,000 p.i load 0.62 0.12 -. 0.64 E. Creep 256r~-Cool untder load -- -- 0.73 1.37 Coomp. --- 129,800 86.000 -- -- 16.2 WADC TR 59-681 26

EFFECT 0 TABLE 4 (CONTINUED) EFFECT OF EXPOSURE TO CREEP PATHS ON ROOM in TEMPERATURE MECHANICAL PROPERTIES OF CIlOM I Nominal Deformation Room Temperature Properties After Exposure (N PlNominal Plastic Ultimate U. o Offset Proportional Plastic^ ^ ^^^.. Total Total Type of Tensile Strength Yield Limit Elongation R.A. ModulusE 00 Path Deformation Specimen No. Exposure Sequence Loading Loading Creep Plastic Test (psi) (psi) (psi) (%) (%) x lO~psi 10) Pre Strain 0. 5 3AB4 A. At 700~F-89,500 psi load 0.98 0.26 -- 0.26 plus Creep B. Reduce load to 34,000 psi 0.55 -- -- 0.26 C. Creep lOOhrs-Cool under load -- -- 0.26 0.52 Tensile 163,000 153,000 139,000 21.5 28.3 15.1 1.0 IC22 A. At 700~F-80,000 psi load 0.75 0.16 -- 0.16 B. Reduce load to 57,000 psi -- -- -- 0.16 C. Creep lOOhrs-Cool under load -- -- 0.85 1.01 Tensile 167,000 156,000 149,000 19.5 28.0 17.0 I ^^ ^1.5 ICDL9 A. At 700~F-92,000 psi load 1.19 0.49 -- 0.49 1^ —^ \ B. Reduce load to 56,000 psi 0.93 -- -- 0.49 \ C. Creep lOOhrs-Cool under load -- -- 1.04 1.53 Tensile 165,500 155,600 146,000 18.3 27.6 14.8 0.5 2ABII A. At 700~F-89,500 psi load 0.95 0.19 -- 0.19 VyS) ~y B. Reduce load to 34,000 psi 0.45 -- -- 0.19 C. Creep lOOhrs-Cool wnder load -- -- 0.23 0.42 Comp. --- 132,500 88,000 -- -- 158 1.5 3AB25 A. At 700~F-92,000 psi load 0.90 0.28 -. 0.28 B. Reduce load to 56,000 psi 0.71 -- -- 0.28''.3 C. Creep 100 hrs-Cool under load -- -- 0.78 1.06 Comp. --- 135,000 88,000 -- -- 15.7 1.5 2C8 A. At 700~F-80,000 psi load 0.76 0.14 -- 0.14 B. Reduce load to 65,000 psi -- -- -- 0. 14 C. Creep lOOhrs-Cool under load -- -- 1.47 1.61 Comp. --- 134,000 83,000 -- -- 164 Data from 0.5 3A33A A. At 700~F-36,000 psi load 0.25 nil -- -- WADC TR B. Creep lOOhrs-Cool under load -- -- 0.26 0.26 Tensile 148,000 141,000 120,000 20 288 16,5 57-150 Pt II 1.0 2A7A A. At 700~F-51,000 psi load 0.36 nil -- -- B. Creep lOOhrs-Cool under load -- -- 0.32 0.32 Tensile 149,000 143,000 115,000 21,7 32.9 15,2 2.0 IA26A A. At 700~F-63,000 psi load 0.50 0.04 -- 0.04 B. Creep lOOhrs-Cool under load -- -- 1.78 1.82 Tensile 162,000 149,000 115,000 17,3 26,2 16,1 3.0 3ABII A. At 700~F-69,000 psi load 0.51 0.05 -- 0.05 B. Creep lOOhrs-Cool under load -- -- 1.89 1.94 Tensile 162,000 152,000 125,000 15,0 23,8 15,2 0.5 2CD26 A. At 700~F-36,000 psi load 0.27 nil -- -- B. Creep lOOhrs-Cool under load -- -- 0.31 0.31 Comp. --- 136,000 89,000 -- -- 16.4 1.0 3AB29 A. At 700~F-51,000 psi load 0.38 nil -- -- B. Creep lOOhrs-Cool under load -- -- 0.67 0.67 Comp. --- 131,000 90,000 -- -- 162 2.0 3C14 A. At 700~F-63,000 psi load 0.51 0.05 -- 0.05 B. Creep lOOhrs-Cool under load -- -- 0.84 0.89 Comp. --- 121,000 83,000 -- -- 16.2 3.0 IC30 A. At 700'F-70,000 psi load 0.61 0.07 -- 0.07 B. Creep lOOhra-Cool under load -- -- 2.91 2.98 Comp. --- 114,000 79,000 -- -- 16,1

