Sintering of loose spherical copper powder aggregates using silica as markers
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m p a r e the m i l l annealed p r o p e r t i e s of Ti-6A1-4V, Ti-7A1-4Mo, and Ti-6A1-6V-2Sn as he did. F i n a l l y , the d i s c u s s o r s t a t e s that he is u n a w a r e of documented evidence that ductile/3 i m p r o v e s s t r e s s c o r r o s i o n r e s i s t a n c e even in those alloys c o n t a i n i n g m a j o r a m o u n t s of/3. We draw his attention to Ref. 28 which shows the " a l l / 3 " alloy, Beta III ( T i - l l . 5 M o - 6 Z r - 4 . S S n ) to be n e a r l y i m m u n e to SCC. The d i s c u s s o r objects to the " d e t a i l e d d e s c r i p t i o n " which e x p l a i n s why the/3 heat t r e a t m e n t didn't i m p r o v e the T i - 5 A 1 - 5 Z r - 5 S n alloy, as well as why the quenched condition of Ti-70 and Ti-5A1-2.5Sn is i n f e r i o r to the /3 quenched condition, but does not p r e s e n t his o b j e c t i o n s in sufficient detail to p e r m i t us to reply to them. We can only state that the KIscc values a r e valid and the m i c r o s t r u c t u r a l e v i d e n c e is r e a l . We thus r e f e r the r e a d e r to our o r i g i n a l a r g u m e n t s on pages 4 6 2 - 3 and ask him to decide for himself. The final point r a i s e d in the d i s c u s s i o n c o n c e r n s the a s - r e c e i v e d and t h e r m o m e c h a n i c a l l y p r o c e s s e d r o l l i n g d i r e c t i o n s . They a r e p a r a l l e l .
Sintering of Loose Spherical Copper Powder Aggregates Using Silica as Markers
duced by f i r s t v a c u u m induction m e l t i n g in Vycor tubes, 1 in. c y l i n d r i c a l b i l l e t s of an alloy with 0.15 wt pct Si. After r e m o v a l of the s u r f a c e l a y e r , by f i r s t g r i n d i n g and then etching in n i t r i c acid, the b i l l e t s were a l t e r n a t e l y cold r o l l e d and a n n e a l e d in h y d r o g e n until they were r e d u c e d to 0.050 in. thick s t r i p s . The s t r i p s were h o m o g e n i z e d in evacuated s e a l e d c a p s u l e s at 1000~ for 24 h r and then c o m p l e t e l y i n t e r n a l l y oxidized by h e a t i n g in a c o p p e r - c u p r i c oxide pack at 1000~ for 20 h r , yielding a u n i f o r m d i s p e r s i o n of s p h e r i c a l SiO2 p a r t i c l e s in the copper m a t r i x . The i n t e r n a l l y oxidized s t r i p s were heated in flowing hydrogen at 1000~ for s e v e r a l h o u r s to r e d u c e any copper oxide p r e s e n t . They were then filed into powd e r . The f i l i n g s w e r e s p h e r o i d i z e d by dropping them through a v e r t i c a l induction heated h y d r o g e n f u r n a c e held at about 1200~ The n o n s p h e r i c a l p a r t i c l e s were s e p a r a t e d by l e t t i n g the powder r o l l down a v i b r a t i n g i n c l i n e d g l a s s p l a t e . The 44 to 100/~ d i a m f r a c t i o n of the s p h e r i c a l p a r t i c l e s were s e l e c t e d b y s i e v i n g . In m a k i n g loose powder a g g r e g a t e s , the copper s i l i c a powder was b l e n d e d with about 10 pct by weight of s p h e r i c a l p u r
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