The impact of welding heat input on microstructure, micro-texture, and mechanical properties of stir zone in friction stir welded DP600 steel

Abstract

In this research, the impact of the heat input (HI) used during friction stir welding (FSW) on the microstructure, micro-texture and mechanical properties of DP600 steel was examined. Two different sets of rotational and transverse speeds were utilized to produce robust welds, one with low HI and the other with high. The outcomes demonstrated that various products such as polygonal ferrite (PF), Widmanstatten ferrite (WF), ferrite-carbide aggregate (FCA), and bainite were created in the stir zone (SZ) during the FSW of DP600 steel. After microscopic analysis, it was found that the high HI weld exhibited a greater amount of WF and bainite, resulting in higher hardness and ultimate tensile strength values than the low HI weld. The low HI weld displayed texture components including D1, D2, and E, with a slight cube component. These components were thought to result from the transformation of a strong B texture component and a weaker R texture component of prior austenite, indicating continious dynamic recrystallization during the FSW process. On the other hand, the high HI sample had a strong cube texture component and a weaker D shear component, a result of the transformation of a strong R shear texture component of prior austenite, suggesting discountinious dynamic recrystallization during FSW. The study determined that the welding HI greatly influences the proportion of microconstituents, the development of micro-texture, and the mechanical characteristics of the SZ during the FSW of DP600 steel.