Abstract: Aiming to address defect repair requirements during rocket tank welding, conventional fusion welding and friction stir welding repair techniques fail to achieve high-quality restoration. Although W-FSAM can potentially break through the above bottlenecks, weak interfacial bonding arising from large-scale defect repair severely restricts its practical engineering application. In this work, W-FSAM repair experiments were carried out on 221 aluminum alloy specimens, where friction stir processing (FSP) was integrated to realize rapid remediation of defects with a cross-sectional dimension of 2 mm × 16 mm. Under coupled thermal-mechanical loading, W-FSAM plasticizes the feedstock for complete defect filling and produces fully defect-free repaired zones. Nevertheless, the sidewall interface acts as a mechanical weak point, with a tensile strength of merely 107 MPa. After post-FSP treatment, the tensile strength increases to 266 MPa, and can be further elevated to 361 MPa when the W-FSAM repair rotational speed is set to 1000 r/min. Microstructural characterizations reveal that dynamic recrystallization takes place within the W-FSAM repaired region, generating equiaxed grains with an average size of 2.39 μm. Subsequent FSP induces secondary recrystallization and refines the average grain size down to 2.20 μm, accompanied by reduced KAM values and a decreased fraction of low-angle grain boundaries. The θ precipitates inside the repaired zone remain fine; these particles slightly coarsen after FSP yet most are still smaller than 500 nm, which enables effective precipitation strengthening of the alloy matrix.