ENGINEERING RESEARCH INSTITUTE THE UNIVERSITY OF MICHIGAN ANN ARBOR, MICH. SIXTH PROGRESS REPORT TO MATERIALS LABORATORY WRIGHT AIR DEVELOPMENT CENTER ON NOTCH SENSITIVITY OF AIRCRAFT STRUCTURAL AND ENGINE ALLOYS by H. R. Voorhees J, W. Freeman Project 2475 Air Force Contract AF 33(616)-3380 Task No, 73605 January 31, 1958

SUMMARY Recent experimental work under Contract No. AF 33(616)-3380 has centered around three phases of a research into notched-bar rupture behavior of A-286 alloy at 1200'F. (1). More-complete evaluation of Heat 21 030 to define the test times and notch geometries for which notch weakening may be encountered, (2), Survey of other available lots of A.286 alloy to determine whether one of these might be more prone to notch sensitivity. (3). Evaluation of creep-rupture behavior of Heat 21,030 under variable simple tension, to provide necessary data for proposed correlation attempts to predict notched-bar rupture behavior from smooth-bar properties, Contrary to original expectationso notch weakening in reasonable test periods was found for some test conditions with material solution treated at 1800yF, but not for specimens with a 2200'F solution temperature, at least for Kt < 4.1 Survey tests with three new heats of A-286 alloy brought to light one which may permit study of A-286 with pronounced notch weakening in short time periods, The difference of this from other heats of the alloy seems to be largely a matter of the time beyond which notch weakening may be found for a given heat treatment and notch geometry, Tests in which the stress level on Heat 21, 030 specimens was lowered in discrete steps for succeeding time periods were evaluated in terms of addibility of rupture life fractions. For the 1800'F solution temperature, the computed sum of rupture life portions fell far short of 100%o, while specimens with 2200-F solution temperature gave computed total lives well in excess of 100%o Reasons for this disparate behavior with the two treatments arenot understood,

2 Priority during the rest of the contract term will be placed on obtaining a quantitative treatment of creep and rupture behavior of A-286 Heat 21, 030 under variable simple tension,

3 INTRODUCTION This research under Contract AF 33(616)-3380 seeks to extend and verify findings from earlier studies into factors which influence the rupture life of notched specimens tested at elevated temperature under steady tension, Specifically, attempts were to be made to find a material which could be made to produce both notch weakening and notch strengthening with different heat treatments and/or test conditions. Efforts were to be directored toward quantitative explanation of the results, following methods developed in earlier studies to correlate notched-bar behavior in terms of stress redistribution under the influence of different creep rates from point to point in the specimen, Sufficient tests were to be conducted on one particular lot of alloy to clarify possible effects of such variables as smooth-bar ductility and strain damage from localized plastic strains during load application. A-286 alloy was selected for the experimental material with the expectation that the notch-rupture response would alter appreciably when different solution temperatures were used in its heat treatment. Previous progress reports (Refs, 1 and 2) include experimental results at 1200'F from the A-286, Heat 21,030, donated for this study by the Allegheny-Ludlum Steel Corporation. Preliminary survey tests covered solution temperatures from as low as 1650F to as high as 2300'F. More intensive investigation has been made for solution temperatures of 1800' and 2200'F, which give roughly comparable smoothspecimen rupture lives but widely-different rupture ductilities. The higher solution temperature resulted in a coarse grain size but was selected to give elongation at fracture of 1%o or less in unnotched specimens,

4 tEarly results for notched bars with theoretical stress concentration factors ranging from Kt 1., 27 to Kt - 10 showed notch strengthening at 55,000 to 70,000 psi nominal stress for all but the sharpest notches, How ever, extrapolation of the trends found with specimens given the 1800'F solution temperature suggested that possible notch weakening might result for long-time tests at lower test stresses, A major portion of the subsequent testing time has been devoted to investigation of this lower-stress region, Simultaneous tests were made to evaluate smooth-bar creep-rupture properties of this lot of alloy when the load is increased or decreased during the test, to obtain basic properties for use in calculation of expected life for notched specimens, When the probability still appeared to be remote for finding decided notch weakening in A 286 Heat 21,030 at reasonable test times, material was sought from other lots of the alloy which might be more prone to notch weakening, Experimental results were obtained with specimens representing several commercial and research heats of A2 8 6 alloy, Available data and current status of tests in progress for these several phases of the experimentation are the principal content of this report, EXPERIMENTAL RESULTS Original plans under the current contract called for extensive tests with A-286, Heat 21,030, to establish and analyze conditions for notch strengthening and notch weakening, When initial tests all showed notch strengthening for stress levels and specimen, geometries permitting reasonable estimate of initial stress patterns the study was broadened to include material from other lots of the alloy

