Mechanical behavior of polycrystalline HoZn 2
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Mechanical Behavior of Polycrystalline HoZn 2 DAVID J. M I C H E L AND E A R L E RYBA T H E m e c h a n i c a l p r o p e r t i e s of i n t e r m e t a l l i c c o m pounds a r e of i n t e r e s t s i n c e this c l a s s of m a t e r i a l s e x h i b i t s a v a r i e t y of o t h e r p r o p e r t i e s which m a k e them somewhat attractive for various applications. Although c o n s i d e r a b l e work on the m e c h a n i c a l p r o p e r t i e s of these m a t e r i a l s has b e e n r e p o r t e d , 1-3 c o m pounds of the r a r e e a r t h m e t a l s have r e c e i v e d m i n i m a l attention. In p a r t i c u l a r , no m e c h a n i c a l p r o p e r t y data have b e e n r e p o r t e d f o r the ABe compounds f o r m e d by the r a r e e a r t h m e t a l s with z i n c , e x c e p t the e l a s t i c c o n s t a n t s of p o l y c r y s t a l l i n e HoZnz. 4 T h i s s p e c i f i c group of i s o s t r u c t u r a l REZn2 compounds is of f u n d a m e n t a l i n t e r e s t si n ce they p o s s e s s a c r y s t a l s t r u c t u r e which is r e l a t e d to the c o m m o n L a v e s p h a s e s and the A1Bz-type s t r u c t u r e . The p u r p o s e of t h i s p a p e r is to r e p o r t the r e s u l t s of r e c e n t c o m p r e s s i o n t e s t s conducted on p o l y c r y s t a l l i n e s p e c i m e n s of one of t h ese c o m p o u n d s , HoZn2. E x p e r i m e n t a l P r o c e d u r e s . Six s m a l l b a r s p e c i m e n s , m e a s u r i n g 0.187 by 0.187 by 0.562 in., w e r e p r e p a r e d by c o l d - p r e s s i n g - 3 2 5 m e s h HoZn~ a l l o y powder at 95,000 psi and s i n t e r i n g at 900~ Both the a l l o y p r e p a r a t i o n and powder m e t a l l u r g y t e c h n i q u e s used have b e e n d e s c r i b e d p r e v i o u s l y . 5'6 All s p e c i m e n s had a p e r c e n t a g e of t h e o r e t i c a l ( X - r ay ) d e n s i t y (pct TD) of 97 pct or g r e a t e r . The g r a i n s i z e in all c a s e s was ASTM #6. A f t e r r e m o v a l of the s u r f a c e r o u g h n e s s of a l l s p e c i m e n s by a b r a d i n g on s i l i c o n c a r b i d e p a p e r , the s p e c i m e n ends w e r e ground flat. Two Budd C40-111 s t r a i n g ag es w e r e c e m e n t e d to opposing s i d e s following d e t e r m i n a t i o n of the d i m e n s i o n s at the m i d - p o i n t of the long d i r e c t i o n . Each s p e c i m e n was p l a c e d in turn in a s l i g h t l y m o d i f i e d v e r s i o n of a c o m p r e s s i o n jig d e s c r i b e d by Hoke and Madden. 7 The jig c o n s i s t e d of b a l l - b e a r i n g joints b e t w e e n the s p e c i m e n s u p p o r t s and the t e s t i n g m a c h i n e , and was u s e d in an a t t e m p t to e l i m i n a t e any unequal s t r e s s e s in the s p e c i m e n s which would r e s u l t f r o m n o n p a r a l l e l s p e c i m e n ends. All s p e c i m e n s w e r e l o a d e d in 50-1b i n c r e m e n t s to f a i l u r e . D u r i n g loading, the m o v a b l e c r o s s - h e a d t r
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