An electron microscopy examination of primary recrystallization in TD-nickel
- PDF / 3,049,613 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 70 Downloads / 191 Views
PETROVIC AND L . J .
EBERT
P r i m a r y r e c r y s t a l l i z a t i o n in T D - n i c k e l 1 in. b a r has p r e v i o u s l y b e e n r e g a r d e d a s the p r o c e s s by which the i n i t i a l fine g r a i n s t r u c t u r e (1 p a v e r a g e g r a i n r a d i u s ) is c o n v e r t e d to a c o a r s e g r a i n s i z e ( i n c r e a s e s in g r a i n s i z e by 500 t i m e s ) u n d e r s u i t a b l e d e f o r m a t i o n and a n n e a l i n g c o n d i t i o n s . T h i s p r o c e s s i s dependent on d e f o r m a t i o n mode. While it o c c u r s r e a d i l y a f t e r r o l l i n g t r a n s v e r s e to the b a r a x i s and a n n e a l i n g (800~ it i s c o m p l e t e l y i n h i b i t e d by l o n g i t u d i n a l r o l l i n g and swaging d e f o r m a t i o n s , even for v e r y high (1320~ a n n e a l i n g t e m p e r a t u r e s . A t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y e x a m i n a t i o n of d e f o r m a t i o n and a n n e a l i n g s u b s t r u c t u r e s i n d i c a t e s that p r i m a r y r e c r y s t a l l i z a t i o n in T D - n i c k e l 1 in. b a r a c t u a l l y occ u r s on the s u b - l i g h t optical l e v e l , to p r o d u c e a g r a i n s t r u c t u r e s i m i l a r in size to the i n i t i a l fine g r a i n e d s t a t e . C o a r s e g r a i n f o r m a t i o n i s the r e s u l t of a b n o r m a l g r a i n growth (or s e c o n d a r y r e c r y s t a l l i z a f i o n ) , which follows p r i m a r y r e c r y s t a l l i z a t i o n .
PRIMARYr e c r y s t a l l i z a t i o n in T D - n i c k e l
1 in. b a r has g e n e r a l l y been r e p o r t e d a s the p r o c e s s by which the i n i t i a l fine (1 p a v e r a g e g r a i n r a d i u s ) g r a i n s t r u c t u r e i s c o n v e r t e d to a c o a r s e g r a i n s i z e by d e f o r m a t i o n a n d a n n e a l i n g . I n c r e a s e s in g r a i n s i z e by 500 t i m e s f r o m the i n i t i a l state d u r i n g this p r o c e s s a r e not u n c o m m o n . However, d e t a i l s of the r e c r y s t a l l i z a t i o n b e h a v i o r of T D - n i c k e l v a r y to an u n u s u a l d e g r e e in the l i t e r a t u r e . 1-12 T h i s a p p e a r s a t t r i b u t a b l e , in p a r t , to d i f f e r e n c e s in f a b r i c a t i o n h i s t o r y of the m a t e r i a l u s e d by v a r i o u s w o r k e r s (e.g. b a r o r sheet m a t e r i a l ) . Doble 13 has r e v e a l e d a highly u n u s u a l c h a r a c t e r i s t i c of r e c r y s t a l l i z a t i o n in T D - n i c k e i , which m a y f u r t h e r explain s o m e of the v a r i a n c e in the l i t e r a t u r e . He found t h i s m a t e r i a l to be s e n s i t i v e to mode of p r i o r d e f o r m a t i o n . F o r 1 in. b a r stock, r e c r y s t a l l i z a t i o n to a c o a r s e g r a i n s i z e o c c u r r e d r e a d i l y (800~ a f t e r r o l l i n g d e f o r m a t i o n , if the r o l l i n g d i r e c t i o n was t r a n s v e r s e to the b a r a x i s (roiling p l
Data Loading...