5 for which limited tests by others suggested that these lots might be more prone to notch sensitivity than was Heat 21, 030, R upture Properties at 1200'F for Notched and Smooth Specimens of A-286 Available chemical analyses and processing conditions for the lots of A-286 investigated are summarized in Table 1, The rupture data obtained are listed in Tables 2 through 5 and plotted on Figures 1 through 5, All test results are given for the new lots of material added to the program, but in the case of the original Heat 21,030 only the data for 1800* and 2200IF solution temperatures have been repeated in this report. Heat 21,030 Specimen blanks were sampled from the 3/4-inch round stock supplied from a commercial heat prepared-by the vacuum consumable-electrode process. Prior to machining, the blanks were solution treated for one hour and oil quenched; aging was at 1325'F for 16 hours with an air cool, Gauge section of unnotched specimens were hand polished after turning. Notches were finished by form lapping after preliminary rough turning and grinding operations. Details of the notching operation have been published in WADC reports (see Reference 3), Data available at the time the last prior progress report was issued suggested weakening from dull or moderate-acuity notches would occur for this heat of alloy only at times in excess of about 1000 hours. The more-complete results of Table 2 demonstrate transition to notch weakening at 300-400 hours for theoretical stress concentration factors of Kt = 5, 7 and 4, 1 with specimens solution treated at 1800'F If the curves of Figure 1 correctly represent the data for the material with 1800 F solution temperature, the dullest notch studied (Kt = 1, 27) should also show notch embrittlement at a nominal stress of 30,000 psi or below,

6 Test results for material solution treated at 2200-F exhibited considerable scatter, particularly in the case of specimens with the dullest notch (Kt = 1, 27), However, no evidence at all was obtained which would suggest transition to notch weakening in reasonable test periods for specimens with theoretical stress concentrations between Kt = 1 27 and 3,0, This is true despite smooth-bar elongation of 1% or less for stresses of 60,000 psi and below, Use of specimens with any sharper notch than Kt = 4. 1 has not been considered for the alloy in the coarse-grained condition left by the high solution temperature, Figure 1 indicates a difference in the notch geometry giving maximum strengthening in samples with the two different solution temperatures, To make the difference more evident, the stress for rupture in 200, 500 and 1000 hours for each specimen geometry was taken from the approximate average curves of Figure 1 and replotted as a function of the theoretical stress concentration factor (see Figure 6), For the 1800'F solution temperature, rupture strength rises with notch acuity at least to Kt of 1, 8 and probably to about Kt = 2 2, The peak strength for the 2200'F solution temperature appears to occur for Kt below 1, 5, The curves of Figure 6 are tentative and approximate, but for each heats treatment condition a minimum seems to be present in the 1000-hour curve for a theoretical stress concentration about 1, 5-2, 0 times that giving maximum strength, If this indication is confirmed by the tests now in progress, an excellent test of any calculation method is whether it will predict such a minimum, The indicated inflections of Figure 6 stem in large measure from the data for Kt = 4. 1, in particular the sharp downward break of the stress -rupture life plot for this theoretical stress concentration in specimens solution treated at 1800'F When the test in progress at 35, 000 psi stress is completed the curve for the 1800'F treatment at Kt = 4. 1 should be well established, but at least one more test (say at 52, 500 psi) seems desirable for the 2200'F solution temperature

7 in order that the indicated shallow slope for Kt = 4, 1 may be confirmed, or else the presence of a "break" in the curve established, Theoretical considerations by others of notched-bar tension tests have indicated a maximum possible strengthening of 1.4 to 1, 5 based on nominal stress, Present results suggest a strength ratio of 1, 6 is attainable with the 2200'F solution temperature, Further testing to confirm the curve of Figure 6 would have limited service application but should be of considerable interest from the standpoint of fundamentals, Figure 6 suggests future studies for two additional stress concentration factors. Results for Kt 2,4 would better define the peak strengthening with the 1800'F solution temperature. Determination of the stress concentration factor to give maximum strength for the 2200'F solution temperature would be aided by tests at Kt = 1 4, These suggested tests could not be completed during the current contract period, but are appropriate and desirable extensions of the research on A 286 Heat 21,030, Heat 43,297 Only a small amount of 7/8-inch diameter bar stock was available from this air-melted heat, one of several used by the Allegheny-Ludlum Steel Corporation in a research study of the alloy, Limited test results plotted in Figure 2 show a transition from pronounced notch strengthening, to mild notch strengthening and then to notch weakening with Kt = 3, 0 as the solution temperature is increased from 1650' to 1800~ to 1985F, The probable greater tendency toward notch sensitivity of Heat 43,297 compared to Heat 2 1,030 may be associated with its corresponding greater susceptibility to weakening from strain damage evidenced by the few prestrain tests conducted