TABLE 5 EFFECT OF SPECIMEN ORIENTATION ON ROOM TEMPERATURE MECHANICAL PROPERTIES OF C11OM AFTER 10 HOURS PRIOR CREEP-EXPOSURE AT 7000F Expoaure Conditions Total Roomrn Temperature Shrt-Time Mechanical Properties After Exposure Total Plastic Ploastic Ul1 T stl. Off Temp. Time Stress Load. Def. Load. Def. Creep Del, Strain Type of Strength Yield Strength Elongato Rdtiono of Modlus, E Hardneea Spec., No. i'F) (hrs) (psi),,Jet (s) (%) La i —,l Test (,/j lnches) Area (%h) 10 p.i) IR"C" Specimens Taken in Rolling Direction 0 (&vOg. of 9) not exposed -- -- -- -- Tensile 14b,200 42,900 22,4 31,3 6.5 33.4 (avg. of 9) not exposed. Conmp. -- 108,000 -- - 16.2 -- ICDIS 700 10none... Tensile 143,000 140,000 23.8 34.0 15.4 39. i 3CD33 700 10 none Tensile 46,000 24.n0 2e7.9 5,4 38. 7 1A4 700 10 56,000 0.43 oil 0.12 0.12 Tenoile 138,000 135,000 21.0 30.0 14.7 38.5 3AB8 700 10 79,000 0.62 0.10 0. 17 0.27 Tenoile 149,000 144,000 23.2 31.4 15. 5 36. b 2AB16 700 10 93,000 1.77 1.07 0.96 2.03 Tensile 150,500 149.500 21.0 31.2 15.2 37,9 3CD14 700 10 100,000 3.76 3.00 5.44 8.44 Tensile 177,000 175,000 7.8 18.2 13.6 34.2 1CD24 700 10 none -- -- - -- Comp. -- 147,000 -- 16. 1 -- 3CD9 700 10 none.. Cormp. 136,000 15.7 1CD33 700 10 56,000 0.43 nil 0. I 0. 11 Comp. - 125,000 16.4 ZAZ 700 10 82,000 0.62 nil 0.32 0, 32 Cornmp, 115,000 15.3 3C27 700 10 90,500 1,27 0.58 0.66 1.24 Conmp. 94,400.. 6. 8 IAB18 700 10 92,000 2 16 1.45 1.43 2.88 Comp. 103,000 -- -16.6 Specimeno Taken 30' to Rolling Direction* S4A-T32 not exposed -- -- - - Tensile 142,400 140,800 29.0 43,7 13.8 34 S4A-T37 not exposed - - -- -- Tensile 140,000 138,000 26.0 342 13.7 36 141,200 139,400 27.5 40.0 13.8 35 S4C-CII cot exposed - - - - Cornmp. 140,500.. -- 19.0 - S4C-C14 not exposed -- -- Comp. 143,200 18.7 141,850 -- 18.9 S4A-T30 700 10 none - - -- Tenile 139,000 139,000 27,5 45,5 14.5 S4A-T36 700 10 80,000 0.98 0.33 0,47 0.80 Tensile 146,000 146,000 25.5 40.6 14,5 S4A-T35 700 10 88,000 3.97(est) 3.0 (eat) 1.71 4. 70(eat)Tensile i62, 500 162,500 11.0 35,5 14.7 S4C-C1Z 700 10 none --. -- Cornp.. 140,000.. — 16.8 S4IC-C13 700 10 none Cor.. 141,000 C 16. 8 S4A-T31 700 10 80,000 0.96 0,.25 0,47 0,.72 Comp. -- 112,000... 15,4 S4A-T33 700 10 88,900 1.90 1,22 3,34 4.56 Conp. - 115,000 17.6 Specilnend Taken 45' to Rolling Direction * S4C-TI ot exposed -- -- - - - Tensle 136,200 134,400 20.5 49,7 15.1 30 S4C-T7 not exposed -- - Tenaile 131,000 -- 27.0 46.2 14.7 35 S4C-CI not exposed Co - 147,00 -- -- 182 S4C-C3 not exposed Corny1. 149,500 I 1. 3 Comp...149, 500...18. 3. 148,600 -- -- 18.2 S4C-TIO 700 10 noneT 136,00 135, 2.5 49.0 14.6 36 T'ens~ie 13b, 000 i35,000 26.5S 4.0 463 $4C-T6 700 10 75,000 0,99 0.40 0.34 0,74 Tentile 150,000 150,000 22,0 445 14.9 S4C-T3 700 10 90,500 3, 15 2., (e.1) 2.00 4. 5 (eet)Tenoile 160,700 159,000 8.5 37,0 15,6 37 37. 0 15.6 ~~~~7 S4C-C6 700 10 none - - -- Cop. - 150,500 - 17,0 S4C-C4 700 10 none.- Coop,j. 148,000 19.9 S4C-T2 700 10 78,000 1.00 0,39 0.37 0.76 Comp. - 11,500.... S4C-T9 700 10 88,000 4.5 (eat) 3.8 (eat) 4.10 7,9 Conp 118,000 15. 0 Spucireno Tak. n 60' to Rollin0g Directio n * 34AoT60 not expo. ed S4A-T67 not exposed —.... Tenoile 146,000 120,500 21.0 39,4 13,6 35 S4A-T60 noat expoted -.... Tensile 145,000 139,000 11.0 14,1 13.9 36 145,500 129,750 16. 0 26. 7 13,8 35,5 S4C-C8 not cxpo,~ed. S4C-CO not exposed Coto, -- 160,500 -- - 19,3 -- S4C-CIO not0 exposed -.. Comp. -- 164,000 22.3 162,250.. -- 208 S4A-T65 700 10 none 44,000 144,00 0 16.3 15.2 - -Tcnsrile 14i, 000 144-, 000 15.0O 1.3 5 S4A-T61 700 10 80,000 0.90 0,40 0,41 0. 81 TooIlv 153,000 153,000 18. 5 40,8 15, S4A -Ti6 700 10 88,600 1.15 0.48 0.76 1,24 Toenolo 153,000 153,000 15,5 43,3 16, 3 S4C-C7 700 10,one - - -- Co 151, 16.4 S4C-C9 700 10 none Co..ni.. -- 16,000 17 54C-C94 700 l0 non e 200 7 4AT4 750 10 80,000 0,89 0,24 0,39 0.63 Coyp. = - 119,000 16. 6 S4A-T62 700 10 90,000 1,48 0,78 1.37 2.15 Cooy. - 11,50 16,3 T44 tnot xpoo,,d -. Tool 149,060 134,.000 21,0 29,8 15. 8 37.9 T43,tot copotod -,... Toatil. 145,500 131,000 21,8 33,0 16,0 37. U 147,250 132,500 21,4 31,4 15,9 37, 4 T141 otolxoyttd. -. Comp.. 112,000..-. 16,3 54A-6''o [6~ae onl. 66,OL 7T42 Not ooy.o.d.Cotynp. 153,000. 16,. 157,500 16.6 T44Ar notU cxpoacd =. T4-A-'5 700 t tI'oloI 156,20t 152,000 27,5 336 159 36 T4A-T6 700 10 90,500 0,81 0,26 0,3 8 0,50 8 It 16, 500 162,500 19,0 33. 3 16,6 35 T4A.T 8 700 10 96,000 1377 0,80 0.90 1,70 Tottatlo 166t,400 166,000 1 9,0 19, 7 16. 6 T47 700 tOU,,,o~ --.... Co,6 00.0. 1 T4A-TIO 700 10, 0.96 035 049 04 C8y. 144,500 170 T4A-T7 700 10 97,000 5 0 45 0 72. 46,31. 000 T4A-T9 700 tO 1t,0000 1, 04 Co 1700 e -0 -01). OU0 1. 0z 0. 4 0 1. 12 2 117,000)'' 0 Diaaoornat lot, otjt bcrrligyoo..oo153,000,,ar Otgooo 3 WAD)C TR 59-681 28

H U, 0 TABLE 6 EFFECT OF ORIENTATION AND EXPOSURE CONDITIONS ON SELECTED STRENGTH RATIOS OF CIIOM TITANIUM Tensile Yield Compressive Yield Ratio: Rto Ultimate Tensile R o Tensile Yield Unstressed Unstressed 10 hr-700F 10 hr-7000F *~EC~ ~Exposure Exposure 1o Total Plastic O. 5 Total Plasti Orientation As Produced 10 hr-700'F As Produced 10 hr-700'F Strain Strain 00 0.98 0.97 0.76 1.01 0.69 0.77 30" 0.99 1.00 1.02 1.01 0.77 0.83 450 0.98 0.99 *12 111 0.81 0.90 600 0.88 1.00 1.25 1.09 0.77 0.85 90- 0.90 0.97 1.18 1.06 0.88 0.96 * Orientation with respect to sheet rolling direction.

