Factors affecting the tensile ductility of a metastable beta titanium alloy
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a m o u n t of c o n t i n u o u s r e d u c t i o n d u r i n g hot w o r k i n g . The p r e s e n t p a p e r d e t a i l s the d u c t i l i t y v a l u e s t h a t were obtained from this material, presenting metall o g r a p h i c e v i d e n c e to a c c o u n t for the l a r g e i n f l u e n c e of g r a i n s i z e on d u c t i l i t y . The T i - 8 8 2 3 a l l o y of c o n c e r n in t h i s s t u d y h a s the c h e m i c a l c o m p o s i t i o n shown in T a b l e I. The final h e a v y s e c t i o n c o n f i g u r a t i o n , (a c y l i n d r i c a l hollow h a v ing the a p p r o x i m a t e d i m e n s i o n s of 11 3 / 8 in. (289 ram) OD and 3 1/8 in. (79 ram) w a l l t h i c k n e s s ) w a s e x t r u d e d by C a m e r o n I r o n W o r k s of Houston T e x a s . The e x t r u s i o n t e m p e r a t u r e w a s 1700~ At t h i s t e m p e r a t u r e no d i f f i c u l t i e s w e r e e n c o u n t e r e d in a c h i e v i n g a r e d u c -
Table I. Composition and Heat Treatment
Element (Wt Pet) Alloy
AI
V
Mo
Fe
Sn Cu
Ti-8Mo-8V-2Fe-3Al 3.08 8.08 7.80 2.07 (Ti.8823)
C
O
H
N
0.035 0.133 0.006 0.010
Alloy
Condition
Solutionizing Temperature and Time Prior to WQ
Aging Temperature and Time Prior to AC
Ti-8823
STA Direct Age
1475~ (1075 K ) - 1 8 9 -
lO00~ K) 8 h 950~ (783 K)--8 h
Heat Amountof Treatment Hot Work 84% 9 DirectAge 84% 9 STA
12--
I. H. L. Marcus and M. E. Fine: J. Amer. Ceram. Soc., 1972, vol. 55, p. 568. 2. W. C. Johnson, D. F. Stcin, and R. W. Ricc: Grain Boundary Chemistry in Sintered A1203 and Hot Pressed MgO, Proc. IV Bolton Landing Conf. AIME, 1974. 3. G. Rossi and J. E. Burke: J. Amer. Ceram. Soc., 1973, vol. 56, p. 654. 4. R. W. Davidge and G. Tappin: J. Mater. Sci., 1968, vol. 3, p. 165. 5. L. A. Simpson: J. Amer. Ceram. Soc.. 1973,vol. 56, p. 7. 6. A. G. Evans and G. Tappin: Proc. Brit. Ceram. Soc., 1972, vol. 20, p. 275. 7. J. A. Coppola and R. C. Bradt: J. Amer. Ceram. Soc., 1973, vol. 56, p. 392.
30~
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Factors Affecting the Tensile Ductility of a Metastable Beta Titanium Alloy
4~
/ 2--
R. CHAIT It has b e e n o b s e r v e d that with m e t a s t a b l e Ti a l l o y s a l a r g e g r a i n s i z e l e a d s to r e d u c e d t e n s i l e d u c t i l i t y , z The p r o b l e m of l a r g e g r a i n s i z e h a s p l a g u e d h e a v y s e c t i o n m e t a s t a b l e b e t a Ti a l l o y s b e c a u s e it h a s b e e n difficult to i m p a r t an amount of continuous hot w o r k i n g that is l a r g e enough to effect r e c r y s t a l l i z a t i o n . F o r e x a m p l e , f o r g i n g a h e a v y s e c t i o n of the m e t a s t a b l e Ti a l l o y , T i - 8 M o - 8 V - 2 F e - 3 A I (Ti-8823), with an a c c u m u l a t e d r e d u c t i o n of 90 p c t did not s i g n i f i c a n t l y r e d u c e the b e t a g r a i n s i z e . 2 As a r e s u l t , the d e s i r e d i m p r o v e m e n t in d u c t i l i t y was not r e a l i z e d . R e c e n t l y , a h e a v y s e c t i o n of Ti-8823 h a s b e e n e x t r u d e d , e f f e c
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