INCLUS ION DF'O RI'MIT TION:i I. THE MECHANISM OF FRACTUITRE AND DEFORMATION IN MnS by H. C. Chao, L. Thomassen, and L. H. Van Vlack"l' ABSTRACT: Manganese sulfide was purified and crystallized froni a melt) obtaining the stable (NaCl-tyeo) strructuxre, Single crrystals were used to determine the glide and fracture systerms. The primary glide system is L111] ((110)). Secondary slip occurs on the ((111)) planes. There was no evidence of ((10')) deformation. Although ((100)) cleavage is predominant, ((110)) cleavage is observed and becomes; the irinlary fracture plane when the MnS is loaded by s u;rface. i'i'd-n-tatio0n.' The ((110) ) fracture originates through; (a); the interaction of dislocation movements on the ((110)) 45 lanes, and (b) tthe interaction of ((111)) slip planes at the ('10) surface, H. C. Chao is a graduate student, and L. Thomassen and L. H. Van Vlack are professors, Department of Chemical and Metallurgical Engineering, The University of Michigan, Ann Arbor, Michigan.

m a. v. I

INTRODUCT ION Whenever sulfide inclusions are present within steels, it is desirable to have the sulfur present as alabandite, or MnS. Manganous sulfide has a higher melting temperature than FeS (1620~C vs 12000C) and therefore does not contribute to hot-shortness of the steel during shaping operations. Also, in free-machining steels where sulfur is intentionally added to steel, the sulfide must have the alabandite structure to be effective. A steel normally has its strength, ductility, and impact resistance lowered when it contains sulfide inclusions. Therefore, a solid sulfide phase is usually considered to be a brittle, non-ductile material. In reality, manganese sulfide can be deformed prior to fracture. This deformation is most obvious in hot-rolled steel where the inclusions have developed an elongated shape (Fig. 1). Also, it has been suggested (but never fully proven) that the improved machinability of resulfurized steel does not depend entirely upon the weakening of the steel by the inclusions for easier chip formation, but also upon a lubricating action of the sulfide phase at the tool surface 2) Direct evidence of the plastic deformation of MnS has been observed recently at room temperatures in two cases. The first was in massive MnS,(3) and the second was within sulfide inclusions in steel(4),2

This paper presents the results of an investigation to determine the dependence of fracture and deformation in MnS upon crystollographic factors. PREVIOUS WORK Structure and Composition. The stable form of MnS has the NaCl-structure. In addition, KrBgeJ5)found that MnS will crystallize with both the ZnO and ZnS-structures from selected aqueous solutions, and Rooksby and Tomb46) report a rhombehedral structure at liquid air temperatures, This present investigation is limited to the NaCl-type structure. The stoichiometry of MnS has not received detailed attention. However, the commonly reported one-to-one ratio of manganese-to= sulfur ions is apparently valid because related worV) by the authors showed 36~8+0.2 percent. The balanced composition of MnS is in contrast to the cation deficient FeS structure of pyrrhotite where the sulfur content varies from 37 to 42 percent8) (vs. 36.5 percent in stoichiometric FeS), Anion solid solution in MnS is limited. Concurrent wori7)' revealed a maximum of 1.7 weight percent Mn0 in MnS which corresponds to a replacement of approximately 2 percent of the sulfur ions by oxygen ions. Cation solid solution is more extensive, Kr8gex 5)reports zinc and cadmium substitution for manganese. Of more importance to nonmetallic inclusion work is the fact that there is rather extensive replacement of manganese by iron.

