Crystallization of amorphous Fe- P- C alloys
- PDF / 4,141,672 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 85 Downloads / 239 Views
TRANSACTIONS A
out c o r r e s p o n d i n g T E M o b s e r v a t i o n s . A g e n e r a l i z e d t r a n s f o r m a t i o n s e q u e n c e w a s s u g g e s t e d by M a s u m e t o et a l 2'11 f o r s e v e r a l d i f f e r e n t a l l o y s . H o w e v e r , t r a n s f o r m a t i o n s e q u e n c e s w h i c h d e p e n d on a l l o y c o m p o s i t i o n w e r e r e p o r t e d by K S s t e r et a l , 8'9 C h e n et a l 6 a n d C h o u et a l . 7 T h e s e d i s a g r e e m e n t s m a y s t e m f r o m the f o l l o w i n g c a u s e s . F i r s t , the t r a n s f o r m a t i o n s e q u e n c e v a r i e s f o r d i f f e r e n t a l l o y s . S e c o n d , t h e r e a r e not enough d a t a f o r m a k i n g a g e n e r a l conclusion, as t h e c o m p l e t e set o f r e s u l t s s h o u l d at l e a s t include r a n g e s o f c o m p o s i t i o n s , a n d a n n e a l i n g t e m p e r a t u r e s a n d DSC, T E M , and XRD r e s u l t s for corresponding phase c h a n g e s . T h i r d , the a s - q u e n c h e d s a m p l e s m a y not be completely homogeneous; m i c r o - or macroscopic inh o m o g e n e i t i e s m a y e x i s t .23'24 T h e s e h e t e r o g e n e i t i e s c o u l d a c c o u n t f o r s o m e d i f f e r e n c e s i n the b e h a v i o r r e p o r t e d by d i f f e r e n t w o r k e r s o n t h e s a m e a l l o y s . T h e c u r r e n t i n v e s t i g a t i o n is a n a t t e m p t to u n d e r s t a n d b e t t e r the n a t u r e of c r y s t a l l i z a t i o n in F e - P - C a m o r p h o u s a l l o y s a s w e l l a s c o m p o s i t i o n a l e f f e c t s on crystallization. F e - b a s e d alloys were s e l e c t e d bec a u s e of t h e i r i n t e r e s t i n g m e c h a n i c a l a n d m a g n e t i c properties. T h e crystallization of F e - P - C alloys has been inv e s t i g a t e d by R a s t o g i a n d D u w e z25 a n d M a s u m o t o a n d K i m u r a .26 Upon a n n e a l i n g , t h e s a m p l e t r a n s f o r m s t o v a r i o u s i n t e r m e d i a t e c r y s t a l l i n e p h a s e s a n d then t o the s t a b l e a F e , F e 3 P , a n d F e a C p h a s e s . T h e m a g n i t u d e of t h e h e a t of c r y s t a l l i z a t i o n i s a b o u t 5.0 t o 5.4 k J mo1-1 (1.2 t o 1.3 k c a l t o o l - l )21 f o r d i f f e r e n t c o m p o s i tions. T h e crystallization sequence a n d t h e " T T T " d i a g r a m w e r e s u g g e s t e d f o r the Fes0P~3C7 a l l o y by M a s u m o t o et a l . 2 I n t h i s s t u d y the i n t e r m e d i a t e s t a g e w a s b c c c~Fe. T h e FeT~Pl~Clo a l l o y s t u d i e d by R a s t o g i a n d D u w e z , h o w e v e r , t r a n s f o r m e d to F e ~ P m e t a s t a b l e p h a s e i n s t e a d of a F e . B e s i d e s t h e d i f f e r e n c e i n t r a n s f o r m e d m e t a s t a b l e p h a s e s , the DSC c u r v e s r e p o r t e d f o r FesoPlaC~ by M a s u m o t o a n d K i m u r a26 w e r e d i f f e r e n t f r o m t h o s e f o r FeaoPlaC7 ( R e f . 2) a n d FeT~P~s Clo. 2~ T h
Data Loading...
