The effect of electron concentration on the thermodynamic properties of two alloy phases in the Al-Zn-Ag system
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I T has long been the d e s i r e of solid state s c i e n t i s t s to explain in a f u n d a m e n t a l m a n n e r the a t o m i c i n t e r a c t i o n s which take place when a n u m b e r of a t o m s a r e brought c l o s e l y t o g e t h e r . T h i s p r o b l e m is even m o r e difficult to u n d e r s t a n d when m o r e than one a t o m i c s p e c i e s is p r e s e n t . With p u r e e l e m e n t s , a s with a l l o y s , a g r e a t effort, both e x p e r i m e n t a l and t h e o r e t i c a l , has b e e n expended to gain a b e t t e r u n d e r s t a n d i n g of these basic atomic interactions. H u m e - R o t h e r y and his c o w o r k e r s 1-3 w e r e a m o n g the f i r s t to optline the v a r i o u s f a c t o r s which d e t e r m i n e a l l o y phase s t a b i l i t y . The effect of the c o n t r i b u t i o n of e l e c t r o n s in the c o n d u c t i o n band was r e c o g n i z e d by noting that a n u m b e r of s o l u b i l i t y l i m i t s o c c u r r e d at a p p r o x i m a t e l y the s a m e e l e c t r o n c o n c e n t r a t i o n . Syst e m s in which the phase s e q u e n c e and c o r r e s p o n d i n g s o l u b i l i t y r a n g e s a p p e a r e d to be functions of e l e c t r o n c o n c e n t r a t i o n were t e r m e d " e l e c t r o n p h a s e s " . A t h e o r e t i c a l e x p l a n a t i o n was i n i t i a l l y p r o v i d e d by H. J o n e s , 4-8 the r e s u l t s of which have b e e n i n c o r p o r a t e d in the r i g i d - b a n d t h e o r y of a l l o y s . T h i s e a r l y theory has s i n c e b e e n modified 7-9 but s t i l l f u n c t i o n s a s a q u a l i t a t i v e guide to thinking in this a r e a . Howe v e r , whether the c u r r e n t e l e c t r o n t h e o r i e s p r o v e to be adequate d e s c r i p t i o n s of r e a l alloy s y s t e m s o r not, it m a y be concluded that if e l e c t r o n i c e n e r g y is an i m p o r t a n t p a r a m e t e r i n a l l o y s t a b i l i t y it m u s t have t h e r m o d y n a m i c c o n s e q u e n c e s . This is t r u e b e c a u s e the r e l a t i v e s t a b i l i t y of the e q u i l i b r i u m p h a s e s is d e RONALD E. MILLER and JERRY L. STRAALSUND,formerly Graduate Students, Metallurgy Department, WashingtonState University, Pullman, Wash., are now Assistant Professor, Department of Metallurgicaland Mineral Engineeringat the University of Wisconsin, Madison, Wisc.;and Senior Research Scientist, WADCO,Richland, Wash., respectively. D. BRUCE MASSON is Professor of Metallurgy at WashingtonState University. This paper constituted a portion of the theses submitted by RONALD E. MILLER and JERRY L. STRAALSUND in partial fulfillment of the requirements of the degree of Doctor of Philosophy in Engineering Science at Washington State University. Manuscript submitted April 1, 1971. METALLURGICALTRANSACTIONS
t e r m i n e d by the Gibbs f r e e e n e r g y of those p h a s e s . T h u s , any f a c t o r which c o n t r i b u t e s to the s t a b i l i t y of a phase m u s
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