M. Sadeghi - Materials Engineering Department, Malek Ashtar University of Technology, Shahin Shahr, Iran
M. Hadi - Department of Materials Science and Engineering, Golpayegan University of Technology, Golpayegan, Iran
O. Bayat - Department of Materials science and Engineering, Hamedan University of Technology, Hamedan, Iran
H. Karimi - Materials Engineering Department, Malek Ashtar University of Technology, Shahin Shahr, Iran.

In this paper a constitutive equation was considered for the isothermal hot compression test of the Mn-Ni-Cr alloy. The hot compression test was performed in the strain rate range of ۰.۰۰۱-۰.۱ s-۱ and deformation temperature was varied from ۷۰۰ to ۹۰۰ °C. A considerable reduction in flow stress was observed regardless of the strain rate when temperature was increased from ۷۰۰ to ۷۵۰ °C. DTA and XRD evaluation revealed that the removal of Mn۳Cr phase and formation of the single solid solution phase were the reason for the flow stress reduction. At the low deformation temperature (۷۰۰°C) and the high strain rate (۰.۱ s-۱), a partially recrystallized microstructure was observed; this was such that with increasing the temperature and decreasing the strain rate, a recrystallized microstructure was completed. Also, the relationships between flow stress, strain rate and deformation temperature were addressed by the Zener-Holloman parameter in the exponent type with the hot deformation activation energy of ۳۰۱.۰۷ KJ/mol. Finally, the constitutive equation was proposed for predicting the flow stress at various strain rates and temperatures.

Hot deformation, Constitutive equation, Zener-Holloman, Mn-Ni-Cr alloy