Self-diffusion in substitutional solid solutions with Fcc lattice
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With the use of the r e s u l t s f r o m the p r e v i o u s p a p e r x and f r o m the p a p e r s of the o t h e r a u t h o r s it h a s been a s c e r t a i n e d that in s o m e s o l i d s o l u t i o n s with fcc l a t t i c e the s e l f - d i f f u s i o n f r e q u e n c y f a c t o r DoAB and a c t i v a t i o n e n t h a l p y &HAABof the e l e m e n t A in the a l l o y A - B a r e given by the equations DoAB = Do A exp (KoXB)
AHAB : T m [ AHATm A
KIRXB 1 '
w h e r e Ko, K~ a r e c o n s t a n t s , T m and TmA a r e m e l t i n g p o i n t s of the a l l o y o r of e l e m e n t A r e s p e c t i v e l y , XB is the a t o m i c p e r c e n t of e l e m e n t B, Do A and ~d/~ a r e diffusion c h a r a c t e r i s t i c s of the p u r e e l e m e n t A. F o r the f r e q u e n c y f a c t o r of r e g u l a r o r n e a r l y r e g u l a r s o l i d s o l u t i o n s with fcc l a t t i c e t h a t p r e s e n t a m u t u a l s o l u b i l i t y and for which the diffusion d a t a for the whole c o n c e n t r a t i o n i n t e r v a l a r e a v a i l a b l e , the following r e l a t i o n has b e e n found DoAB
= (Do~)XA/IO0 . (DoAB)XB/IO0
F o r the a c t i v a t i o n e n t h a l p y of t h e s e s o l u t i o n s the equation AHAB = ~Tm
LTmA[AHAxA+ T---~-B xBAHBA]
is s a t i s f i e d , w h e r e DoBA and AHB A a r e the c h a r a c t e r i s t i c s of h e t e r o d i f f u s i o n of e l e m e n t A in e l e m e n t B and TmB is the m e l t i n g point of e l e m e n t B.
IN
the p r e v i o u s p a p e r x the E q s . [7] and [8] for c o n c e n t r a t i o n d e p e n d e n c e of d i f f u s i o n c h a r a c t e r i s t i c s ( f r e q u e n c y f a c t o r and a c t i v a t i o n e n t h a l p y ) have b e e n found. Eqs. [7] and [8] have a m o r e c o m m o n c h a r a c t e r than e.g. the r e l a t i o n given b y R o w l a n d and N a c h t r i e b a and it is p o s s i b l e to c o m b i n e t h e m into one equation Cu Cu log DCuAI(XA1, aTm) = log Dcu(aTmcu) + kXAl [1] in which a = T/T m is a n u m b e r f r o m the i n t e r v a l (1, 0) and k = (0.016 • 0.001)(at. p e t A1)-1 is a t e m p e r a t u r e i n dependent experimental constant. In m a n y b i n a r y s o l i d s o l u t i o n s , h o w e v e r , for which d i f f u s i o n c h a r a c t e r i s t i c s have b e e n m e a s u r e d in a wide c o n c e n t r a t i o n i n t e r v a l , t h e r e can b e found such s o l u tions which do not r e s p e c t the s i m p l e r e l a t i o n [1], e.g. A g - A u 3 and o t h e r s . The a i m of the p r e s e n t p a p e r is to obtain m o r e g e n e r a l r e l a t i o n s which m a k e it p o s s i b l e to c a l c u l a t e d i f fusion c h a r a c t e r i s t i c s e.g. of e l e m e n t A in a s o l i d s o lution A - B using the c h a r a c t e r i s t i c s of s e l f - d i f f u s i o n o r h e t e r o d i f f u s i o n of e l e m e n t A in A o r in B, r e s p e c t i v e l y . The r a t h e r g r e a t n u m b e r of e x p e r i m e n t a l d a t a c o n c e r n i n
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