Direct evidence for boron segregation to grain boundaries in a nickel-base alloy by secondary ion mass spectrometry
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Author's Reply JOHN
CHIPMAN
There is undoubtedly a great deal of truth in the first paragraph of Kirchner and Uhrenius. They might well have added: he writes badly and is easily misunderstood. It i s unfortunate that m y G~ h a s b e e n i n t e r p r e t e d a s a v a l u e f o r the l a t t i c e s t a b i l i ~ of fec C r . It i s only a d i l u t e - s o l u t i o n s t a n d a r d s t a t e u s e f u l within the s t a t e d r a n g e : 0 < XCr < 0.122. I did not deduce a p h a s e d i a g r a m b e c a u s e I w a s quite s a t i s f i e d b y that of K i r c h n e r et al. which w a s u s e d a s the b a s i s f o r m y c a l c u l a t i o n s . K i r c h n e r and U h r e n i u s have s u s t a i n e d t h e i r point that m a c h i n e c a l c u l a t i o n y i e l d s s u p e r i o r r e s u l t s f o r the p h a s e b o u n d a r i e s . My kind of c a l c u l a t i o n i s u s e f u l only f o r a m o r e l i m i t e d s i t u a t i o n in which the p h a s e b o u n d a r i e s a r e known a s w e l l a s the a c t i v i t y in one p h a s e and i t i s r e q u i r e d to find the p a r t i a l m o l a r f r e e e n e r g y in the o t h e r p h a s e . My e q u a t i o n s do j u s t this, a n d g i v e n the p h a s e b o u n d a r y of the a - p h a s e , t h e y r e p r o d u c e t h a t of the y - p h a s e within • 0.002 in the v a l u e of XCr . The equation m u s t be l i m i t e d to t e m p e r a t u r e s and c o n c e n t r a t i o n s r e p r e s e n t e d in the y - l o o p and a r e not r e l e v a n t to p u r e f c e c h r o m i u m . 1. J. Chipman: Met. Trans., 1974, vol. 5, pp. 521-3. See also discussionby L. Kaufman: Met. Trans., 1974, vol. 5, pp. 1688-9. 2. G. Kirchner, T. Nishizawa and B. Uhrenius: Met. Trans., 1973, vol. 4, pp. 167-74. 3. G. Kirchner, G. Larbo and B. Uhrenius: in Fortschritte in der Metallographie, Berichte der III. Intemationalen Metallographie-Tagungin Leoben, 14. bis 16. Oktober 1970. R. Mitsche, F. leglitsch and G. Petzow, eds., pp. 545-57, Dr. Riederer-Verlag, Stuttgart, 1972. Pract. Metallogr., 1971, vol. 8, pp. 641-54. 4. G. Kirchner, H. Harvig,K.-R. Moquist and M. Hillert: Arch. EisenhiJttenw., 1973, vol. 44, pp. 227-34. 5. H. Harvig, G. Kirchner and M. Hinert: Met. Tram,, 1972, vol. 3, pp. 329-32. 6. G. Kirchner, H. Harvig and B. Uhrenius: Met. Trang, 1973, vol. 4, pp. 105967. 7. G. Kirchner and B. UhreniusrActaMet., 1974, vol. 22, pp. 523-32. 8. G. Kirchner: in Symposium Thermodynamik der Legierungen, pp. 26-9, MiJnster, Bundesrepublik Deutschland, September 1972. 9. R. L. Orr and J. Chipman: Trans. TMS-AtME, 1967, vol. 239, pp. 630-3. 10. R. J. Weissand K. J. Tauer: Phyg Rev., 1956, vol. 102, pp. 1490-5. 11. L. Kaufman: Computer Calculation of Phase Diagrams, Academic Press, New York, 1970. 12. G. Kirchner and H. Harvig: in Hauptversammlung der Dcutschen Gesellschaft fiir Metallkunde, p. 60, Stuttgart, Bundesrepublik Deutschland, May 1972. 226-VOLUME 6A, JANUARY 1975
Direct Evidence for Boron Segregation to Grain Boundaries in a Nickel-Base Alloy by
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