Effect of Mo on Dynamic Recrystallization Behavior of Nb–Mo Microalloyed Steels

The influence of the Mo addition on the dynamic recrystallization behavior of Nb microalloyed steels was studied. The initial austenite grain size, the amount of microalloying elements in solid solution and the deformation conditions (temperature and strain rate) affect dynamic recrystallization kinetics of both Nb and Nb–Mo steels. Continuous torsion tests were carried out to characterize the dynamic recrystallization behavior of the microalloyed austenite, after reheating the specimens at different temperatures between 1100 and 1460°C, this brought a wide range of initial grain sizes, from 22 to 805 μm. It was observed that decreasing the values of the Zener–Hollomon parameter and of the initial grain size promotes dynamic recrystallization. Mo in solid solution produces a large retardation effect in the dynamic recrystallization and brings higher values in the characteristic critical, εc, and peak, εp, strains, being this effect independent of the Mo content. A corrective factor has been applied to quantify the retardation produced by Mo in solid solution. This means that it was possible to propose a unique relationship to predict the peak strain for Nb, Nb–Ti and Nb–Mo steels.