Hot compression experiment was conducted on Gleeble-3800 thermal simulation testing machine to investigate the hot deformation behavior of Cr5 die casting mold steel, with deformation temperatures of 1100–1300 °C and strain rates of 0.01−10s−1. The experimental results indicated that deformation temperature and strain rate have significant impacts on dynamic recrystallization(DRX) of Cr5 die casting mold steel, the critical strain of DRX decreased as deformation temperature increased and strain rate decreased. According to the Arrhenius model, the activation energy for deformation was 427.85 kJ/mol, and the constitutive equation of hot deformation was derived. Validation of high temperature flow stress model showed that the fitted model emerged appreciable accuracy and reliability. The processing map was constructed based on DMM theory, which was concluded that the unstable region is mainly concentrated around the deformation condition of 1300 °C/10s−1. Cr5 die casting mold steel exhibits the best hot processing performance under the deformation condition of 1250 °C/0.1s−1, with an excellent efficiency of power dissipation(η = 0.36) and a lower value of Kernel average misorientation(KAM average = 1.675°). Discontinuous dynamic recrystallization (DDRX) is the main mechanism for recrystallization nucleation and growth during hot deformation of Cr5 die casting mold steel.
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