High Strain-Rate Compressive Response of Friction Stir Welded AA7075-T651 Joints

High strain-rate compressive responses of AA7075-T651 and its welds as produced by the friction stir welding (or FSW) process are investigated using the conventional split Hopkinson pressure bar. Cylindrical specimens machined along the thickness direction of the base material (AA7075-T651) and the friction stir (FS) welds are used in the static and impact compression tests. The micro-hardness tests are conducted across the centerline of a FS welded AA707-T651 joint in order to examine the microstructural change. It is shown that FSW reduces the compressive flow stress of the FS weld (weld nugget) to below that of the base material, and both the base material and the FS weld exhibit almost no strain rate effects up to nearly € ε˙ =103/s.