Compressive creep rates of partially melted Al-Ga alloys
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In s u m m a r y , the o b s e r v a t i o n s r e p o r t e d i n d i c a t e that a l i n e a r r e l a t i o n s h i p e x i s t s , f o r a given p a r t i c l e shape, b e t w e e n y i e l d s t r e s s and i n v e r s e c a r b i d e s i z e , and b e tween u l t i m a t e t e n s i l e s t r e n g t h and the s q u a r e r o o t of i n v e r s e c a r b i d e s i z e f o r AISI 4140 o v e r a wide r a n g e of m i c r o s t r u c t u r e s and s t r e n g t h . As noted e a r l i e r , a d ditional work is b e i n g conducted to p r o v i d e a t h e o r e t i cal ex p l an at i o n f o r the UTS v s ( l / a ) x/z r e l a t i o n s h i p , and a l s o with a v i e w to d e t e r m i n i n g w h e t h e r this is indeed a g e n e r a l e f f e c t which could be u t i l i z e d in the d e s i g n of e n g i n e e r i n g m a t e r i a l s of s p e c i f i e d u l t i m a t e t e n s i l e strength. T h i s w o r k h as b e e n s u p p o r t e d by the N a t i o n a l R e s e a r c h Council of Canada u n d er G r a n t - i n - A i d No. A-2103.
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1. W. R. Tyson:ActaMet., 1963, vol. 11, p. 61. 2. J. Gurland: Stereology and Quantitative Metallography, ASTMSTP No. 504, p. 108, Amer.Soc. for Testingand Matls., Philadelphia, 1972. 3. M.-W.Lui and I. Le May:MetatScience, 1974,vol.8, in press. 4. M.-W.Lui and I. Le May:Microstntctural Science Vol. II, AmericanElsevier, New York, 1974, p. 35. 5. M.-W.Lui and I. Le May:Proc. 4th Bolton Landing Conf. on Grain Boundaries in Engineering Materials, 1974,in press. 6. J. Gurland and J. Plateau: Trans. ASM, 1963, vol. 56, p. 442. 7. D. Broek:A Study on Ductile Fracture, NLR Rept. TR71021U,NationalAerospace Laboratory, Netherlands, 1971. 8. J. I. Bluhmand R. J. Morfissey:Proc. Ist Int. Con]:. on Fracture, vol. II, p. 1739, Sendal, 1966.
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Fig. 3--Ultimate tensile strength as a function of carbide size.
F i g s . 2 and 3 r e s p e c t i v e l y , show plots of the y i el d s t r e s s v s 1 / a and UTS v s ( l / a ) ~/z, and it m a y be s e e n that l i n e a r r e l a t i o n s h i p s a r e followed b e f o r e and a f t e r the b r e a k o c c u r r i n g b e t w e e n 300 and 550~ The b r e a k , w h e r e p a r t i c l e s i z e r e m a i n s constant, c o r r e s p o n d s to that shown in Fig. 1. The l i n e a r r e l a t i o n s h i p b e t w e e n YS and ( l / a ) is r e a d il y e x p l a i n e d f r o m O r o w a n ' s equation f o r d i s l o c a t i o n bowing, 3 but an e x a c t e x p l a n a t i o n is not yet a v a i l a b l e f o r the r e l a t i o n s h i p b e t w e e n UTS and ( 1 / a ) ~/~. H o w e v e r , f r a c t o g r a p h i c e x a m i n a t i o n showed that a ll f r a c t u r e s u r f a c e s i n v o l v e d d i m p l e r u p t u r e , and it has b e e n shown by Gurland and P l a t e a u 6 that the s t r e s s r e q u i r e d f o r m i c r o v o i d initiation (aN) is r e l a t e d to the s i z e of s e c o n d p h a s e p a r t i c l e s *
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