Constitutive equation for structural steels
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Fig. 5 - - S E M micrograph of a tensile-deformed 357-T5 thixoformed specimen showing the cracks in the eutectic area in the vicinity of the necked area.
fraction of primary OZ.[12] The low volume fraction of primary a therefore would increase the stress concentration at primary a/eutectic phase boundary due to the longer cracks developed in the eutectic area, and therefore would encourage primary a shearing mechanism. Consequently, a greater tensile ductility was rendered for the specimen with higher volume fraction of primary a.
This work has been supported by the National Research Laboratory program, which is funded by the Ministry of Science and Technology, Korea.
REFERENCES 1. D.B. Spencer, R. Mehrabian, and M.C. Flemings: Metall. Trans., 1972, vol. 3, pp. 1925-32. 2. M.C. Flemings: Metall. Trans. A, 1991, vol. 22A, pp. 957-81. 3. M. Modigell and J. Koke: J. Mater. Proc. Technol., 2001, vol. 111, pp. 53-58. 4. Y.B. Yu, S.S. Kim, Y.S. Lee, and J.H. Lee: Metall. Mater. Trans. A, 2002, vol. 33A, pp. 1399-1412. 5. Y.B. Yu, P.Y. Song, S.S. Kim, and J.H. Lee: Scripta Metall. Mater., 1999, vol. 41, pp. 762-71. 6. C. Park, S.S. Kim, Y.S. Lee, and J.H. Lee: J. Kor. Inst. Met. Mater., 2002, vol. 40, pp. 1071-77. 7. H.K. Jung and C.G. Kang: Metall. Mater. Trans. A, 1999, vol. 30A, pp. 2967-77. 8. S.B. Brown and M.C. Flemings: Adv. Mater. Proc., 1993, vol. 1, pp. 36-40. 9. J.P. Gabathuler and C. Ditzler: Proc. 4th Int. Conf. on Semi-Solid Processing of Alloys and Composites, D.H. Kirkwood and P. Kapranos, eds., Sheffield, England, 1996, pp. 331-35. 10. M. Stucky, M. Richard, L. Salvo, and A.K. Dahle: Proc. 5th Int. Conf. on the Semi-Solid Processing of Alloys and Composites, C. Dardano, M. Francisco, and J. Proud, eds., Golden, CO, 1998, pp. 513-20. 11. D. Brabazon, D.J. Browne, and A.J. Carr: Mater. Sci. Eng. A, 2003, vol. 356, pp. 69-80. 12. E. Ogris, A. Wahlen, H. Lfichinger, and P.J. Uggowitzer: J. LightMet., 2002, vol. 2, pp. 263-69. 1410--VOLUME 35A, APRIL 2004
A "constitutive equation" describes the dependence of the flow stress of a metal on strain rate, temperature, and strain, and may be derived empirically or from the theory of thermally activated rate processes applied to models of dislocation motion. An excellent description of the general theory of thermally activated plastic flow was given by Conrad. [1'2]The thermal activation theory was later reviewed by Kocks et al. ~3~ and applied to copper. H For steels, a specific form of equation was developed by Zerilli and Armstrong; ~5~this equation, with constants determined from Armco iron data, has been widely cited and used in the literature, e.g., References 6 and 7. The Zerilli-Armstrong equation depends heavily on semiempirical fits to data. The present work intends to derive a concise form of constitutive equation that is compatible with current understanding of the rate-controlling mechanism in steels, and to demonstrate the application of the equation to data from the literature for a range of steel types and to some new data for two (ferrite/pearlit
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