Determination of thermodynamic interaction parameters in solid V-Ti alloys using the mass spectrometer
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In aTi = R T lnNTi +N~(1.82 ± 0.13) kcal per g-atom
while the activity of vanadium is: RT
2
Inn v = R T InNV +NTi(I.82± 0.13) kcalper g-atom.
The experimental result on the pairwise interaction parameter agrees well with the theoretically calculated value.
THERE is presently a substantial interest in the theory and properties of transition metal alloys. The investigation of the thermodynamic properties of transition metal binary systems can also yield useful inf o r m a t i o n i f the t h e r m o d y n a m i c b e h a v i o r c a n be r e l a t e d to o b s e r v e d p h y s i c a l p r o p e r t i e s . I n a d d i t i o n , m a s s s p e c t r o m e t e r t e c h n i q u e s h a v e b e e n s h o w n t o be q u i t e u s e f u l i n s e v e r a l b i n a r y a l l o y s y s t e m s s t u d i e s .1-~ T h e p u r p o s e of t h e p r e s e n t s t u d y w a s t o i n v e s t i g a t e the utility of the time-of-flight m a s s spectrometer t e c h n i q u e to r e l a t i v e l y l o w v a p o r p r e s s u r e e l e m e n t s in the s o l i d solution p h a s e and w h e r e electromotive f o r c e m e a s u r e m e n t s a r e not r e a d i l y a p p l i c a b l e . T h e V - T i s y s t e m was c h o s e n b e c a u s e o f i t s c o m p l e t e s o l i d s o l u b i l i t y i n t h e 1400 ° t o 1625°C t e m p e r a t u r e r a n g e ,4 p o s s i b l e a p p l i c a t i o n t o a l l o y t h e o r y , a n d p o t e n t i a l u t i l i t y of some V-Ti alloys for cladding material in liquid m e t a l , fast breeder reactors.~ The use of the effusion technique coupled with the mass spectrometer presents certain problems of calibration, sensitivity, and reproducibility whichhave b e e n d i s c u s s e d by B e l t o n a n d F r u e h a n ,~ R e e s e et a l . , S a n d B i d w e l l8 w i t h r e s p e c t t o a c t i v i t y m e a s u r e m e n t s . B r i e f l y , t h e m e t h o d o f R e e s e e t a l . ,3 w h e r e i o n c u r r e n t s in t h e a l l o y a r e m e a s u r e d a n d r a t i o e d w i t h a n o t h e r i o n c u r r e n t i n t h e p u r e s t a t e , s u f f e r s b e c a u s e of d i f f e r e n c e s in t e m p e r a t u r e r e p r o d u c i b i l i t y a n d m a c h i n e c o n s t a n t v a r i a t i o n . I n o r d e r t o c i r c u m v e n t t h i s , H o c h et al ~-9 EDMUND J. ROLINSKI, formerly Graduate Student, Department of Materials Science and Metallurgical Engineering, University of Cincinnati, Cincinnati, Ohio, is now Materials Engineer, Air Force Materials Laboratory, Wright-Patterson Air Force Base, Ohio. MICHAEL HOCH and CHARLES J. OBLINGER are Professor of Materials Science and Head of Department of Materials Science and Engineering, and Research Assistant, respectively, at the abovementioned university. This paper is based upon a portion of a thesis submitted by EDMUND J. ROLINSKI submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Materials Science at the University of Cincinnati. Manuscript submitted August 1 3 , 1 9 7 0 .
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