Abstract
In the present research, a comparative study on influence of friction stir welding (FSW) and gas tungsten arc welding (GTAW) processes on the microstructure and tensile properties of dual phase steel welds is carried out. The results indicate that the microstructure of weld metal and inner part of the heat affected zone (HAZ) in the GTA welded sample is composed of coarse bainite, Widmanestatten ferrite and ferrite–carbide (FC) aggregate. The sample welded by FSW exhibits the formation of fine ferrite, FC aggregate, and bainite in the weld nugget and inner part of the HAZ. Microhardness measurements reveal the formation of a softened zone in the subcritical area of the HAZ due to the tempering of the pre‐existing martensite. Both joints show lower tensile strength, tensile elongation and work hardening exponent compared to the base metal (BM), and fail in the softened HAZ during the uniaxial tensile test. However, the joint efficiency, work hardening rate and work hardening exponent of the sample welded by FSW are superior to those for the GTA welded sample. The predominant fracture mechanism for all samples is ductile with dimples on the fractured surfaces.
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