Abstract: Dynamic recrystallization (DRX) behaviors of a heat-resistant martensitic stainless steel 403Nb during hot deformation have been investigated by single-pass thermo-mechanical simulative experiment at temperatures of 900-1150°C and strain rates of 0.01-1 s^-1. The results show that the true stress-true strain curves of this alloy can be classified into two types, one is of dynamic recovery and the other is of dynamic recrystallization. The DRX in 403Nb alloy is easy to occur at strain rates lower than 0.5 s^-1 and deformation temperatures higher than 1000°C. Using regression analysis, the stress multiplier (α) and apparent stress exponent (n) were calculated to be 0.0153 and 3.22, respectively, while the activation energy (Q_d) for DRX of 403Nb was calculated to be 367.293 kJ/mol. The constitutive equation of peak stress for DRX was also obtained. Based on P-J method, the critical strain for DRX was accurately  determined. The mathematical models of peak strain and kinetic equation for DRX of 403Nb steel were finally established.

Key words: 403Nb steel, Dynamic recrystallization, Hot deformation, Critical strain