8 on these materials. (See Tables 2 and 3), At the start of these prestrain tests a momentary overload was applied to produce the desired amount of plastic yielding, the excess weight was immediately removed and the creep measurements started, Extensometer readings taken during the load application and during its reduction permitted calculation of the plastic strain at the start of the test and of the correct nominal stress present when creep determinations were begun, assuming the plastic strain was uniform along the gauge section of the specimens, Material remaining from this lot of alloy would conveniently serve to make only from 8 to 12 test specimens, wherefore extensive studies are not possible, The stock on hand has been placed in reserve for possible future use in checks of correlations obtained with other heats of A-286, Heat 52,853 Originally this lot of alloy was one of four materials in a research into effects of processing variables on fracture of notched disks at elevated temperatures, That research by the General Electric Company under Contract No, AF 33(616)-2778 included tests at 1100-F with notched and unnotched specimens of A-286 in two conditions of heat treatment. At the 1100'F test temperature, borderline notch properties were obtained after the following treatment: 2150'F, 2 hr, O, Q, + 1650'F, 2 hr, O. Q. + 1300'F, 16 hr + 1200*F, 16 hrs, Specimen blanks were cut from disks forged from 2000'F, Portions of the 4-1/2-inch diameter billet transferred from General Electric were re-rolled to 1/2-inch square bars at The University of Michigan prior to sampling and heat treating. Three different rolling temperatures (2100', 1950' and 1800-F) were surveyed for specimens solution treated at 1800F, Limited data indicated mild notch weakening at 20-60 hours for a Kt = 4, 1 with specimens rolled from 1950-F (See Figure 3), Material rolled at the more conventional temperature of 2100'F produced test results quite comparable to those found

9 with Heat 21,030, Solution temperatures of 1800~, 2000' and 2200'F all failed to produce notch weakening at 1200-F in fragmentary studies on Heat 52,853 material rolled from 2100F,. From these preliminary tests, no evidence has been found favoring Heat 52, 853 in the search for conditions of notch sensitivity in A-286, Heat K-65-X: In the course of an investigation relating melting variables to properties of certain alloys, research personnel at Firth Sterling, Inc. procured an experimental heat of A-286 produced by the vacuum consumable-electrode method, This material, designated by them as "K-65-X", gave indications of notch embrittlement at 1200F and 65, 000 psi stress for bars samples from an 8, 5-inch square billet and then solution treated at 1800'F, oil quenched, aged at 1300'F for 16 hours and air cooled to room temperature, Knowing of the attempts to locate notch-sensitive A-286 for the present program, Firth Sterling representatives arranged to supply enough of the experimental billet to permit comparison against Heat 2 1, 030, Property scatter in notched specimens sampled directly from the billet was very wide. Re-rolling from 2100F before sampling appeared to eliminate this scatter (See Figure 5), For both conditions, specimens with the 1800'F solution treatment and subsequet 1325tF aging for 16 hours developed mild-tomoderate notch weakening in test times of a few hundred hours, Corresponding specimens from other heats studied to date in this program produced notch strengthening, Heat K-65-X thus seems to offer the best opportunity found so far to study a lot of A-286 with pronounced notch weakening in reasonable test periods,

10 Comparison of notch behavior for the several lots of A-286 alloy: Results from this and other research programs at the University of Michigan point out the important changes in creep-rupture properties that can be brought about by small variations in trace-element content and by different working conditions prior to the final heat treatment. Accurate delineation of the influence from one of these variables demands the others be held fixed, but this desirable aim is difficult to fulfill, Quantities of boron, oxygen and nitrogen known to have measurable effect on rupture life of heat-resistant alloys are near the limits of present quantitative analysis for these elements. What other trace elements might produce helpful or harmful effects of like magnitude and how these different elements interact in effect remains largely unknown, Similarly, the ways in which prior processing conditions carry through to influence later mechanical properties are little understood. Even for the same nominal rolling conditions, the actual local history of temperature and strain for different portions of the final rolled stock is subject to wide uncontrollable variation, Despite these complications, the four heats of A-286 studied can profitably be compared for the common conditions of rolling from 2050'-2100'F and subsequent 1800'F solution temperature. At rupture times of the order of 100 hours, Heats 21,030, 43,297 and 52,853 all exhibited notched-specimen rupture strengths 10-200 above the smooth-bar values for Kt's of 2 to 4, Heat K-65-X, on the other hand, showed mild notch weakening under roughly comparable conditions. The most plausible explanation lies in the boron contents for the four lots of material. The single analysis available for boron in Heat K-65-X was below the average boron content indicated by the pairs of analyses obtained for the other three heats. Unfortunately, the analysis for boron in the low

