Analysis of local necking in a biaxially stretched sheet
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Fig . 5 - - M o l y b d e n u m c o n t e n t of f e r r i t e in e q u i l i b r i u m w i t h Mo2C d e t e r m i n e d b y p r e c i s i o n l a t t i c e p a r a m e t e r m e a s u r e ments.
Temperature, ~
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D~o (J.L. Horn)
A r r h e n i u s plots of the v a l u e s of D c a l c u l a t e d f r o m the Z e n e r - H i l l e r t equation and the data of T a b l e I and F i g . 5, and of those e x t r a p o l a t e d f r o m the c o n v e n t i o n a l i n t e r d i f f u s i o n coefficient m e a s u r e m e n t s in a F e - M o r e p o r t e d by H a m 8 The a g r e e m e n t b e t w e e n t h e s e two s e t s of d i f f u s i v i t i e s i s u n c o m m o n l y good, and not only p r o v e s c o n c l u s i v e l y that MozC n e e d l e s grow wholly within the a p h a s e , but a l s o i n d i c a t e s that the t i p s of t h e s e n e e d l e s have a d i s o r d e r e d i n t e r f a c i a l s t r u c t u r e . S i m i l a r r e s u l t s on a n e e d l e s p r e c i p i t a t e d f r o m / 3 C u - Z n have b e e n r e c e n t l y r e p o r t e d . 9 On the other hand, p l a t e s of a in/3 T i - C r , 1~ of a in y F e - C , ~ of 0' in A1-Cu, z2 and of y in a A1Ag ~3 exhibit a s s o r t e d p e c u l a r i t i e s in t h e i r l e n g t h e n i n g b e h a v i o r which a r e d o u b t l e s s due to the p r e s e n c e of a m i s f i t d i s l o c a t i o n or c o h e r e n t s t r u c t u r e and of ledges at t h e i r edges. It thus b e g i n s to a p p e a r that the tip of a n e e d l e may f u r n i s h a r e a s o n a b l y r e l i a b l e e x a m p l e of a disordered interphase boundary, presumably because the l a r g e and r a p i d c h a n g e s in b o u n d a r y o r i e n t a t i o n p r e c l u d e the f o r m a t i o n of a p a r t i a l l y c o h e r e n t i n t e r facial s t r u c t u r e . 1. K. Relander: Acta Polytech. Scand., 1964, No. 34, p. 7. 2. F. G. Berry, A. T+ Davenport, and R. W+K. Honeycombe: The Mechanism o f Phase Transformations in Crystalline Solids, p. 288, Institute of Metals, London, 1969. 3. F. G. Berry and R. W. K. Honeycombe: Met. Trans., 1970, vol. 1, p. 3279. 4. F. E. Bowman, R. M. Parke, and A. J. Herzig: Trans, ASM, 1943, vol. 31, p. 487. 5. C. Zener: Trans. AIME, 1946, vol. 167, p. 550. 6. M. Hillert: JernkontoretsAnn., 1957, vol. 141, p. 757. 7+ R+ D. Townsend and J. S. Kirkaldy: Trans. ASM, 1968, vol+61, p. 605. 8. J. L. Ham: Trans. ASM, 1945, vol. 35, p. 331. 9. G. R. Purdy: Met. ScL Jnl., 1971, vol. 5, p. 81. 10. H. 1. Aaronson, W. B. Triplett, and G. M. Andes: Trans. TMS-AIME, 1958, vol. 212, p+ 624. 11. E. P. Simonen and R. Trivedi, Iowa State University, Ames, Iowa and H. I. Aaronson, Ford Motor Company, Dearborn, Mich.: unpublished research, 1970. 12. H. I. Aaronson andC. Laird: Trans. TMS-AIME, 1968, vol. 242, p. 1437. 13. C. Laird and H. I. Aaronson: ActaMet., 1969, vo[. 17
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