Precipitation of carbides in low-carbon Fe-AI-C alloys
- PDF / 1,110,930 Bytes
- 7 Pages / 613 x 788.28 pts Page_size
- 90 Downloads / 204 Views
T H E effect of s u b s t i t u t i o n a l s o l u t e s on the p r e c i p i t a tion of c a r b o n f r o m or-iron has long b e e n a s u b j e c t of c o n s i d e r a b l e i n t e r e s t . D e s p i t e a n u m b e r of p r e v i o u s s t u d i e s 1-n on the effects of v a r i o u s a l l o y i n g e l e m e n t s we can p r e d i c t in only a v e r y g e n e r a l way how each e l e m e n t will modify the r a t e of p r e c i p i t a t i o n , the type of p r e c i p i t a t e , and the n u c l e a t i o n s i t e s . As d i s c u s s e d previously,2 an alloying element having a higher solubility in the carbide than in ferrite is not likely to have a large effect on the rate of growth of the carbide, although it may govern the structure of the carbide precipitated, the rate of nucleation and the nucleation sites. On the other hand, if the alloying element is essentially insoluble in the carbide, it can have a very large effect on the rate of growth of the carbide. Beyond this, it is still necessary to determine experimentally the effects of each alloying element on the morphology, structure, and rate of growth of carbide particles. Herein we describe the results of a study of the effect of aluminum on the precipitation of carbon from or-iron. Although diffusion of carbon and the rate of precipitation of carbon in Fe-AI-C alloys have been studied by i n t e r n a l f r i c t i o n t e c h n i q u e s ~ , z z and by m a g n e t i c a f t e r - e f f e c t s , lz i t a p p e a r s that t h e r e has b e e n no s y s t e m a t i c study of the effect of a l u m i n u m on the p r e c i p i t a t e s t h e m s e l v e s . To r e m e d y this lack, we used t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y , s u p p l e m e n t e d by m e a s u r e m e n t s of c o e r c i v e f o r c e and yield s t r e n g t h , to det e r m i n e the type of c a r b i d e p r e c i p i t a t e d , its r a t e of growth, and how both type and growth r a t e a r e modified by a l u m i n u m content.
EXPERIMENTAL PROCEDURES The c o m p o s i t i o n s of the alloys a r e l i s t e d in T a b l e I. The i m p u r i t y content given for " B a s e " is that of the P l a s t i r o n A104 e l e c t r o l y t i c i r o n b a s e . The alloys were v a c u u m m e l t e d and cast, hot r o l l e d , cold rolled, heated 4 h at 730~ to d i s s o l v e c a r b i d e s , then quenched W. C. LESLIE is Professor of Materials Engineering,University of Michigan, Ann Arbor, MI 48109 and G. C. RAUCHis Senior Engineer with the Magnetics Department, R & D Center, WestinghouseElectric Corporation, Pittsburgh, PA 15235. The work was done while the authors were employed at the E. C. Bain Laboratory, U.S. Steel Corporation. Manuscript submitted April 29, 1977. METALLURGICALTRANSACTIONSA
into iced b r i n e c o n t a i n i n g 10 pct NaC1 and 1 pct NaOH. A l l s p e c i m e n s had a v i r t u a l l y i d e n t i c a l g r a i n s i z e of about ASTM No. 6. T h e r e was no e v i d e n c e of u n d i s solved c a r b i d e s or p r e c
Data Loading...