11 amounts present is difficult and agreement between laboratories was unsatisfactory for a successful correlation attempt. Re-evaluation of these four heats would be desirable on the basis of boron contents all determined by the same laboratory with the same set of standards, Although the amount of boron or other trace elements in the alloy seems to affect notch sensitivity, the effect is probably not one of either permitting or eliminating notch sensitivity, but rather one of shifting the test time at which notch weakening begins for a given notch geometry, For short test times, the bulk of the test data suggest notched-bar rupture plots have the same slope as do those for unnotched specimens, The rupture-test results for Heat 21,030 with the 1800'F solution temperature produced three good examples of a definite and abrupt change in slope for notched-specimen curves at times beyond 150-250 hours, More extensive testing would probably verify this finding for other notch geometries, treatment conditions or lots of the alloy, Creep-Rupture of A-286 Heat 21, 030 Under Variable-Stress Loading The analysis developed to compute rupture life of notched specimens from smooth-specimen data requires knowledge of creep and rupture behavior when the stress level on a metal fiber increases or decreases during the test (See Ref, 3). The research under the current contract included a number of tests devised to obtain the required data for A-286 Heat 21,030 at a test temperature of 1200'F, These particular tests differed from usual constant-load tests only in that the applied stress was changed from one discrete level to another one or more times during the test, Experimental conditions and test results are summarized in Table 6 for both the 1800' and 2200'F solution temperatures, The table lists first the plastic deformation on loading as percent plastic strain, Continuing across the page,

for each period of constant stress is listed the stress level, the length of time the stress acted, the ratio of this time to the rupture life in a conventional rupture tests at the stress and the increment of creep (inches/inch) which occurred during the period. Finally the ductilities (percent elongation and percent reduction of area) at fracture are listed, together with the sum of the rupture-life portions for all creep periods, In the first experiments performed for each solution temperature, the test started and ended at the same nominal stress, with the stress level either raised or lowered during a mid-portion of the test, Stresses used were all below the yield range and the change in stress was moderate. Under these conditions the sum of the rupture-life portions was substantially equal to 100%, in agreement with past results for other alloys tested under conditions of good metallurgical stability. The bulk of the results reported in Table 6 iivolve step-down tests in which the starting stress produced measurable initial plastic strain, and in which the stress level was lowered for each succeeding portion of the test period. For all specimens with 0, 17% or greater plastic strain on loading, the computed sum of rupture-life portions for the material treated at 1800'F fell far short of 100%o, while specimens with 2200'F solution temperature gave calculated total lives well in excess of 100%, Reasons for the apparent disparate behavior under variable stress for the two heat treatments are not understood, The observed results must be clarified because a major objective for the remainder of the contract period will be quantitative evaluation of notched-bar rupture behavior, This evaluation requires firm knowledge of how to compute rupture life under varying stress,

13 FUTURE WORK During the balance of the current contract term priority will be placed on obtaining a quantitative method for treating creep and rupture behavior under variable stress at 1200IF for A-286 Heat 21,030, Once this information is satisfactorily in hand, calculations may proceed to determine how well rupture lives of notched specimens of this material can be predicted by the analysis developed in past research, Any future continuation of the program should include metallographic and allied studies to seek the reasons for the observed behavior under variable simple tension, A logical extension would include determination of the general creep rupture performance under variable multi-axial stresses, The influences of trace elements, particularly boron content, has not been adequately covered in the research to date, Extensive testing with A-286 Heat K-65-X and with experimental melts to be prepared at the University with minimum boron content should be most valuable if adequate precision in the boron determinations can be obtained, Results from Heat 52, 853 listed in this report suggest the greatest tendency toward notch weakening will probably be found for material rolled from 1800'-2000'F and subsequently given an 1800'F solution before aging at 1325 Fo

14 BIBLIOGRAPHY 1. H. R. Voorhees and JO W. Freeman, Fourth Progress Report to Materials Laboratory, Wright Air Development Center on'TNotch Sensitivity of Structural Alloys," (Contract AF 33(616)-3380), June 30, 1957. 2. H, R, Voorhees and J, W. Freeman, Fifth Progress Report to Materials Laboratory, Wright Air Development Center on "Notch Sensitivity of Structural Alloys," (Contract AF 33(616)-3380), September 30, 1957. 3. Howard R. Voorhees and James W. Freeman, "Notch Sensitivity of HeatResistant Alloys at Elevated Temperatures," WADC Technical Report TR 54-175, Part 3. (ASTIA Document No. AD 97253), September 1956, 4, Richard Sakamoto, "Effects of Processing Variables on Fractured and DiskBursting Characteristics of Four High Temperature Materials," WADC TR 57-154, May 1957,

