The microstructural evolution and mechanical properties of resistance spot welded Fe-31Mn-3Al-3Si TWIP steel

In this study, similar resistance spot weldability of an Fe-31Mn-3Al-3Si Twinning Induced Plasticity (TWIP) steel was investigated. The microstructural evolution was studied by means of optical microscopy (OM) and scanning electron microscopy (SEM) in order to evaluate the effects of experimental conditions on spot welded (RSW) joints. In addition, tensile-shear load bearing capacity of welded materials and failure modes were precisely inspected to determine the mechanical properties and fracture behavior of welded joints. The results illustrated that due to the expulsion phenomenon, optimum welding parameters for the experimental TWIP steel are shifted to lower values. Meanwhile, OM indicated that the fusion zone (FZ) held a dendritic structure; however, heat affected zone (HAZ) exhibited a significant grain growth in the narrow band. At upper welding parameters, shrinkage cavities and, in certain specimens, in microscopic scale inter-dendritic micro-pores were observed.