Microstructure and mechanical properties of hot-rolled V-microalloyed Al-containing medium-Mn steel

Abstract

The microstructure and mechanical properties of a V-microalloyed Al-containing medium-Mn steel after hot rolling and intercritical annealing (IA) are explored. The tested steel exhibits a fine multiphase microstructure consisting of bimodal sizes of ferrite and retained austenite plus considerable amount of fine VC and/or M3C precipitates. Physical–chemical phase analysis shows that about 71.0% of the total V is in VC phase and more than 93% of VC particles is less than 5 nm. The calculated precipitation strengthening values of VC are ~ 347 and ~ 234 MPa for the specimens intercritically annealed at 625 and 750 °C, respectively. An excellent combination of strength and ductility as high as ~ 50 GPa% and yield strength (YS) of 890 MPa was obtained at intercritical temperature (TIA) of 725 °C, although it does not correspond to the maximum precipitation strengthening of VC phase. Therefore, it is suggested that an optimization of TIA corresponding to both excellent combination of strength and ductility and high YS should be further explored through chemical composition and IA process optimization.