TABLE 1 CHEMICAL ANALYSES AND PROCESSING CONDITIONS FOR THE VARIOUS LOTS OF A-286 ALLOY INVEST] [GATED Heat No, Type of Melt 21,030 Vacuum consum= able electrode 43297 Two -ton air 52853 Not Stated K-65X Vacuum cons umable electrode — ' - - ' ---- I C 0.06 Mn 1, 35 Chemical Compositions, percent by weight Si Cr Ni Mo Ti V Al S 0.47 14.58 25,30 1,38 2,00 0.21 0. 17 0,014 "g — -" -- P 0.018 Fe Bal 0.025 1.21 0,86 15. 12 26. 16 1.32 1.94 0,23 0.40 0.017 0.016 Bal B *(0, 004 ) (0. 0019) *(0. 002 ) (0. 0008) *(0, 0016) (<0, 001) 0. 0007 *(0. 06 (0. 064 0. 053 Other: 1.,21 1. 37 1.32 W 0. 13 0,66 0.62 0.54 Co 0. 11 15. 12 26. 06 1. 3 15,55 26,50 1.2 14,75 26.60 1 3 Cu Pb 0, 06 0.0009 38:7 38 2. 12 2, 12 0 2.00 0. 08 0,16 0,20 0.012 0. 10 0. 10 0. 010 0.25 0.146 0.012 H N 0, 0008 0. 04 0. 022 0. 023 0. 025 Bal) Bal) Bal Heat No. Processing Procedure Prior to Receipt at the University of Michigan 21,030 20" round ingot pressed and cogged to 4-1/4" square from 2150'F, Recogged to 2-7/8" square frc Rolled to 3/4" diameter from 2100'F, Bars neither straightened nor annealed before shipping, 43297 Hot rolled from 2050F; As-rolled hardness BHN 163-179, (Finishing temperature approximately Supplied as 7/8" diameter rounds, 52853 5-1/2" round-corner square billets ground all over; soaked at 2025-2050'F; rolled as a hand round 4-3/4" diameter billet with finishing temperature approximately 1850-F, air cooled. Rough turnec 4-1/2" diameter, K-65X 19" diameter ingot reduced to 8. 5" square from 2075-2100'F * Check analyses by different Laboratories, )m 2100'F; 1650 F). d to

TABLE 2 RUPTURE-TEST RESULTS AT 1200F FOR A-286 HEAT 21,030 Heat Treatment: 1 hr Solution, Oil Quench + 16 hr Age at 1325'F, Air Cool UNNOTCHED SPECIMENS................. Stress (psi) Rupture Life (hours) 1800~F Solution Temperature, ' 1 I I I I 1 i. '.. ' J: I l Elongation at Rupture (%) Reduction of Area (%) 112, 000 100, 000 909000 80, 000 a)70, 560 70, 000 70,000 65,000 b)60,540 60,000 60,000 50,000 459 000 45,000 40,000 (Short-time tensile strength) 0,26 1.45 4 25 17. 9 14. 9 20 3 62.4 59. 8 79 9 99. 1 384, 6 615 5 771, 3 In progress 1140 hours 18, 170 8. 8. 8. 9. 5 6. 5 5. 5 6. 5 5. 7. 6. 4. 3. _m 19. 18. 9. 8. 5 9. 5 13.5 8. 5 10, 5 11, 10, 8. 5 8, 8. 4. 5 2200'F Solution Temperature 101, 500 80, 000 75 000 70,000 c)60,790 d)60, 240 60, 000 55,000 50, 000 (Short-time tensile strength) 0.87 3. 8 7. 2 99. 8 307, 0 308, 7 587. 9 2068. 3 10, 5 4. 2, 5 1, 5 2. 5 1, 5 1. 1. <0.5 12, 5 7. 5. 5 7, 4. 5 4. 2. 5 2, 1, a) 0.80% b) 0 90% c) 1.31%o d) 0 90% plastic prestrain from momentary initial overload to plastic prestrain from momentary initial overload to plastic prestrain from momentary initial overload to plastic prestrain from momentary initial overload to >1009 000 psi. 108,240 psi. 84, 070 psi. 81,000 psi.

TABLE 2 (con'd ) NOTCHED SPECIMENS 1800'F Solution Temperature Stress Rupture Life (psi) (hours) 2200'F Solution Temperature Stress. R upture Life (psi) (hours) Kt = 1.27 70,000 70,000 65,000 60,000 50, 000 47,500 22. 6 97, 2 241, 6 319, 3 840. 0 1043. 6 80,000 75,000 70,000 70,000 65,000 60,000 60,000 55,000 127 4 264. 5 451.3 996. 0 416.4 417.5 1242, 5 783. 5 Kt = 1, 54 80,000 70,000 70,000 65,000 60,000 215. 3 292, 3 481.3 225.0 657. 5 568. 7 (In Progress 2475 hr) (In Progress 2310 hr) 60,000 55,000 55,000 80, 000 70,000 65,000 60,000 55,000 109 5 239, 6 366 2 543 4 994 3 Kt = 1, 82 Kt = 3. 0 70,000 65,000 60,000 55,000 206 3 257. 7 1151, 1 727 4 70,000 45,000 167.5 (In Progress 290 hr) 65,000 60,000 50,000 219. 3 414 2 (In Progress 1900 hr) Kt = 4. 1 80,000 70,000 65,000 60,000 50,000 45,000 40,000 35,000 20. 9 112, 8 168. 1 227. 6 363. 0 490. 3 508 8 (In Progress 315 hr) 70,000 65, 000 60,000 14. 2 43. 5 288 8

