LAUSR

Friction stir repairing was successfully used to repair shrinkage cavity and porosity defects in Al–Cu casting alloy plates with T5 treatment. Effects of welding speeds on microstructures and mechanical properties of repaired region were mainly discussed. The results show that heat affected zone has the minimum microhardness due to coarser grains, where the tensile fracture is located. Through the thickness of the stir zone (SZ), the grain size decreases with increasing distance from the top surface of the repaired region due to the difference of heat input and cooling rate. The tensile strength and elongation of the SZ characterized by finer grains are both higher than those of the repaired region. These values of the SZ at 900 rpm and 150 mm/min reach 336.8 MPa and 11.75%, equivalent to 90.7 and 81.6% of BM without casting defects, respectively.