• Circular oscillation frequency of 200 Hz refines weld grain size, achieving a tensile strength of 264.96 MPa (61.19% of base metal) in 2219-T6 alloy.
• Post-weld heat treatment (solid solution + artificial aging) reduces grain boundary segregation and induces nanoscale precipitates, raising tensile strength to 386.35 MPa (89.23% of base metal).
• Combining beam oscillation with PWHT effectively mitigates keyhole instability and porosity defects typical of medium-thickness aluminum alloy laser welding.
• Provides a theoretical basis and technological reference for manufacturing high-strength, low-porosity joints in aerospace-grade aluminum alloy plates.