TABLE 2 (con'd.) NOTCHED SPECIMENS 1800~F Solution Temperature Stress Rupture Life (psi) (hours) 2200 F Solution Temperature Stress Rupture Life (psi) (hours) Kt = 5. 7 - 6. 0 70,000 65,000 *65,000 60,000 55, 000 45,000 40,000 27, 3 106.7 43.4 119 7 257. 1 464, 8 (In Progress 985 hr) 6. 5 6.65 11.1 451.9 Kt = 8. 7 - 10, 0 *70,000 *65,000 *60,000 40,000 * Aging step performed after notching operation.

TABLE 3 R ESULTS OF SURVEY TESTS AT 1200sF ON A-286 HEAT 43,297 Heat Treatment: 1 hr Solution, Oil Quench + 16 hr Age at 1325 F, Air Cool Solution Temp ('F) Stress (psi) Rupture Life (hrs), Elongation at Rupture (%/2 in. ) Reduction of Area (%) R emarks SMOOTH BARS,,.v~... 1650 1650 1650 1650 1800 1800 1800 1985 1985 1985 65,000 60,000 55,000 55,000 65,000 55,000 59,850 65,000 55,000 55,020 24. 9 41 9 75, 4 30. 1 29, 2 121.4 34. 4 73. 5 385. 5 176. 2 10 5 8. 5 9. 10 5 4, 9. 4. 14, 5 12. 5 13, 19. 6, 5 11 5 7. 5 5. 5 5. 5 4. 5 1, 0% plastic prestrain by momentary initial overload to 108,060 psi 0, 76% plastic prestrain by momentary initial overload to 104,520 psi 1. 13% plastic prestrain by momentary initial overload to 98, 000 psi 3. 4. 1. 5 a)NOTCHED BARS ~. i,. 1650 1650 1650 1800 1800 1800 70,000 65,000 60,000 65,000 60,000 55,000 86, 5 126. 8 109 2 60, 4 124. 9 284, 1 4, 0 270. 8 1985 65,000 1985 55,000 a)Nominal Geometry: Diameter of Shank, D = 0 460 inch Min. drain, at base of notch, d = 0, 325 inch Notch root radius, r = 0. 017 inch Theoretical stress conc., Kt = 3. 0

TABLE 4 RESULTS OF SURVEY TESTS AT 1200-F ON A-286 HEAT 52853 Heat Treatment: 1 hr Solution, Oil Quench + 16 hr Age at 1325'F, Air Cool (Rolled to 1/2-inch squares at the University of Michigan prior to heat treatment) Rolling Temp, (*F) 1800 1950 1950 1950 2100 2100 2100 2100 2100 2100 2100 2100 2100 Stress (psi) 65,000 65,000 60,000 55,000 70,000 60,000 50,000 70,000 65,000 60, 000 70,000 60,000 55 000 UNNOTCHED SPECIMENS Rupture Life Elongation at (hours) Rupture (%) 1800'F Solution Temperature 15,5 8, 16.4 6, 60,5 5, 125.2 5 5 8,.7 7. 5 27,4 7. 145.0 8. 2000 F Solution Temperature 11.7 3, 114 5 5. 281,1 3.5 2200 F Solution Temperature 24.2 2. 120,4 2. 501.4 1 5 Reduction of Area. (%) 11, 7. 11, 8, 5 10. 11. 9. 5 6. 6. 5 7. 3. 3. 5 2.

TABLE 4 (con'd.) NOTCHED SPECIMENS R oling Temp. ('F) Stiess (psi) Rupture Life (hours) Rolling Stress Temp. ('F) (psi) Rupture Life (hours) 1800'F Solution Temperature I I I l IlIlI l lI1 I I! I _ I E [ I Kt = 1, 27 Kt = 4. 1 1800 1800 1950 1950 2100 2100 65,000 60,000 70, 000 65,000 70,000 60,000 81, 1 220. 7 55. 5 140. 5 41 8 115. 5 1800 1800 1950 1950 1950 2100 2100 65, 000 60,000 65,000 60,000 55,000 70,000 60, 00 21 8 88, 9 17. 4 45.6 63. 8 16.0 58, 2 2000 F Solution Temperature,:~~~~~~~ ~~~~ mpIJ S i ~ J - '~ _...... Kt = 3 1 2100 2100 2100 75,000 70,000 65,000 381. 1 531 6 793.4 2200 F Solution Temperature.,j. Ml I _,l,, l I f l I I I l l 2100 2100 2100 Kt = 1. 72 75,000 70,000 65,000 73. 1 171.0 389. 6

