General method of phase analysis for individual multicomponent alloys
- PDF / 583,063 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 9 Downloads / 210 Views
C o n s t r u c t i o n of a c o m p l e t e p h a s e d i a g r a m f o r a 5- (or h i g h e r - ) c o m p o n e n t s y s t e m is s o t i m e c o n s u m i n g a s to be i m p r a c t i c a l at p r e s e n t . The usual type of i n f o r m a t i o n about the p h a s e s p r e s e n t , t h e i r c o m p o s i t i o n s , and t h e i r a m o u n t s can be obtained for a p a r t i c u l a r C - c o m p o n e n t a l l o y by the p r e s e n t method" C is the n u m b e r of c o m p o n e n t s and m a y be a s l a r g e a s d e s i r e d . The a l l o y is b r o u g h t to an e s s e n t i a l l y e q u i l i b r i u m condition at the t e m p e r a t u r e of i n t e r e s t , and the c o m p o s i t i o n s of the p h a s e s a r e d e t e r m i n e d by a s u i t a b l e technique; for e x a m p l e , by e l e c t r o n b e a m - m i c r o p r o b e a n a l y s e s of the quenched s p e c i m e n . The g e n e r a l i z e d l e v e r law, in d e t e r m i n a n t f o r m , is used to d e t e r m i n e the a m o u n t s of the p h a s e s . R e p e t i t i o n of this a n a l y s i s at a s e c o n d t e m p e r a t u r e in the s a m e p h a s e r e g i o n p e r m i t s i d e n t i f i c a t i o n of the t y p e of v a r i a n t r e a c t i o n ( p s e u d o e u t e c t i c , and s o forth) that is o ~ c u r r i n g . F o r i n v a r i a n t r e a c t i o n s , a technique such a s q u a n t i t a t i v e m e t a l l o g r a p h y is e m p l o y e d to d e t e r m i n e the a m o u n t s of the p h a s e s at an e a r l y and a l a t e s t a g e in the r e a c t i o n . The type of r e a c t i o n (eutectic, q u a s i p e r i t e c t i c , and so forth) c a n then be d e t e r m i n e d . F r o m e x p e r i m e n t a l d a t a on a l l o y E an e s t i m a t e can be m a d e of two a s p e c t s of the b e h a v i o r of a n e i g h b o r i n g c o m p o s i t i o n , a l l o y N; 1) liquidus t e m p e r a t u r e , and 2) i n v a r i a n t r e a c t i o n . T h e r m o d y n a m i c p r o c e d u r e s should p e r m i t useful e x t e n s i o n s of the p r e s e n t m e t h o d . A t y p i c a l p r o b l e m in m o d e r n m a t e r i a l s s c i e n c e is to d e t e r m i n e the b e h a v i o r d u r i n g s o l i d i f i c a t i o n and a s a r e s u l t of p o s s i b l e s o l i d - s t a t e r e a c t i o n s of a s p e c i f i c C - c o m p o n e n f a l l o y . H e r e C is the n u m b e r of c o m p o n e n t s : a t y p i c a l 5 - c o m p o n e n t a l l o y might be 10 p e t A1, 2 p e t Nb, 30 p e t C r , 10 p e t Mo, and 58 p c t Ni. U s u a l l y one w i s h e s to o b t a i n the kind of i n f o r m a t i o n ( e s s e n t i a l l y that f o r e q u i l i b r i u m c o n d i t i o n s ) given for the u s u a l 2 c o m p o n e n t a h o y by the p h a s e d i a g r a m . Two a p p r o a c h e s to this p r o b l e m a r e i m p r a c t i c a l at p r e s e n t , in both c a s e s b e c a u s e an e x c e s s i v e amount of e x p e r i m e n t a l d a t a would be n e e d e d . The f i r
Data Loading...
