Observations on the microstructure and orientation relations in the vanadium-hydrogen system
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EXPERIMENTAL All o p t i c a l o b s e r v a t i o n s w e r e done on a R e i c h e r t M e - F i n v e r t e d s t a g e m e t a l l o g r a p h e q u i p p e d with Nom a r s k i i n t e r f e r e n c e c o n t r a s t . The low t e m p e r a t u r e o b s e r v a t i o n s w e r e m a d e t h r o u g h a g l a s s window in the b o t t o m of an e v a c u a t e d Dewar. 4 The s a m p l e was m o u n t e d on a c o p p e r b l o c k c o n n e c t e d b y a b r a s s tube to a c o p p e r r o d extending up into the coolant. The t e m p e r a t u r e was r a i s e d b y r e s i s t a n c e h e a t i n g and m e a s u r e d with a p l a t i n u m r e s i s t a n c e t h e r m o m e t e r . The d i f f e r e n t c o o l a n t s u s e d w e r e liquid n i t r o g e n , p r o p y l a l c o h o l c o o l e d with liquid n i t r o g e n , d r y ice in a c e t o n e , and ice. The s p e c i m e n s u r f a c e s w e r e s u c c e s s i v e l y ground with wet 600, 800, and 1200 g r i t s i l i c o n c a r b i d e on a g l a s s p l a t e and then s u c c e s s i v e l y p o l i s h e d on a cloth wheel with 1 and 0.3 ~t a l u m i n a a b r a s i v e m i x e d in a solution of equal p a r t s H20 , NH4OH, and 30 pct HzOv The low t e m p e r a t u r e X - r a y w o r k was done in the s a m e Dewar a r r a n g e m e n t e x c e p t the s a m p l e was mounted on the s i d e of the c o p p e r b l o c k and t h e r e was a c o r r e s p o n d i n g m y l a r window f o r the e n t r a n c e of the X-ray beam. Electron microscope specimens were o b t a i n e d f r o m s i n g l e c r y s t a l s of v a n a d i u m containing a few at. p c t h y d r o g e n . 250 ~ m t h i c k s e c t i o n s w e r e cut with a s t r i n g saw and then ground down to 75 ~ m with wet 600 g r i t s i l i c o n c a r b i d e p o w d e r on g l a s s . T h e s e s a m p l e s w e r e then c h e m i c a l l y p o l i s h e d in a c o o l e d solution (< 10~ of 2 p a r t s H F and 1 p a r t HNO3. This method h a s b e e n shown to c o n s i d e r a b l y i n c r e a s e the h y d r o g e n content of v a n a d i u m . 5'B'7 The e l e c t r o n d i f J. WANAGEL, S. L. SASS, and B. W. BATTERMAN are Research Associate, Associate Professor, and Professor, respectively, Department of Materials Science and Engineering, Cornell University, Ithica, New York 14850 Manuscript submitted January 1l, 1973. METALLURGICAL TRANSACTIONS
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Fig. 1--A partial phase diagram for the V-H system. The ~ phase is an interstitial solid solution of hydrogen in bcc vanadium, the/3-hydride is a bct structure, and the T-hydride is fcc. 9 Maeland, 1 9 Zanowick and Wallace, 2 9 Reilly and Wiswallfl f r a c t i o n p a t t e r n s showed that the s p e c i m e n s p r e p a r e d in this m a n n e r w e r e g e n e r a l l y in the s i n g l e p h a s e /3r e g i o n f Cooling the c h e m i c a l s o l u t i o n is i m p o r t a n t , o t h e r w i s e
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