A technique for studies of ductile fracture in metals containing voids or inclusions
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c o m i t a n t c a r b i d e p r e c i p i t a t i o n a n d / o r d i s s o l u t i o n that a r e r e s p o n s i b l e f o r the i n t e r n a l d e f o r m a t i o n and c a r bon s e g r e g a t i o n r e q u i r e f u r t h e r study. We g r a t e f u l l y acknowledge the s u p p o r t of this r e s e a r c h by the A r m y R e s e a r c h O f f i ce. The a s s i s t a n c e in thin foil p r e p a r a t i o n by S. Y a g i e l s k i and L. Hahn of the H o m e r R e s e a r c h L a b o r a t o r i e s of the B e t h l e h e m S t e e l C o r p o r a t i o n is a l s o a c k n o w l e d g e d with thanks.
A Technique for Studies of Ductile Fracture in Metals Containing Voids or Inclusions
A t e c h n i q u e of s a m p l e p r e p a r a t i o n i s p r e s e n t e d f o r t h e study of t h e d u c t i l e f r a c t u r e which o c c u r s in m e t a l s containing f a i l u r e i n i t i a t i n g v o i d s o r i n c l u s i o n s . A n u m b e r of r e c e n t p u b l i c a t i o n s ~-~6 have d e a l t with d u c t i l e f r a c t u r e in m e t a l s containing i n t e r i o r d e f e c t s but many of t h e e x p e r i m e n t a l d a t a have been s o m e what l i m i t e d in t h e i r s c o p e b e c a u s e th e s a m p l e s have b e e n e i t h e r p e r f o r a t e d s h e e t s o r s o l i d s with d e f e c t s of r a n d o m s i z e and d i s t r i b u t i o n . F o r b e s t c o m p a r i s o n with t h e o r e t i c a l m o d e l s , s a m p l e s a r e needed in which a v a r i e t y of c a r e f u l l y c h o s e n d e f e c t s a r e i n c o r p o r a t e d into a s o l i d . T h i s p a p e r p r e s e n t s a t e c h n i q u e which a l l o w s t h e e m b e d d i n g of v o i d s and i n c l u s i o n s , with c o n t r o l l a b l e s i z e , s h a p e and n u m b e r t o g e t h e r with s o m e d u c t i l e f r a c t u r e m e a s u r e m e n t s obtained with s a m p l e s p r e p a r e d by the t e c h n i q u e . B a s i c to the t e c h n i q u e is t h e diffusion bonding p r o c e s s ~7 in which two m e t a l s u r f a c e s a r e bonded in a way to r e m o v e all t r a c e s of the bond l i n e . By way of e x a m p l e , F i g . 1 shows a c r o s s - s e c t i o n of a h e m i -
s p h e r i c a l void c r e a t e d by diffusion bonding t o g e t h e r the end f a c e s of two s h o r t c y l i n d e r s , one with a s m o o t h s u r f a c e and the o t h e r with a c e n t r a l l y l o c a t e d , g r o u n d in h e m i s p h e r e . A d e t a i l e d look at the r e g i o n w h e r e the bond was m a d e shows the c o m p l e t e d i s a p p e a r a n c e of t h e bond line by g r a i n g r o w t h a c r o s s it. U l t r a s o n i c n o n d e s t r u c t i v e m e a s u r e m e n t s c a r r i e d out in t he r a n g e f r o m 2.5 MHz to 15 MHz a l s o do not r e v e a l the p r e s e n c e of t h e bond l i n e . F o r the m e a s u r e m e n t s discussed here, c o m m e r c i a l g r a d e T i - 6 pct A1-4 p ct V was m a c h i n e d into t he f o r m of r i g h t
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