Radial Distribution Characteristics of Microstructure and Mechanical Properties of Ti-6Al-4V Butt Joint by Rotary Friction Welding

Ti-6Al-4V rods were butt-welded by rotary friction welding in this study. Additionally, the radial differences in microstructure and mechanical property of joints were investigated by hierarchy slicing method. The results displayed that the width of weld zone and heat-affected zone of joints became wider along radial direction. Meanwhile, the tensile strength of joints decreased gradually along the radial direction. According to the theoretical analysis, the temperature gradient and inhomogeneous forging pressure leaded to the radial differences. Through K-type thermocouples, the actual temperatures at different locations were measured, and the results were consistent with the theoretical analysis. Theoretically, the radial differences of rotary friction welding joint are an inherent phenomenon; thus, the size of weldment should be limited strictly below the corresponding critical size. In order to prevent radial differences from enlarging, the welding surface profile of weldment can be processed into oval shape, and a larger forging pressure can be used within the scope of the joint deformation allowed according to causes for radial differences.