Recrystallization of W-1 wt pct ThO 2 wire
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T H E m e c h a n i c a l p r o p e r t i e s of wrought t u n g s t e n - b a s e m a t e r i a l s a r e m a r k e d l y changed by r e c o v e r y and r e c r y s t a l l i z a t i o n , l'z As a r e s u l t , knowledge of the r e c r y s tallization p r o c e s s and f a c t o r s affecting it is of cons i d e r a b l e value. While the r e c r y s t a l l i z a t i o n b e h a v i o r of unalloyed and lamp doped tungsten has been studied e x t e n s i v e l y ; s-21 t h e r e is a r e l a t i v e d e a r t h of i n f o r m a tion c o n c e r n i n g the r e c r y s t a l l i z a t i o n of W-ThO2 m a t e r i a l s . The data which is a v a i l a b l e on W-ThO2 r e c r y s tallization has been collected on l a r g e d i a m e t e r rod 22-24 and sheet 2S'28 s p e c i m e n s with the exception of a few i s o l a t e d wire s a m p l e s 3'4'6'7 tested in conjunction with pure or lamp doped t u n g s t e n w i r e s . T h e r e is c o n s i d e r a b l e d i s a g r e e m e n t a m o n g the v a r i ous w o r k e r s as to the actual p r o c e s s e s o c c u r r i n g d u r ing the a n n e a l i n g of wrought W-ThO2 m a t e r i a l s . This is p r i m a r i l y due to the l i m i t e d a m o u n t of work dealing s p e c i f i c a l l y with the W-ThOz r e c r y s t a l l i z a t i o n p r o c e s s and the wide d i v e r s i t y of s a m p l e g e o m e t r i e s and c o m p o s i t i o n s . Davis s'4 concluded that s e c o n d a r y r e c r y s t a l l i z a t i o n of a W-0.8 wt pct ThOz 0.2 m m wire i s a g r a d u a l p r o c e s s r e s u l t i n g in l a r g e equiaxed g r a i n s . He also indicated that the p r o c e s s is not affected by heating rate and is p r e c e d e d by a w e l l defined p r i m a r y r e c r y s t a l l i z a t i o n stage. Jaffee et al.,2s have also r e p o r t e d evidence of s e c o n d a r y r e c r y s t a l l i zation in a W-ThO2 sheet. In c o n t r a s t W a l t e r and S e y b o l t ' s 26 data from a W - 0 . 2 5 wt pct ThO2 0.025 m m foil s p e c i m e n suggest that the d e v e l o p m e n t of the f i n a l stable g r a i n s t r u c t u r e is solely dependent on the r a t e of heating to the p r i m a r y r e c r y s t a l l i z a t i o n t e m p e r a t u r e and that the s e c o n d a r y r e c r y s t a l l i z a t i o n in the m a t e r i a l does not o c c u r . Schultz, ~ in t a c i t a g r e e m e n t with W a l t e r and Seybolt, 28 c o n f i r m s that s e c o n dary r e c r y s t a l l i z a t i o n does not occur in W-ThOz m a t e r i a l s and his data s u g g e s t that what Davis calls p r i m a r y r e c r y s t a l l i z a t i o n is in r e a l i t y a r e c o v e r y process. Since little or no d e s c r i p t i o n of the ThO2 d i s p e r s i o n T. E. DUNHAMand R. L. DAGAare Manager and Research Metallurgist, respectively, Research and Development, Refractory Metals Laboratory, General Electric Company, Cleveland, Ohio 44117. Manuscript submitted May 16, 1972. METALLURGICALTRANSACTIONS
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