Microstructural evolution, coarsening behavior of vanadium carbide and mechanical properties in the simulated heat-affected zone of modified medium manganese steel

The microstructural evolution, coarsening behavior of vanadium carbide (VC) and the mechanical properties of the simulated heat-affected zone (HAZ) of modified medium manganese steel (MMMS) were investigated as a function of peak temperature (Tp). Cementite precipitated at the grain boundary at 650°C–850°C, and the formation of a carbide network was not observed even at a higher Tp. The nucleation of VC precipitates occurred at a Tp of 650°C, and with increasing Tp, they grew at a rate that is greater than the theoretical value calculated according to the volume diffusion-controlled mechanism. However, coarse VC particles disappeared when the Tp reached 1250°C, and VC particles less than 2.0nm precipitated during cooling. The lattice parameter of austenite in the simulated HAZ first decreased with VC precipitation, then increased with VC dissolution and finally decreased again at 1250°C due to VC regeneration. Meanwhile, the formation of the VC nanoparticles increased the microhardness and tensile strength of the simulated HAZ. [Display omitted] •Microstructural evolution in simulated heat-affected zone of medium manganese steel was investigated.•The Oswald ripening mechanism was applied to the welding thermal cycle.•The change in the lattice parameter provided an agreement with the carbide precipitation behavior.•The mechanical properties improved because of the formation of the VC nanoparticles.