Wentru~9) reports a maximum of 75 percent replacement near 12000~C. Current worlt0) shows a maximum of 72 percent at 1181~C. Deformation and Fracture. Except for a brief note 4) no previous work has been reported on the deformation or fracture of MnS. However, since the structure of MnS is the same as that of NaCl, LiF and MgO, attention should be given to their behavior under mechanical stressing. Gilmarll) gives a complete review and indicates that, except for PbS and PbTe which are highly polarizable, all rock salt-type crystals have a [110] glide direction and a (110) glide plane for primary deformation. His review included MgO, LIF, NaF, NaC1, NaBr, NaI, KC1, KBr, KI, RbC1, NH 1, AgCl and AgBr. In addition, secondary glide systems were reported asL[llo10 ((100)) on most of the above halides. Buerger 2)reported[[110]] ((111)) glide in the sodium halides. It is significant that all reported glide directions are the[l[110o]directions, even in PbS and PbTe. Also of interest is the fact that the[[ll0]] ((100)) glide system has not been reported for periclase (MgO). KeAl used surface indentations to study the deformation of single crystals of periclase, After indentation, etch rosettes appeared in the (100) surfaces which permitted the interpretation of dislocation movement. Only the[[110]] ((110)) glide system was identified. The hardness of MnS decreases as the temperature is increased 10) This indicates that slip occurs more readily with increased temperatures, much as expected. -4

Fracture in the NaCl-type crystals is characterized by ((100)) cleavage. GilmaAl) reports secondary cleavage on the ((110)) planes as does Keh who concluded that they were the result of interactions of dislocations on the ((110))4S planes, (i.e., ((110)) planes which are inclined at 45~ to the external (100) indentation surface). The relative energies required for the formation of the ((100)) and the ((110)) surfaces by cleavage has been calculated for alkali halides by Van Zeggeren and Bensont4) who indicate that the energy for the latter planes should be from 2 to 5 times the energy for the ((100)) planes. EXPERIME:NTAL PRO CEDURE Manganese sulfide was purified and prepared in both the single crystal and polycrystalline forms. Pyramid indentation was used to analyze the deformation systems. MnS.urification. Although several procedures were used to prepare MnS for subsequent melting and crystal growth (Appendix A), only the procedure yeilding the purest MnS will be described here. It utilized a sulfur deoxidation of reagent grade manganese sulfate as shown in Fig. 2. In essence, sulfur was vaporized at 4100C and one atmosphere pressure before coming in contact with MnS04 powder at 900~C. The relationship, MnSO4 + S2 - MnS + 2S02, appears to be appropriate When the reactiorn was completed, it

gave an analysis of 36.8o0.2 percent sulfur. The metal ion content is shown in Table 1. Neither x-ray diffraction nor optical examination revealed other phases; however, it became apparent that in powder form the surface would oxidize with time. Therefore, the purified MnS powder was melted and solidified for later use. The lattice constant for the purified MnS was 5.225A, as compared to the value of 5.224A reported by ASTM(15 A second and third type of manganese sulfide sample were used in this study. (2) Manganese sulfide with about one percent calcium is listed in Table 1. Microscopic and diffraction data indicated that the calcium ion entered the alabandite (MnS) as a solid solution; a = 5.232A. However, there was some indirect evidence of precipitation at elevated temperatures. (3) The third type was manganese sulfide which contained minor amounts of MnO as a grain boundary precipitate, This meant that the MnO slightly exceeded 1.7 percent 7 ) Sample preparation. All of the MnS was briefly melted and solidified in a graphite crucible before analyses were made. In a few cases this product was used directly as polycrystalline MnS. However, most of the MnS in this study was used as large crystals for single crystal examination. Three procedures were utilized for single crystal preparation. These include: (1) the vapor depositions of MnS by iodide transport, (2) E Bridgman cell technique, and (3) a zone refining procedure. The latter proved to be most satisfactory and will be described briefly. (The others are described in Appendix B.) About 60 ginms -6

of the previously melted MnS were crushed to about 3 mm and remelted under a purified argon and/or nitrogen atmosphere in a graphite boat within a horizontal moving coil induction furnace. After two or three initial passes, a final pass was made at the rate of about 1 inch per hour in which time a coarsely crystalline (up to 1 cm) grain size developed. Fracturing revealed cleavage planes which were used for orientation checks and as guides for further cutting. Fracture and Deformation tests. A diamond hardness indentor was used for fracture and deformation. Cleavage was used to locate the (100) surfaces. However, these were generally polished and etched prior to indentation. Other crystal planes were ground to the correct orientation before polishing, etching and indenting, Slip lines were directly observable after indentation on the previously prepared surface. The dislocation lines were revealed by etching with three percent of equal parts of concentrated H2S04, concentrated H3P04, and a saturated solution of oxalic acid, RESULTS AND DISCUSSION Fracture. Both grain boundary and cleavage fracture were observed within the samples. The grain boundary fracture was a direct consequence of the precipitation of small quantities of nearly submicroscopic particles of Mn0 at the boundary. It can not be concluded from this investigation that MnO is inherently r7

