• PDF / 1,288,737 Bytes
• 3 Pages / 612 x 792 pts (letter) Page_size
• 22 Downloads / 232 Views

DOWNLOAD

REPORT

---

Defect Structure in Quenched and Deformed Gold Single Crystals

o p t i c a l m i c r o g r a p h . T h e n , this d i r e c t i o n a l i n f o r m a t i o n was t r a n s f e r r e d to a low m a g n i f i c a t i o n e l e c t r o n m i c r o g r a p h of the hole. As final high m a g n i f i c a t i o n e l e c t r o n m i c r o g r a p h s showing the defect s t r u c t u r e were always taken i m m e d i a t e l y following the low m a g n i f i c a t i o n m i c r o g r a p h , the d i r e c t i o n a l c o r r e l a t i o n a m o n g the t e n s i l e d i r e c t i o n , the slip c r y s t a l l o g r a p h y , and the d i r e c t i o n of the a l i g n e d rows c a n be r e a d i l y m a d e . The i m p o r t a n t f e a t u r e of the s t r u c t u r e is the p r e s ence of the a l i g n e d rows along the (110) type d i r e c t i o n of t e t r a h e d r a l stacking faults i n t e r m i n g l e d with d i s l o cation loops and o t h e r d e f e c t s , F i g s . 1 to 3. No a l i g n e d rows of defects were found by us in an u n d e f o r m e d s p e c i m e n ; thus i n d i c a t i n g that the p l a s t i c d e f o r m a t i o n of the s p e c i m e n , i n t e n t i o n a l , a c c i d e n t a l , o r due to quenching s t r a i n , is r e q u i r e d for the f o r m a t i o n of

M. S. BAPNA AND M. MESHII

IT

is g e n e r a l l y b e l i e v e d that the defect s t r u c t u r e produced in a quenched m e t a l is s t r o n g l y i n f l u e n c e d by the n u c l e a t i o n of v a c a n c y c l u s t e r s . The n u c l e a t i o n a l s o depends s e n s i t i v e l y on quenching conditions and the p u r i t y of the m a t e r i a l . In addition to the r a n d o m d i s t r i b u t i o n of d e f e c t s , the rows of defects along (110) d i r e c t i o n s have been found in a wide v a r i e t y of m a t e r i a l s ; such as a l u m i n u m , ~ a l u m i n u m a l l o y s , 2-5 s i l v e r , ~'4 s i l v e r - t i n a l l o y s , 6 and gold. ~'v-~~ This a l i g n m e n t of the defects is a t t r i b u t e d to the p l a s t i c d e f o r m a t i o n d u r i n g o r a f t e r quenching. ~'~~ Since the i n v e s t i g a t i o n s so f a r w e r e confined to p o l y c r y s t a l l i n e m a t e r i a l s , the r e l a tionship between the a l i g n e d rows and the c r y s t a l l o g raphy of plastic d e f o r m a t i o n were not o b t a i n e d . In this c o m m u n i c a t i o n , s o m e r e s u l t s of the study of s i n g l e c r y s t a l s to identify such r e l a t i o n s h i p s a r e p r e s e n t e d . The p r o c e d u r e of o b t a i n i n g quenched and d e f o r m e d s i n g l e c r y s t a l s has b e e n d e s c r i b e d e l s e w h e r e , n'~2 In o r d e r to avoid u n c o n t r o l l e d c l u s t e r i n g of v a c a n c i e s , the s p e c i m e n s were quickly t r a n s f e r r e d f r o m the quenching bath (-40~ to the liquid n i t r o g e n bath in which the plastic d e f o r m a t i o n was p e r f o r m e d by extending the s p e c i m e n s to about 5 pct