DEPARTT OF NGINRING RSSEARCH UNIVERSITY 0F RICHIGAN ANN ARBOR Report on rALLOGRAPIC EXINAION OF SILVSR-4ICKEIrflON.ND 8ILVBR-lRON-NICKBL?TRIMTALB;rw. W tr Fnuuz ProJect-:Nf*r M332 for VW. I. Chace Company Detroit, Mihigan February 26, 1942

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.ttWAL&~PUIC~ EXAUINATION OF SI.LVE-A0ICKtE IYW M.AD SlLVER-IThRON- ICKIL TRI TA& This report presents photomicrographs of the structures of silver-nickel-Armco iron and silver-Armco iron-nickel tri-met-wls, Typical examples of the type of bond between the layers of met:ais and th-e strucetures of ll1 the samples are The information obtained from'the metallographie examTi.nation may be s umarized as follows: I. $ith the exception of ono sample, te bond between the silver and nickel appeared to be better than between the silver and Armeo iron. 2.. In all cases the bond betwe-n the nickel and Armco iron appeared to be superior to the silver bonds,. Aetual alloying between the two materialts took place. 3. The bond between the silver and the other materials appeared to be mechanical in nature rather than by an alloyin.g effect. 4, The t samples of silver-Armco iron-nickel tri tal which were supposed to have been annealed at 1600*F. apparently amd not beenteat treated,

2. Seven samples of nickel-armco iron bimetal with the nickel side silver faced and seven samples with the Armco iron side faced with silver were submitted, Bach specimen was approxinately one half inch square, These saples rind their treatment, as indicated in a letter from Ur S, *, RHood on February 20, 1942, are given in the following tabulation: 1 Silver-NickeI-Armco Iron As Cast r2'4 s "-~~ 50e Fbcr~Rolled 50f Reduction 4'4'e - " 8Rolled 50% Reduction, Ann. 1200?*F 5' 4 t'' Rolled 50j Reduetion 6 RIt 1 1- b led 82< eduction, Ann# 1600?*. ir o l IedRol 82- Reductions, Ann 1200?Fi 9''4' Rol led 52 % Reduction 10 4' 4 ti ll 50% Seduction, Ann 1600*'? 6I.t t. 4.Rolled 50% Heduc tion, Ann. 1200'.F 12 w Ro " Rolled 82% Reduetion 13 B'' R olledt 8o2% 4Reduction, Ann. 1600*F 1,4,,, " Rolled $2% Reduction Ann. 1200'?* The tallogrph examination was tion ducted byn, cutting the small squares into two or three pieces a mounting them side 1 y side in bakelite The polishinga procedu" consisted of grinding throuh successive grades eof t Ilographic paper by hand, and -then on three cloth covered whIXs containing successively tine grads of ebrafsive. Finl polishing ws carrled out wtth magnea ia od-e on a s$ilk brodclaoth coered wheel,

3,* It was found necessary to etch and rtepolish on the final wheel several times to reveal the structures essentially free from polishin cold work. This latter procedure was especially true of the silver, The silver was etched with a dichromatechromic acid solution, the Arco iron with 4 per cent nitric acid in alcohol, and the nickel with a 50 pr cnt 11N03 - 50 per cent acetic acid solution. The photomicrograph; taken are shown in bCharts through 7* the bod ten the various layers were examined betor etching the samples. Charts i, 4 mdd 5 show typical hotomicrorapths at 50OX. In so far as wras observed photomicrographs la rnd lb were typical of the unete ad appearance of the silveraickel raid nicrkel-Ar~mco iron bonds, with the exeoption of sample',.Apparently the silver had septr4ted from the nickel in the 82 per cent redued samples annealed at 16:OPr., as is shown in The samples were then subjected to to e etching and repolisahin? procedure until the structure was clearly revealed. Typical photomierographs of the bonds in the "as ceastt samples are shown in Charts 1 and 5. Similar photomid rographs of the 50 per cent reduction samples annealed at 1200?F* are shown in Charts 3 and 6, The other charts show the s tretures of the 8samples in the etheed condition at XOOD magnieication,

4* The bond between the nickol and the silver appeared to be better th n the silver-Armco iron, Apparently the surface of the nickel was rough and allowed fingers of silver to penetrate into the surface as shown in the photomicrographs of Chart I* The silver-Armeo iron bond appeared as a straight line very similar to that which would be obtained when two metals were pressed together. The nickel-A ruco iron bond showead the presence of a diffusion layer and could only be observed by a ditference in color of the two metals with no line of demarcation visible. The line of demarcation between ther silver andh oh the thr two metals was visible in all ases During the etchin'g aMd repolishing operations it was Impossible to avoid the development of a difference in level between the various layers, This was caused by more of one materitl being removed, durtng polishing and etching. Therefore in many cases the bonds appeaeid worse than they actually uring the mounting operation bakelite did not penetrate between the sections of the samples. In the grinding operations the silver "burred" over into th over into ths empty space. Theref'ore the photomicrogrtphs do not show a clean line of demarcation.

Nu erous inclusions were present in the Armeo iron, In some eases it was iampossible to prevent their removal res.ulting in a -pitted surface, Nerous holie were present in the silver layers in the as cast condition. This was particularly true of the silver in Samples I throuh 7* The silver wals talso very coarse grained in the as east condition, Attention is also called to tVe strained appearance o Camples 10 and 13 which were supposed to have been anneaed at 1600*F. The only evidence of separation of the silver layer was found in Smple fumber 6 as shown in Phototicrographs (b1 and (e) of Chart 4*

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