Improving microstructure, tensile properties and corrosion resistance of AA6016 and AA2519 alloys friction stir lap joints via TIG arc

Abstract

The effects of tungsten inert gas arc-assisted friction stir welding (TIG-FSW) on the microstructure, tensile properties and corrosion resistance of AA6016 and AA2519 alloys lap joints were investigated by means of optical microscope, scanning electron microscope, tensile test at room temperature, corrosion immersion tests and electrochemical measurements. The results show that the introduction of TIG arc during FSW process results in a more uniform microstructure of the joint with no tunnel hole defects. Furthermore, it enhances tensile strength and elongation of the joint with increased rates of 11.5% and 50.0%, respectively; meanwhile, the corrosion current density and largest corrosion depth are decreased with reduction rates of 78.2% and 45.7%, respectively. TIG-FSW can promote flow, contact and diffusion of materials, thus improving microstructure of the joint. Additionally, it reduces the size and number of secondary phase particles. Consequently, these factors contribute to the higher tensile properties and corrosion resistance of the joints.