Q> C7% 00 TABLE 7 MECHANICAL PROPERTIES OF METALLOGRAPHIC SPECIMENS Room Temperature Mechanical Properties After Exposure Ultimate Tensile Est. Creep Elongation Hardness Figure No. Specimen No. Exposure Tensile(psi) Yield (psi) Yield(psi) (%) Rockwell'C" 21 As-produced 146,200 142,900 108,100 22.4 33.4 22 3A8 650~-100hr-0.4% def. 151,000 147,000 120,000 21.0 37.5 23 ICD15 700~-10hr-no stress 143,000 140,000 141,500 23.8 35.0 Z4 3CD14 700~-10hr-8.4% def. 177,000 175,000 90,000 7.8 34.2 25 3A4 700~-100hr-no stress 154,000 146,000 133,000 24.0 38.5 26 1A26A 700~-100hr-1.81% def. 162,000 149,000 118,000 17.3 39.4 27 A 15A 800~-10hr-no stress 146,000 133,000 150,000 24.0 35.1 28 1CD11 800~-10hr-0.33% def. 144,000 134,000 133,000 22.5 36.0 29 2CD31 800~-100hr-no stress 147,000 125,000 138,500 19.3 34. 1 30 1C3C 800~-100hr-2.67% def. 145,000 130,000 129,000 19.5 33.1

Section CD Section CC(or C) Section AB Section AA(or A) Strip _ I I _ _ _ _ _ _ No. 0 ^ o 1 I 1 -1 1 7^ __________________________________________________________9__ _____________________________________________________________ _e______10 ^ ~~~____________________________, ___________________________ _________________________^_______11_____ _Dimensions:_22 (prolx6in____________________ __apetiplbldi________12 ______________________________________________________________________________ 14 ___________________________________ _______________________j_______________________I1 IZ _________________________________________________________________________________ 16_ 111111meed11111:4ab_______________________________________________ip______18 _______________________________________________________________________________ 19 Fiur 18-Smln rcdr o het fC1MTtnu lo 12 ____________________________________________________ ____________________23 24 ____________________________________________________ ____________________25 11111111____________________________________ ____________________26 ____________________________________________________________________________ 28 ___________________________________ ____________________ ___________________230 __________________________________ _____________________________________________ 31 ________________________________________________________________________32_____ ________________ _______________ _________34 36 ~^~~~~~~~~~~~~~~~~~~~~~z ~~3 1.''' ^ Sheet Dimensions: 36x90x0. 064 inches Specimen Code: (She et)(Section)(Strip) Strip Dimensions: 22 (approx)xlx0~ 064 inches *Example: Strip labeled * is 2CD17T, Sheets Numbered 1, 2, 3, or 4 (arbitrarily) i. e. a tensile specimen from Strip 1'^ Section CD of Sheet 2. Figure 1. - Sampling Procedure for Sheets of CIIOM Titanium Alloy

> a $0 Exposure Spec. 0. 530 on ^ Tensile Spec. 0. 500 ~~ -15/1 H~ 4.8 15/1 ~I ^~ ~^ ^~IR Ai-1pprox./4 ~Ir \ > Grind last 1/32 each edge, 3/ D~ longitudinally _ 5/32 D D o <3/8 D c........ 27.Z^.....~^22 Tensile or Creep-Exposure Specimen IL DO NOT SCALE 0. 500 ALL SPECIMENS {+ 0. 003) FULL SHEET THICKNESS ALL DIMENSIONS.IN INCHES (_. 03 064 INCHES._____ 2-3/4 ~ Compression Specimen Figure 2. Details of Test Specimens

E 1896-65 HI DGaCV:|tt o1 o8rltnf11wItlo tt:>wl 4 tntt" Pt rlP -t T.-) 11 DO nlPo o1-1M,T, tow ~ rnrlotdltma1 tmooH ir C AAnTD #tUdtllS T IC; PLOlO -T) pill F1loUftnT - * FJnlliUl /- / / 0-X1 08 / / / oZ 0 L 0/ -~0 091 08 - a ^ -1 o0 /,A - 01 OL l 0~ __/001

R +20 - ___ _'rd Exposure to Temperature Alone / (Recovered Value) Effect of 10hr Exposure at No hQ)^ |t\ ~/^ r ] gStress on Yield Ratio of C IOM o n___________R Comp. Yield Io Temp. t Tens, Yield As Rec. 0.78 0 650 0. 79 lOhr - 800'F 700 0. 99 i0' I. R00 i 12 4-i - \ al Plac Sr - 700 00 -40 50 0 1.0 2*0 3.0 40 5.0 Total Plastic Strain - percent Strength of C lOM (Ti-8 Mn) WADC TR 59-681 34

0 o150............... 140. 800F, 800 - 1320 130-\ ~ _ 120.... r~' /^'\' As Produced,I \.......650O _ 100 ~ { \\ [^'70Q0 OF Calculated from o 9 _____\^ l ________ l Maykuth's data for o 90 (J \^ cold -s tretching 80 0 i. 0 2.0 3.0 4.0 5 0 Total Plastic Strain-percent Figure 5. - Effect of 10-hours Creep Exposure on Compressive Yield Strength of C11OM. WADC TR 59-681 35

0140 H 1o 160 " " 16 150 1 Prior Creep at 700~F 04 40 S preheat time) o a0t ~ lOOhrfr As- \ 10hr o 4,100 produced- _______ k 90 o 80 0 1,0 2.0 3.0 4.0 5.0 6.0 Total Plastic Strain-percent Figure 6. - Effect of Prior Creep Time and Total Strain at 7000F on Room Temperature Compressive Yield Strength of CI1OM.

