Influence of Laser Power on Microstructure and Mechanical Properties of Laser Welded Medium Manganese Transformation-Induced Plasticity Steel

In this study, laser welding was employed to butt-weld warm-rolled 6.86% medium Mn transformation-induced plasticity (TRIP) steel (MMS). The investigation focused on the microstructure and mechanical properties of the base metal (BM) as well as the welded joint (WJ). The BM exhibited a mixed microstructure consisting of austenite and d-ferrite, while the fusion zone (FZ) contained martensite and d-ferrite. In terms of hardness, the cross section of the FZ in the WJ displayed higher values compared to the BM. The heat-affected zone (HAZ) did not exhibit significant hardness reduction. Tensile testing revealed that the WJ of the MMS exhibited ductile fracture behavior, with the elongation initially increasing and then decreasing with the rise in laser power. Notably, experimental data demonstrated that a laser power of 1500 W outperformed all other power settings in terms of macro morphology and performance.