Critical Conditions for Dynamic Recrystallization of S280 Ultra-High-Strength Stainless Steel Based on Work Hardening Rate

Isothermal and constant-strain-rate compression experiments for S280 ultra-high-strength stainless steel were carried out under deformation temperatures of 1000-1150 degrees C and strain rates of 0.001-10 s(-1) with a Thermecmaster-Z thermal simulator. The flow-stress behavior of the alloy was studied and the hot deformation activation energy was calculated. A critical strain model of the dynamic recrystallization (DRX) of the alloy was established using the work hardening rate for the first time. The results show that S280 ultra-high-strength stainless steel was positively sensitive to the strain rate and negatively sensitive to temperature, and its flow-stress curve showed characteristics of flow softening. The hot deformation activation energy corresponding to the peak strain was 519.064 kJ/mol. The DRX critical strain of the steel was determined from the minimum value of the -partial derivative(ln theta)/partial derivative epsilon - epsilon curve. The relationship between the DRX critical strain and peak strain could be characterized as epsilon(c)=0.599 epsilon(p) and the relationship between the DRX critical stress and peak stress could be characterized as sigma(c)= 0.959 sigma(p) The critical strain model of DRX could be expressed as epsilon(c)=0.010Z(0.062). The research results can provide theoretical support for avoiding the generation of actual thermal processing microstructure defects such as coarse grains and for obtaining products with excellent microstructure and properties.