Silicon-Carbon interaction and its effect on the notch toughness of mild steel
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f r a c t i o n of the neck width a f t e r s i n t e r i n g for 1 h r which i n d i c a t e s that d e f o r m a t i o n d u r i n g the f a b r i c a tion of the wire a r r a y s or d u r i n g p r e s i n t e r i n g cannot account for the o b s e r v e d width of the p a r t i c l e containing area. If m a r k e r p a r t i c l e s were p r e s e n t i n the neck as a r e s u l t of c e n t e r to center m o t i o n of the w i r e s during s i n t e r i n g , one would expect that the p a r t i c l e c o n t a i n i n g n e c k r e g i o n should b e c o m e wider with i n c r e a s i n g s i n t e r i n g t i m e since c e n t e r to c e n t e r m o t i o n would p r o c e e d c o n t i n u o u s l y d u r i n g s i n t e r i n g . Such widening was not o b s e r v e d . N e i t h e r was any high d e n s i t y line of m a r k e r s seen at the junction b e t w e e n w i r e s , a n o t h e r expected c o n s e q u e n c e of c e n t e r to c e n t e r m o t i o n . It i s t h e r e f o r e concluded that the p r e s e n c e of the p a r t i c l e s in the neck r e g i o n s m u s t be a r e s u l t of d i s location m o t i o n (slip) as the o p e r a t i n g m e c h a n i s m of m a t e r i a l t r a n s p o r t d u r i n g the e a r l y s t a g e s of s i n t e r i n g . T h i s e a r l y stage where slip o c c u r s e n d s after a p p r o x i m a t e l y 1 hr of sintering~ p r o d u c i n g a n e c k width of a p p r o x i m a t e l y 15 ~t for the 100 ~t d i a m w i r e s or app r o x i m a t e l y 18 ~ for the 180 p diam w i r e s . As neck growth p r o c e e d s beyond this point, the s t r e s s e s due to s u r f a c e t e n s i o n f o r c e s d e c r e a s e and the t r a n s p o r t m e c h a n i s m c h a n g e s to diffusional flow. The work r e p o r t e d in this c o m m u n i c a t i o n was supp o r t e d by the R e s e a r c h D i v i s i o n of the United States Atomic E n e r g y C o m m i s s i o n at the NASA I n t e r d i s c i p l i n a r y M a t e r i a l s R e s e a r c h C e n t e r at R e n s s e l a e r P o l y t e c h n i c I n s t i t u t e . T h i s is a r e v i s e d v e r s i o n of a talk p r e s e n t e d at the Second E u r o p e a n S y m p o s i u m on Powder M e t a l l u r g y in S t u t t g a r t , G e r m a n y , May 1968. 1. J. Brett and L. Seigle:ActaMet., 1966,vol. 14, pp. 575-82;also,Smtering and Related Phenomena, Kuczynskl,Hooton,and Gibbon,Eds.,pp. 273-95, Gordonand Breach, 1967.
Fig. 2--Array of 180/~ Ag-A1 oxide wires sintered 1 hr at 935~ Magnification 580 times.
Silicon-Carbon Interaction and Its Effect on the Notch Toughness of Mild Steel P H I L I P ABRAMOWITZ AND RICHARD A. MOLL T H E effect of s i l i c o n on the notch t o u g h n e s s of m i l d s t e e l i s somewhat a n o m a l o u s . Up to a p p r o x i m a t e l y 0.5 wt pct, s i l i c o n i m p r o v e s t o u g h n e s s , but a m o u n t s in e x c e s s of this have an e m b r i t t l i n g effect. The i n i t i a l i m p r o v e m e n t in toughness is g e n e r a l l y a t t r i b u t
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