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Thermal compression test of C630R rotor steel was carried out by Gleeble-3800 thermal simulation testing machine at temperature range of 1 000-1 200 ℃ and strain rate of 0.01-1 s-1， the thermal deformation behavior and the influence of different process parameters on the microstructure were studied， the constitutive equation and hot processing map of the C630R rotor steel at true strain of 0.8 was constructed. The experimental results indicate that the true stress of the C630R rotor steel decreases with the enhancement of deformation temperatures to 1 200 ℃ and the reduction of true strain rate to 0.01 s-1. When the deformation temperature is higher and the compression strain rate is lower， C630R rotor steel is preferred to produce dynamic recrystallization. Thermal deformation activation energy Q of the C630R rotor steel is calculated to be 530.155 kJ/mol by using the corrected flow stress curves， and the constitutive equation is ε= 5. 85 × 1018[sinh (0. 011 4σ) ]4. 852∙ exp (-530 155/RT）），the processing maps at true strain of 0.8 are plotted．The reasonable thermal processing parameters for C630R rotor steel under true strain of 0.8 is： deformation temperature of 1 075-1 200 ℃， strain rate of 0.01-0.11 s-1.

Fe40Mn20Cr20Ni20 medium-entropy alloy (MEA) has a single-phase crystal structure with high strength and good ductility at room temperature. It is important to study the hot deformation behavior for this alloy at a partially recrystallized state for possible high-temperature applications. In this investigation, the tensile tests were conducted on sheet materials treated via cold rolling combined with annealing at strain rates of 1 × 10−3–1 × 10−1 s−1 and deformation temperatures of 573–873 K. And the hyperbolic sine model was used to study the relationship between the peak stress, deformation energy storage and Zener–Hollomon parameter (Z parameter) of Fe40Mn20Cr20Ni20 medium-entropy alloys under high-temperature tension. According to the Arrhenius-type model, the constitutive equation of the alloys based on the flow stress was constructed, and the deformation activation energy and material parameters under different strain conditions were obtained. Based on the power dissipation theory and the instability criterion of the dynamic material model, the power dissipation diagram and the instability diagram were constructed, and the hot working map with a strain of 0.1 was obtained. The results show that the hyperbolic sine relation between the peak stress and Zener–Hollomon parameters can be well satisfied, and the deformation activation energy Q is 242.51 KJ/mol. Finally, the excellent thermo-mechanical processing range is calculated based on the hot working map. The flow instability region is 620–700 K and the strain rate is 2 × 10−3–4 × 10−3 s−1, as well as in the range of 787–873 K and 2 × 10−3–2.73 × 10−2 s−1. The optimum thermo-mechanical window is 850–873 K, ε ˙ = 1 × 10−3–2 × 10−3 s−1. [ABSTRACT FROM AUTHOR]