Elevated temperature elastic constants of Fe-30 wt pct Ni in austenitic and martensitic conditions
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e x p l a n a t i o n s of p h e n o m e n a a s s o c i a t e d with m a r t e n s i t i c t r a n s f o r m a t i o n s in i r o n b a s e a l l o y s r e q u i r e a c c u r a t e knowledge of the e l a s t i c m o d ulL F o r e x a m p l e , r e l a t i v e m a g n i t u d e s of the e l a s t i c c o n s t a n t s a r e u t i l i z e d to e x p l a i n the e f f e c t s of a l l o y a d d i t i o n s ~ and s t r e s s e'3 on the m a r t e n s i t e and a u s t e n ire s t a r t t e m p e r a t u r e s and in a c c o u n t i n g for the s t r e n g t h of m a r t e n s i t e . 4's While c o n s i d e r a b l e a t t e n t i o n h a s b e e n given to o b t a i n i n g m o d u l i of both the m a r t e n s i t e and a u s t e n i t e p h a s e s of i r o n - n i c k e l a l l o y s at r o o m t e m p e r a t u r e and below, 6-1o o n l y l i m i t e d d a t a on the h i g h - t e m p e r a t u r e m o d u l i of m a r t e n s i t e 2 and a u s t e n ite2,~,~a in such a l l o y s have b e e n r e p o r t e d . An e x c e l lent r e v i e w of p r e v i o u s w o r k is given by L e d b e t t e r and Reed. ~3 This l a c k of h i g h - t e m p e r a t u r e e l a s t i c c o n s t a n t d a t a h a s i n t r o d u c e d u n c e r t a i n t i e s into the i n t e r p r e t a tion of e x p e r i m e n t a l r e s u l t s . F o r e x a m p l e , i n i t i a l a t t e m p t s to e x p l a i n the e f f e c t of h y d r o s t a t i c p r e s s u r e on the a u s t e n i t e s t a r t t e m p e r a t u r e of an F e - 3 0 . 3 wt pct Ni a l l o y ~4 u s e d the e x t a n t h i g h - t e m p e r a t u r e e l a s t i c c o n s t a n t s of s i n g l e c r y s t a l a u s t e n i t e ~ and p o l y c r y s t a l l i n e m a r t e n s i t e , c a l c u l a t i n g p o l y c r y s t a l l i n e m o d u l i for the a u s t e n i t e f r o m the s i n g l e c r y s t a l e l a s t i c c o n s t a n t d a t a b y weI1 known m e t h o d s , x5 This i n i t i a l i n t e r p r e t a t i o n was found to r e q u i r e c o n s i d e r a b l e m o d i f i c a t i o n l a t e r when a c c u r a t e , e x p e r i m e n t a l l y d e t e r m i n e d p o l y e r y s t a t l i n e e l a s t i c m o d u I i for m a r t e n s i t e and a u s t e n i t e p h a s e s of the a l l o y b e c a m e a v a i l a b l e . 2 Additional i n c o n s i s t e n c i e s a r i s e when r e p o r t e d s h e a r and Young's m o d u l i x a r e u s e d to c a l c u l a t e o t h e r e l a s t i c moduli o r longitudinal and s h e a r wave v e l o c i t i e s . Small e r r o r s in the r e p o r t e d d a t a a r e a m p l i f i e d by the m a t h e m a t i c a l m a n i p u l a t i o n s r e q u i r e d ~a and m e a n i n g l e s s n u m b e r s m a y b e c a l c u l a t e d . Thus, c a r e m u s t be t a k e n in using the l i m i t e d r e p o r t e d m o d u l i to c a l c u l a t e o t h e r e l a s t i c p r o p e r t i e s . F u r t h e r m o r e , m a n y of the r e p o r t e d k E. POPE, formerly with Sandia Laboratories,
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