The effects of devitrification on the mechanical properties of Cu 46 Zr 54 metallic glass
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1. INTRODUCTION
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has b e e n o b s e r v e d that m a n y p r o p e r t i e s e x h i b i t e d by m e t a l l i c g l a s s e s f o r m e d f r o m n u m e r o u s a l l o y s y s tems are altered significantly by devitrification. E x a m p l e s of p r o p e r t i e s which e x p e r i e n c e s u c h c h a n g e s a r e e l e c t r i c a l r e s i s t i v i t y , 1 magnetization,2, 3 h a r d n e s s , 4-6 t e n s i l e f r a c t u r e s t r e s s , ~,%7 and d u c t i l i t y . 8,9 F e w of t h e s e s t u d i e s c o n c e r n i n g c h a n g e s in m a t e r i a l s p r o p e r t i e s upon d e v i t r i f i c a t i o n have c a r e f u l l y c o r r e l a t e d the change in p r o p e r t i e s to the m i c r o s t r u c t u r e . T h i s is of p r i m a r y i m p o r t a n c e , in p a r t i c u l a r , for u n d e r s t a n d i n g c h a n g e s o b s e r v e d in the m e c h a n i c a l p r o p e r t i e s of the p a r t i a l l y c r y s t a l l i n e m a t e r i a l s . The p u r p o s e of t h i s p a p e r is to o b s e r v e m e c h a n i c a l p r o p e r t y c h a n g e s in a C u - Z r m e t a l l i c g l a s s of the c o m p o s i t i o n Cu46Zr~4,* which o c c u r a s a r e s u l t of *Subscriptsrefer to atomicpercentages.
i.e.,15~
d e v i t r i f i c a t i o n b y i s o t h e r m a l aging at 375~ below the o b s e r v e d g l a s s t r a n s i t i o n t e m p e r a t u r e . P r o p e r t y c h a n g e s w i l l be a c c u r a t e l y r e l a t e d to m i c r o s t r u c t u r a l c h a n g e s which o c c u r in the g l a s s a s the r e s u l t of d e v i t r i f i c a t i o n . T h e C u - Z r a l l o y s y s t e m was u t i l i z e d in t h i s study b e c a u s e it is a r e l a t i v e l y s i m p l e b i n a r y s y s t e m which is known to f o r m m e t a l l i c g l a s s e s o v e r a wide c o m p o s i t i o n r a n g e when p r o c e s s e d by s p l a t quenching. ~ In t h i s m a n n e r , the m e c h a n i c a l and d e v i t r i f i c a t i o n c h a r a c t e r i s t i c s c a n b e e x a m i n e d and c o m p a r e d with o t h e r C u - Z r m e t a l l i c g l a s s e s which a r e c o m p o s e d at e q u i l i b r i u m of d i f f e r e n t c r y s t a l l i n e p h a s e s . Cu46Zr54, at e q u i l i b r i u m and b e l o w 928~ i s c o m p o s e d of 70 p c t C u Z r and 30 pct CuZr2 ~2 A s i n d i c a t e d by F r e e d and V a n d e r Sande ~~ t h i s g l a s s d e v i t r i f i e s when i s o t h e r m a l l y a g e d 15~ < v i a a n u c l e a t i o n and g r o w t h p r o c e s s of the e q u i l i b r i u m c r y s t a l l i n e p h a s e s .
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ROBERT L. FREED formerly with the Department of Materials Science and Engineering, MIT, is now with E. I. Du Pont de Nemours and Co., Engineering Technology Laboratory, Wilmington, DE 19898. JOHN B. VANDER SANDE is Associate Professor, Department of Materials Science and Engineering, MIT, Cambridge, MA 02139. Manuscript submitted August 2, 1978. METALLURGICAL TRANSACTIONS A
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