more brittle than MnS because the fracture may be controlled by the phase boundary. However, the presence of the MnO changes the fracture characterization markedly so that individual MnS grains are separable. In the absence of observable oxide precipitation, cleavage fracture predominates in polycrystalline MnS. The ((100)) planes are the most prominent cleavage surfaces when grains are crushed. Additional secondary cleavage is developed on the ((110)) planes, often observable as oblique offsets to the ((100)) cleavage (Fig. 3). The preceding observations are directly correlatable to other compounds with the (11) NaC1 struc turel. Indentation tests favor fracture along the ((110)) planes (Fig. 4 a and b). Although deformation has not been discussed as yet, it may be noted here that the ( (10) ) planes are the principal slip planes, and movements along the several ((110))450 planes would induce tensile stresses at the surface of the sample normal to the ((110))90o planes. Thus the fracture in MnS may be considered to be analogous to that in periclase (MgO) as (13) determined by Keh.3 The absence of ((100)) cleavage should be expected in samples deformed by indentation because the movement along the several ((110)) 4D planes is parallel to the ((100))900 planes, and the location of tensile stresses from ((110))90~ displacement are in the compressive zone below the indentor. The role of temperature upon cleavage is complicated by the simultaneous change in plastic deformation. Because plastic -8

deformation does occur more readily at higher temperatures, the relative amount'of fracture is reduced. Deformation, Results and interpretation of deformation of MnS was obtained by three procedures. The first of these included measurements of the broadening of x-ray diffraction lines, followed by annealing at increasingly higher temperatures. The second was through the study of etch pits of dislocation lines that terminated on the crystal surfaces, and the third involved the examination of slip lines on the crystal surfaces. Diffraction lines of powdered MnS are too broad to permit accurate lattice parameter measurements, thus indicating plastic distortion of the crystal structure. The line broadening must be attributed to deformation rather than fine grain size because subsequent heating permitted annealing and gave a measurable sharpening of the diffraction lines as shown in Fig. 5. Dislocations were revealed by etch pit rosettes as shown in Figo 6 and 7. The patterns of dislocation are identical to those discussed by KeA13) for periclase (MgO), and may be interpreted as follows. The indentor displaces MnS along the ((110)) planes in the [,l,0J] directions, and in effect prorvides a dislocation "loop" which swings under the indentation emerging on the other side. Both edge and screw dislocations are observed, with the edge dislocation emerging perpendicular to the (100) etch surface and the screw dislocations emerging at 450 to the (100) surfaces. In MnS the edge dislocations are more readily etched than the screw dislocationsO This agrees wisth the behavior in MgO01,g,~~~~~~~~~

If planes other than ((100f)) are used as an indenting surface, the dislocation etch pits are less obvious, but present (Fig, 8), This difference is a consequence of the plane of etching rather than the deformation mechanism or the dislocation alignment, because the difference may be revealed on the same samples as those which possess good etching characteristics on the (100) planes, It may be concluded that the ((110)) planes of MnS are relatively stable in the etchant solution which was used0 Not only are the dislocations poorly revealed on a (i10) surface, but alsos the ((110)) facets are those remaining in the dislocation pits on a. (100) surface (Fig 9) o At higher temperatures, the etch pit rosettes are more diffuse but involve more dislocations (Figo 10). In effect, plastic deformation is nucleated more generally0 S1ip tLraces from deformation are revealed without etching, but with oblique illumination if the crystal surface is polished before indentation (Fig~ 11). There has been an upward disp'lacement of the surface along ((ll0)) 4 planeso However, it may be shoiwn that slip along any particular side of the indentor is not a simp-le dis= placement along parallel (1l0)45planeso Rather, slip occurs aling two sets of (110)4 planes as indicated in Fig0 12 and interpreted from Figo 13. In the latter figure, the surface used for indentation was inclined a few degrees from the (001) plane through a rotation around the [00] axis0 As such, the surface traces of the two sets of planes in Fig~ 13(b) are skewed in oppos-Lite 10

