Fatigue strength improvement in Ti-6Al-4V subjected to foreign object damage by combined treatment of laser shock peening and shot peening

•LSP + SP treatment shows the highest surface micro-hardness and residual compressive stress and the deepest affecting layer for Ti-6Al-4V aerofoil specimen.•Dislocations and deformation twins are induced in the subsurface layer of LSP + SP treated specimens and the original coarse grains are refined, especially in 15 μm near-surface.•At low-energy impact, LSP + SP treatment has the greatest inhibitory effect on notch depth.•LSP + SP treatment improve the fatigue strength of FODed specimens most, despite the effect will reduce with the increasing of impacting energy.