The effect of aging temperature on the fracture surface morphology of a fe-2.5 at. pct ni-7.5 at. pct al alloy
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of the e f f e c t s of a g i n g c o n d i t i o n s on t e n s i l e p r o p e r t i e s and f r a c t u r e s u r f a c e m o r p h o l o g y of t h i s a l l o y . The a l l o y u s e d has a s i m i l a r c o m p o s i t i o n ( F e - 2 . 5 6 at. p c t Ni-7.50 a t . p c t A1) to t h o s e u s e d in the p r e v i o u s s t u d y . 4 F l a t t e n s i l e s p e c i m e n s 4 m m wide (20 m m gage length) with r a d i u s of c u r v a t u r e of 4 m m at t h e s h o u l d e r s w e r e m a c h i n e d f r o m the s h e e t (0.5 m m in t h i c k n e s s ) which w a s p r e p a r e d a s d e s c r i b e d p r e v i o u s l y . 4 A f t e r v a c u u m a n n e a l i n g at 800~ for 60 rain followed by i c e d b r i n e quenching, t h e s e s p e c i m e n s w e r e aged r e s p e c t i v e l y at 540~ and 650~ f o r v a r i o u s t i m e s in v a c u u m , and then t e n s i l e t e s t e d at a c o n s t a n t s t r a i n r a t e of 3 • 10-4/min a t r o o m t e m p e r a t u r e . F l o w s t r e s s (0.2 p c t s t r a i n ) of the a g e d s p e c i m e n s a s w e l l a s the s o l u t i o n t r e a t e d s p e c i m e n w e r e shown in F i g . 1 a s a function of aging t i m e at 650~ and 540~ T h e s p e c i m e n a g e d at 650~ f o r 20 m i n had a flow s t r e s s of 53 K $ / m m z, which c o r r e s p o n d s a p p r o x i m a t e l y to the m a x i m u m v a l u e o b t a i n e d in the s e r i e s of the s p e c i m e n s aged at 650~ and was about 20 K g / m m 2 h i g h e r than the v a l u e o b t a i n e d f r o m the s o l u t i o n t r e a t e d s p e c i m e n . The s a m e v a l u e of flow s t r e s s w a s a t t a i n e d in the s p e c i m e n a g e d at 540~ f o r 10 min,
The Effect of Aging Temperature on the Fracture Surface Morphology of a Fe-2.5 At. Pct Ni-7.5 At. Pct AI Alloy
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L o w - a l l o y Ni-A1 s t e e l s have r e c e i v e d much a t t e n t i o n b e c a u s e of t h e i r i n t e r e s t i n g a g e - h a r d e n i n g c h a r a c t e r i s t i c s . T h e p r e c i p i t a t e s of i n t e r m e t a l l i c compound NiAlo(CSCl-type) with a l a t t i c e p a r a m e t e r about 2.88 to 2.90A w e r e c o m m o n l y r e c o g n i z e d in t h e s e s t e e l s aged at t e m p e r a t u r e s b e t w e e n about 520~ and 680~ H o w e v e r , it i s s t i l l a m b i g u o u s that w h e t h e r o r not s o m e m e t a s t a b l e o r d e r i n g r e a c t i o n o c c u r s d u r i n g the e a r l i e r s t a g e of the aging p r o c e s s in t h e s e s t e e l s . R e c e n t l y , T o k i z a n e and c o a u t h o r s 4 have i n v e s t i g a t e d the a g i n g k i n e t i c s of F e - 2 . 5 a t . p c t N i - 7 . 5 a t . p c t A1 f e r r i t i c a l l o y in d e t a i l by m e a n s of e l e c t r i c a l r e s i s t i v i t y and s p e c i f i c heat m e a s u r e m e n t s , e l e c t r o n m i c r o s c o p y and M b s s b a u e r s p e c t r o s c o p y . They s u g g e s t e d that the i s o t h e r m a l a g i n g p r o c e s
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