directions so that they are not parallol (F1L~o 1a) oa These results also exclude the possibility of secondary slip on the ((100)) planes because this type of crystal inclination would not alter the traces at the surface. Secondary slip was observed on ((111)) planes as illustrated in Fig. 14. These slip traces can not arise from ((110)) planes because they would require movement in a [100] direction, a direction which has extremely high ion repulsiono The secondary slip on the ((il1)) planes is often associated with the ((1I1))e0 fracture (Fig B14b)o The sequence of events appears to beo (1) fracture along the (110)90. (2) progression of slip deformation orn closely associated (111) planes, and then (3) fracture on the come plementary (110)9 0 plane in the vicinity of the (111) slip0 As such, the latter (110)90 fracture would arise from interaction of dislocation movements in the ((111)) planes, much as the initial (,10))90O fracture arose from dislocation movements in the ((110))~ 90 planes 13) Neither the reason for the periodic location of the ((ll)) slip lines along the (110)90 crack nor direction of the slip along these planes is known; however, it may be concluded that their explanation, as well as that of the (111) slip proper, must take into account the (110) surface which has been exposedo CONCLUSIONS (1) The deformation and fracture of manganese sulfide in its alabandite form may be compared directly with other NaCltype compounds.

(2) The primary glide system in MnS is [[O110] ((110)) and is easily revealed as slip traces or as dislocation etch pits, (3) A secondary glide system involving ((11(1)) planes developed subsequent to ((110))90~ fracturing. There wans no evi2dence of secondary ((100)) glide planes, (4) Grain boundary fracture occurs in MnS when a minor amount of MnO is present. ( 5) Primary fracture occurs as ((100)) cleavage. Ho-wever, ( li), cleavage steps may be observed on the ((100)) sturfaces, (6) The ((110))9Q0 cleavage becomes the primary fracture system during surface loading. Such fracture develops by the interaction of ((il0l))L4 slip and the (001) surface; in addltiorn a. mr.or amount of ((ll10)90o fractulre can occur through the inter.actl;rJ of ((11)) slip and the (110) surface, A CKNO WLEDGEMENTS The authors wish to acknowledge the support of the Edgar Co Bain Research Laboratory o:f Uo S. Steel. Specifi thanks sh 1otlaldl be giv-en to Drs, R. Rickett and Ao So Keh for their crit inc al discus ions and suggestions. -12

REFERENCES I. F. WO Boulger, Machining Theory and Practice, ASM, Metal.Park, Ohio, (1950) 77. 2, JO D. Armour, Machining Theory and Practice, ASM, Metals Park, Ohlo, (1950) 136. 3. L, Ho Van Vlack, 0. K, Riegger, R. J. Warrick, J. Mo Dahl, Sulfide Inclusions in Steel, Trans, AIME, 221 (1961) 227. /4 La Wood and Lo H. Van Vlack, Fracture and Deformation of Sulfide Inclusions in Steel, Technical Note, Submitted for public ation, 5. Fo A, Kr3ger, Solid Solutions in the Ternary System ZnS-CdS-MinS, Zeit. fo Krist,, 102A (1939) 132, 6. H, P. Rooksby and N, C. Tombs, Structure of Monoxides of some Transition -Elements at Low Temperatures, Nature, 165 (1950) 142 o 7. H, C, Chao, Yo E, Smith, and L, Ho Van Vlack, The MnO-MnS Phase Diagram, Technical Note, To be submitted for publication, 8. J, Chipman, Fe-S Iron-Sulfur, Metals Handbook, ASM, Metals Psrk oh-o, (1948) 1215. 9, H. Wentrup, Die Bildung von Einschldssen im Stahl, Tech. Mitt~, KrU'pp, 5 (1937) 139. o0. H, C, Chao, L. H, Van Vlack and L, Thomassen, Inclusion Defoxmation II, Hardness of FeS-MnS Microstructures. To be su.bmitted for publication.

