Work strengthening in a Fe-Ni-Co-Cr-Mo alloy
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Table I gives the composition of the alloy which was air induction-melted as a 136-kg (300-1b) heat, deoxidized with aluminum and poured at 1549~ (2820~ The 15.2 c m b y 15.2 c m (6 in. b y 6 in.) ingot was h o m o g e n i z e d for 4 h at 1177~ (2150~ hammer forged to 10.2 e m b y 10.2 e m (4 in. b y 4 in.), a i r c o o l e d and cut in two. The ingot was p r o c e s s e d to b a r b y two r o u t e s . The f i r s t path was hot r o l l i n g to 15.9 m m (5/8 in.) s q u a r e and m a c h i n i n g to 12.7 m m (1/2 in.) r o u n d b a r for c o l d d r a w i n g . P l a t e s for s h e e t t e n s i l e s p e c i m e n s w e r e p r e p a r e d b y the s e c o n d r o u t e . T h i s c o n s i s t e d of hot r o l l ing p l a t e to 19 m m (3/4 in.), c o l d r o l l i n g to 6.4 m m (1/4 in.), and s u r f a c e g r i n d i n g to the f i n i s h e d t e n s i l e s p e c i m e n t h i c k n e s s of 3.6 m m (0.140 in.). A l l m a t e r i a l was s o l u t i o n a n n e a l e d for 1 h at 1204~ (2200~ followed b y a w a t e r quench p r i o r to f u r t h e r m e c h a n ical working. In p r e p a r a t i o n f o r e l e c t r o n m e t a l l o g r a p h y , a n n e a l e d sheet tensile specimens were uniformly elongated by H. T. MICHELS and R. M. FORBES JONES are with The International Nickel Company, Inc., Paul D. Merica Research Laboratory, Sterling Forest, Suffern, N. Y. 10901. Manuscript submitted August 6, 1973. METALLURGICAL TRANSACTIONS
3, 10, and 20 p e t o v e r a 2.54 c m (1 in.) gage length a s m o n i t o r e d with an e x t e n s o m e t e r . G r e a t e r a m o u n t s of u n i f o r m d e f o r m a t i o n , e q u i v a l e n t to e l o n g a t i o n s of 48 and 75 p e t w e r e o b t a i n e d b y c o l d d r a w i n g f r o m 12.7 m m (1/2 in.) round r o d . S a m p l e s f o r o p t i c a l m e t a l l o g r a p h y w e r e e t c h e d with a 10 p c t c h r o m i c a c i d - w a t e r solution. S p e c i m e n s for transmission electron microscopy were pre-dished in D i s a A - 2 solution and final thinning was c a r r i e d out in 10 p c t p e r c h l o r i c - a c e t i c a c i d . RESULTS Microstructure The a n n e a l e d a l l o y i s t y p i c a l of a s i n g l e p h a s e a u s t e n i t i c m a t e r i a l c o n s i s t i n g of e q u i a x e d g r a i n s with many annealing twins. Electron metallography rev e a l e d d i s s o c i a t e d d i s l o c a t i o n s in the f o r m of nodes a s i l l u s t r a t e d in F i g . 1. C a l c u l a t i o n of s t a c k i n g fault e n e r g y (y) f r o m t h e s e c o n f i g u r a t i o n s ' r e s u l t e d in the v a l u e s of a p p r o x i m a t e l y 18 e r g s / c m a. T h i s i s a low s t a c k i n g fault e n e r g y and i s in good a g r e e m e n t with the v a l u e of 15 e r g s / c m a which is given b y F r i e d e l a f o r F e - N i - C r ( s t a i n l e s s s t e e l ) , and is r e a s o n a b l y c l o s e to the 25 e r g s / c m z v a l u e r e p o r t e d b y D r a p i e r , V i a t o u r , C o n t s o u r d i s , and H
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