Un 00 a 140 0 —"Normal" oO I {{0 0 ~ I I _ 0.05% or less 130 t4hr at 700~F and no stress, short-time strain D 120 (the pre-heat time) I 120...I 0 _ 5 ^ 110 As-produced |_ \_1% Total plastic strain t'S. I t 1T' at 700~F (Preheated ~ 80g I I I.~ l~ l4 hrs before loading) o 0 10 20 30 40 50 60 70 80 90 100 Creep Time-hours Figure 7. - Effect of Exposure Time to Reach 1-Percent Total Plastic Strain at 700F on Room Temperature Compressive Yield Strength of COM. at 700~F on Room Temperature Cornpressive'field Strength of CIIOM.

lOhr +20 ~.-..........-_... —-. - -...-' -- +20 5lr l ~50hr - Exposure to / fir 4 temperature alone / +10 / I' 4) r I ^ --—'^ l00fr )l' --------- Tension n,~ _ _ ___________~.h Compression -zo --------— I ---- -t - - 50 h l \ \ \ l -40........50 hr 10 hr 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Total Plastic Strain-(Loading plus Creep)-percent Figure 8. Percent Change il Yield Strength eft Cl 1M J1 roni 10, 50, or 100-I-lour Creep-Exposure at 700~F. WADC TR 59-681 38

Path I Pre-Strain Path 2 - Post-Srain ath 3 - Cyclic Prestrain Path - Cyclic Post-strain Ii..........J ILJ. J a ~170 170 0 170 170 5 6 160 __ 160 - - -- -- 160 -- i o 160 ------— ___ - IO 0_ _ 0 0 00 4 _ __ H150 - ~ 150 1504 - ~5^~1401 ~ 1401 ~J ~~10 0 -0 1701 ~1 170 0 1 170 170 14 / Y0 II YS 0150-0 150 -~0. 0- 150 - - 001 0 -8 PL 0 0 / 160 1409 A - -- 140 1-' 0 —--- 0 ___~~~ -......... V,' -oPL AA1200 1 0 1 l I A I -- I __ 110 110 100I ~- 1O 100 100- rU lo - PL - 90 90 ------ 90 — -.- ---- —. 9- _ ___ -I Code \ S1EO ~ 80 80 -- 80 Tens. Corrp 80 a80 8 Ult. and H ____- Yield-.PL 70 70 70r 70l 70 - --- I0 I Limit [ _ 60- - 60 Unexposedd f A % 60 _._~__ 5011 0 L 50 50____________ 0 1.0 2.0 0 1.0 2.0 0 1.0 2.0 0 1.0 2, 0 301 ~ 30 ~ 30.. 30.. ~. ~ {' - o- 0,0{_ 0 0 10 10 _______________j_______0-~~_0_~ 0 ~I 0' 0 10 2...0 0 1.0 2.0 0 1.00 0 0 1.0 2,0 0 1,0, 2,0 Total Plastic Strain-% Total Plastic Strain-lo Total Plastic Strain-%o Total Plastic Strain-lo Figure 9. - Effect of Short- Time Strain Paths on Room Temperature Properties of ClIOM Exposed 100-hours at 700F,. WADC TR 59-681 39

100 hours at 700~F 170 m 0 160 ~.. -::-:':Q YS 0 6. 150 P 140."4 130 -., I_ _..... to 100 90.. k.~ 80 70Prop Limit ---- H 60 o Unexp d 5,, Figure 100 2- Effect0 3of Pt-Stran (Path 2) and 2nd0 Total Plastic-Strain- rai Pth ) percent CODE Tension Compression Yield Strength and Prop. Limit ----- COM ExposedStrain for 2nd Load of Cyclic Tests at 700 F UnexposedC TR 59-681 40 Figure 10. - Effect of Post-Strain (Path 2) and 2nd Proportional Limit o~ ClIOM Exposed

Path 5 - Creep only Path 5a - Slight Pro-strain plus Creep Path 10 - Pre-strain plus Creep Path 6 - Poet-Creep 1 t i + /s,+ IL$ _ LDp =O LDp=. 05-. 07 g 170 170 170 (6) 1 0 o _ _ _ 1'J 2 1660 160 160 (.49) 160 150 150 I -5 150[ ~50 t 0, 140o 140 L- - 40L 140. o.... 1 0 1.0 2.0 3.0 00 2. 2.0 3.0 Q 1.0 2,.0 0 1,0 2.0 170 170 ____ rU- 1.. 170 150 150 150 150 16i 0 160 TODE 1' -- 60 - 1: PL PL 170 1470~ a' - S 130 / 130 130 (-,19) 130 _ PL 1201 ~ 120 I 120 I 20, YS 50 5~0 100 I I0 11 0 00 110 t -- 110 ta in d in 6 ~ \I 1 50 1 1 1 50 1 501 No o.90 o 90I 90 0 1.0 2.0 \30 0 2.0 0 2 0 10 Tot-l P c Strain-% Total Pl..tic Strain-% Totl Pl-.tic Str0in- Tot-l Plantic Strain-r Figure 11. - Effect of Variable Creep Pa ths on Room Temperatur e Tension WADC TR 59-681 41 0 1.0 2.0 3.0 0 1.0 2.0 3.0 0 1. 0 2.0 01.0 Z. 20 __30 _______30 30 30 0 0 I 11.0 S. 0 I. 2.0 3.0 0 1.0 2.0 3.0 0 1.0 2.0 0 0 2.0 Total Plastic Strain-% Total Plastic Strain-% Total Plastic Strain-% Total Plasgie Strain-% Figure 11 - Effect of Variable Creep Paths on Room Temperature Tension WADC TR 59-681 41

