Hot Deformation of the Mn-Ni-Cr Alloy During Compression

In this paper a constitutive equation was considered for isothermal hot compression test of the Mn-Ni-Cr alloy. Hot compression test was performed in strain rate range of 0.001-0.1 s-1 while deformation temperature was varied from 700 to 900 °C. A considerable reduction in flow stress was observed regardless of the strain rate when temperature raised from 700 to 750 °C. DTA and XRD evaluation revealed that removal of Mn3Cr phase and formation of the single solid solution phase was the cause of the flow stress reduction. At low deformation temperature (700°C) and high strain rate (0.1 s-1), a partially recrystallized microstructure was observed; so that with increasing the temperature and decreasing the strain rate, a recrystallized microstructure was completed. 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 301.07 KJ/mol. Finally, the constitutive equation was proposed for prediction of the flow stress at various strain rates and temperatures.