Reinforcement of laser-welded stainless steels by surface mechanical attrition treatment

The laser-welded stainless steel was treated by surface mechanical attrition treatment (SMAT) in order to improve its mechanical properties. The microstructure was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties were measured by means of microhardness and tensile tests. Results show that the microstructure of weldment after SMAT is composed of ultra-fine grains, multiscale twins, and residual dendrites. The mechanical properties of laser-welded stainless steels after SMAT are significantly improved. The strengthening of weldment can be attributed to the refinement of dendrites and formation of multiscale twins during SMAT. The influence of dendrites on the formation of twins is discussed.