.. o JO JO Gilman, Mechanical Behavior of Ionic Crystals, Progre-:s in Ceramic Science, J. E. Burke, Pergamon Press, New York. (1961) 1460 12. M. J, Buerger, Translation-Gliding in Crystals, Amer. Mir.eral-i ogist, 15 (1930) 450 13 A, S, Keh, Dislocations in Indented Magnesium Oxide Crystals,. Journ, App. Phys., 31 (1960) 1538. L.4 F. Van Zeggener and G. C. Benson, Calculation of the Surface Energies of Alkali Halide Crystals, Journ, Chem. Phys., 2. (l957) 1077. 15. Swanson, et al., N.B.S,, Circular 539, IV, (1955) 11. 16. R. M. Fulrath, personal communication, -14

TABLE I The Impurity Level of Three Types of MnS Elements Samples 1 & 3 Sample 2 (pure) (with 1% Ca) Ca 0.01 lo0 Mg 0.001 0.1 Fe 0.003 0.1 Ti 0.003 0.01 Cr 0.0003 0.005 Ni 0.001 0,002 Al 0.02 0,02 Cu 0.0002 0o0005 a 15

i... i~iiii~iiii-ii -iiiiiiiiii{iiiiiiiiiii~iii.iiii.. Fig. 1. Sulfide inclusions defornmed by hot-rolling. Example: desulfurized steel. X500. Fig. 2. MnS purification. Reagent grade MnSO4 was deoxidized with sulfur vapor. (1) Lower furnace, 400. (2) Upper furnace, 9000C. (3) MnSO0 charge. (5) S02 exhaust.!:...~. i (6) Reaction tube. (7) Stirrer. (8) Support of graphite felt and a porcelain filter to hold the change. a s'a- —::i —_-i:::-~-:~-; S S - ^ > 0 E S S ~':::::::: -ES —E~:::::"i:i__-~.....-::::I;.E::: i:.. ___:::. _::..::::::. v...:::::i:: ~::: -,;:j i i;:ii -iB; i-::.'-''B a:::'-: —'`.:-::-:::: -:-: —.. a <.-:...,|.l i i i-:. -:-.... ~.B.B; t- Fig. 1. Sulfide inclusions deformed by hot-rolling.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:::::::_::.__::i:: —-_ —-.::_:-:_i.: --::~:::::::::::::: i::::::::arnple:,::::::.i:i.:-;desu -~ii-:lfu iizedi st el X500.: —--—:::::::::~:~::::: ~:....~~~ ~~ ~~ ~~ ~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~::;::::::::::-:: —i::i::::::::::::::~-:~~::::~: u ~ ~ ~ ~~~~~~~~~~~~~..::_::_::o:-___::: iii:i_:-ii~:-~m-::::::::::::::~:::::::-.:.-::_-: —: -::::-..... — ii::::::::i:.::ii:ii:: -~-::ii:: -:-~-::-:~i i:i-~~i:::~~:~-i:: —: -: —-:::-:i:~-: —::-:-:::::::::__i:.~-.~- iii:iii-i~i~i:i-: - -::: —~-:: ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.:iiii-,iiii: —::-:::: iii~ii:~.:.:-:-i:-:~~~i~i.iiiii~iii:-.a::: —i:l;l;_-i-iii::::::-::::iiii~~ i -i-:-::-::i:*-::: i~~~:-iiiii~::~i —-- i: —:-:iiiii:-iii-~ P~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:ij::_li:::1:i, _~~,:_:,:::1:::::::: I:~.~~~ifi:-~~d~_~~i.. iai2-iiii-~~ ~:_:ii-li t - iiiii-l ii:-.iii:iiii " —::::~:::::-::i::-:: —::::::::: -~~-::-: —-': -:- -: ---'-ii:-::::~:i~-:iii-~-~:iiiii _ J _ ~~~~~~:.:::::::-::::::: — i::::::: —-:::j:.:: -:: —: —-—:-::::x::: L L~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:::::::::::::: Fig. 2.:: MnS-::-:i-::~: puritication:::::.::::::::i:::.-:::-:i-i,~:j':_ niiiii~:~i~iiiii~:i: R e a g e nt:1::-:: g ra de: M nS 04 w asi_~::_::I_ _:,~:-:,-_-:::,:::::::::::::::::::-::-~:: —-::::.:-~-::i::iiii:i: i-i —diiiiiiiiiiii:::::ii-i~i".:~ ~ deoxidized:::: w i: th- su lfu r vapor.:::::::-_ —:: -::-~:::::.::::iiai-,,,,i~::~: ~~~ -i-:~::: —:lc~ii~il::-::::::::_:::: —i;i:::: —::: (1)-::. L o w er:~:: —:-::::.:: fu r a c e 4 1 0 ~ G.::-:-:::-j:::.:; -....i:::~ |~~~~~~~~~~~~~~~~~~~:~:j: -: I (2) Upper rurnace, 900~C.-:-.

