Effect of Friction Stir Welding Process Parameters on Mechanical Properties and Macro Structure of Al-Li Alloy

Al-Li alloys play a significant role in current aerospace components due to their exceptional strength and stiffness-to-density ratios and are most competitive or superior to a composite based design in an aircraft or space launcher. Since integral components of aerospace vehicle requires very large sheets, which size is not available commercially, joining of smaller pieces are required. It is known that fusion welding of Al-Li alloys is difficult due to the low melting temperature of element Li and causes porosity, cracking and low joint efficiency. Therefore, a solid-state joining process, like friction stir welding, is generally appropriate for joining of Al-Li alloys. In friction stir welding process, a non-consumable rotating welding tool is used to generate the frictional heat and plastic deformation of the material in the welding zone, which is a combination of extrusion and forging. In this article, experimental investigation provided the influence of rotating and welding speed on microstructure, mechanical properties, and joint quality. Valuable information about processing window which results in a successful friction welded joining of this alloy is presented.