Microstructural studies of a Ni-W directionally solidified eutectic composite
- PDF / 7,746,843 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 106 Downloads / 263 Views
EUTECTIC
c o m p o s i t e s have r e c e i v e d an i n c r e a s i n g a m o u n t of s t u d y f o r the p a s t ten y e a r s . Many e u t e c t i c c o m p o s i t e s a r e b r i t t l e and such b r i t t l e n e s s has r e tarded their application. Fewer ductile composites have been e x a m i n e d but s y s t e m s which have d u c t i l i t y a r e p o t e n t i a l l y a t t r a c t i v e . In this r e g a r d , Cline and Johnson 1 have shown that N i - W e u t e c t i c c o m p o s i t e s a r e r e l a t i v e l y d u c t i l e , and it h a s b e e n shown s u b s e quently t h a t both the m a t r i x and r e i n f o r c e m e n t p h a s e s a r e c a p a b l e of e x t e n s i v e d e f o r m a t i o n by s l i p . 2 F u r t h e r m o r e , i n s p e c t i o n of the N i - W c o n s t i t u t i o n d i a g r a m s u g g e s t s that the m i c r o s t r u c t u r e of the N i - W c o m p o s i t e can be w i d e l y v a r i e d b y a p p r o p r i a t e t h e r m a l t r e a t m e n t . L i m i t e d v a r i a t i o n s in m i c r o s t r u c t u r e have b e e n d e m o n s t r a t e d in an e a r l i e r p a p e r . 2 N e a r l y a l l o t h e r s y s t e m s s t u d i e d to d a t e h a v e b e e n i n v e s t i g a t e d in a s i n g l e m i c r o s t r u c t u r a l condition (the " a s - g r o w n " condition) b e c a u s e m a n y of t h e s e m a t e r i a l s e x h i b i t i n v a r i a n t m i c r o s t r u c t u r e s with r e g a r d to s o l i d s t a t e t r a n s f o r m a t i o n s and b e c a u s e the e m p h a s i s of m o s t s t u d i e s has been p l a c e d on m e c h a n i c a l b e h a v i o r . We have s e l e c t e d the N i - W s y s t e m to i n v e s t i g a t e the r e l a t i o n b e t w e e n m i c r o s t r u c t u r e and p r o p e r t i e s of a d u c t i l e e u t e c t i c c o m p o s i t e . The i n v e s t i g a t i o n which we will r e p o r t h e r e h a s c o n c e n t r a t e d on the v a r i a t i o n s in m i c r o s t r u c t u r e which can be p r o d u c e d in N i W e u t e c t i c s while a c o r o l l a r y p a p e r 3 w i l l d e s c r i b e the influence of such m i c r o s t r u c t u r a I v a r i a t i o n s on the p r o p e r t i e s of the e u t e c t i c c o m p o s i t e s . E X P E R I M E N T A L TECHNIQUE A Ni-45 wt p c t W a l l o y was p r e p a r e d f r o m Ni and W p o w d e r s . T h e s e p o w d e r s w e r e w e i g h e d out and J. C. WILLIAMSis Program Development Manager, Structural Materials, and G. GARMONG is a Member of the Technical Staff, Science Center, Rockwell International, Thousand Oaks, CA 9 t 360. Manuscript submitted November t 9, 1974. METALLURGICAL TRANSACTIONS A
m i x e d b y t u m b l i n g for 24 h, then s u b s e q u e n t l y cold p r e s s e d into c y l i n d e r s of a p p r o x i m a t e l y 6.4 m m d i a m • 15.9 m m high. T h e s e cold p r e s s e d c y l i n d e r s w e r e s i n t e r e d at 1300~ in an a t m o s p h e r e of a r g o n and h y d r o g e n . The s i n t e r e d p e l l e t s w
Data Loading...
