Some observations on carbide precipitation and grain boundary migration in a duplex stainless steel
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Some Observations on Carbide Precipitation and Grain Boundary Migration in a Duplex Stainless Steel C. S. TEDMON, JR. AND D. A. VERMILYEA
BOTH continuous and d i s c o n t i n u o u s (cellular) p r e c i p i t a t i o n at g r a i n b o u n d a r i e s of the c a r b i d e M23Co have been r e p o r t e d in a u s t e n i t i c a l l o y s . Kotval and Hatwell 1 o b s e r v e d that in W a s p a l l o y , a c o m m e r c i a l nickel-base superalloy, discontinuous precipitation o c c u r r e d if the alloy was h e a t - t r e a t e d to produce l a r g e s u p e r s a t u r a t i o n , but u n d e r conditions of low s u p e r s a t u r a t i o n , c o n t i n u o u s p r e c i p i t a t i o n took place with the g r a i n b o u n d a r y c a r b i d e s a s s u m i n g a g l o b u l a r morphology. Lewis and H a t h e r s l e y 2 have o b s e r v e d what a p p e a r e d to be the e a r l y s t a g e s of d i s c o n t i n u o u s p r e c i p i t a t i o n of M2sC6 at g r a i n b o u n d a r i e s in a u s t e n i t i c s t a i n l e s s s t e e l s . Singhal and M a r t i n 3 s t u d i e d c a r b i d e p r e c i p i t a t i o n in an a u s t e n i t i c s t a i n l e s s s t e e l and o b s e r v e d that g r a i n b o u n d a r y m i g r a t i o n o c c u r r e d d u r i n g the growth of the c a r b i d e . They cited the model of Tu and T u r n b u l l 4 as a m e c h a n i s m by which the b o u n d a r y could m i g r a t e , but f a i l e d to o b s e r v e the C. S. TEDMON, JR. and D. A. VERMILYEAare Metallurgists,General Electric Research and Development Center, Schenectady, N. Y. Manuscript submitted January 19, 1970. METALLURGICALTRANSACTIONS
(d) G129. The e x p e r i m e n t a l work was p e r f o r m e d at the Catholic U n i v e r s i t y of A m e r i c a , W a s h i n g t o n , D.C. 1. V. S. Mes'kinand E. A. Al'ftan:Fiz. Metal. i Metalloved., 1961,vol. 11, no. 4, pp. 533-44. 2 H. V. Fairbanksand F. J. Dewez,Jr.: Ind. Eng. Chem., 1955,vol.47, p. 1181. 3. S. Tanaka,T Yoshida,and K. Takage:Chem. Abstr., 1953,vol.47, pp. 1560d, 12176g. 4. J. G. Morris:DoctoralDissertationSeries,PublicationNo.:16,483, 1956,UmversityMlcrof'llms,AnnArbor,Mmh. 5. E. P. Kherand T. H. Yeh: Trans. ASM, 1961,vol. 53, pp. 75-93.
c e l l u l a r m o r p h o l o g y c h a r a c t e r i s t i c of that type of b o u n d a r y m i g r a t i o n , p r e s u m a b l y b e c a u s e the volume f r a c t i o n of the p r e c i p i t a t i n g c a r b i d e was too s m a l l for the c e l l u l a r p r e c i p i t a t e to f o r m . Since the morphology of the g r a i n b o u n d a r y c a r b i d e p r e c i p i t a t e i n f l u e n c e s both m e c h a n i c a l p r o p e r t i e s 1 and r e s i s t a n c e to i n t e r g r a n u l a r a t t a c k , s : an u n d e r s t a n d i n g of the p r e c i p i t a t i o n and growth of the c a r bide is i m p o r t a n t ~. It is the p u r p o s e of the p r e s e n t note to r e p o r t on some o b s e r v a t i o n s of c a r b i d e p r e cipitation and c o n c o m i t a n t g r a i n b
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