Effect of Welding Parameters on the Microstructure and Tensile Properties of Friction Stir-Welded DP600 Steel

• Published in: SAE International journal of materials and manufacturing 2019-01, Vol.12 (3), p.165-178, Article 05-12-03-0013
• Main Authors: Ashrafi, Hamid, Shamanian, M., Emadi, R., Sarmadi, M. Ahl
• Format: Article
• Language: English
• Subjects: Bainite; Base metal; Comparative analysis; Degassing of metals; Dual phase steels; Dual-phase steel; Duplex stainless steels; Elongation; Ferrite; Friction; Friction stir welding; Grain boundaries; Hardness; Heat affected zone; Iron compounds; Mechanical properties; Metal sheets; Metals; Microstructure; Sheet-metal; Softening; Steel; Tensile properties; Ultimate tensile strength; Welding; Welding parameters; Widmanstatten structure
• ISSN: 1946-3979; 1946-3987; 1946-3987
• DOI: 10.4271/05-12-03-0013

The aim of this study was to investigate the effect of friction stir welding (FSW) parameters on the micro-structure and tensile properties of dual-phase (DP) steels. In this regard, DP600 steel sheets were joined using FSW under different tool rotational (ω) and transverse speeds (v). Optical microstructure of the stir zone exhibited a mixture of bainite, Widmanstatten ferrite, grain boundary ferrite, and ferrite-carbide (FC) aggregate, which resulted in a hardness increase compared to the base metal (BM). The fraction of bainite and Widmanstatten ferrite in the stir zone increased with increasing the welding heat input. Formation of a softened zone in the subcritical area of the heat-affected zone (HAZ) resulted in the reduction of ultimate tensile strength and total elongation compared to those for the BM, while the yield strength was only marginally affected. Based on the experimental results, it was found that the joint efficiency of friction stir (FS)-welded DP600 steel decreased in a parabolic trend with increasing ω/v value.