Surface Residual Stress Analysis in GMAW and LBW of the Dissimilar TRIP-DP Steels Joint: An Experimental Approach

A transformation-induced plasticity (TRIP) steel and a dual-phase (DP) steel were paired together by employing gas metal arc welding (GMAW) and laser beam welding (LBW) processes. The post-weld microstructure, the hardness profile, and the uniaxial tensile behavior of the welded steels have been analyzed in detail. The experimental surface residual stress distribution across the weldment was measured through the X-ray diffraction sin2Ψ technique. The results indicate that although a harder microstructure composed of predominant martensite was observed along the weldment, the uniaxial tensile behavior resulted in better elongation properties and a higher UTS in the LBW specimen as compared to the GMAW specimen. The resultant residual stress distribution in the heat-affected zone (HAZ) had an increase to a maximum value, followed by a steady decrease up to the base metal following the trend: upper-critical UC-HAZ (maximum) → inter-critical IC-HAZ (moderated) → subcritical SC-HAZ (lowered), which was particularly more evident on the GMAW specimen. Overall, the resultant residual stresses along the weldment were lower on the LBW specimen (172 MPa maximum) which clearly contrasts to the GMAW specimen (421 MPa maximum). Finally, the tensile residual stresses in both the GMAW or LBW did not influence the overall tensile properties of the weldments.