Oxygen distribution in internally-oxidized Ta-8 pct W-2 pct Hf alloy
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Khnmin Khnmax Fig. 5--Variation in R and P with difference in Knoop hardness extremes. The e l l i p s e s w e r e s c a l e d to c o i n c i d e with the t e n s i l e s t r e s s at the 1:0 s t r e s s r a t i o . The m o s t s i g n i f i c a n t r e s u l t s e e n f r o m F i g s . 1 t h r o u g h 4 is that in no c a s e does the Knoop h a r d n e s s t e c h n i q u e p r e d i c t the shape of the y i e l d l o c u s , at l e a s t in the f i r s t qua d r an t . The g r e a t e s t d i f f e r e n c e o c c u r s f o r the m o s t
Oxygen Distribution in Internally-Oxidized Ta-8 Pct W-2 Pct Hf Alloy C. T. LIU, R. W. C A R P E N T E R , AND H. INOUYE R e c e n t l y s e v e r a l s t u d i e s of i n t e r n a l oxidation and its c o r r e l a t i o n with m e c h a n i c a l p r o p e r t i e s of the b c c al l o y T a - 8 wt pct W-2 wt pct Hf (T-111) have b e e n publ i s h e d . ~-~ T h e r e a r e u n e x p la in e d d i f f e r e n c e s e x i s t i n g b e t w e e n the r e s u l t s 1's'4 r e g a r d i n g the oxygen d i s t r i b u t i o n at v a r i o u s r e a c t i o n t e m p e r a t u r e s . B a s e d on m i c r o h a r d n e s s m e a s u r e m e n t s and m i c r o s c o p i c e x a m i n a t i o n , Liu, Inouye, and C a r p e n t e r ~ found only a s m a l l oxygen g r a d i ent in s p e c i m e n s i n t e r n a l l y - o x i d i z e d at 1273~ and s u b s e q u e n t h e a t t r e a t m e n t b e t w e e n 1673 and 1973~ p r o duced a u n i f o r m d i s t r i b u t i o n of HfO 2 p r e c i p i t a t e s a c r o s s the s p e c i m e n s . On the o t h e r hand, E t t e r and Smith, z and S c h a e f f e r 4 o b s e r v e d a r e a c t i o n zone containing oxide p r e c i p i t a t e s , f o r m e d n e a r the s p e c i m e n s u r f a c e when o x i d i z e d at 1673~ The m e c h a n i c a l p r o p e r t i e s of the c e n t r a l r e g i o n w e r e s i m i l a r to t h o s e of the o x y g e n - f r e e a l loy. The t h i c k n e s s of the r e a c t i o n zone i n c r e a s e d with a v e r a g e oxygen c o n c e n t r a t i o n , and at a l e v e l of 3300 to 3600 ppm (by wt) the c e n t r a l p r e c i p i t a t i o n - f r e e - r e g i o n d i s a p p e a r e d e n t i r e l y . T h e s e r e s u l t s a p p e a r to c o n f l i c t with e a c h o t h e r in the s e n s e that oxygen was d i s t r i b u t e d l e s s u n i f o r m l y at the h i g h e r r e a c t i o n t e m p e r a t u r e . This note will show t h e r e is indeed no conflict, but the d i f f e r C. T. L/U, R. Wl CARPENTER, and H. INOUYE are Metallurgists, Metals and Ceramic Division, Oak Ridge National Laboratory, Oak Ridge, Tenn. 37830. Manuscript submitted June 6, 1974. METALLURGICAL TRANSACTIONS A
a n i s o t r o p i c c r o s s - r o l l e d m a t e r i a l , while the l e a s t o c c u r s f o r the m i l l - a n n e a l e d m a t e r i a l , which is the m o s t i s o t r o p i c of t h o s e e x
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