The tantalum-palladium constitution diagram
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c o u r s e of an extended study of the phase d i a g r a m s of r e f r a c t o r y m e t a l s , a n u m b e r of Ts-Tlo s y s t e m s , i . e . , b i n a r y s y s t e m s composed of one of the T5 t r a n s i t i o n m e t a l s V, Nb (Cb), and T a on the one side and one of the Tlo m e t a l s Pd and P t on the other, have been i n v e s t i g a t e d in a c o l l a b o r a t i v e effort. Of the six s y s t e m s thus defined, s t u d i e s of the V - P t s y s t e m ~ and the p o r t i o n of the T a - P t s y s t e m between 50-100 at. pct P t (Ref. 2) have a l r e a d y b e e n p r e s e n t e d ; for V - P d a phase d i a g r a m is given in the l i t e r a t u r e , s The p r e s ent p a p e r r e p o r t s the T a - P d s y s t e m ; the r e m a i n i n g two s y s t e m s , N b - P d and N b - P t , will be r e p o r t e d in subsequent publications. The e a r l i e s t p u b l i s h e d work on the T a - P d s y s t e m is a p p a r e n t l y that of G r e e n f i e l d and Beck 4 who p r e p a r e d t h r e e a l l o y s , a n n e a l e d t h e m at 1000~ and concluded that no i n t e r m e d i a t e p h a s e s e x i s t at this t e m p e r a t u r e . L a t e r work by D a r b y e t al, 5 however, e s t a b l i s h e d the e x i s t e n c e of s e v e r a l i n t e r m e d i a t e p h a s e s . Acr phase was d i s c o v e r e d , a phase with a b o d y - c e n t e r e d t e t r a gonal B l l - t y p e s t r u c t u r e was found at the c o m p o s i t i o n T a P d and a phase having a TiA13 type s t r u c t u r e was r e p o r t e d n e a r the c o m p o s i t i o n TaPd3. F u r t h e r , an unidentified phase was o b s e r v e d at the c o m p o s i t i o n TaPd2. The s t r u c t u r e of TaPd2 was r e p o r t e d by G i e s s e n and G r a n t 6 and was s u b s e q u e n t l y identified as b e i n g of the MoPt2 type.7 Kane, G i e s s e n and G r a n t 8 c o n f i r m e d T a P d and TaPd3 as having a B l l (or TT i C u ) - t y p e s t r u c t u r e and a TiA13-type s t r u c t u r e , r e s p e c t i v e l y . A f u r t h e r c o n f i r m a t i o n of all of these p h a s e s was i n d e p e n d e n t l y p r o v i d e d by Maldonado and Schubert. 9 A phase d i a g r a m for the T a - P d s y s t e m was p r e s e n t e d by S a v i t s k i i e t al; ~~ however, this work was b a s e d on a r a t h e r s m a l l a m o u n t of e x p e r i m e n t a l data and the phase b o u n d a r i e s were a p p a r e n t l y not p r e c i s e l y defined. The p r e s e n t , complete i n v e s t i g a t i o n of the T a - P d R. M. WATERSTRATand R. C. MANUSZEWSKIare Research Associates, American Dental Association Health Foundation Research Unit, National Bureau of Standards, Washington,D. C. 20234. B. C. GIESSEN and ROSEMARIE KOCH, both formerly with Massachusetts Institute of Technology, are now Professor of Chemistry and Mechanical Engineering,Northeastern University, Boston, MA. 02115 and EngineeringAssistant, Center for Materials Research, Stanford University, Stanford, CA. 94305 respectivel
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