TABLE 5 RESULTS OF SURVEY TESTS AT 1200I F ON A-286 HEAT K65X Heat Treatment: 1800F, 1 hr, Oil Quench + 1325'F, 16 hr, Air Cool UNNOTCHED SPECIMENS Stress (psi) Rupture Life (hours).. I.......... Elongation at Rupture (%)............ Reduction of Area (%) Specimens Sampled Lengthwise from the Billet Supplied 70,000 60,000 55,000 49. 1 192. 6 300. 4 2, 2, 1o 3, 5 2. 5 1. 5 Material Rerolled from 2100'F Before Sampling 65,000 55,000 50,000 35. 6 116. 8 209. 6 3. 5 4. 5 4. 7. 5.5 5. NOTCHED SPECIMENS Stress (psi) Rupture Life (hours) Stress (psi) Rupture Life (hours) Kt = 1 72 Kt = 4 1 Specimens Sampled Lengthwise from the Billet Supplied 65,000 55,000 137.0 232, 3 70,000 65,000 60,000 55,000 55,000 50,000 41 8 109. 6 90. 8 35. 3 44. 9 128 4 Material Rerolled from 2100'F Before Sampling 65,000 55,000 50,000 36. 1 87. 8 146, 1

TABLE 6 MULTIPLE-STRESS CREEP-RUPTURE TESTS AT 1200'F FOR A-286 HEAT 21,030 Initial Plastic Strain (%) 0 0 0 0. 135 0. 18 0. 11 0.40 0. 505 0.295 1st Creep Period Portion of Creep Rupture IncreStress Duration Life ment (psi) (hr) (%) (in/in) 2nd Creep Period 3rd Creep Period Portion of Creep Rupture IncreStress Duration Life ment (psi) (hr) (%) (in/in) Portion of Creep Rupture IncreStress Duration Life ment (p3i) (hr) (%) (in/in) Portion of Creep Rupture IncreStress Duration Life ment (psi) (hr) (%) (in/in) Sum of Total Plastic Rupture Strain at Life Fracture Portions % Elong, % Red. of Area (%) 4th Creep Period Specimens with 1800~F Solution Temperature ' O fl' 50,000 65,000 50,000 90,000 90,000 90,000 100,000 100,000 100,000 105. 0 12. 0 40. 0 0. 1 0. 1 0. 1 0. 0167 0.0167 0. 004 31. 5 26. 1 12.0 9.8 9.8 9.8 5.4 5. 8 1.2 0. 00315 0. 002 19 0. 00070 0.00932 0.01105 0. 00622 0. 00718 0. 00952 0. 00287 65, 000 12. 0 50,000 105.0 55,000 27.0 80, 110 0.55 80, 140 0.9 60,110 42.8 60,240 38. 5 90,500 0. 1 90,270 0.021 26. 1 0. 00792 31.4 0.00104 15.8 0.00135 12.8 0.0233 21.0 0.0-15 49.3 (0. 063) 44.2 (0,_ 11.0 0.0119 2.1 0.00091 50,000 i6. 5 43.4 65,000 2:. 9 5. 2 60,000 56.5 62.8 70,090 3.25 16. 1 70, 125 2.4 11.9 2. 4 Il9 (0. 01) 0.0506 >0. 03 60,080 0. I 0. 1 5. 7. 6. 9.5 10. [, -5 /o It. /If * fl' 9. 9. 8. 11. 31. 5 10. 5 12. 5 11. 5 101.0 111.7 90.6 38. 7 42. 7 59. 1 49.6 52.9 0 t.I 80, 400 0.983 23.9 80, 20 0.1 2.i 5th Creep Period 0.0362 0.00116 70,400 2.35 12.2 ~"/ 70,210 0.375 1.9 0.001051 6th Creep Period 0 50,000 258.1 0 none 77.4 0. 00602 60,180 2.5 2.9 00013 50,150 187.6 Short Time Tensile Test at 1200~F: 112,500 psi T.S.; 99,000 psi 0. 2% Y.S.; 12% El.; 14% R.A. Short Time Tensile Test at 1200'F: 112,000 psi TS.; 18% El.; 19% R.A. 62.6 (0.071) 1 8.5 73. 1 Specimens with 2200~F Solution Temperature 0.025 0 0 0 0.04 0.41 1.62 0.73 65,000 15. 0 55,000 210.0 50,000 50. 0 65,000 52. 7 70,000 0. 5 70,000 1. 0 80,000 0.004 0. 1 0.000488 258 -- 2.6 0.00005 33.4 0,00202 2.0 0.00185 4.0 0.00916 0.5 -- 55,000 210.0 65,000 15. 0 55,000 52.0 60,000 159. 1 65,000 5.0 60,250 24. 0 73,200 0.096 25. 8 10. 1 6.3 42.7 3.2 6.7 1.2 0.000423 65,000 73.9 0.00061 55,000 612.3 0.00015 60,000 236.6 (0. 005) 0. 0001 60,000 351.1 0. 00046 50,200 2232.6 0.000179 69,100 1. 1 46.9 (0.0042) 75.4 (0.002) 63.4 (0. 01) 2. 0.5 1, 1, 1, 3. 3, 82.8 2,5 111.3 5. 72 3 3.5 76 1 3. 99.4 2, 131,8 94.2 121. 1 3.2 > 0.006 0.000253 65,000 14.0 8.9 0.000663 5th Creep Period 76,000 0. 02 0.6 61,000 353.8 110.0 0.00178 72,600 0.05 0.5 0.00152 68,500 3.45 8.1 0.00047 64,500 26.0 13.6 0.00050 5th Creep Perioa 60,400 521.7 148.5 >0,0084 0. 000956 Short Time Tensile Test at 1200*F: 98,200 psi T.S.; 85, 500 psi 0. 2% Y. S.; 6. 5% El.; 8% R.A. Short Time Tensile Test at 1200IF: 101,500 psi T.S.; 10. 5% El.; 12.5% R.A. 4. 5.5 123.8 3. 4.5 171.3 0 0 60,000 246.8 none 66. 1

