Journal of Welding Science

In this study, the effects of welding current intensity (9 and 10 kA) and holding time (5 and 40 cycles) on the energy absorption and failure mode of a dissimilar joint between DP590 and HSLA440 steels in the resistance spot welding process were investigated. For this purpose, four parameter combinations were prepared, and a tensile–shear test was performed on each sample. The results showed that increasing the current from 9 to 10 kA at a holding time of 5 cycles led to an increase of about 1 kN in strength; however, at a hold time of 40 cycles, changing the current resulted in a decrease of approximately 1.6 kN in strength. Therefore, the role of current is limited and dependent on the saturation of the weld nugget diameter. In contrast, increasing the hold time from 5 to 40 cycles had the most significant effect, increasing the energy absorption by about 217 J. Failure mode analysis also revealed that samples with longer hold times predominantly exhibited pull-out failure (PF), absorbing significantly more energy compared to interfacial failure (IF). Overall, the results indicate that controlling cooling through increasing the holding time is the most effective factor in enhancing absorbed energy and altering the failure mode in DP590/HSLA440 joints.

In the present study, 316L stainless steel walls were fabricated using the WAAM process under controlled primary parameters including welding current, voltage, torch travel speed, and wire feed rate. The solidification behavior, microstructural evolution, and mechanical performance of the WAAM-produced 316L stainless steel were systematically investigated. Microstructural observations revealed that the final structure consists of a γ austenitic matrix containing approximately 8.5% δ ferrite. Tensile testing demonstrated the simultaneous achievement of high strength and ductility. Specimens extracted perpendicular to the build direction exhibited an ultimate tensile strength of about 569 MPa, a yield strength of 378 MPa, and an elongation of approximately 69%. Mechanical anisotropy was estimated to be around 7.5%, attributed to the directional growth of columnar grains. The enhanced ductility compared to conventional cast steels is associated with the fully austenitic matrix, the controlled amount of δ ferrite, the refined dendritic microstructure, and the localized annealing effect resulting from the deposition of successive layers. Microhardness measurements along the build height indicated a gradual decrease in hardness with increasing distance from the substrate, caused by grain coarsening due to heat accumulation and the lower cooling rates in the upper layers. Overall, the findings demonstrate that the WAAM process is capable of producing 316L stainless steel with a balanced combination of high strength and ductility, provided that solidification behavior and thermal history are properly controlled. These results may serve as a basis for microstructure optimization and anisotropy reduction in industrial additive manufacturing applications.