Joining Aerospace Aluminum 2024-T4 to Titanium by Friction Stir Extrusion

Abstract

The welding of titanium and aluminum is difficult due to differences in their material properties and the formation of intermetallic compounds (IMCs) which can weaken the weld. A new process, Friction Stir Extrusion (FSE), has been used to join dissimilar materials by using Friction Stir Processing to extrude a top sheet of material into a pre-made, concave groove in the bottom sheet of material. FSE has been used to create a strong, mechanically interlocking joint between aluminum 6061 and steel that eliminates IMCs. However, FSE hasn’t been applied to any other material combinations. This current research applies the FSE process to join aluminum 2024-T4 to commercially pure titanium. The process was optimized by adjusting the RPM, traverse rate, and groove geometry. The Al–Ti joints are evaluated based on shear strength and ultimate tensile strength. The groove geometry proved to be the most important parameter as different geometries can enhance the strength by mechanical means and by optimizing the volume and shape of the material extruded. Successful joints were created by the FSE process and can be used as a viable alternative for joining aluminum to titanium.