Path 7 - Pre-Creep Path 8 - Cyclic Creep Path 9 - Interrupted Creep /L /// /_/ ZSi~ ~ ~ ~~,o 1 ~,_ _.... ___ 07 1 4.0 2.0 0 l 2.0 3.0 0 1.0 2.0 17 170 170 160 ~160 ~__~- 160 ~ L"^ tO 150~ \ 150 - 50 Cl.'Q 140I 140o 140 1 0 1120 ~ - 12Z 3.-~ 0 10 0 22 0 170 170 160 160 160 oys 1 IS~o - -PL -.!U. YS,.,. o 1001 - - 1400 140 0oL K! Z Pr op. 13 80 130 --- 80 ~ - 1 60 60 120o 3' l Unexposed f f f f 20~ 20 o 50 0 10 0 1.0 2.0 0 1.0 2.0 3.0 0 1.0 2.0 doTotal Plastic Strain-% Figure 11. (Continued) - Effect of Variable Creep Paths on Room Temperature Tension and Compression Properties of ClIOM Exposed 100-hours at 700~F. W ADC TR 59-681 42 ~NADC;rR 59-681 0

+40I Code +30 T- Tensile yield c.C —— _ Compressive yield X) L Test in direction of stretch +20 D +20 90* Test at 90~ to direction of stretch l +10 *..._ -. 90"-.o b ^\ AD R T L 0 -20 ~T 90~ -30 I ~ Data of Waisman and Yen (Ref, 17) -40 0 1 2 3 4 5 6 7 8 9 10 Stretch-percent Figure 12, - Effect of Stretching on Tensile and Compressive.Yield Strengths of Commercially Pure Titanium at 0" and 900 to the Stretching Direction (Ref, 17). WADC TR 59-681 43

1A 00 w -^~ Rolling Direction~ — 30 450 300 600 450 Transvers 6 S S I 0~~~~~~~~~~~~~~~~~ S30 ^~p 1~TI TIO S67 I SI 600 Longitudinal / Q00 3Q 0^ ^ 60" Figure 13. - Cutting Pattern and Identification Code for Orientation Studies of CIIOM Titanium.

St 1T99-6S H1I DCa)VI'Wd01 JO saTliadoJJ IlezTey~!uy a,.nj-e.rodura.T uaooa uo uoTlzao.tT Butlto EI joaqS o!:oodseI tqlTM uot.lju9t.JO uatu.Tadg Jo 93aoJjL -'VlIoanNT s99012tp - uoTo.x9 JTC UTIoT o9:0 jds0 o t{d HlW. U0oT3a.JTCa IS9L 06 08 OL 09 05 0, 0E 0 01 001 o.~L ~ -- 1~1~1~1~1~1~1~1~1~. ~1~. 0 1 0 I o 01,I 0~.EA. Ql,I bo I^^^^ uoRFnp9H 0 I i-. -1 ~ 1 ~-~ 1-1-1 ~ 1 ~,001 I ~ \ ~ ~ ~ ~ ~ ~ OC\I -4 ~ ~ ~ ~ ~ ~ ~ ~~OZ CJ

160 o 1 50 1 30 ~ Irt g 120 ~ - ~ ~ - ~ ~~,. 0 10 20 30 40 50 60 70 80 90 100 170..... I I I....I....1~. I I I I Ll _Compressive Yield o O150 -140 i _.. Tensile Yield __ W130.. ___ 0 10 20 30 40 50 60 70 80 90 100 50 40 Reduction of Area 40 bo 20 Elongation - i 110 ___[ 20 t0 -- __ 0 10 20 30 40 50 60 70 80 90 100:20 Compression Tensionli 0 t1 20 30 40 50 60 70 80 90 100 Test Direction with Respect to Rolling Direction-degrees Figure 15. - Effect of l0-hours Unstressed Exposure at 700~F on Room Temperature Mechanical Properties of CIIOM Titanium at Various Orientations with Respect to the Sheet Rolling Direction. WADC TR 59-681 46

Code -. o As Produced 0 1.2 _ O10hr-700~F-no stress - 4 ~ A 10hr-700~F-0.5% ~ a v total plastic strain I I 10hr-700I F-I 0% -' _lOhr-700'F-1.0% - 0. 5% Total Plastic 1, 1 itotal plastic strain 1., - -trrain(tension) Unstressed- I.4 0.9 ~-~ o o, ---- I I I I I | | ZAs -Produced 0,8 ~ - 0.7 0 10 20 30 40 50 60 70 80 90 100 i1 3 0~I As-Produced tr I ra! Unstressed ExY.' i^S 13~( ~ ~ ~ ~^*~ ^,~( O.OO'F-I0hrs.^. 1l 0^'~." —.~ —W.ice h|l * 1 700F-4 hr / 0.5% Total Plastic Strain fig ~ no stress (in tension) o Q) 0, ^^ — atios o CI O Total -u-m. W~~~eCd TR 59-681 47I~I _I^ ___'"___ I 1%,%oCreep Strain 0,6 7 ~___ 0,6 NMI 0 10 20 30 40 50 60 70 80 90 100 Specimen Orientation with Respect to Sheet Rolling Direction - degrees Figure 16, - Effect of Exposure Conditions on Yield and Tensile Ratios of CIIOM Titanium, WADC TR 59-681 47

0 10 HOURS PRIOR CREEP AT 700~F Q0- 60~ to Rolling 90~ to Rolling 0~ to Rolling Direction 30* to Rolling Direction 45~ to Rolling Direction Direction Direction H ^ 180 (~1 ~ \ ~ } ~ 1 180 180 18~1-1-1-1-01 180 180 1 I I _ _, 0 wJI 170 170: 17. 170 7170 5 bO ~ ~ ^~' ~ ~ ~~ ~ / ~ ~^0 1~~. 0'160 1 iO 160 1 150 0 ~ 1 ~ -I~ 1501, 01 0 ~ 150 ~ ~ 150 H 140 - ~~ 140 ~ ~~ 140 ~~~ ~ 140 140 ~ r'; 1t4I - 130 1301 130 130 0 1.0 Z.0 3.0 4.0 5.0 6.0 7.0 8.0 0 1.0 2.0 3.0 4.0 5.0 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 0 1.0 2.0 3.0 0 1.0 2.0 3.0._ 1 180 ( F 1~ 1 ~ 1801 180 1~~~~ 180 1 180 ~\ 0 \ Tension \10 ^I10 0 1 16 0' ^ 170 _ \_~|170 15 1 ~~ 0 _0 | Ts7,' ~ i^ ^^^ / Tension 1: _ 1 0 16 0 Cod 10".00 Defrma!ioTension D ert Tension Ciom-p, 106.0 ____17 Efcop ~ - 10retto0 wt Rp to~ Se 0 Tot Tpatre -- ~ ~- P r- of 100 100 ExposuUexpose 0'F..140J______ ___ ___ ___ __ 140 1 140 10 130 130 - 30 3 120 2 Compression-~ 120 - 1 - ------- 120 20 ^ 110 I~\ _______ ______ ______ ______ ______ ______ ~ ~ 110 ^ i ~~ \ ~ 110 ~ Code ~ 110 0 2 ~- / \'-Tension Comp I. \ & A Creep Deformation -— 0~ — -eor o ] i; 1 00 0 ~ 10 0 1 -0 Total Plastic Def. — ~ ~ -A —- 100. 1 90 _ I90 I 90 90 1 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 0 1.0 2.0 3.0 4.0 5.0 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 0 1.0 2.03.0 0 1.0 2.0 3.0 1 20 2. O20~ — - 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 9.0 0 1.0 2.0 3.0 4.0 5.0 0 1.0O2.0 3.0 4.0 5.0 6.0 7.0 8.0 0 1.02.03.0 0 1.02.03.0 Deformation - % Deformation-% Deformation-% Deformation-% Deformatinn-% Figure 17. - Effect of Specimen Orientation with Respect to Sheet Rolling Direction on Room Temperature Mechanical Properties of CIOM After 10 Hours Prior Creep Exposure at 700"F.

