Microstructure and Mechanical Properties of a Hot-rolled High Manganese TWIP Steel Containing 0.3%V

In this paper, the microstructure, precipitates and mechanical properties of a 0.3%V-alloying high Mn austenitic TWIP steel after hot rolling and aging treatment were investigated, aimed to improve the yield strength of high Mn austenitic steel. Experimental results showed that an elongated and unrecrystallized grain structure could be obtained at a finish rolling temperature of 850°C or below in 0.3V steel. The amount of VC precipitates was very small and most vanadium remained in solution after hot rolling. Therefore, the solute drag effect of dissolved vanadium rather than the Zener pinning effect of VC precipitates was mainly responsible for the inhibition of recrystallization. The yield strength increase of 0.3V steel with deceasing finish rolling temperature was much more remarkable than that of V-free steel. Quantifying possible strengthening mechanisms revealed that most of the YS increase was due to the dislocation strengthening in 0.3V steel. The aging treatment for 30 min promoted the precipitation of VC, but the precipitation amount was still much less than the equilibrium precipitation amount. The comparative analysis on precipitation kinetics of VC in high Mn and low Mn steels indicated that the former had a more sluggish precipitation rate than the latter. This result was further analyzed in terms of the effect of Mn on the solubility product of VC in austenite.