Plastic deformation of hafnium-oxygen alloys
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a h e a v y e l e m e n t b e l o n g i n g to the s a m e c o l u m n of the p e r i o d i c t a b l e a s t i t a n i u m and z i r c o n i u m . All t h r e e e x i s t in hcp f o r m at r o o m t e m p e r a t u r e and u n d e r g o a hcp .-~ b c c t r a n s i t i o n at a h i g h e r t e m p e r a t u r e ; for Hf the t e m p e r a t u r e s of t r a n s f o r m a t i o n and of m e l t i n g a r e T a - ~ ~ 1750~ and T m = 2222~ 1 The m e c h a n i c a l p r o p e r t i e s of t i t a n i u m and z i r c o n i u m have b e e n e x t e n s i v e l y i n v e s t i g a t e d (see, for e x a m p l e , C o n r a d et a l . , 2 Tysona), and it h a s b e e n e s t a b l i s h e d that the m e c h a n i c a l p r o p e r t i e s of t h e s e m a t e r i a l s a r e s e n s i t i v e l y dependent on s m a l l c o n c e n t r a t i o n s of i n t e r s t i t i a l i m p u r i t i e s . The s t r e n g t h and r a n g e of the i n t e r a c tion b e t w e e n i n t e r s t i t i a l s and d i s l o c a t i o n s h a s b e e n d e t e r m i n e d f o r Ti 4 and Z r . 5 F r o m the s i m i l a r i t i e s in t h e i r p h y s i c a l p r o p e r t i e s it is e x p e c t e d that in Hf a s well a s in Ti and Zr i n t e r s t i t i a l s would d o m i n a t e the m e c h a n i cal b e h a v i o r . Goodwin and T r o u t 6 have i n v e s t i g a t e d the effect of d i s s o l v e d oxygen on a v a r i e t y of m e c h a n i c a l p r o p e r t i e s of Hf p o l y c r y s t a l s . T h e i r w o r k d e m o n s t r a t e d the i m p o r t a n c e of i n t e r s t i t i a l content, but was not e x t e n d e d to an a n a l y s i s of the d e t a i l s of the i n t e r a c t i o n . The o b j e c t i v e of the p r e s e n t w o r k is to o b t a i n t h i s i n f o r m a t i o n f o r oxygen d i s s o l v e d in Hf and t h e r e b y c o m p l e t e the c h a r a c t e r i z a t i o n of the i n t e r a c t i o n b e t w e e n d i s l o c a t i o n s and oxygen in Hf, Ti, and Z r . C o m p a r i s o n of the t h e r m o d y n a m i c d a t a f o r t h e s e r e l a t e d m a t e r i a l s will then a i d in identifying the p h y s i c a l o r i g i n of the i n t e r a c t i o n . It h a s b e e n e s t a b l i s h e d n8 that Hf d e f o r m s b y s l i p p r e d o m i n a n t l y on the p r i s m a t i c {10i0} p l a n e s . The {10i0} (1910) s y s t e m was the only one o b s e r v e d b y Das and M i t c h e l l 9 in t h e i r w o r k with highly p u r e s i n g l e c r y s t a l s . They a l s o d e t e r m i n e d a c t i v a t i o n p a r a m e t e r s for t h e i r m a t e r i a l , which t h e y a s s o c i a t e d (at l e a s t at low s t r a i n s ) with i n t e r s t i t i a l i m p u r i t i e s ; t h e i r r e s u l t s will be c o m p a r e d with the p r e s e n t d a t a below. I. E X P E R I M E N T A L METHODS 1. M a t e r i a l s Two lots of iodide c r y s t a l b a r hafnium f r o m Wah Chang, Albany, Oregon 97321 w e r e u s e d ; the l e v e l s of the p r i n c i p a l i m p u r i t i e s a
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