100 ~ ~ 900 0 t'0- 0 ~90 uo'~ a Code / /O i l l (est) (est) 80. -/ 0 I I 0/ 0~ 60 / _ 30~ Specimen Orientation i O 10 45~ with Respect to u~xa /I~ IV 60~ Rolling Direction. *J 50 BO 90~ k0 40 _ _ 30 - \= Average curve for longitudinal specimen (0 0) from short-time tensile tests at 7000F, 20 10 O 1.0 2.0 3.0 4.0 5.0 Loading Strain - percent Figure 18. - Effect of Specimen Orientation on Loading Deformation of CIIOM at 700~F. WADC TR 59-681 49

100 _o~ 90~ -. -' o o' 8090 80 -o ----- ~ 70 /T o IIOCode o 0 60 - ~ ~ 0 - -___ 0 0~ i 0 o 30~ Specimen Orientation:o 0 45~ with Respect to 50 V 60~ Rolling Direction h 0 90J 40 30 g0 20 - Note: Creep strain is time-dependent strain following completion of loading, 10 0 1.0 2.0 3.0 4.0 5,0 6.0 Creep Strain in 10hrs. at 700~F - percent Figure 19. - Effect of Specimen Orientation on Creep Strain Reached in 10 hours for CIIOM Creep Tested at 700~F. WADC TR 59-681 50

230 Specimen Orientation With ^ ___ __ __220___ _ _ _ _ __ Respect to Sheet Rolling.220,~^~~~ < X N - rDirection 0) o 210 ~ ~_ 0~ t Uo. I 5 I - i I 300 ____ 45, 200 - 600 >: I Z 90" 0 190 - 180 0 00 1 170 ~ 90 ao~~~~ ^^^^300 - 160 -____ d \/ 60" ^^^^^6 5 * Fg 0- Ee o Tensile Yield Strength a) t40 I Compressive Yield Strength 130 90 0 120 - \......\......................... LA 20~ 6 45~ 110 100 ~0 0 - 0 1 2 3 4 5 6 7 8 9 10 11 12 Total Plastic Strain - percent in l0hrs at 700~F Figure 20b - Effect of 10-hrs Exposure to Stress at 700~F on Tensile and Compressive Yield Strengths of CIIOM Taken at Various Orientations with Respect to Sheet Rolling Direction, WADC TR 59-681 51

+30 +20 + I _ 0~~ +lo -- —'. or 0 " ~' Tensile Yield Strength = 0 - 10 \- ~~ i Compressive Yield Strength ~ <u bV \, _90~ _ I > -3 0 D _ ~ 0 ~___ ___ ___ ___ ______ 30.00 -40 -50. _____. - 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 +30 - _ ~ +20 - Ultimate Tensile - 0 I -- 30' + 10 600 900 0I7I 4-b 0 0 1 0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 -T0.... 60S~~ ~ Orientation With Respect Fiu. 214 to Rolling Direction So ~oF Elongation 00~ D -10 30* ^ O \ \ - 450.9 -20 - - 90 I~ ^ \ \ [~ Note: "Zero" points are 1 900 N. I based on exposure J -30 \ to temperature 0 \ alone. > -40 \1 \45\0 300o00 1 -50 - _ ___ ______________ 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 Total Plastic Strain-percent Figure 21. - Effect of Plastic Deformation on Percentage Change in Room Temperature Mechanical Properties Following 10-hours Creep. Exposure at 700Fo WADC TR 59-681 52

........... ~....:...,:iZi::::i:~ ~::!:!~!~. ~....... VS % x500 Etchant: IHF, I G ly. Figure ZZ -2 CIIOM As Produced-Longitudinal Surface - Sheet Rolling Direction, WADC TR 59-681 53

C 10OM 500x / 7 " * >*~.~..; /. -/' ^ y - - ^'...::: - -— ^....;. ^ CIIOM 3500x As -Produced (Electron Micrograph) Figure 23. - Optical and Electron Micrographs of C I10M As-Produced (Transverse Sections). WADC TR 59-681 54

Figure 24 x8200 Figure 25 x8200 As Produced Creep Test: 650~F- 100 hours0. 40% def. No stress 8 44% def. Figure 28 x8200 Figure 29 x8200 Exposure Test: 700~F-100 hours- Creep Test: 700~F-100 hoursNo stress 1.81% def. Note: Deformations are total plastic deformation in indicated creep-exposure. Figures 24-29. - Electron Micrographs of C I1OM Titanium (Transverse Sections). WADC TR 59-681 55 477 7'7 4~~~~~~~~~~~~~~W..I" M 47777 7'7~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 47 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~A~~~~~~~~~~~~~~~~~~' N~~~~~~~~~~~~~~~~~~~................ 747 477 4777~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~47'7 7 7 7~~~~~~~~~~~~~~~~~~~~~~~~~~~~~77\ 47~~........

