Thermomechanical processing of a molybdenum alloy using hydrostatic extrusion
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n i (x) = n o ( x ) + A n ( x ) = n o ( x ) + ~ m ( y ) p o (x - y) y:0 Then p i (x) = n i ( x ) / N i + Nz
[~]
[6]
The s e c o n d i t e r a t i o n yields x
n~(x) =nl(x) + ~ m(y)pl(x-y) y=O
[7]
then P2 (%) = n2 (x)/N1 + N~
[8]
T h i s p r o c e s s was r e p e a t e d for s e v e n i t e r a t i o n s to y i e l d the r e s u l t s shown in Fig. 2. It is n e c e s s a r y to point out that in the case d e s c r i b e d the r a t i o of N2/N~ was g r e a t e r than would be p r e f e r a b l e and thus m o r e e m p h a s i s is placed on the i t e r a t i v e p r o c e d u r e , as opposed to d i r e c t a n a l y s i s , than would n o r m a l l y be desirable. METALLURGICALTRANSACTIONS
1. B. W.Rosen:AIAA J., 1964,vol.2, p. 1985. 2. B. W.Rosen:FiberCompositeMaterials, p. 37, AmericanSocietyfor Metals, MetalsPark,Ohio, 1965. 3. E. Friedman:Proceedings22ndANTEC.Soc.PlasticsInd.,Inc.,Washington, D. C., February,1967. 4. E W. Crossman,A. S. Yue, and A. E. Vidoz: Trans. TMS-AIME, 1969,vol.245, p. 397. 5. J. Mullin,J. M. Berry,and A. Gatti:Z Comp. Mat, 1968,vol. 2, p. 82.
Thermomechanical Processing of a Molybdenum Alloy Using Hydrostatic Extrusion P E T E R L. R A F F O T H E strongest molybdenum alloys which have been developed a r e t h o s e s t r e n g t h e n e d by p r e c i p i t a t i o n of e i t h e r t i t a n i u m , z i r c o n i u m , o r h a f n i u m c a r b i d e s . 1-5 The e l e v a t e d t e m p e r a t u r e s t r e n g t h of t h e s e alloys is m a r k e d l y i n c r e a s e d when d y n a m i c s t r a i n aging o c c u r s e i t h e r d u r i n g c r e e p or s h o r t t e r m t e n s i l e t e s t s . ~,~-8 The effects of d y n a m i c s t r a i n aging a r e m a x i m i z e d when such alloys a r e given a solution t r e a t m e n t to d i s solve the c a r b i d e s p r i o r to t e s t i n g , s In c o n t r a s t , m a x i m u m low t e m p e r a t u r e toughness in c a r b i d e s t r e n g t h ened m o l y b d e n u m alloys is obtained in the s t r a i n h a r d ened condition. %3 E x t e n s i v e c a r b i d e p r e c i p i t a t i o n and c o a r s e n i n g o c c u r d u r i n g the w a r m w o r k i n g of m o l y b d e n u m alloys which is n e c e s s a r y to p r o d u c e this s t r a i n h a r d e n e d condition. ~ The p r e c i p i t a t i o n which o c c u r s r e s u l t s in a l o s s of the p o t e n t i a l for d y n a m i c s t r a i n aging and lower t h a n p o s s i b l e high t e m p e r a t u r e strength. A useful m a t e r i a l might r e s u l t if the s t r a i n h a r d e n ing could be r e t a i n e d in a m o l y b d e n u m alloy solution t r e a t e d to give m a x i m u m r e s p o n s e to d y n a m i c s t r a i n aging. Molybdenum alloys cannot be f a b r i c a t e d at low t e m p e r a t u r e s to p r e v e n t c a r b i d e p r e c i p i t a t i o n by conv e n t i o n a l m e a n s (i.e. swagging or r o l l i n g ) . However, m o l y b d e n u m a l l o y s can be s t r a i n h a r d e n e d at r o o m t e m p e r a t u r e u s i n
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