Microstructure and Toughness of Friction Stir Weld of Thick Structural Steel

摘要

Friction stir welding (FSW) was performed with single-sided one-pass butt welding using 12 mm thick structural steel plates with 400 N mm"2 grade of tensile strength. The microstructures and mechanical properties such as the Vickers hardness, tensile strength, and Charpy V-notch toughness of the weld joint were investigated, which verified the inhomogeneous features of the microstructure and toughness within the stir zone (SZ). Thermal cycle examinations with or without deformation at the peak temperature were undertaken using a thermomechanical testing apparatus in order to study the predominant factors on the microstructural evolution and resulting toughness within the SZ. It is indicated that the variation in the thermal cycle, especially the peak temperature, within the SZ plays a predominant role in defining the inhomogeneous features within the SZ.