Correlation between precipitation reactions and bulk density changes in type 18-12 austenitic stainless steels
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s a m p l e s w e r e cut f r o m the g a g e length of 18 c m • 1.27 c m d i a m e t e r t e n s i l e s p e c i m e n s which had r e c e i v e d 20 p c t u n i f o r m e l o n g a t i o n a f t e r the s o l u t i o n h e a t t r e a t m e n t . The d e f o r m a t i o n was i n t r o d u c e d to s i m u l a t e the 20 p c t c o l d w o r k r e c e i v e d by fuel e l e m e n t c l a d d i n g d u r i n g a p a r t i c u l a r p r o c e s s i n g s e q u e n c e . T h e r m a l a g i n g was c o n d u c t e d at 725~ and 810~ f o r t i m e s up to 1500 h. The m i c r o s t r u c t u r e s and t i m e - t e m p e r a t u r e - p r e c i p i t a t i o n s e q u e n c e s r e s u l t i n g f r o m the v a r i o u s p r e t r e a t m e n t s and a g i n g t r e a t m e n t s had b e e n c h a r a c t e r i z e d p r e v i o u s l y f o r the a i r m e l t e d s t e e l s . 3'4 Q u a n t i t a t i v e a n a l y s i s of the p h a s e s p r e s e n t in the Type 304 and v a c u u m m e l t e d 316 w a s p e r f o r m e d b y the b u l k - e x t r a c tion m e t h o d d e s c r i b e d in Ref. 4.
E X P E R I M E N T A L PROCEDURES a) M a t e r i a l s and T r e a t m e n t C o m p o s i t i o n and p r e t r e a t m e n t s of the v a r i o u s s t e e l s u s e d in the p r e s e n t i n v e s t i g a t i o n a r e l i s t e d in T a b l e I. A l l o y d e s i g n a t i o n s and p r e t r e a t m e n t s f o r the T y p e 316L and 316 s t e e l s a r e s u m m a r i z e d in T a b l e H. All of the s a m p l e s , with the e x c e p t i o n of one h e a t of T y p e 316 w e r e t a k e n f r o m a i r m e l t e d h e a t s . The v a c u u m m e l t e d and c a s t Type 316 was t a k e n f r o m a h e a t u s e d in the f a b r i c a t i o n of fuel e l e m e n t c l a d d i n g . Solution t r e a t m e n t and a g i n g of the a i r m e l t e d s t e e l s was c o n d u c t e d in e l e c t r i c muffle f u r n a c e s in s t a g n a n t a i r while the s p e c i m e n s f r o m the v a c u u m m e l t e d and c a s t lot of Type 316 w e r e f i r s t s o l u t i o n t r e a t e d in a r gon a t m o s p h e r e , w a t e r quenched, and then s e a l e d in e v a c u a t e d q u a r t z c a p s u l e s u n d e r a v a c u u m of b e t t e r than 10 -6 T o r t f o r e x t e n d e d aging. The c o l d w o r k e d
J. A. SPITZNAGEL is Senior Engineer in Reactor Materials Section, Westinghouse Research Laboratory, Pittsburgh, Pa. 15235. R. STICKLER, formerly with the Westinghouse Researqh Laboratory, Pittsburgh, Pa., is now Professor at the University of Vienna, Vienna, Austria. Manuscript submitted October 26, 1973 METALLURGICAL TRANSACTIONS
b) D e n s i t y M e a s u r e m e n t s The s a m p l e s which w e r e in the f o r m of s m a l l c y l i n d e r s , a p p r o x i m a t e l y 1.27 c m d i a m . , w e r e g r o u n d and e l e c t r o p o l i s h e d p r i o r to m a k i n g bulk d e n s i t y m e a s u r e m e n t s to r e m o v e the o x i d i z e d o r c a r b o n d e p l e t e d s u r f a c e l a y e r s
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