Secondary recrystallization in heavily drawn ETP copper wire
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t e m p e r a t u r e s e c o n d a r y r e c r y s t a l l i z a t i o n phen o m e n o n in c o m m e r c i a l E T P Cu m a g n e t w i r e with e m p h a s i s on the r o l e of d r a w i n g p r o c e s s i n g . I n s o f a r a s the p r o p e n s i t y for s e c o n d a r y r e c r y s t a l l i z a t i o n is o b s e r v e d (as p r e s e n t e d below) to v a r y r a d i a l l y in the w i r e , a s e r i e s of s t u d i e s has b e e n u n d e r t a k e n to a s s e s s the r o l e of p r o c e s s v a r i a b l e s known to effect r a d i a l s t r u c t u r e and p r o p e r t y g r a d i e n t s . T h e r e s u l t s of t h e s e s t u d i e s p r o v i d e a u s e f u l context for c o n s i d e r ing the b a s i c m e c h a n i s m of the s e c o n d a r y r e c r y s t a l lization reaction. MATERIALS The p r i n c i p a l i n v e s t i g a t i o n c o n c e r n s E T P Cu m a g n e t w i r e d r a w n to v a r i o u s r e d u c t i o n s f r o m c o n t i n u o u s - c a s t and s u b s e q u e n t l y hot r o l l e d r e d r a w rod. The r e d r a w rod d i a m e t e r v a r i e d but was t y p i c a l l y 12.7 m m . The oxygen content of the s u b j e c t m a t e r i a l was app r o x i m a t e l y 300 ppm.
THE GENERAL ANNEALING RESPONSE AND THE INFLUENCE OF DRAWING REDUCTION A series of six drawn wire samplings was selected involving commercial-practice drawing reductions ranging from 97.39 pct to 99.95 pct. The respective reductions were achieved by progressive drawing from the hot rolled redraw stock without intermediate annealing. Each drawing pass effected a one AWG (American Wire Gage) reduction, or an area reduction of about 21 pct. Since multidie, continuous drawing machines were used, the drawing speed increased with each pass, ranging to roughly 2000 cm/s for the smallest diameters. Lubrication was achieved with a p r o p r i e t a r y soap s o l u t i o n . A s u b s e r i e s of s p e c i m e n s f r o m each of the six d r a w i n g r e d u c t i o n s was s u b m i t t e d to a s e r i e s of 1 h, a r g o n a t m o s p h e r e a n n e a l s at t e m p e r a t u r e s r a n g i n g , at 28°C i n t e r v a l s , f r o m 149°C to 427°C. M e t a l l o g r a phic, m i c r o h a r d n e s s and t e n s i l e t e s t i n g e v a l u a t i o n s r e v e a l e d the following: a) the h a r d n e s s of the a s d r a w n w i r e s v a r i e d r a d i a l l y , r a n g i n g f r o m a 25 g Knoop h a r d n e s s of about 115 at the w i r e c e n t e r to a v a l u e of about 100 n e a r the w i r e s u r f a c e ; b) the i n VOLUME 7A, DECEMBER 1976 1891
f e r e n c e of t h e t e n s i l e d u c t i l i t y m e a s u r e m e n t s was that recrystallization was complete after a 1 h anneal i n t h e 250°C r a n g e ; m e t a l l o g r a p h i c i n s p e c t i o n r e vealed, however, that the recrystallization response w a s a l s o r a d i a l l y d e p e n d e n t w i t h t h e o u t e r p o r t i o n s of t h e w i r e r e c r y s t a l l i z i n g a s l o w a s 175°C w h i l e a r a n g
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