The vanadium-platinum constitution diagram
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The Vanadium-Platinum Constitution Diagram R. M. W A T E R S T R A T The system V-Pt was investigated over the entire composition range by metallography, X-ray diffraction and electron microprobe studies. There are at least four equilibrium intermediate phases in this system and they are stable to progressively higher temperatures with increasing vanadium concentration. The phases which have been observed are: ~', cubic, CusAu type; 0, tetragonal, TiAla type; 5, orthorhombic, MoPt2 type; ~, orthorhombic, AuCd type; and fl, cubic, CrsSi type (AI5). The ~' phase is possibly metastable. A very stable ribbon-like growth of ~ phase in the fcc platinum terminal solid solution has been observed in alloys containing about 43 at. pct V. The platinum terminal solid solution forms a congruent melting maximum at about 1805~ A eutectic reaction occurs at 1720~ + 10~ and a peritectic reaction is indicated at 1800~ + 10~ Vanadium is soluble in the fcc platinum terminal solid solution up to about 57 at. pct at 1720~ Platinum dissolves only to the extent of about 12 at. pct at 1800~ in bcc c~-V. A P P A R E N T L Y t h e r e have b e e n no p r e v i o u s s t u d i e s d e s i g n e d to e l u c i d a t e the c o n s t i t u t i o n d i a g r a m of the V - P t a l l o y s y s t e m . H o w e v e r , t h e r e has b e e n s u f f i c i e n t s t u d y of i n d i v i d u a l a l l o y s to e s t a b l i s h that v a r i o u s i n t e r m e d i a t e p h a s e s a r e f o r m e d and to d e t e r m i n e t h e i r c r y s t a l s t r u c t u r e s . 1-3 Some of the p h a s e s which have b e e n identified a r e a p p a r e n t l y not in a s t a t e of s t a b l e e q u i l i b r i u m at r o o m t e m p e r a t u r e . " O t h e r p h a s e s s e e m to r e s u l t f r o m c o n t a m i n a t i o n of the a l l o y s a m p l e s by oxygen o r by n i t r o g e n , a T h e r e is s o m e e v i d e n c e that a m e t a s t a b l e p h a s e can be obtained by cold w o r k i n g the a l l o y p o w d e r s . 4 An i n v e s t i g a t i o n of the c o n s t i t u t i o n d i a g r a m i s , t h e r e f o r e , e s s e n t i a l in o r d e r to identify which of t h e s e s t r u c t u r e s belong to e q u i l i b r i u m p h a s e s , and p e r h a p s a l s o to s u g g e s t s o m e r e a s o n s for the e x i s t e n c e of the v a r i o u s s t r u c t u r e s which have been observed. E X P E R I M E N T A L METHODS S a m p l e P r e p a r a t i o n and T r e a t m e n t The s t a r t i n g m a t e r i a l s u s e d in this i n v e s t i g a t i o n were: 1) V a n a d i u m m e t a l in the f o r m of e l e c t r o l y t i c d e n d r i t e s having a n o m i n a l p u r i t y of 99.95 p c t . T h i s m a t e r i a l was obtained f r o m the U.S. B u r e a u of M i n e s , B o u l d e r C i t y M e t a l l u r g y R e s e a r c h L a b o r a t o r y , and a c h e m i c a l a n a l y s i s f u r n i s h e d by t h e m l i s t e d the f o l lowing p r i n c i p a l i m p u r i t i e s : F e , 135 p p m ; C r , 60 ppm; Cu, 32 p p m ; C
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