• PDF / 227,427 Bytes
• 2 Pages / 612 x 792 pts (letter) Page_size
• 11 Downloads / 238 Views

DOWNLOAD

REPORT

---

60

Effect of Solutes on Preferred Orientation in High-Purity Aluminum R. V. B E L L U Z and K. T. AUST P r e v i o u s s t u d i e s i n d i c a t e that the d e v e l o p m e n t of p r e f e r r e d o r i e n t a t i o n s of the c o i n c i d e n c e s i t e type in r e c r y s t a U i z e d , z o n e - r e f i n e d l e a d and c o p p e r i s d e p e n dent upon the type and a m o u n t of s o l u t e a d d i t i o n s . 1 T h i s o b s e r v a t i o n w a s i n t e r p r e t e d in t e r m s of the b o u n d a r y c o i n c i d e n c e m o d e l ~ and a s e l e c t i v e b o u n d a r y s o l u t e i n t e r a c t i o n , l e a d i n g to g r a i n b o u n d a r y m o b i l i t y d i f f e r e n c e s with i n c r e a s i n g d e v i a t i o n f r o m i d e a l c o i n c i d e n c e o r i e n t a t i o n s . ~ In addition, m a n y of the c o i n c i dence r e l a t i o n s h i p s o b t a i n e d d u r i n g the a n n e a l i n g of the l e a d and c o p p e r w e r e i n t r o d u c e d into the s p e c i m e n s when twinning o c c u r r e d d u r i n g g r a i n b o u n d a r y m i g r a t i o n . 1 The d r i v i n g e n e r g y f o r t h i s twinning p r o c e s s i s due to the l o w e r i n t e r r a c i a l e n e r g y of the " i d e a l " c o i n c i d e n c e b o u n d a r i e s a s c o m p a r e d to o t h e r g r a i n b o u n d a r i e s which d e v i a t e f r o m the i d e a l c o i n cidence orientations. 3 The p r e s e n t e x p e r i m e n t s w e r e c o n d u c t e d using z o n e r e f i n e d a l u m i n u m , with and without s o l u t e a d d i t i o n s , in o r d e r t o m i n i m i z e the r o l e of twinning on growth s e l e c t i v i t y and, t h e r e b y , l a r g e l y d e t e r m i n e the effect of s o l u t e s a l o n e . Although twinning and the r e s u l t i n g f o r m a t i o n of c o i n c i d e n c e b o u n d a r i e s d u r i n g b o u n d a r y m o t i o n have b e e n o b s e r v e d in z o n e - r e f i n e d a l u m i n u m , 4 t h e i r o c c u r r e n c e p a r t i c u l a r l y in doped A1 i s much l e s s than f o r z o n e - r e f i n e d Pb o r Cu~ The s t a r t i n g m a t e r i a l w a s h i g h - p u r i t y a l u m i n u m zone r e f i n e d to a p u r i t y of 99.9999 pct, a s d e t e r m i n e d f r o m s p e c t r o g r a p h i c a n a l y s i s and e l e c t r i c a l r e s i s t i v i t y m e a s u r e m e n t s . V a r i o u s a m o u n t s of Sn, Cu, o r Ti w e r e a d d e d in c o n c e n t r a t i o n s of 5, 10, 50 and 100 p p m b y weight. The s p e c i m e n s w e r e in the f o r m of single c r y s t a l s , about 0.6 c m sq and and 12.5 c m . long, grown f r o m the m e l t in h o r i z o n t a l , h i g h - p u r i t y g r a p h i t e b o a t s . The c r y s t a l s w e r e g r o w n u n d e r v a c u u m (10 -s t o r r ) a t a r a t e of 0.6 o m . p e r min, p r o d u c i n g l i n e a g e o r s t r i a t i o n substructure. Recrystallized, lineage-free grains w e r e i n t r o d u c e d into one end of the s t r i a t e d c r y s t