Morphological and structural studies of thermoelastic martensites in a Ag-38 At. Pct Zn alloy
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IkECENTLY, thermoelastic martensitic transform a t i o n s such as those found in C u - A I - N i alloys ~ have b e e n the s u b j e c t of many s t u d i e s . Both s c i e n t i f i c a l l y and t e c h n o l o g i c a l l y i n t e r e s t i n g p h e n o m e n a such as the shape m e m o r y and p s e u d o e l a s t i c effects have been found in a n u m b e r of alloys and these p h e n o m e n a a r e c o n s i d e r e d to be a s s o c i a t e d with the t h e r m o e l a s t i c n a t u r e of the m a r t e n s i t i c t r a n s f o r m a tions in such m a t e r i a l s . 2'3 Noble m e t a l a l l o y s such a s C u - Z n , A u - Z n , Au-Cd, Ag-Cd, and so forth a r e known4 to exhibit a t h e r m o e l a s t i c m a r t e n s i t i c t r a n s f o r m a t i o n and the shape m e m o r y and p s e u d o e l a s t i c i t y effects. However, A g - Z n alloys were thought for some t i m e to be an exception to such b e h a v i o r s i n c e no m a r t e n s i t i c t r a n s f o r m a t i o n was found on cooling to liquid n i t r o g e n t e m p e r a t u r e . 5'6 R e c e n t l y , however, A y e r s and H e r r i n g 7 found a t h e r m o e l a s t i c m a r t e n s i t i c t r a n s f o r m a t i o n in s e v e r a l A g - Z n alloys u s i n g a s c a n ning e l e c t r o n m i c r o s c o p e equipped with a liquid h e l i u m cooling stage, and C o r n e l i s and W a y m a n 8 r e p o r t e d that a Ag-38 at. pct Z n alloy exhibited a t h e r m o e l a s t i c m a r t e n s i t i c t r a n s f o r m a t i o n and also showed the shape m e m o r y effect. Thus, the A g - Z n a l l o y s come within the c a t e g o r y of the noble m e t a l a l l o y s a s m e n t i o n e d above, but a s yet e x p e r i m e n t s on the d e t a i l s of the morphology and c r y s t a l s t r u c t u r e of the t h e r m o e l a s t i c m a r t e n s i t e s in A g - Z n alloys have not b e e n r e p o r t e d , p r o b a b l y due to e x p e r i m e n t a l d i f f i c u l t i e s a r i s i n g f r o m the low M s t e m p e r a t u r e and H. KUBO and C. M. WAYMANare Research Associate and Professor, respectively, Department of Metallurgyand MiningEngineering and Materials Research Laboratory, University of Illinois at UrbanaChampaign, Urbana, IL 61801. The former is on leave of absence from Osaka University. K. SHIMIZUis Professor, Institute of Scientific and Industrial Research, Osaka University, Yamadakami, Suita, Osaka 565, Japan. Manuscript submitted September 3, 1976. METALLURGICALTRANSACTIONSA
the i n e v i t a b l e o c c u r r e n c e of a m a s s i v e t r a n s f o r m a t i o n d u r i n g quenching. On the o t h e r hand, d e f o r m a t i o n induced m a r t e n s i t e s in A g - Z n a l l o y s with h i g h e r Zn c o m p o s i t i o n s (above 39 at. pct Zn) have been p r e v i o u s l y studied to s o m e extent. Brown and Stewart 9 c a r r i e d out an X - r a y diff r a c t i o n study of d e f o r m a t i o n induced m a r t e n s i t e s by u s i n g filed s p e c i m e n s with c o m p o s i
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