The effects of particles on fracture processes in magnesium alloys
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The Effects of Particles on Fracture Processes in Magnesium Alloys C . D . CALHOUN AND N . S . S T O L O F F The influence of c o h e r e n t and n o n c o h e r e n t p a r t i c l e s on the m e c h a n i s m of d u c t i l e f r a c t u r e h a s b e e n s t u d i e d in two m a g n e s i u m b a s e a l l o y s : M g - 3 . 7 pct T h - 0 . 4 pct Z r and M g - 0 . 6 pct Z r . The t e r n a r y a l l o y was t e s t e d in the solution t r e a t e d condition, and a s a function of aging t i m e at the t e m p e r a t u r e of peak h a r d e n i n g , 325~ the b i n a r y a l l o y was t e s t e d in the solution t r e a t e d condition and a f t e r h y d r i d i n g to f o r m c - Z r H 2 p a r t i c l e s . F r a c t o g r a p h i c s t u d i e s w e r e c a r r i e d out on s m o o t h - b a r and notched t e n s i l e s a m p l e s a f t e r t e s t i n g at - 1 9 6 ~ 25 ~ and 210~ Fractographic f e a t u r e s o b s e r v e d in the solution t r e a t e d a l l o y s w e r e e x p l a i n a b l e in t e r m s of the o p e r a t i v e s l i p s y s t e m s in m a g n e s i u m . F e a t u r e s o b s e r v e d in a g e d M g - T h - Z r and h y d r i d e d M g - Z r w e r e r e l a t e d to p a r t i c l e s i z e , m o r p h o l o g y , and d i s t r i b u t i o n , with e m p h a s i s on d i m p l e - p a r t i c l e r e l a t i o n ships. C o h e r e n t , p l a t e - l i k e p a r t i c l e s (250]k long) p r o d u c e d d i m p l e s in M g - T h - Z r , a s did l a r g e r , n o n c o h e r e n t p a r t i c l e s . H o w e v e r , m a n y c a s e s of d i m p l e f o r m a t i o n without a s s o c i a t e d p a r t i c l e s a l s o w e r e noted. M i c r o v o i d s i z e s o b s e r v e d by light m i c r o s c o p y w e r e 20X d i m p l e s i z e s r e v e a l e d by e l e c t r o n f r a c t o g r a p h y . When s u b m i c r o s c o p i c v o i d s (
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