Application of subgrain control to aluminum wire products
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E . HENRY CHIA AND E. A . STARKE, J r S u b s t r u c t u r e s t r e n g t h e n i n g h a s b e e n u t i l i z e d by the w i r e i n d u s t r y to p r o d u c e high s t r e n g t h , high conductivity, d u c t i l e a l u m i n u m w i r e s u i t a b l e f o r e l e c t r i c a l u s a g e . T h i s p a p e r d e s c r i b e s the choice of a l l o y a d d i t i o n s and p r o d u c t i o n m e t h o d s n e c e s s a r y for p r o d u c i n g and s t a b i l i z i n g a s m a l l s u b g r a i n s t r u c t u r e . The i n t e r r e l a t i o n b e t w e e n the v a r i o u s m a n u f a c t u r i n g s t e p s , such a s c a s t i n g , r o l l i n g , and d r a w i n g , and the r e s u l t i n g m i c r o s t r u c t u r e which c o n t r o l s the e l e c t r i c a l and m e c h a n i c a l p r o p e r t i e s i s d i s c u s s e d . T h e n e c e s s i t y f o r s t r i c t c o n t r o l of the p r o c e s s i n g p a r a m e t e r s e s t a b l i s h e d f o r v a r i o u s aluminum wire products is emphasized.
A m a j o r move to s u b s t i t u t e a l u m i n u m f o r c o p p e r in e l e c t r i c a l a p p l i c a t i o n s began in 1954 when the U.S. U n d e r w r i t e r s L a b o r a t o r y (UL) l i s t e d EC g r a d e a l u m i n u m in c i r c u i t s i z e c a b l e f o r the w i r i n g of b u i l d ings. T h e e c o n o m i c a d v a n t a g e s o f f e r e d by a l u m i n u m a r e s i g n i f i c a n t ; h o w e v e r , EC a l u m i n u m h a s p o o r m e c h a n i c a l p r o p e r t i e s and t h e r m a l s t a b i l i t y , both of which u l t i m a t e l y l e a d to t e r m i n a t i o n f a i l u r e s d u r ing s e r v i c e . An a n a l y s i s of the m e c h a n i s m of t h e s e f a i l u r e s , 1 and the r e q u i r e m e n t s of o t h e r p o t e n t i a l m a r k e t s , e.g., c o m m u n i c a t i o n s c a b l e , 2,3 m a g n e t w i r e , 4 and so forth, e s t a b l i s h e d p r o p e r t y r e q u i r e m e n t s unatt a i n a b l e by EC a l u m i n u m in any condition. T h i s led to the d e v e l o p m e n t of new " m i c r o " a l u m i n u m a l l o y s which u t i l i z e a fine s u b s t r u c t u r e f o r o b t a i n i n g the n e c e s s a r y c o m b i n a t i o n of conductivity, s t r e n g t h , d u c t i l i t y , c r e e p r e s i s t a n c e , and t h e r m a l s t a b i l i t y . The m o r e c o n v e n t i o n a l m e t h o d s of s t r e n g t h e n i n g a l u m i n u m , e.g., w o r k h a r d e n i n g , s o l i d s o l u t i o n s t r e n g t h e n i n g , d i s p e r s i o n a n d / o r age h a r d e n i n g a r e u n a c c e p t a b l e for e l e c t r i c a l a p p l i c a t i o n s s i n c e they r e s u l t in p r o d u c t s that a r e e i t h e r t h e r m o d y n a m i c a l l y u n s t a b l e o r have a high r e s i s t i v i t y . 5 H o w e v e r , a l u m i n u m h a s a high s t a c k i n g fault e n e r g y and d e v e l o p s w e l l - d e f i n e d s u b g r a i n s d u r i n g d e f o r m a t i o n , which m a k e s
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