eU 0 ~A s0 0 0 0 a, 0 1.2 Kt 1.54 2200~F Solution Temperature 80 c I I.- - 70 '~L — ' <U 60 - —,-.,~ ' -g.- Tests in 4 Progress 50 OJ I 10 Rupture Life, hours 100 1,000 a CL o 0 0 0 UA m 10,000 IF 10,000 Rupture Life, hours Fig. 1 - Rupture Properties at 1200 ~F for Smooth and Notched Specimens of A-286 Heat 21,030.

a, 0 0 0 0 am <%5 O70 - 70 1. 0% Plastic Prestrain 50 16500F Solution Temperature 4n i I I I I ii I 10 100 1000 Rupture Life, hours._ 0 o o 0 80 70 60 0.76% 1 ' Plastic Prestrain 1 0 50 18000F Solution Temperature 40 L I I I II I I II I I I II 10 100 1000 Rupture Life, hours 0. 0 0 0 S el 80 70- 60 Smooth Specimens 0 Normal Test 1.13% 50_ Noma TestI I I I ___Plastic Prestrain 50 - f Prestrain Test Notched Specimens 1985~F Solution Temperature N- 30 I l I 1 1 1l A t,, A I II I I I.IV I 10 100 1000 Rupture Life, hours Fig. 2 - Rupture-Test Results at 1200 ~F for A-286 Heat 43,297.

V. 7 0. 0 0 o 6 I~ 5 4 4 O. 0. 0 1 0 ( o E 0ti u, LA Rupture Life, hours 500 Rupture Life, hours V, O. 0 0 0 U' Vo U,) 0 A 8O 70 Kt= -.1 Unnotched -' - - — _ —. 60 --- —- Kt = 1.,27 50 — 18000F Solution Temperature (Rolled from 1800~F) 40 JI I I 5 10 100 500 Rupture Life, hours Fig. 3 - Results of Survey Tests on A-286 Heat 52,853 for 18000F Solution Temperature.

Q. 0 0 0 o u, U, 0 ho 0 0. 0,_ 4, 0 80 70 0 70 0_____________._______ ___ _ - _ - _ 0~ 4 - Unnotched = 3 ' 50 2000~F Solution Temperature (Rolled from 2100~F) 40-! I I I - 100 Rupture Life, hours 1000 2000 10 100 1000 2000 Rupture Life, hours Fig. 4 - Results of Survey Tests on A-286 Heat 52,853 for 20000and 22000F Solution Temperatures.

aQ 0 Co 0 0 0 a. I) Q. Cn )0 0 0 tfi C-. 1000 Rupture Life, hours 80 ---70 60 __ - -- -------- ---- 5 050~ ~~0 1800~F Solution Temperature Unnotched Kt = 4. 1 (Re-rolled from 21000F Before Sampling) 4An0i I I I I I 1 10 100 1000 Rupture Life, hours Fig. 5 - Results of Survey Tests on A-286 Heat K-65-X.

0 / o- / ' _________A200 hr>y _ 6O ^ 60|// z00 hr --- " 1 ---? --- —-..500 hr ~,S I/^. ---" \ 1_1000 hr A t~ \ /, rRI upture Strength I, - - ' O 50 1 I_ T o Ical, Stres Co-nc-entrtio F00r Kt 100012 401 2 3 4 5 6 7 8 9 Theoretical Stress Concentration Factor, K, Fig. 6 - Effect of Notch Acuity on Rupture Strength at 12000F for A-286 Heat 21,030.