The creep behavior of W-5 re
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T U N G S T E N is s u b j e c t to b r i t t l e f r a c t u r e at room t e m p e r a t u r e , and as a r e s u l t , the use of t u n g s t e n at t e m p e r a t u r e s above 1400~ where t u n g s t e n has high s t r e n g t h r e l a t i v e to m o s t m a t e r i a l s , has b e e n s e v e r e l y l i m i t e d . An effective way to lower 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 of t u n g s t e n i s to alloy with r h e n i u m , although the t r a n s i t i o n t e m p e r a t u r e for the W-Re alloys s t r o n g l y depends on the c h e m i c a l , m e c h a n i c a l , and t h e r m a l h i s t o r i e s of the m a t e r i a l as well as r h e n i u m c o n t e n t . l - s Room t e m p e r a t u r e duct i l i t y in W-25 Re* has b e e n obtained for a wider *In the remainderof this report W-5Re and W-25Re refer to W5and 25 pct Re, respectively. v a r i e t y of p r o c e s s i n g h i s t o r i e s than for any o t h e r c o m p o s i t i o n , and c o n s e q u e n t l y , both the low- and hight e m p e r a t u r e p r o p e r t i e s of this a l l o y have been s t u d ied in g r e a t e r detail than for any other c o m p o s i t i o n . While the addition of 25 pct Re s i g n i f i c a n t l y i m p r o v e s the ductility of tungsten at room t e m p e r a t u r e , it has little effect on the h i g h - t e m p e r a t u r e c r e e p s t r e n g t h of tungsten. ~ In the t e m p e r a t u r e region 1400 ~ to 1900~ W-25 Re has a s l i g h t l y g r e a t e r c r e e p r e s i s t a n c e at s t r e s s e s above 2500 psi, but pure tungsten has g r e a t e r c r e e p r e s i s t a n c e at lower s t r e s s e s . A second r h e n i u m a l l o y i n g effect has been found in the W-Re s y s t e m : a h a r d n e s s m i n i m u m e x i s t s at a c o m p o s i t i o n of about 5 pct Re. 2,7'~ L i m i t e d data on the m e c h a n i c a l p r o p e r t i e s of this alloy have shown that W-5 Re can be ductile at room t e m p e r a t u r e if the f a b r i c a t i o n h i s t o r y is c a r e f u l l y c o n t r o l l e d , 2 and that W-5 Re has the highest c r e e p s t r e n g t h of all solid solution W-Re alloys at 1925~ 4 The o b j e c t i v e s of this study were: 1) to study the c r e e p b e h a v i o r of W-5 Re in detail by d e t e r m i n i n g the effect of s t r e s s , t e m p e r a t u r e , and m i c r o s t r u c t u r e on c r e e p r a t e ; 2) to c o m p a r e the c r e e p s t r e n g t h of W-5 Re with r e s p e c t to t u n g s t e n and W-25 Re, and 3) to find the r e a s o n for the r e l a t i v e l y high c r e e p s t r e n g t h of the W - 5 Re alloy.
m e n s were h i g h - p u r i t y t u n g s t e n and r h e n i u m powders about 2 p in d i a m . The powders were dry b l e n d e d and i s o s t a t i c a l l y compacted at room tempe r a t u r e , and then the b i l l e t was s i n t e r e d in hydrogen at 2400~ for 4 hr. The a s - s i n t e r e d b a r was about 19 by 1-~ by 3 in. The 1 in. b a r was Dynapak forged to a t h i c
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