Exposure Test: 800~F-10 Creep Test: 800~F-10 hourshours-No stress 0. 330 def. - ~-tit~attE ~~~; l000 0 "-.: ^ ~"f''-'::?^:::~ A..'v;;. T;" 0:' ^ ~~_~- -..'.:,0 -0 ~'. ll.:......l....':........ -...,l..'. >'.... t:..: ~ ~.~ ~^~i i -ig'>!!i~iiiiiiiiiii ^ 0is0+i 4 E 4 i i Ai'iiieiiiii'iiiii'E'lifiNS iiiiii-^ V Figure 32 x8200 Figure 33 x8200 N.ot: Deform s ae t.ati a ta ps d i ic creep-exposure. Figures 0 - -,er MicrographsFoi gCre iai ( S e c tio n)..."'''''"*".'-E''"'''l:.E'g''"' " "'>.':. o"'E''.''* i'.'l'.'."E X " " ":'':' "'::'^'" * v'm','::: i..E.''g' i.X,.!:'.' WADC:','*S:.:'S~l TBg.: 59-681.,-.............. -:,:.-,-,:.-*,;..... S.: -:,.,:,,S:,,:,- 56.,::::::.;.;;............... ^...: *> -:.'l: l'" *<'R..: S:.:z., w >T6<SS8S~aS~yi'S.'' o'S.''.'.i:. o~k' i'.. ", i'"SN' S','y,,S, N E, S.... * *E, %,,,,,, jy S.' S S S~ S SS' s yii iS,,f,->..................,, S., ~ SS''S:o tRitSq

UNCLASSIFIED I UNCLASSIFIED The University of Michigan Research Insti- U The University of Michigan Research Institute, Ann Arbor, Michigan tute, Ann Arbor, Michigan FURTHER INVESTIGATIONS OF THE EF- I FURTHER INVESTIGATIONS OF THE EFFECT OF PRIOR CREEP ON MECHANICAL FECT OF PRIOR CREEP ON MECHANICAL I PROPiERTIES OF CLIIOM TITANIUM WITH PROPERTIES OF CIIOM TITANIUM WITH EMPHASIS ON THE BAUSCHINGER EFFECT EMPHASIS ON THE BAUSCHINGER EFFECT I by J.V.Gluck and J.W. Freeman, September by J. V. Gluck and J. W. Freeman. September 1959. 56 p. incl. illus, tables, 24 refs. 1959. 56 p. incl. illus. tables, 24 refs, I (Proj. 7360;Task 73604) WADC TR 59-681 (Proj. 7360;Task 73604) WADC TR 59-681 (Contract AF33(616)-3368). (Contract AF33(616)-3368). Studies of the effect of creep at 650 to 800"F Studies of the effect of creep at 650 to 800"F on room temperature mechanical properties on room temperature mechanical properties of CI IOM sheet showed changes character- of CIIOM sheet showed changes characteristic oI the Bauschinger effect. After creep istic of the Bauschinger effect. After creep in tension, the tensile yield strength was in tension, the tensile yield strength was increased and the compressive yield I increased and the compressive yield Unclassified Report (over) Unclassified Report (over) UNCLASSIFIED UNCLASSIFIED (over) v (o v er) - The\- - - - - - - - - - NC LAJSSIFIED~- UNCLASSIFIED i The University of Michigan Research Insti- *CASFE The University of Michigan Research Institute, Ann Arbor, Michigan j tute, Ann Arbor, Michigan FURTHER INVESTIGATIONS OF THE EF- I FURTHER INVESTIGATIONS OF THE EFFECT OF PRIOR CREEP ON MECHANICAL FECT OF PRIOR CREEP ON MECHANICAL PROPERTIES OF CI OM TITANIUM WITH PROPERTIES OF CO 1 1M TITANIUM WITH EMPHASIS ON THE BAUSCHINGER EFFECT * EMPHASIS ON THE BAUSCHINGER EFFECT by J. V. Gluck and J.W. Freeman, September by J. V. Gluck and J.W. Freeman. September I 1959. 56 p. incl. illus. tables, 24 refs, 1959. 56 p. incl. illus. tables, 24 refs. (Proj. 7360;Task 73604) WADC TR 59-681 (Proj.7360;Task 73604) WADC TR 59-681 (Contract AF33(6T 6)-3368). (Contract AF33(6 6)-3368). Studies of the effect of creep at 650 to 800"F I Studies of the effect of creep at 650 to 800"F on rooin temperature mechanical properties I on room temperature mechanical properties Iof CIIOM sheet showed changes character- of CIIOM sheet showed changes characteristic of the Bauschinger effect. After creep istic of the Bauschinger effect. After creep in tension, the tensile yield strength was in tension, the tensile yield strength was I increased and the compressive yield increased and the compressive yield I Unclassified Report (over) Unclassified Report (over) L ( O v)UNCLASSIFIED NCLA SSIFIED j___ (___ _1 _- L _ _ _ _ _I_ _ _ _ _ _ 1over ove )r

F- UNCLASSIFIED UNCLASSIFIED strength was decreased. The effect after strength was decreased. The effect after 700'F creep was almost as large as that 700 OF creep was almost as large as that reported after cold-stretching. The extent j reported after cold-stretching. The extent of the effect was governed by the creep tin-e of the effect was governed by the creep tire and the direction of creep with respect to I and the direction of creep with respect to the sheet rolling direction. Studies of var- the sheet rolling direction. Studies of variable strain paths revealed no apparent diff- * iable strain paths revealed no apparent difference between rapid strain and creep erence between rapid strain and creep strain in inducing a Bauschinger effect. As strain in inducing a Bauschinger effect. As creep time or temperature increased, re- creep time or temperature increased, recovery reduced the extent of the effect. Un- I covery reduced the extent of the effect. Unstressed exposure at 700'F removed the stressed exposure at 700'F removed the effect. The test stock also exhibited a seffect. The test stock also exhibited adr stress-activated structural instability dur- stress-activated structural instability du — ing creep that increased strength and de- ing creep that increased strength and decreased ductility. Strain hardening was a creased ductility. Strain hardening was a minor factor, j minor factor. UNCLASSIFIED I UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED strength was decreased. The effect after U strength was decreased. The effect after 700'F creep was almost as large as that 700'F creep was almost as large as that reported after cold-stretching. The extent reported after cold-stretching. The extent of the effect was governed by the creep tin-e I of the effect was governed by the creep tine and the direction of creep with respect to ( and the direction of creep with respect to the sheet rolling direction. Studies of var- j the sheet rolling direction. Studies of variable strain paths revealed no apparent diff- iable strain paths revealed no apparent difference between rapid strain and creep erence between rapid strain and creep strain in inducing a Bauschinger effect. As strain in inducing a Bauschinger effect. As creep time or temperature increased, re- creep time or temperature increased, recovery reduced the extent of the effect. Un- covery reduced the extent of the effect. Unstressed exposure at 700'F removed the stressed exposure at 700'F removed the effect. The test stock also exhibited a effect. The test stock also exhibited a i stress -activated structural instability dur- stress-activated structural instability during creep that increased strength and de- I ing creep that increased strength and decreased ductility. Strain hardening was a creased ductility. Strain hardening was a minor factor. minor factor. UNCLASSIFIED I UNCLASSIFIED

