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

The influence of Nb-V microalloying on the 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 concluded the following consequences of Nb-V alloying for MMS. (i) The critical strain increases and the increment diminishes with the increasing deformation temperature, suggesting that NbC precipitates more efficiently retard dynamic recrystallization (DRX) in MMS compared with solute Nb. (ii) The deformation activation energy of MMS is significantly increased and even higher than that of some reported high Mn steels, suggesting that its ability to retard DRX is greater than that of the high Mn content. (iii) The hot workability of MMS is improved by narrowing the hot processing window for the unstable flow stress, in which fine recrystallized and coarse unrecrys-tallized grains are present.