Deformation suppression and microstructure-property evolution of ultrasonic-assisted laser-welded 7075 aluminum alloy thin-sheet joints

Abstract

The Ultrasonic-assisted laser welding was used to investigate the effect of ultrasonic input on the quality of 7075 aluminum alloy thin-sheet joints. Post-weld deformation, weld formation, microstructure, and mechanical properties were evaluated by deformation measurement, metallographic observation, tensile testing, and microhardness testing. The results show that ultrasonic input significantly reduced buckling deformation and angular distortion, while improving weld formation. Within the ultrasonic power range of 0–600 W, directional growth near the fusion line was weakened, and the dendritic structure in the weld center became finer and more uniform. As the ultrasonic power increased from 0 W to 1200 W, the tensile strength increased from 207.49 MPa to 244.18 MPa, and the elongation after fracture increased from 3.02% to 4.58%. Although the transverse microhardness still showed an approximately W-shaped distribution, the hardness in the weld zone and heat-affected zone increased.