High strength copper alloys by thermomechanical treatments
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of the p rN o m i n e n t a p p l i cE a t i o n s of copper a l l o y s is O t h e i r u s e as s p r i n g m a t e r i a l in e l e c t r o m e c h a n i c a l r e l a y s a n d in e l e c t r o n i c device p a c k a g e s . C u r r e n t e f f o r t s t o w a r d s m i n i a t u r e r e l a y s and device a s s e m b l i e s have r e s u l t e d in higher s t r e s s e s on the s p r i n g c o m p o n e n t and h e n c e a n e e d for i n c r e a s e d s t r e n g t h of the a l l o y s . To t h i s end we made a d e t a i l e d s t u d y of the effect of t h e r m o m e c h a n i c a l p r o c e s s i n g on the m e c h a n i c a l p r o p e r t i e s of s e v e r a l c o m m o n l y u s e d a l l o y s . T h e s e i n c l u d e CA-510, phosphor b r o n z e (5 pct Sn); C A - 7 6 2 , n i c k e l s i l v e r (12 pct Ni-28 pct Zn); CA-725, t i n - m o d i fied c u p r o n i c k e l (9 pct N i - 2 pct Sn); and C A - 1 7 2 , C u Be (2 pct Be).
GENERAL
CONSIDERATIONS
As-received commercial materials are generally designated by various tempers. These tempers correspond to specific levels of the tensile strength and are normally obtained by different degrees of cold work. A half-hard temper strip, for example, corresponds to about 20 pct reduction in thickness, while extra-spring temper corresponds to about 70 pct reduction. Reductions beyond extra-spring temper are not generally employed, chiefly because of the degradation of ductility that accompanies large deformation. It i s well known, h o w e v e r , that the flow s t r e n g t h g e n e r a l l y i n c r e a s e s with d e f o r m a t i o n b e c a u s e of strain hardening. Moreover, increased deformation often l e a d s to a p r e f e r r e d c r y s t a l l o g r a p h i c o r i e n t a tion of the g r a i n s . Since ~low s t r e n g t h of a m a t e r i a l is d e p e n d e n t on c r y s t a l o r i e n t a t i o n , i n c r e a s e d d e f o r m a t i o n o f f e r s the a d d i t i o n a l p o s s i b i l i t y of " t e x t u r e h a r d e n i n g " , x-4 F i n a l l y , cold w o r k often a c c e l e r a t e s the k i n e t i c s of solid state p h a s e t r a n s f o r m a t i o n s , s t h e r e b y o f f e r i n g a third p o s s i b i l i t y , that of a g e h a r d e n i n g . Of the a l l o y s s t u d i e d , only the C u - B e alloy n o r m a l l y exhibits age-hardening c h a r a c t e r i s t i c s .
R. R. HART, B. C. WONSIEWICZ,and G. Y. CHIN are Associate Member of the Technical Staff and Members of the Technical Staff, respectively, Bell Telephone Laboratories, Murray Hill, N. J. Manuscript submitted April 15, 1970. METALLURGICAL TRANSACTIONS
EXPERIMENT A L T a b l e I l i s t s the a n a l y z e d c o m p o s i t i o n s of the four a l l o y s studied. T h e i n i t i a l s u r v e y was conducted with c o m m e r c i a l g r a d e phosphor b r o n z e r o l l e d at Bell T e l e p h o n e L a b o r a t o r i e s ( M u r r a y Hill). S u b s e q u e n t l y , both phosphor b r o n z e and n i c k e l s i l v e r s a m p l e s were p
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