DAMPING CAPACITY AND MECHANICAL PROPERTIES OF Zn-Al ALLOY CASTINGS

This paper describes damping capac i t y and mechanical p roper t ies o f Zn-8-20%A1 and Zn-8-20%Al-0.02-0.04XMg a l l o y cast ings. Zn-8-20%A1 a l l o y casti ngs show h igh damping when quenched from 573K. Small amount o f Mg a d d i t i o n t o these a l l o y cast ings lowers damping capaci ty considerably b u t e f f e c t i v e t o reduce decomposition through aging a t 423K f o r 48hrs a f t e r water quenched from 573K. According t o the r e s u l t s obtained i n t h i s inves t iga t ion , t h e amount o f Mg added should be l e s s than 0.02%. App l i ca t ion o f these a l l o y cast ings f o r a t tenua t ion a re discussed. 1 . I n t r o d u c t i o n . R e c e n t l y i t has been r e c o g n i z e d t h a t Zn-A1 a l l o y s show h i g h damping when q u e n c h e d f r o m above e u t e c t o i d t e m p e r a t u r e ( 5 4 8 K ) . The m o s t o f s t u d i e s o n t h i s phenomenon w e r e done w i t h r o l l e d o r d rawn s p e c i m e n s . Zn-A1 a l l o y s a r e u s e d m o s t l y f o r c a s t i n g s , and g e n e r a l l y , s m a l l amount o f Mg a r e added t o t h e s e a l l o y c a s t i n g s i n o r d e r t o i m p r o v e t h e i n t e r g r a n u l a r c o r r o s i o n r e s i s t i v i t y . The p u r p o s e o f t h i s i n v e s t i g a t i o n was t o measure damping c a p a c i t y and m e c h a n i c a l p r o p e r t i e s o f Zn-A1 a n d Zn-A1-Mg a l l o y c a s t i n g s . F r e q u e n c y a n a l y s i s f o r c a s t p l a t e s a n d c a s t t u b e j o i n t s were done t o e v a l u a t e t h e r e d u c i n g e f f e c t o f v i b r a t i o n o f t h e s e a l l o y c a s t i n g s . 2. E x p e r i m e n t a l P r o c e d u r e . C h e m i c a l c o m p o s i t i o n o f s p e c i m e n s a r e shown i n T a b l e 1 . A l l s p e c i m e n s w e r e h e a t t r e a t e d u n d e r two modes. 1 ) 573K x 2 h r . W . Q . 2 ) 573K x 2 h r . W . Q . , 423K x 4 8 h r . W . Q . L o g a r i t h m i c d e c r e m e n t 6 and e l e c t r i c a l r e s i s t i v i t y w e r e m e a s u r e d f o r 2 x 5 ~ 1 0 0 mm s p e c i m e n s a t room t e m p e r a t u r e . C h a r p y i m p a c t t e s t were c a r r i e d o u t f o r 1 0 x 1 0 ~ 5 0 rnm n o t c h l e s s s p e c i m e n s a t 273K. C a s t p l a t e s and c a s t t u b e j o i n t s were m a n u f a c t u r e d f r o m Zn-8-20%A1 a l l o y s a n d q u e n c h e d f r o m 573K ( 573K x 4 h r . W . Q . ) . S i z e o f t h e p l a t e and t h e t u b e j o i n t were shown i n F i g . 1 and F i g . 2 r e s p e c t i v e l y . F r e q u e n c y a n a l y s i s f o r c a s t p l a t e were shown i n F i g . 3 . F r e q u e n c y o f t h e o s c i l l a t o r was change d f r o m 200 t o 3000 Hz. Same a n a l y s i s f o r c a s t s t e e l p l a t e and f l a k e g r a p h i t e c a s t i r o n p l a t e were c a r r i e d o u t t o e v a l u a i t h e r e d u c i n g e f f e c t o f v i b r a t i o n o f Zn-A1 a l l o y c a s t i n g s . F i g . 4 i l l u s t r a t e s Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19815144