Superplasticity and residual tensile properties of a microduplex copper-nickel-zinc alloy
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structure is produced by simultaneous recrystallization and/3 phase precipitation from a heavily cold worked metastable a structure. A replica electron micrograph of the lightly etched microduplex structure is shown in Fig. 1. Compositions of the experimental heats p r e pared for the present experiments are shown in Table II. Two different deoxidants were explored since this factor had been found to be of importance in another alloy. 9 Table I. Preparation Sequence for Experimental Microduplex Copper-Nickel-Zinc Alloys 1. Aar induction melt virgin raw materials. 2. Deoxidize with Mg or Ti preceded by Mn. 3. Cast as 30 lb. (13.6 Kg), 4 X 4 in. (t0 X 10 cm) ingots. 4. Forge and hot roll at 1500~176 to 0.5 in. (1.3 cm) plate. 5. Solution anneal at 1300~176 and water quench to retain single phase fcc alpha structure. 6. Cold roll metastable alpha 85 pet. 7. Microduplex anneal at 950~176 to reerystallize alpha and precipitate beta.
EXPERIMENTAL PROCEDURES P r o c e s s i n g steps to produce the microduplex alloys are similar to those previously reported 4 and are listed in Table I. The microduplex structure is a fine grained intermixture of the fcc ~ and bcc/3 phases having an lnterphase spacing of approximately 1 pm. The R. D. SCHELLENGis with The International Nickel Company,Inc., Paul D. Medea Research Laboratory, Sterling Forest, Suffern, New York 10901. G.H. REYNOLDSformerly with The International Nickel Company, is now with Gulf Energy and Environmental Systems, Materials Science Department, P. O. Box 608, San Di~go,Calif. 92112. Manuscript submitted March 1, 1973. METALLURGICAL TRANSACTIONS
F i g . 1 - - R e p l i c a e l e c t r o n m i c r o g r a p h of m i c r o d u p l e x ~ ture.
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VOLUME 4, SEPTEMBER 1973-2199
S t r a i n r a t e s e n s i t i v i t y t e s t s z~ w e r e p e r f o r m e d on s t r i p t e n s i l e s p e c i m e n s [0.25 • 1.125 in. (0.63 • 2.86 cm) gage section] in an a r g o n a t m o s p h e r e at t e m p e r a t u r e s r a n g i n g f r o m 850 to 1200~ (454 to 649~ on an I n s t r o n t e s t i n g m a c h i n e . The s t e a d y s t a t e l o a d s at v a r i ous c o n s t a n t c r o s s h e a d s p e e d s w e r e t a k e n f r o m a c o n tinuous r e c o r d of l o a d v s t i m e . T r u e flow s t r e s s e s and t r u e s t r a i n r a t e s w e r e c o m p u t e d f r o m t h e s e data. Additional strip specimens were superplastically ext e n d e d to t o t a l ( e n g i n e e r i n g ) s t r a i n s of 20 to 316 p c t with the " G l e e b l e " * , lz an a p p a r a t u s which subj e c t s *Registered Trademark of Duffers Associates, Troy, New York.
s p e c i m e n s to a p r o g r a m m e d t i m e - t e m p e r a t u r e - s t r a i n c y c l e . By t r i a l and e r r o r , it was found that a 1 • 9 in. (2.5 • 21.6 cm) s t r i p s p e c i m e n (heated e l e c t r i c a l l y to the t e s t t e m p e r a t u r e ) p r o v i d e d r e a s o n a b l y u n i f o r m d e f o r m a t i o n o v e r a 1 in. (2.5 cm) s e c t i o n at the c e n t e r of the s t
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