Behavior of a nickel-base high-temperature alloy under hot-working conditions
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MAHMOUD M. FARAG is Professor of Materials Engineering, The American University in Cairo, Egypt. MOHAMEDM. HAMDY is Lecturer, Basra Institute of Technology, Iraq. Manuscript submitted June 17, 1975. METALLURGICALTRANSACTIONSA
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The present work was carried out on the Nimonic 105 alloy supplied by Henry Wiggin & Co. England. The chemical analysis of the alloy in wt pct was: C, 0.14; Si, 0.15; Cu, 0.02; Fe, 0.3; Mn, 0.04; Cr, 14.4; Ti, 1.27; Al, 4.65; Co, 19.7; Mo, 4.96; B, 0.006; Zr, 0.095; Ni, Balance. The material was supplied in the form of 19 mm diam extruded bars heat treated for 4 h at 1423 K and air cooled followed by 16 h at 1323 K and air cooled. S a m p l e s for m e c h a n i c a l b e h a v i o r s t u d i e s w e r e in the f o r m of c y l i n d e r s 18.6 + 0.01 m m d i a m e t e r and 19.2 ~: 0.01 m m height. C e n t e r l e s s g r i n d i n g was used to m a c h i n e the c y l i n d r i c a l s u r f a c e s and a b r a s i v e wheels followed by lapping to a r o u g h n e s s of 1-2 m i c r o m e t e r were used to m a c h i n e the flat s u r f a c e s . All s p e c i m e n s were inspected using the u l t r a s o n i c technique for i n t e r n a l c r a c k s and the f l u o r e s c e n t - p e n e t r a n t (Zyglo) test for s u r f a c e ones. Axial s y m m e t r y hot c o m p r e s s i o n t e s t s w e r e c a r r i e d out on a die f o r g i n g h a m m e r , f r i c t i o n s c r e w p r e s s , h y d r a u l i c p r e s s and a h o r i z o n t a l u p s e t t i n g m a c h i n e to obtain true s t r a i n r a t e s (~) of 64.3, 11.8 to 6.35, 2.22, and 0.38 s -1 r e s p e c t i v e l y . The test t e m p e r a t u r e s w e r e v a r i e d in the r a n g e 1223 to 1523 K in s t e p s of 50 K. In all c a s e s the c o m p r e s s i o n t e s t s were p e r f o r m e d using a s u b p r e s s fitted with a s t r a i n gage load cell and inductive d i s p l a c e m e n t t r a n s d u c e r for m e a s u r i n g the d e f o r m a t i o n load and s t r a i n r e s p e c t i v e l y . The s i g n a l s were r e c o r d e d by a light beam o s c i l l o g r a p h with a r e s p o n s e time of one ps. To c a r r y out a c o m p r e s s i o n test, the s p e c i m e n and the lapped p l a t e n s s u r f a c e s were coated with graphite (Aquadag) s u s p e n d e d in alcohol and then heated together with the p l a t e n s to a t e m p e r a t u r e slightly higher than the test t e m p e r a t u r e to allow for the VOLUME 7A, FEBRUARY 1976-221
t e m p e r a t u r e drop d u r i n g t r a n s p o r t i n g f r o m the f u r n a c e to the s u b p r e s s . The t r a n s f e r t i m e was about two s e c o n d s and the t e m p e r a t u r e drop was in the r a n g e of 15 to 25 K depending on the test t e m p e r a t u r e . The t e m p e r a t u r e d i f f e r e n c e between the s p e c i m e n s u r face and middle due to this t r a n s f e r was in the r a n g e of 8 to 12 K. The d e f o r m e d s p e c i m e n s were w a t e r quenched within about two s e c o
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