Mechanical Properties and Formability of Cold Rolled Friction Stir Welded Sheets in AA5754 for Automotive Applications

The effect of cold rolling on mechanical properties and formability of friction stir welded blanks in AA5754 aluminium alloy was investigated. To this purpose, FSW experiments were performed on 2.5mm thick sheets with rotational and welding speeds equal to 1200rpm and 100mm/min, respectively, and tool sinking of 0.1mm. Part of the FSWed sheets was cold rolled, with the rolling direction perpendicular to the welding line, until the obtaining of a constant sheet thickness equal to 2.2mm. Finally, the mechanical properties and formability of joints, both before and after cold rolling, were evaluated by means of uniaxial tensile and hemispherical punch tests; the experimental results, in terms of stress vs. strain curve, microstructure, and limiting dome height, were analysed and discussed.