The Er-Rh system
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EXPERIMENTAL
PROCEDURE
The experimental procedure adopted in this study i s n e a r l y the s a m e a s u s e d in p r e v i o u s s t u d i e s of a n a l o g o u s s y s t e m s and can be r e f e r r e d to e a s i l y . 1,3 We u s e d e r b i u m and r h o d i u m of 99.9+ p c t and 99.92+ p c t p u r i t y , r e s p e c t i v e l y . The a r c - m e l t e d a l l o y s w e r e w r a p p e d in m o l y b d e n u m f o i l s and a n n e a l e d at v a r i o u s t e m p e r a t u r e s ( i n d i c a t e d in the p h a s e d i a g r a m , F i g . 1) H. GHASSEM, formerly Graduate Student, Department of Engineering Science, Louisiana State University, Baton Rouge, La. 70803, is now with the Iranian Oil Co., Teheran,/ran. A. RAMAN is Associate Professor, Department of Engineering Science, Louisiana State Univeristy. Manuscript submitted May 31, 1972. METALLURGICAL TRANSACTIONS
in e v a c u a t e d q u a r t z c a p s u l e s . A n n e a l i n g t i m e s v a r i e d g e n e r a l l y b e t w e e n 4 d and 1 w e e k , the l o n g e r t i m e s being c h o s e n for the a n n e a l s at low t e m p e r a t u r e s below 900~ P o w d e r X - r a y d i f f r a c t i o n p a t t e r n s of the a l l o y s in the a s - c a s t and a n n e a l e d c o n d i t i o n s w e r e t a k e n in a G u i n i e r - d e Wolff f o c u s s i n g c a m e r a with m o n o c h r o m a t i c CuK~ X - r a y s . T h e s e p h o t o g r a p h s w e r e u s e d to identify the p h a s e e q u i l i b r i a and the c r y s t a l s t r u c t u r e s of p h a s e s in the a l l o y s . S u i t a b l e c o r r e c t i o n s to the sin20 v a l u e s of the l i n e s w e r e a p p l i e d e m p l o y i n g a c o r r e c t i o n c u r v e which was g e n e r a t e d f r o m the d a t a of highly p u r e zinc and a n t i m o n y o b t a i n e d under similar conditions. D i f f e r e n t i a l t h e r m a l a n a l y s i s of the a l l o y s w a s c a r r i e d out in v a c u u m in a D T A - 6 6 8 Stone d i f f e r e n t i a l t h e r m a l a n a l y z e r . The r e a c t i o n t e m p e r a t u r e s a t t a i n e d f r o m the p e a k s w e r e c o r r e c t e d f o r e r r o r s using a c a l i b r a t i o n c u r v e g e n e r a t e d f r o m the e x p e r i m e n t a l d a t a of highly p u r e P b , A1, F e ( ~ ~ 7 t r a n s f o r m a t i o n ) , Cu, and Si u n d e r s i m i l a r c o n d i t i o n s . The a r r e s t t e m p e r a t u r e s d e n o t e d in F i g . 1 a r e judged to be a c c u r a t e to • 10~ M e t a l l o g r a p h i c e x a m i n a t i o n of the a l l o y s in the a s - c a s t and a n n e a l e d c o n d i t i o n s s u p p l e m e n t e d the X - r a y and the DTA findings. RESULTS E i g h t i n t e r m e d i a t e p h a s e s w e r e e n c o u n t e r e d in t h i s s y s t e m , i n c l u d i n g the f o u r which w e r e known a l r e a d y . T h e i r c r y s t a l s t r u c t u r a l d a t a a r e c o m p i l e d in T a b l e I. B a s e d on the r e s u l t s of the e x p e r i m e n t a l d a t a a f i r s t e q
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