Microstructure and properties in the weld surface of friction stir welded 7050-T7451 aluminium alloys by laser shock peening

Laser shock peening (LSP) was used to treat the weld surface of friction stir welded joints of 7050-T7451 alloys. After the LSP, a large number of micro-holes were formed in the shock region. The hardness of thermo-mechanically affected zone (TMAZ) and heat-affected zone (HAZ) at a distance from the upper surface of 0.5 mm increased obviously. The average hardness increased 9HV. The fatigue life after the LSP increases 30%, 27% and 5% when the loading stress is 200 MPa, 250 MPa and 300 MPa. The residual stress in weld nugget zone, TMAZ and HAZ generated a compressive residual stress, and the biggest value is 100 MPa after the LSP.