Calculation of superalloy phase diagrams: Part I
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p u b l i c a t i o n s in t h i s s e r i e s 1-6 have e m p h a s i z e d the p r a c t i c a l a d v a n t a g e s which could r e s u l t f r o m e x p l i c i t d e f i n i t i o n of the f r e e e n e r g y of s o l u t i o n and compound p h a s e s in m e t a l l i c s y s t e m s , in t e r m s of the l a t t i c e s t a b i l i t y , s o l u t i o n and c o m pound p a r a m e t e r s . The p r e s e n t s e r i e s of p a p e r s i s d e s i g n e d to i l l u s t r a t e t h e s e a d v a n t a g e s by c a l c u l a t i n g s i g n i f i c a n t n u m b e r s of i s o t h e r m a l s e c t i o n s in i m p o r tant t e r n a r y s u p e r a l l o y s y s t e m s f r o m the l a t t i c e s t a b i l i t y , s o l u t i o n and compound p a r a m e t e r s d e r i v e d p r e v i o u s l y f o r p u r e m e t a l s and b i n a r y s y s t e m s . The c a l c u l a t i o n s w e r e c a r r i e d out along the l i n e s d e s c r i b e d using the l a t t i c e s t a b i l i t y d a t a a l r e a d y r e p o r t e d 1'3 along with the p u b l i s h e d d e s c r i p t i o n s of the following b i n a r y s y s t e m s . T h e s e f o r m u l a t i o n s p r o v i d e e x p l i c i t m a t h e m a t i c a l d e s c r i p t i o n s of the e x c e s s f r e e e n e r g i e s of a l l the s o l u t i o n p h a s e s in the b i n a r y s y s t e m s of i n t e r e s t . The l a t t e r a r e c o m b i n e d with l a t t i c e s t a b i l i t y and fusion d a t a to p r o v i d e the b e s t p o s s i b l e d e s c r i p t i o n of e x p e r i m e n t a l t h e r m o c h e m i c a l and p h a s e d i a g r a m d a t a . The following l i s t c i t e s the r e f e r e n c e s o u r c e s f o r the b i n a r y s y s t e m s noted: C r - N i , C r - F e , N i - F e , C o - F e , C o - N i and C o C r ; 3 N i - C b ; 2,s N i - M o , C r - M o , C b - M o and N i - T i 5 and T i - C r . 4 T h r e e - p h a s e f i e l d s a r e l o c a t e d by the i n t e r s e c t i o n of r e l e v a n t t w o - p h a s e f i e l d s . 1 The t e r n a r y s y s t e m s c o n s i d e r e d w e r e c o m p a r e d with l i m i t e d e x p e r i m e n t a l d a t a a s i n d i c a t e d below, C r - N i - F e , 7 C o - F e - N i , 8 C o - C r - F e and C o - C r - N i , 9 N i - C r - M o , 1~ N i - C b - M o 11 and N i - T i - C r.12 I. RESULTS
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As i n d i c a t e d in r e c e n t s t u d i e s 2-s the e x c e s s f r e e e n e r g y of m i x i n g of the s o l u t i o n p h a s e s i s c u r r e n t l y b e i n g d e s c r i b e d f o r the /3 p h a s e in the i-j s y s t e m by Eq. [1] FIlE = (1 - x)[(1 - x)g[T] + xh[T]] c a l / g . a t .
the b i n a r y s y s t e m s of i n t e r e s t . T h e s e functions gene r a t e the p h a s e d i a g r a m s of the b i n a r y s y s t e m s in q u e s t i o n a s w e l l a s the o b s e r v e d t h e r m o c h e m i c a l p r o p e r t i e s . The t e r n a r y solution p h a s e d e s c r i p t i o n s a r e d e r i v e d f r o m the b i n a r y c o m p o n
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