The effects of impurities and heat treatment on the internal friction of tungsten at high temperatures
- PDF / 1,553,514 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 79 Downloads / 191 Views
T H E m e c h a n i c a l , physical, and m e t a l l u r g i c a l p r o p e r ties of t u n g s t e n a r e v e r y s e n s i t i v e to the p r e s e n c e of i m p u r i t i e s . 1-~~ T h e s e i m p u r i t i e s , w h e t h e r added i n t e n t i o n a l l y f o r t h e i r b e n e f i c i a l effects o r picked up d u r i n g m a t e r i a l p r o c e s s i n g and handling, a r e u s u a l l y p r e s e n t in t r a c e a m o u n t s which defy the c o n t r o l and q u a n t i t a tive a s s e s s m e n t of t h e i r c o n c e n t r a t i o n s . In addition to i m p u r i t i e s , m a t e r i a l t r e a t m e n t s such a s working, a n n e a l i n g , i r r a d i a t i n g , and a l l o y i n g play an i m p o r t a n t r o l e in d e t e r m i n i n g the p r o p e r t i e s of t u n g s t e n . The i n t e r n a l f r i c t i o n is one p r o p e r t y which is e x t r e m e l y s e n s i t i v e to the m i c r o s t r u c t u r a l c h a n g e s i n f l u e n c e d by these i m p u r i t i e s and t r e a t m e n t s . 7-~~ F o r this r e a s o n it can s e r v e a s a useful tool to study the b e h a v i o r of t u n g s t e n at high t e m p e r a t u r e s . It was the purpose of the p r e s e n t work to apply the i n t e r n a l f r i c t i o n technique u n d e r c a r e f u l l y c o n t r o l l e d c o n d i t i o n s to the study of r e l a x a t i o n p r o c e s s e s in t u n g sten and some of its alloys. The u s u a l definition of the i n t e r n a l f r i c t i o n was used: Q - l _ Z~E _ 5 2~E ~
62 2~~
[ 1]
w h e r e AE/E is the r e l a t i v e change of e l a s t i c e n e r g y d u r i n g one cycle, and 5 is the l o g a r i t h m i c d e c r e m e n t . E x p e r i m e n t s were p e r f o r m e d on worked and r e c r y s t a l l i z e d s p e c i m e n s in the t e m p e r a t u r e r a n g e of 300 ~ to 3000~ Damping and s h e a r m o d u l u s a s a function of t e m p e r a t u r e w e r e c o m p a r e d with m e t a l l o g r a p h i c o b s e r v a t i o n s and the r e s u l t s of c h e m i c a l and s p e c t r o graphic analyses. EXPERIMENTAL PROCEDURE The i n t e r n a l f r i c t i o n was m e a s u r e d with the f a m i l i a r t o r s i o n p e n d u l u m a p p a r a t u s n housed in an i m p r o v e d g l a s s - m e t a l c h a m b e r . The c h a m b e r was connected by m e a n s of a copper gasket to an ion pump and could be evacuated to 10 -s t o r r . Most of the e x p e r i m e n t s w e r e p e r f o r m e d in a v a c u u m of 10 -7 and 10 -~ t o r r . Specim e n s w e r e heated by s e l f - r e s i s t a n c e u s i n g a highly r e c t i f i e d d i r e c t c u r r e n t . The f r e e end of the p e n d u l u m was i m m e r s e d in a pool of high p u r i t y g a l l i u m to p r o I. BERLEC is Research Staff Member, Lighting Research Laboratory, General Electric Co., Nela,Park, Cleveland, Ohio. Manuscript submitted December 18, 1969. METALLURG[CALTRANSACTIONS
vide the e l e c t r i c a l contact. G a l l i u m was chosen b e c a u s e of i
Data Loading...
