Mechanical properties of electron-beam-melted molybdenum and dilute Mo-Re alloys
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Mechanical Properties of Electron-Beam-Melted Molybdenum and Dilute Mo-Re Alloys WILLIAM D. K L O P P AND WALTER R. WITZKE A L T H O U G H r h e n i u m is b e t t e r known for its r e m a r k able " d u c t i l i z i n g " effect in M o - 3 5 - and W - 2 6 - R e a l loys, x it also p r o m o t e s r e d u c e d h a r d n e s s and i m p r o v e d l o w - t e m p e r a t u r e d u c t i l i t y in the Group VIA e l e m e n t s at a l l o y i n g l e v e l s below 10 at. pct. 8 This l a t t e r effect is t e r m e d " s o l u t i o n s o f t e n i n g " and is a l s o p r o m o t e d to l e s s e r d e g r e e s by e l e m e n t s o t h e r than r h e n i u m , that is, b y the p l a t i n u m - g r o u p m e t a l s . Recent s t u d i e s of W-Re a l l o y s showed that additions of 2 to 4 at. pct Re to t u n g s t e n r e d u c e d the d u c t i l e b r i t t l e b e n d t r a n s i t i o n t e m p e r a t u r e by about 150~ s Since m o l y b d e n u m is s i m i l a r in m a n y r e s p e c t s to t u n g s t e n and also exhibits r e d u c e d l o w - t e m p e r a t u r e h a r d n e s s on dilute r h e n i u m alloying, 4 s i m i l a r r e d u c t i o n in the d u c t i l e - b r i t t l e t r a n s i t i o n t e m p e r a t u r e can be e x pected in dilute Mo-Re a l l o y s . The p r e s e n t study was u n d e r t a k e n p r i m a r i l y to d e t e r m i n e the effects of s m a l l r h e n i u m additions on the lowt e m p e r a t u r e d u c t i l i t y of m o l y b d e n u m . A s e c o n d a r y o b j e c t i v e was to c h a r a c t e r i z e the m e c h a n i c a l p r o p e r t i e s of dilute Mo-Re a l l o y s . Ingots of unalloyed m o l y b d e n u m and t h r e e Mo-Re a l loys w e r e e l e c t r o n - b e a m - m e l t e d f r o m c o m p a c t e d powd e r m e t a l l u r g y e l e c t r o d e s . B i l l e t s m e a s u r i n g 2 in. i n d i a m e t e r by 4 to 6 in. long w e r e m a c h i n e d f r o m the i n gots and e x t r u d e d at 1425 ~ to 1540~ The e x t r u s i o n s w e r e c o n v e r t e d into sound r o d and s h e e t by swaging and r o l l i n g in the t e m p e r a t u r e r a n g e 815 ~ to 1175~ A n a l y s e s on the f a b r i c a t e d m a t e r i a l s i n d i c a t e d that the t h r e e a l l o y s contained 3.9, 5.9, and 7.7 at. pct Re, r e s p e c t i v e l y . Oxygen c o n t e n t s of the four m a t e r i a l s r a n g e d f r o m 11 to 35 wt ppm, n i t r o g e n f r o m 2 to 15 wt ppm, and c a r b o n f r o m 5 to 37 wt ppm. Bend t r a n s i t i o n t e m p e r a t u r e s (defined as the lowest t e m p e r a t u r e for a 90 deg 4 T bend at 1 ipm without f r a c t u r e ) for u n a l l o y e d m o l y b d e n u m and the t h r e e MoRe a l l o y s in the a s - r o l l e d condition and a f t e r a n n e a l ing at 1260 ~ o r 1370~ a r e shown in Fig. 1 a s a function o f r h e n i u m content. It is obvious that dilute r h e n i u m additions affect s i g n i f i c a n t r e d u c t i o n s in the d u c t i l e - b r i t t l e t r a n s i t i o n t e m p e r
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