Recrystallization and grain growth in metastable beta III titanium alloy
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M E T A S T A B L E beta t i t a n i u m a l lo y with a n o m i n a l c o m p o s i t i o n T i - 1 1 . 5 Mo-6 Z r - 4 . 5 Sn, p r o v i d e s a n u m b e r of a d v a n t a g e s o v e r the m o r e c o n v e n t i o n a l alpha and a l p h a - b e t a a l l o y s . Some of the s i g n i f i c a n t p r o p e r t i e s of this alloy a r e its cold f o r m a b i l i t y , r e s p o n s e to aging t r e a t m e n t s to d e v e l o p high s t r e n g t h s and f r a c t u r e t o u g h n e s s , d e e p h a r d e n a b i l i t y and good c o r r o s i o n r e s i s t a n c e . ~-3 T h e unique c h a r a c t e r i s t i c s of this alloy a r e its v a r y i n g r e s p o n s e to t r a n s f o r m a t i o n s r e s u l t i n g f r o m p r i o r d e f o r m a t i o n . F r o e s , e t al 4 have shown that in the p r e s e n c e of r e l a t i v e l y s m a l l a m o u n ts of d e f o r mation (>-5 pct), the r a t e of t r a n s f o r m a t i o n f r o m /3 ~ c~ + /3 is s i g n i f i c a n t l y i n c r e a s e d o v e r a wide r a n g e of t e m p e r a t u r e v a r y i n g f r o m 700 to 975 K. T h e y have r e p r e s e n t e d this b e h a v i o r in a T T T d i a g r a m fo r the alloy in the d e f o r m e d and u n d e f o r m e d conditions. B e c a u s e of this d e f o r m a t i o n - i n d u c e d t r a n s f o r m a t i o n , the n a t u r e of the r e c r y s t a l l i z a t i o n and g r a i n growth in this alloy is i m p o r t a n t in o p t i m i z i n g f a b r i c a t i o n p r o c e d u r e s and the r e s u l t i n g m e c h a n i c a l p r o p e r t i e s . R e c r y s t a l l i z a i i o n s t u d i e s to identify the k i n e t i c s of the p r o c e s s in p o l y c r y s t a l l i n e t i t a n i u m a l l o y s have a l ways been difficult b e c a u s e of the lack of c l e a r cont r a s t b et ween the r e c r y s t a l l i z e d and u n r e c r y s t a l l i z e d a r e a s . H o w e v e r , this difficulty does not e x i s t in this a l l o y b e c a u s e a f t e r an a p p r o p r i a t e r e c r y s t a l l i z a t i o n anneal, s a m p l e s could be s u b j e c t e d to a low t e m p e r a t u r e aging t r e a t m e n t f o r a p e r i o d i n t e r m e d i a t e to the two t r a n s f o r m a t i o n s t a r t c u r v e s which would d e c o r a t e the u n r e c r y s t a l l i z e d r e g i o n of the s a m p l e with the B. B. RATHis Head, AlloyTransformation and KineticsBranch(Code 6320), NavalResearchLaboratory, Washington,DC 20375, R. J. LEDERICHis Scientist, McDonnell-DouglasResearchLaboratories,St. Louis,MO63166, C. F. YOLTONis StaffMetallurgist,Colt Industries/CrucibleMaterialsResearch Center, Pittsburgh, PA 15213, and F. H. FROESis Air ForceMaterialsLaboratory, Wright-PattersonAir Force Base,Dayton, OH 45433. This paper is based on a presentation made at a symposiumon "Recovery, Recrystallizationand Grain Growthin Materials"held at the Chicagomeeting of The MetallurgicalSocietyof AIME,October 1977, under the sponsorship of the PhysicalMetallurgyCommittee. METALLURGICALTR
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