Study of a splat cooled Cu-Zr-noncrystalline phase
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T H E s p l a t cooling t e c h n i q u e d e v e l o p e d by Duwez et 1~2 al. about ten y e a r s ago h a s been shown to b e an e x c e e d i n g l y u s e f u l tool f o r t h e study of a b r o a d r a n g e of s t r u c t u r e s in m a t e r i a l s 3,4 A r e c e n t c h r o n o l o g i c a l l i t e r a t u r e r e v i e w s shows an o b v i o u s l y r a p i d l y i n c r e a s i n g i n t e r e s t in s p l a t - c o o l i n g of n u m e r o u s a l l o y s . P r o b a b l y one of the m o s t i n t e r e s t i n g f e a t u r e s of t h i s t e c h n i q u e of u l t r a - f a s t quenching i s t h e p o s s i b i l i t y of p r e p a r i n g a l l o y s in the n o n c r y s t a l l i n e f o r m . The w o r d n o n c r y s t a l l i n e i s u s e d to d e s i g n a t e both a m o r p h o u s a s w e l l a s m i c r o c r y s t a l l i n e s t r u c t u r e s s i n c e both d e v e l o p s i m i l a r d i f f r a c t i o n p a t t e r n s c h a r a c t e r i z e d by a s m a l l n u m b e r of b r o a d r i n g s f '7 So f a r , a f a i r l y l a r g e n u m b e r of a m o r p h o u s a l l o y s h a s b e e n found; 8-12 they a r e r e v i e w e d in Ref. 3. It i s i n t e r e s t i n g to o b s e r v e that a l m o s t i n v a r i a b l y t h e s e a l l o y s involve a m e t a l l o i d (Si, Ge, P) a s one of the c o n s t i t u e n t s . It h a s b e e n p r o p o s e d that t h i s i s a condition f o r the f o r m a t i o n of an a m o r p h o u s a l l o y phase.6 The p u r p o s e of t h i s p a p e r i s to d e s c r i b e a study of the p r o p e r t i e s of a n o n c r y s t a l l i n e p h a s e p r e p a r e d by s p l a t cooling of an a l l o y m a d e of two t r a n s i t i o n m e t a l s , n a m e l y , c o p p e r and z i r c o n i u m . L e a d i n g up to t h i s p r o g r a m w a s the finding of a n o n c r y s t a l l i n e p h a s e o v e r a wide r a n g e of c o m p o s i t i o n s in the C u - Z r s y s t e m . .3 In t h i s p h a s e d i a g r a m , we l i m i t e d o u r s e l v e s to a w e l l defined c o m p o s i t i o n (60 at. p c t Cu) f o r which the nonc r y s t a l l i n e p h a s e w a s e a s i l y f o r m e d at cooling r a t e s g r e a t e r t h a n about 107 ~ p e r s e c . It i s i n t e r e s t i n g to note that t h i s c o m p o s i t i o n i s v e r y c l o s e to a low t e m p e r a t u r e e u t e c t i c in t h e C u - Z r p h a s e d i a g r a m , and h e n c e f i t s one of the c o m p o s i t i o n r e q u i r e m e n t s f o r the f o r m a t i o n of a n o n c r y s t a l l i n e p h a s e . 14 EXPERIMENTAL
METHOD
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RESULTS
The alloy (60 Cu, 40 at. pct Zr) was prepared in the form of small buttons by nonconsumable arc melting of pure van Arkel zirconium (99.99 pct) and pure copper (99.9 pct) under an argon atmosphere in a copper, water-cooled crucible. The buttons were inverted and remelted twice to promote homogenization of the alloy. Chips weighing 50 to 70 mg were cut from the buttons and used for remelting and splat cooling. Rapid que
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