Grain boundary damping in substitutional alloys
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EXPERIMENTAL S p e c t r o s c o p i c a l l y p u r e c o p p e r and n i c k e l w e r e obt a i n e d in r o d f o r m (5 m m d i a m by 15 c m long) f r o m M e s s r s J o h n s o n Mathey Ltd. M e t a l l i c i m p u r i t i e s w e r e ~ 9 ppm f o r both, in addition the n i c k e l c o n t a i n e d ~ 2 0 ppm O. Small m e t a l p i e c e s cut f r o m the r o d s w e r e s t a c k e d in a r e c r y s t a l l i z e d a l u m i n a boat, 4 in. in length, which was co n t ai n ed in a l a r g e r g r a p h i t e boat used as a s u s c e p t o r . T w e l v e ingots of v a r i o u s c o m p o s i t i o n s w e r e m e l t e d in an a r g o n a t m o s p h e r e by high f r e q u e n c y induction. The co o l i n g p r o c e s s was c o n t r o l l e d to r e duce c o r i n g to a m i n i m u m . A f t er c a s t i n g , the d e n d r i t i c s t r u c t u r e was b r o k e n down by r o l l i n g o r swaging. This was followed by a 1000~ anneal in flowing h y d r o g e n f o r 1 week to e n s u r e c o m p l e t e h o m o g e n i z a t i o n . The ingots w e r e then c o l d s w a g e d to 0.08 in. d i a m , and d r aw n down to 0.03 in. d i a m without an i n t e r m i t t e n t anneal. B e f o r e i n s e r t i o n in the i n t e r n a l f r i c t i o n a ppa r a t u s each s p e c i m e n was w a s h e d in a s o l u t i o n of 50 pct HCl, followed by an a c e t o n e r i n s e . Weinig and Machlin 3 have shown that this o p e r a t i o n r e m o v e s any i r o n p i c k e d up during swaging. An i n v e r t e d t o r s i o n pendulum, which h as b e e n d e s c r i b e d p r e v i o u s l y , 7'8 was used to m e a s u r e i n t e r n a l f r i c t i o n . A f t er t e s t i n g , the w i r e s w e r e cut into s e c t i o n s f o r m i c r o p r o b e a n a l y s i s , g r a i n s i z e d e t e r m i n a t i o n , and chemical analysis. Representative microprobe traces showed that the a l l o y i n g addition was h o m o g e n e o u s l y d i s t r i b u t e d . The C u - N i a l l o y s w e r e a n a l y z e d f or c o p p e r content by e l e c t r o l y s i s . The r e s u l t s of c h e m i c a l a n a l y s e s of the t w e l v e a l l o y s a r e p r e s e n t e d in Tab l e I.
Table I. Chemical Analysis of Cu-Ni Alloys
NominalCopper Content, Wt Pet
ChemicalAnalysis, Wt Pet
1.0
1.08
5.0 8.0 20 30 50 70 80 87 95 99 99.5
5.46 8.54 19.85 29.7 49.1 69.2 79.54 86.94 94.82 99.1 99.5
Copper Content At. Pet [At. Pet Ni] 1.0
5.1 7.9 18.6 28.1 47.1 67.5 78.2 [21.81 86.0 [14.01 94.4 [5.61 99.0 11.0] 99.5 [0.5]
VOLUME 1,SEPTEMBER 1970-2487
RESULTS In o r d e r to study the i n f l u e n c e of a l l o y c o n c e n t r a t i o n on g r a i n b o u n d a r y d a m p i n g it was n e c e s s a r y to m a i n t a i n a c o n s t a n t g r a i n s t r u c t u r e . A change in g r a i n s i z e s o m e t i m e s has a profound e f f e c t on the g r a i n b o u n d a r y d a m p i n g of p u r e m e t a l s . 7-9 All the a l l o y s w e r e a n n e a l e d f o r 1 h r at 900~ in situ b e f o r e t e s t
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