Precipitation-hardening in Cu-3.6 wt PCT Ti
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has b e e n known f o r m a n y y e a r s ~ that C u - T i a l l o y s a r e a g e - h a r d e n a b l e . T h e m a x i m u m t e n s i l e s t r e n g t h for a l l o y s r a n g i n g f r o m (k7 to 5.8 wt pct T i was o b t a i n e d a f t e r aging at 400~ 2 although no p r e c i p i t a t e was obs e r v e d by light m i c r o s c o p y . T r a n s m i s s i o n e l e c t r o n m i c r o s c o p y s t u d i e s 3'4 have been c a r r i e d out on t h e s e a l l o y s , but they a r e i n c o m p l e t e and only l i m i t e d m e c h a n i c a l t e s t data w e r e p r e s e n t e d . It i s the p u r p o s e of this i n v e s t i g a t i o n to e x a m i n e t h i s alloy in v a r i o u s s t a t e s of aging by both light and t r a n s m i s s i o n e l e c t r o n m i c r o scopy with e m p h a s i s p l a c e d on the c o r r e l a t i o n of m e c h a n i c a l p r o p e r t i e s with 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 s . EXPERIMENTAL
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A Cu-3.6 wt pct Ti alloy composition was chosen because a maximum hardening was observed between 3 and a wt pct Til. '2 The alloy was prepared from O.F.H.C. copper and low interstitial grade titanium sponge by American Metals Climax, Inc. and supplied in the form of hot-rolled 0.I0 in. thick sheet. It was then further cold-rolled to 0.015 in. and sheared into strips for electron microscopy foils and tensile testing. Macrotensile specimens, 0.25 in. wide and with a 1.0 in. gage length, were prepared on a "Tensile-kut" machine. H. T. MICHELS, formerly Graduate Student, Department of Metallurgy and Materials Sciences, New York University, Bronx, N. Y., is now with The International Nickel Company, Inc., Paul D. Merica Research Laboratory, Sterling Forest, Suffern, N.Y.I.B. CADOFF and E. LEVINE aie Professor and Associate Professor, respectively, Department of Metallurgyand Materials Sciences, New York University. This paper is based upon a thesis submitted by H. T. MICHELS in partial fulfillment of the requirements of the degree of Doctor of Philosophy at New York University. Manuscript submitted August 9, 1971. METALLURGICALTRANSACTIONS
Solution t r e a t m e n t was for 1 h r at 885~ in a s i n g l e phase field, followed by a b r i n e quench. Aging was p e r f o r m e d f o r v a r i o u s t i m e s and t e m p e r a t u r e s and s a m p l e s w e r e a i r cooled f r o m t h e i r final state of t r e a t m e n t . All heat t r e a t m e n t s w e r e c a r r i e d out with the s p e c i m e n s s e a l e d in evacuated q u a r t z tubes. B r i n e quenching was a c c o m p l i s h e d by having the s p e c i m e n s , which w e r e s e a l e d in a q u a r t z tube, s l i d e f r o m a t i l t i n g f u r n a c e and s t r i k e an i n c l i n e d m e t a l plate. T h i s r e sulted in f r a c t u r i n g the tube, thus allowing the s p e c i m e n s to s l i d e into the b r i n e solution located in a v e s sel i m m e d i a t e l y below. A i r cooling w a s p e r f o r m e d by r e m o v i n g the evacuated q u a r t
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