Fig. 3. MnS cleavage surface (001) Cracks also form at 45~ to the [100] direction. X59O. -17

NS Fig. 4. Fracture in MnS from indentation. (a) Cracks are formed along (110) planes normal to the (001) surface. (b) The indentor is rotated 45~. x500. -18

9.0 8.0 04 0, N 0 100o 200 300 400 500 600 700 800 900 1000 ANNEALING TEMPERATURE - C Fig. 5. Line broadness vs. annealing temperature.

.1 A 1 -,a~~~~~NN::'M a),x2~ ~ ~ ~ ~ ~~~P ~ s N 1101 1 4% \0) V~~~~~~~~~~~~ A (b) (e) Fig 6.Dislocation rosette. Example: (00l) sU;rface. (a) Etched after indentation. X2.50. (b) Edlge dislocation development on the ((110))900 planes. See Fig. 7 for th~e dislocations with the ((l10))~,o ps ( (pis Bue~ge,s vector ts llO. -20Kc ~r N- - ~P( Vs A ~~~~~~>' ~ ~ ~ b (ITO) tio V A V?~~ V'"-l:iix`iV V~~~~~~~P~jhr (b)::, (c)o j Fig 6. Disocaionrcisete. Exaple (01) urfce (a)Ethe ate inetton 2 ()Eg diloato dveopet n h (ll))0 pans r ~ ~ e i.7frtedsoain ihte(lO)$ ~~plns (c (l)90pae addsoainlns ~~~Bere' vetri 1 ~~~~~~~~~0

-:~(a),0/., ~ (b) (c)" Fig. 7. Dislocation rosette (vertical cross-section). (a) The MnS crystal of Fig. 6 was ground to below the indentation, then cleaved on the (100) plane, polished and etched. X250. (b) Edge dislocation development on the ((110))45o planes. These appear as screw dislocations in Fig. 6. (c) ((110))45o planes and dislocation lines. Buerger's vector is 110. -21Dilcto oete(etclcrs-et n

Fig. 8. Dislocation rosette on a (110) surface. The more rapid etching of the (110) surface prevented good rosette development. X200. (Bl) i,{B~el'b-. ) (B).ami i- tM - Fig. 9. Dislocation etch pits. (a) dge dislocations from (110)90o planes. (b) Screw dislocations from (110)4~o planes. (c) Small angle boundary. (d) Random dislocations. In each case the ((110c)) surfaces are developed. X500. -22ax~~~~c~~~~~ ~~~a":~~~~~ITr %~~~~~~~~~~~~~o..7 7~ (B) (C)~'ZS

Fig. 10. Dislocation rosette from 7000~C indentation. No ((110)) cleavage cracks were formed above 300~C. X100. (The indentor was spherical in this case; however, cracks were also absent with pyramid indentations.) -23

