Strengthening mechanisms of Nb and V microalloying high strength hot-stamped steel

Effects of adding Nb and V components on the microstructure and mechanical properties of hot-stamped steel and corresponding strengthening mechanisms were investigated by both qualitative and quantitative methods, which include grain refining strengthening, dislocation strengthening, solid solution strengthening and precipitation strengthening. Results revealed that adding 0.046 wt% Nb to 30MnB5 steel can significantly improve the strength and hardness in comparison with other investigated steels with the same heat treatment processes. For the studied two steels adding both Nb and V, with the V content increases, the strength and hardness show a downward trend as dispersed nanometer precipitates, which play various strengthening roles, consume a part of carbon content and then reduce dislocation density. Our study shows that the major strengthening mechanism of the investigated four steels is the dislocation strengthening, which accounts for about 60% of total yield strength.