Maintaining an elongated grain structure after deformation of mechanically alloyed NiCrAlY
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c o n t a i n i n g n o m i n a l l y (by weight) 16 pct c h r o m i u m , 4 pct a l u m i n u m , and 2 to 3 pct y t t r i a (Y203), with the b a l a n c e b e i n g n i c k e l . It was s u p p l i e d by the Stellite D i v i s i o n of the Cabot C o r p o r a t i o n i n the f o r m of hot e x t r u s i o n s , 3 in. by 3/4 in. in c r o s s s e c t i o n . The ext r u s i o n s w e r e made f r o m m e c h a n i c a l l y a l l o y e d powd e r , p r o d u c e d f r o m the powdered i n g r e d i e n t s cited D. M. TRELA, T. K. GLASGOW, AND L. J . E B E R T above. In the a s - e x t r u d e d condition, the a v e r a g e g r a i n d i a m e t e r was 0.6 ~, with the g r a i n s b e i n g By v i r t u e of t h e i r b a s i c design, Oxide D i s p e r s i o n slightly elongated (length to width r a t i o of about 2 : 1). S t r e n g t h e n e d (ODS) NiCrA1 alloys exhibit i n h e r e n t l y P r e l i m i n a r y r o l l i n g t r i a l s i n d i c a t e d that the m a t e high m e l t i n g points, and e x c e l l e n t oxidation r e s i s t a n c e . r i a l could not be cold worked in the a s - e x t r u d e d conF u r t h e r , they have v e r y good high t e m p e r a t u r e m i c r o dition. C o n s e q u e n t l y , the a s - r e c e i v e d e x t r u s i o n s w e r e s t r u c t u r a l s t a b i l i t y and good high t e m p e r a t u r e s t r e n g t h given a full a n n e a l as an i n i t i a l t r e a t m e n t , p r e p a r a a s a r e s u l t of the d i s p e r s i o n s t r e n g t h e n i n g p h e n o m e n o n . 1 tory to cold working. The a n n e a l i n g t r e a t m e n t c o n s i s t T h i s fortunate c o m b i n a t i o n of p r o p e r t i e s m a k e s t h e m ing of h e a t i n g for 1 h at 245~ (1343~ in a n a r g o n l e a d i n g candidate m a t e r i a l s for application a s ada t m o s p h e r e , and a i r cooling. A f t e r t h i s a n n e a l , the v a n c e d gas t u r b i n e s t a t o r v a n e s . 2 In this v e r y d e m a n d e x t r u s i o n s w e r e capable of cold ( a m b i e n t t e m p e r a ing r o l e , t h e i r use would offer s i g n i f i c a n t e c o n o m i e s i n engine o p e r a t i o n t h r o u g h a r e d u c e d d e p e n d e n c e on cooling a i r and p r o t e c t i v e coatings. T h e p o t e n t i a l o p e r a t i n g cost e c o n o m i e s of the ODS NiCrA1 alloys tend to be offset to a c o n s i d e r a b l e d e g r e e by the high cost in the m a n u f a c t u r e of the v a n e s by m a c h i n i n g the c o m p l e x shapes f r o m c u r r e n t l y a v a i l a b l e extruded ODS NiCrA1 Stock. It is not u n c o m m o n to find that the input weight of the e x t r u s i o n is ten t i m e s that of the f i n i s h e d vane. To r e d u c e this v e r y s u b s t a n t i a l m a t e r i a l l o s s , it would be highly des i r a b l e to be able to f o r m a i r f o i l g e o m e t r i e s by nonm a c h i n i n g p r o c e s s e s , s u c h a s forging, r o l l i n g , e t c . However, such f o r m i n g methods m u s t be excluded f r o
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