Steady-state electrotransport of carbon in nickel and in nickel-copper and iron-copper alloys
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KABE, formerly Postdoctoral Fellow, Department of Metallurgical and Materials Engineering, University of Florida, GainesviUe, Florida, is now Assistant Professor of Dental Materials, Department of Restorative Dentistry, School of Dentistry, Medical College of Georgia, Augusta, Ga. 30902. A. G. GUY is Professor, Department of Materials Science and Engineering, University of Florida, GainesviUe, Fla. 32611. Manuscript submitted May 13, 1974. METALLURGICAL TRANSACTIONS A
EXPERIMENTAL
METHOD
The e x p e r i m e n t a l m e t h o d u s e d in t h i s i n v e s t i g a t i o n was i d e n t i c a l with that d e s c r i b e d p r e v i o u s l y , x An i m p o r t a n t f a c t o r in d e s i g n i n g an e x p e r i m e n t is the choice of c a r b o n content such that the c a r b o n d i s t r i b u t i o n a f t e r e l e c t r o t r a n s p o r t r e m a i n s within the s o l u b i l i t y l i m i t . To f a c i l i t a t e c o m p a r i s o n with the p r e v i o u s d a t a on s t e a d y - s t a t e e l e c t r o t r a n s p o r t of c a r b o n in a u s t e n i t e , an i n i t i a l u n i f o r m c a r b o n c o n c e n t r a t i o n of about 0.1 wt pet was e m p l o y e d both in the n i c k e l and in the n i c k e l - c o p p e r and i r o n - c o p p e r a l l o y s . The s o l u b i l i t y l i m i t at 1273 K is about 0.23 wt p c t c a r b o n in n i c k e l , B 0.18 vet pct in a n i c k e l - 2 0 c o p p e r a l l o y , 7 and p r o b a b l y c o n s i d e r a b l y h i g h e r in an i r o n - 7 c o p p e r a l l o y . The n i c k e l and i r o n u s e d in t h i s r e s e a r c h w e r e v a c u u m melted metals received from Materials Research Corporation. Their analysis (supplied by Materials R e s e a r c h C o r p o r a t i o n ) a r e given in T a b l e I. The n i c k e l - c o p p e r a l l o y was p r e p a r e d b y m e l t i n g the p u r e m e t a l s under h e l i u m in a f u s e d a l u m i n a c r u c i b l e in a m o l y b d e n u m r e s i s t a n c e f u r n a c e . The i r o n c o p p e r a l l o y s w e r e m a d e in an e l e c t r o n - b o m b a r d m e n t f u r n a c e in a v a c u u m a t m o s p h e r e (1.3 to 4.0 • 10 -s Pa). In both c a s e s 99.999 p u r e c o p p e r f r o m A. D. M a c k a y Inc. was used. The c a s t a l l o y s w e r e c o l d r e d u c e d 60 pot and then a n n e a l e d at 1273 K f o r 100 h to i m p r o v e h o m o g e n e i t y . S a t i s f a c t o r y h o m o g e n e i t y was c o n f i r m e d b y e x a m i n a t i o n in the e l e c t r o n m i c r o p r o b e a n a l y z e r . M i c r o s c o p i c e x a m i n a t i o n c o n f i r m e d that no s e c o n d p h a s e was p r e s e n t . Quantitative a n a l y s e s of c o p p e r content b y the e l e c t r o n m i c r o p r o b e a n a l y z e r gave 20.0 wt p c t c o p p e r in the n i c k e l - c o p p e r a l l o y and 7.2 wt pct in the i r o n - c o p p e r a l l o y . The a b s e n c e of a s e c o n d p h a s e in the F e - 7 . 2 wt pct Cu a l l o y a g r e e s with the p h a s e d i a
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