Tensile deformation of polycrystalline beta prime-AuZn
- PDF / 750,158 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 51 Downloads / 190 Views
The t e n s i l e d e f o r m a t i o n b e h a v i o r of the i n t e r m e t a l l i c compound AuZn h a s b e e n i n v e s t i g a t e d o v e r a r a n g e of t e m p e r a t u r e , c o m p o s i t i o n , and g r a i n s i z e . P o l y c r y s t a l l i n e AuZn was found to b e h a v e in a d u c t i l e m a n n e r o v e r the t e m p e r a t u r e r a n g e 77 ~ to 533~ and the c o m p o s i t i o n r a n g e 48.0 to 52.0 at. pct Au, e x c e p t for the a l l o y s containing l e s s than 49.5 at. pct Au at 77~ which w e r e b r i t t l e . The y i e l d s t r e s s and flow s t r e s s w e r e found to i n c r e a s e l i n e a r l y with dev i at i o n f r o m s t o i c h i o m e t r y over the t e m p e r a t u r e r an g e 133 ~ to 463~ A r e g i o n of t e m p e r a t u r e independent w o r k h a r d e n i n g was o b s e r v e d for al l c o m p o s i t i o n s at t e m p e r a t u r e s b e l o w 300~ The n o n s t o i c h i o m e t r i c a l l o y s d i s p l a y e d a s h a r p i n c r e a s e in w o r k h a r d e n i n g r a t e at t e m p e r a t u r e s b e l o w 150~ a l s o . In addition to the p r e v i o u s l y a c c e p t e d slip on the {110}(001> s y s t e m , slip on the {211}(111> s y s t e m has b e e n p o s t u l a t e d to a c c o u n t f o r the o b s e r v e d d u ct i l i t y and high w o r k h a r d e n i n g r a t e . T H E p l a s t i c d e f o r m a t i o n of C s C l - t y p e i n t e r m e t a l l i c c o m p o u n d s has b e e n the s u b j e c t of s e v e r a l i n v e s t i g a ti o n s in r e c e n t y e a r s , 1-a p a r t i c u l a r l y with r e s p e c t to the f a c t o r s d e t e r m i n i n g the d u c ti li ty and flow s t r e s s c h a r a c t e r i s t i c s at t e m p e r a t u r e s b e l o w 0.45 Tin, w h e r e T m is the m e l t i n g point. The ductility has b e e n r e l a t e d to s e v e r a l f a c t o r s , such a s the o p e r a t i v e s l i p s y s t e m s 2 9 and the c o m p o s i t i o n . R a c h i n g e r and C o t t r e l l 9 found that i n t e r m e t a l l i c compounds which had a low bonding e n e r g y w e r e m e t a l l i c in n a t u r e and e x h i b i t e d s l i p in the (111) d i r e c t i o n and thus w e r e duct i l e , e . g . , AgMg and ~3-CuZn. On the o t h e r hand, c o m pounds which had a high bonding e n e r g y w e r e ionic in n a t u r e and e x h i b i t e d s l i p in the (001> d i r e c t i o n , and t h u s , s i n c e they f a i l e d to s a t i s f y the von M i s e s c r i t e r i o n , 1~ w e r e b r i t t l e , e . g . , NiA1, AuCd, and AuZn. Subsequent w o r k h a s v e r i f i e d the o b s e r v a t i o n s f o r AgMg and /3-CuZn. H o w e v e r , c o n t r o v e r s y e x i s t s conc e r n i n g NiA1, with the (001> slip d i r e c t i o n b e i n g d o cu mented3,7,11 and the (111 > slip d i r e c t i o n in dispute.12 The p r e s e n t w o r k was c a r r i e d out to i n v e s t i g a t e the p r e d i c t i o n m a d e f o r p o l y c r y s t a l l i n e AuZn. R a c h i n g e r and C o t t r e
Data Loading...
