Strengthening CrFeCoNiMn0.75Cu0.25 high entropy alloy via laser shock peening

•Laser shock peening is an effective way to introduce gradient structures that improve the mechanical properties of high entropy alloy (HEA).•A hardened layer of several hundred micrometers is produced on the surface of HEA via laser shock peening.•Twin boundaries, dense dislocations, and grain refinement in the laser affected layer result in enhanced yield strength of HEA.•Excellent plasticity during loading of the laser-treated HEA is mainly accommodated by dislocations in the laser unaffected core region.