Effect of vibration on the formation of porosity in aluminum alloy ingots
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have d e c l i n e d m a r k e d l y , a t t r i b u t e d in the m a i n to o t h e r f e a t u r e s attendant to the l e a c h i n g p r o c e s s . T h e r e was no e v i d e n c e of p r e c i p i t a t i o n (such as i r o n j a r o s i t e s ) . It m ay be expedient, on c o n s i d e r i n g the i m p l i c a t i o n s of F i g . 1, to c a r e f u l l y e x a m i n e both the m i c r o b i o l o g i c a l e c o s y s t e m as w e l l as the l i x i v i a n t c h e m i s t r y in e a s e s w h e r e l e a c h i n g r a t e s d e c l i n e u n e x p e c t e d l y . Th e c o n t a m i n a t i o n of l i x i v i a n t s used in the b i o l e a c h i n g of c o a l as p a r t of i n o r g a n i c d e s u l f u r i z a t i o n p r o c e s s e s 1'6 might a l s o have to be c a r e f u l l y c o n t r o l l e d b e c a u s e the a b s o r p t i o n of l a r g e a m o u n t s of i r o n by fungi could d r a s t i c a l l y a l t e r the p r o c e s s k i n e t i c s . T h i s r e s e a r c h was s u p p o r t e d by the New M e x i c o E n e r g y and M i n e r a l s D e p a r t m e n t G r a n t E M D - 7 8 - 3 3 1 9 a d m i n i s t e r e d by the E n e r g y Institute at New M e x i c o T e c h .
Effect of Vibration on the Formation of Porosity in Aluminum Alloy Ingots
p u r i t y . C h e m i c a l c o m p o s i t i o n of the a l l o y s u s e d in the p r e s e n t i n v e s t i g a t i o n is g i v e n in T a b l e I. C a s t i n g s w e r e made in a c y l i n d r i c a l g r a p h i t e m o l d 83 m m in height and 35 m m in d i a m e t e r which was c l a m p e d r i g i d l y on the table of an e l e c t r o d y n a m i c v i b r a t o r . Th e inside of the mold was p r o v i d e d with s l i g h t t a p e r f o r e a s y e j e c t i o n of the c a s t ingot. P r e h e a t i n g of the m o l d to 350~ was c o n s i d e r e d n e c e s s a r y to avoid chilling of the c a s t i n g and to a c h i e v e m e a s u r a b l e i n f l u en ce of v i b r a t i o n on ingot s t r u c t u r e . V i b r a t i o n s of d i f f e r e n t i n t e n s i t i e s w e r e i m p o s e d on s o l i d i f y i n g m e l t s in the p e a k a c c e l e r a t i o n r a n g e of 1 to 20 g at 30 Hz and 5 to 120 g at 150 Hz f r e q u e n c i e s (Table II). The mold was kept v i b r a t i n g at p r e s e t v a l u e of f r e q u e n c y and peak a c c e l e r a t i o n throughout the e n t i r e p e r i o d of pouring and s u b s e q u e n t s o l i d i f i c a t i o n . C a s t hags w e r e a l s o m a d e in s t a t i o n a r y m o l d s . Th e p o u r i n g t e m p e r a t u r e (750~ the m o l d p r e h e a t t e m p e r a t u r e (350~ and o t h er conditions w e r e kept i d e n t i c a l in p r e p a r a t i o n of the c a s t i n g s both in s t a t i c and v i b r a t ing m o l d s . No d e g a s s i n g agent was u s e d during m e l t ing and c a s t i n g of t e s t ingots.
D. P. SHUKLA,
D. B. GOEL,
AND
P. C. PANDEY
A r e v i e w of l i t e r a t u r e 1-~ r e v e a l s that v i b r a t i o n s of both sonic and u
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