Effect of Nb-V microalloying on hot deformation behavior of medium Mn steels

Influence of Nb-V microalloying on hot deformation behavior and microstructures of medium Mn steel (MMS) was investigated by uniaxial hot compression tests. By establishing the constitutive equations for simulating the measured flow curves, we successfully constructed deformation activation energy (Q) maps and processing maps for identifying the region of flow instability. We may conclude the following consequences as the Nb-V alloying of MMS: (i) The critical strain is increased and the increment diminishes with the increasing deformation temperature, suggesting that NbC precipitates could retard dynamic recrystallization (DRX) in MMS more than the solute Nb; (ii) The deformation activation energy of MMS is significantly increased and even more than high Mn steels, suggesting that it retards DRX more than high content of Mn; (iii) The hot workability of MMS is improved by narrowing the hot processing window for the unstable flow stress, in which the mixed presence of both fine recrystallized and coarse unrecrystallized grains has been confirmed.