UNCLASSIFIED I UNCLASSIFIEDi The University of Michigan Research Insti- U The University of Michigan Research Institute, Ann Arbor, Michigan tute, Ann Arbor, Michigan FURTFER INVESTIGATIONS OF THE EF- FURTHER INVESTIGATIONS OF THE EFFECT OF PRIOR CREEP ON MECHANICAL FECT OF PRIOR CREEP ON MECHANICAL PROPERTIES OF CIIOM TITANIUM WITH PROPERTIES OF CIIOM TITANIUM WITH EMPHASIS ON THE BAUSCHINGER EFFECT I EMPHASIS ON THE BAUSCHINGER EFFECT by J.XV.Gluck and J.W.Freeman. September by J.V.Gluck and J.W. Freeman. September 1959. 56 p. incl. illus. tables, 24 refs. 1959. 56 p. incl. illus. tables, 24 refs. (Proj. 7360;Task 73604) WADC TR 59-681 (Proj. 7360;Task 73604) WADC TR 59-681 (Contract AF33(616)-3368). (Contract AF33(616)-3368). Studies of the effect of creep at 650 to 800"F Studies of the effect of creep at 650 to 8000F on room temperature mechanical propertie I on room temperature mechanical properties of C11CM sheet showed changes character- of C11GM sheet showed changes characteristic of the Bauschinger effect. After creep istic of the Bauschinger effect. After creep in tension, the tensile yield strength was in tension, the tensile yield strength was increased and the compressive yield I increased and the compressive yield Unclassified Report (over) I Unclassified Report (over) UNCLASSIFIED I UNCLASSIFIED (over) (over) The University of Michigan Research Insti- UNCLASSIFIED The University of Michigan Research Insti1 tute, Ann Arbor, Michigan j tute, Ann Arbor, Michigan FURTHER INVESTIGATIONS OF THE EF- I FURTHER INVESTIGATIONS OF THE EF1 FECT OF PRIOR CREEP ON MECHANICAL FECT OF PRIOR CREEP ON MECHANICAL PROPERTIES OF CIlOM TITANIUM WITH PROPERTIES OF ClIOM TITANIUM WITH I EMPHASIS ON THE BAUSCHINGER EFFECT * EMPHASIS ON THE BAUSCHINGER EFFECT by J.V.Gluck and J.W.Freeman. September byJ.V.Gluckand J.W. Freeman. September 1 1959. 56 p. incl. illus. tables, 24 refs. 1959. 56 p. incl. illus. tables, 24 refs. (Proj. 7360;Task 73604) WADC TR 59-681 (Proj. 7360;Task 73604) WADC TR 59-681 I (Contract AF33(616)-3368). (Contract AF33(616)-3368). Studies of the effect of creep at 650 to 8000F I Studies of the effect of creep at 650 to 8000F on room temperature mechanical properti on room temperature mechanical properties I of ClIOM sheet showed changes character- of C11GM sheet showed changes character*istic o the Bauschinger effect. After creep istic of the Bauschinger effect. After creep in tension, the tensile yield strength was in tension, the tensile yield strength was I increased and the compressive yield increased and the compressive yield I Unclassified Report (over) U Unclassified Report (over) UNCLASSIFIED(ov j ( ~~~~~~~~~over )\(ov~r \

K UNCLASSIFIED UNCLASSIFIED I strength was decreased. The effect after strength was decreased. The effect afterha 700'F creep was as 7 a t7 F creep was almost as large as that reported after cold-stretching. The extent reported after cold-stretching. The extentiI of the effect was governed by the creep tirme of the effect was governed by the creep time j and the direction of creep with respect to and th direction of creep with respect to the sheet rolling direction. Studies of var- ( the sheet rolling direction. Studies of variable strain paths revealed no apparent diff- iable strain paths revealed no apparent diff. erence between rapid strain and creep erence between rapid strain and creep strain in inducing a Bauschinger effect. As strain in inducing a Bauschinger effect. As creep time or temperature increased, re- { creep time or temperature increased, recovery reduced the extent of the effect. Un- I covery reduced the extent of the effect. Unstressed exposure at 700'F removed the stressed exposure at 700'F removed the effect. The test stock also exhibited a effect. The test stock also exhibited a I stress-activated structural instability dur- stress-activated structural instability during creep that increased strength and de- ing creep that increased strength and decreased ductility. Strain hardening was a creased ductility. Strain hardening was a minor factor, minor factor. UNCLASSIFIED I UNCLASSIFIED UNCLASSIFIED s UNCLASSIFIED strength was decreased. The effect after strength was decreased, The effect after 700'F creep was almost as large as that 700'F creep was almost as large as that reported after cold-stretching. The extent reported after cold-stretching. The extent of the effect was governed by the creep tirme of the effect was governed by the creep tine and the direction of creep with respect to \ and the direction of creep with respect to the sheet rolling direction. Studies of var- the sheet rolling direction. Studies of variable strain paths revealed no apparent diff- iable strain paths revealed no apparent difference between rapid strain and creep erence between rapid strain and creep strain in inducing a Bauschinger effect. As strain in inducing a Bauschinger effect. As creep time or temperature increased, re- creep time or temperature increased, recovery reduced the extent of the effect. Un- i covery reduced the extent of the effect. Unstressed exposure at 700'F removed the stressed exposure at 700'F removed the effect. The test stock also exhibited a effect. The test stock also exhibited a i stress-activated structural instability dur- stress-activated structural instability during creep that increased strength and de- ing creep that increased strength and decreased ductility. Strain hardening was a creased ductility. Strain hardening was a Iminor factor. minor factor. UNCLASSIFIED I UNCLASSIFIED L _ _ _ _ -~~

UNIVERSITY OF MICHIGAN 3 9015 03127 3272 3 9015 03127 3272