Residual stress, phase, microstructure and mechanical property studies of ultrafine bainitic steel through laser shock peening

•Low energy laser shock peening without coating enhanced the surface properties of ultrafine bainitic steel.•The martensite phase transformations trend and the lattice misorientation in the crystalline structure.•Grain refinement features such as nano-twins, micro shear bands and shear cells are observed.•The high strain work hardening enhanced mechanical properties.