The preparation and some mechanical properties of high-purity vanadium
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AND
R. J. ARSENAULT
E l e c t r o n beam m e l t i n g of v a n a d i u m at total d y n a m i c p r e s s u r e s of l e s s than 10-9 has been shown to r e d u c e the oxygen content. I n t e r n a l f r i c t i o n a n a l y s e s and c h e m i c a l a n a l y s e s show good a g r e e m e n t . The p u r i f i c a t i o n is a t t r i b u t e d to the m e t a l l i c v a p o r envelope a r o u n d the m o l t e n zone which m a y have the effect of r e d u c i n g the p a r t i a l p r e s s u r e of oxygen below 10 -'3 a d j a c e n t to the m o l t e n m e t a l and a l s o to the v a p o r i z a t i o n of VO m o l e c u l e s from the s u r f a c e of the m o l t e n zone. T h r e e s t a g e s of w o r k h a r d e n i n g have b e e n shown to e x i s t in v a n a d i u m . However, a s m a l l i n t e r s t i t i a l c o n c e n t r a t i o n is r e q u i r e d to o b s e r v e stage II. Opt i c a l m i c r o s c o p e e x a m i n a t i o n r e v e a l s that s e c o n d a r y slip l i n e s a p p e a r as stage II p r o c e e d s . The m a x i m u m r a t e of w o r k h a r d e n i n g of 14 kg p e r sq m m i s in good a g r e e m e n t with the r a t e of work h a r d e n i n g o b s e r v e d in other bcc m e t a l s . I N V E S T I G A T I O N S of the p a r a m e t e r s which affect the t h r e e s t a g e s of work h a r d e n i n g have been conducted to v a r y i n g e x t e n t s for some of the bcc m e t a l s . '-4 Howe v e r , the v a r i o u s s t a g e s have not b e e n s u c c e s s f u l l y i n v e s t i g a t e d in v a n a d i u m , and the m o s t p r o b a b l e r e a son i s that to o b s e r v e t h r e e s t a g e s of work h a r d e n i n g in b c c m e t a l s , the i n t e r s t i t i a l c o n c e n t r a t i o n has to be s m a l l s The v a n a d i u m p r e v i o u s l y a v a i l a b l e c o n t a i n e d a l a r g e a m o u n t of v a r i o u s e l e m e n t s a s i n t e r s t i t i a l i m purities. H i g h - v a c u u m e l e c t r o n - b e a m zone m e l t i n g has p r o v e n to be an efficient method of p u r i f y i n g some of the b c c m e t a l s f '7 A t t e m p t s have b e e n m a d e to zone r e f i n e v a n a d i u m 6'a-1' at p r e s s u r e s in the high 10-8 t o r r r a n g e but, in g e n e r a l , t h e r e is a d e a r t h of knowledge c o n c e r n ing the high v a c u u m e l e c t r o n b e a m zone m e l t i n g of v a n a d i u m . The e x i s t i n g l i t e r a t u r e c o n c e r n i n g the p u r i f i c a t i o n of v a n a d i u m is r a t h e r n e g a t i v e , i.e., the p r e v i o u s r e s u l t s and the e x i s t i n g t h e o r i e s '~'13 indicate that i t i s a l m o s t i m p o s s i b l e to r e d u c e the oxygen c o n c e n t r a t i o n of v a n a d i u m by v a c u u m t e c h n i q u e s . The r e a s o n for the i n t e r e s t in the r e m o v a l of oxygen i s due to the l a r g e t e t r a g o n a l s t r a i n a s s o c i a t e d with i n t e r s t i t i a l oxygen. '4,'s The d i l a t a t i o n a l s t r a i n d
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