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Fig. 12. Multiple ((110))45o slip adjacent to the indentor. See Fig. 13. (a) Fig. 13. Multiple slip planes. (a) Indentation surface tilted 5.50 from (100). X100. (b) Sketch of disaligned slip traces. The angle 9 - 2' for small tilt angles, 4.

ii i:::i:i:....................................:.. i::::::.:::: E:::: i:.'::. i:: ~:t: E.:'~::,::::::::::::::::i:'::::::: z:::::::.. (a) tru i;;;E; i;4- -04 Ei i i: h,~~. ~~. ii i -i F::. i i E i iii~iiiii~ i i;;ii e E-i ii i i-ii i..iii iii.i.i.ii. i.-i.ii- (b) Fig. 14. (a) ((111)) deformation (arrow). Also see the large indentation of Fig. 11(a). These 45~ slip lines can not arise from ((110)) slip. They lead to (110) fracture. Examples: (a) (MnFe)S with 75/25 ~~~~~~~~~~~r rX100. Obl ique il lmi nat- i-.on. _ i t f / i'l:.''tlig.'S;;S.'.>-'.S~gSE;0004SE0.i~id00000.' t tt ffft a~ti: ^00000;0000000000,0000 j 00 0j:00; tj002 L\,.''"C'S: ~~~ iii t::?;;;;j ~~jS; ~l I S E ~'4Sg00LSXtA0XS: ~Sk: large~~~~~~~:ne tto:,::::::::r::::E. Ila):iLs iC5 s i.'t lines~~~~ ~~~~~~~~~~~~ 70t'jii4i t:0iittai t:;0200:iS tiS3SE: ((1 0) slip The le'S Wt;iE;io''EiE4SS!,XEA2~,''''y (110) frac~~~~~~~~~~~~~~~~~~i000i00''t!X000;eE;;.; 0;iiEif;.;00;EEt;0k;';x;00;amp';';itX'ttlE''S'';ef;0;;,is;;0.: (a) (,;fti4X'S;T,''';'

APPENDIX A'~ ALTERNATE METHODS OF PREPARING MnS Alternate methods of preparing MnS are summarized in Table AIo-l In each case trace amounts of MnO were always present in the final product. In addition, sulfur condensation problems arose in the exit end of the equipmento The previously described sulfur deowx idation procedure is preferred. * This appendix, which is included in the report for record, will not be incorporated into the published version, TABLE A-1. Gas Treatment of MnS (850-900C) Starting Materi _al Commercial "Reagent' MnS MnSO 4 Dry Argon + CS2 X Dry Nitrogen + CS2 X X Dry Nitrogen + H2 X Dry Nitrogen + H2 + H2S X A-1

APPENDIX B " ALTERNATE METHODS OF SINGLE "CRYSTAL GROWTH Two alternate methods of single crystal preparation were utilized with incomplete success. These included (1) an iodide vapor transport procedure and (2) a Bridgeman cell procedure. The iodide vapor transport procedure utilized purified MnS powder which was sealed in an evacuated vycor tube with a side-arm containing AuI3o The latter was thermally dissociated and the 12 collected in the main tube before removing the side-arm, The tube was then exposed to a thermal gradient of 9500~C at the MnS powder end, and 550~C at the other end. New MnS crystals grew at mid-gradient. Of prime interest was the fact that the MnS crystals formed plates in which the main surface was (111)o However, only a few crystals could be made to exceed 1 mm, in their greatest dimensiono The Bridgoman cell was a graphite mold with a cavity of I cm, diameter and 6.6 cm. length plus a constricted 2 mm, neck at the base for seeding. A dried nitrogen atmosphere and a zone refining procedure were used for heating with the induction coil moving vertically past the constriction. Successful results were not obtained, The limitations of the procedure arose from extraneous vibrations and from the inability to know the temperature in the part of the MnS ingot which could not be seeno The range of temperature is narrow between MnS melting and MnS dissociation to mangan ese carbide and sulfur gas *: This appendix, which is included in the report for the record, will not be incorporated into the published version, B-1

UNIVERSITY OF MICHIGAN 3 9011 115 028271 11 411901131 3 0502827 4903