Short-range order effects on the tensile behavior of a nickel-base alloy
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A N D J. F. K I N G
A n i c k e l b a s e weld f i l l e r m e t a l alloy with n o m i n a l c o m p o s i t i o n of 67 pet Ni, 20 pct C r , 3 pct Mn, 3 pct F e , and 2.5 pct Nb (Cb) is used to make a u s t e n i t i c - f e r r i t i c d i s s i m i l a r m e t a l j o i n t s . T e n s i l e p r o p e r t i e s were d e t e r m i n e d for this alloy over the range 25 to 732~ at s t r a i n - r a t e s of 3 • 10 -6 and 3 • 10-a/s. Above about 450~ both the yield s t r e n g t h and the u l t i m a t e t e n s i l e s t r e n g t h in the low s t r a i n - r a t e t e s t s showed s i g n i f i c a n t i n c r e a s e s over the s t r e n g t h s at the higher s t r a i n - r a t e . The e n h a n c e d v a l u e s for the yield s t r e n g t h p e r s i s t e d to the highest t e s t t e m p e r a t u r e (732~ w h e r e a s the u l t i m a t e t e n s i l e s t r e n g t h for the low s t r a i n - r a t e fell below the c u r v e for the higher s t r a i n - r a t e at about 600~ Above 600~ the u l t i m a t e t e n s i l e s t r e n g t h dropped off r a p i d l y and at 677~ a p p r o a c h e d the yield s t r e n g t h (i.e., the u n i f o r m elongation dropped to l e s s than 1 pct). The s t r a i n - r a t e effects have b e e n a t t r i b u t e d to " K - s t a t e " f o r m a t i o n , an effect that i n v e s t i g a t o r s have a t t r i b u t e d to s h o r t r a n g e o r d e r in other N i - C r base a l l o y s .
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n i c k e l b a s e weld f i l l e r m e t a l with A m e r i c a n Welding Society d e s i g n a t i o n AWS A5.14 C l a s s E R N i C r - 3 iS c o m m o n l y used for joining 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 to f e r r i t i c s t e e l s . P r e s e n t d e s i g n s for b r e e d e r r e a c t o r s call for the i n t e r m e d i a t e h e a t e x c h a n g e r piping to be type 316 s t a i n l e s s s t e e l and t h e s t e a m g e n e r a t o r s to be the f e r r i t i c 2 1/4 C r - 1 Mo s t e e l . The E R N i C r - 3 weld f i l l e r m e t a l is a p r i m e candidate for the f i l l e r m e t a l for t h e s e j o i n t s . As a r e s u l t of that application, we have b e e n involved in d e t e r m i n i n g the m e c h a n i c a l p r o p e r t i e s of E R N i C r - 3 weld m e t a l . T h e E R N i C r - 3 weld m e t a l is b a s i c a l l y a N i - C r alloy that c o n t a i n s s e v e r a l other e l e m e n t s . The specified c h e m i c a l c o m p o s i t i o n is given in T a b l e I, along with t h e c o m p o s i t i o n of the m a t e r i a l used in this study. T h i s f i l l e r - m e t a l alloy is a l s o known as I n c o n e l 82, the t r a d e n a m e of Huntington A l l o y s . In the wrought f o r m , the Huntington A l l o y s t r a d e n a m e is I n c o n e l 606. Our t e n s i l e s t u d i e s on the weld m e t a l indicate a s t r a i n - r a t e effect. A s i m i l a r effect o c c u r s in the alloy in the wrought f o r m . In this p a p e r , these o b s e r v a t i o n s will be p r e s e n t e d , and a p o s s i b
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