Multistage laser shock improves surface structural properties of aluminum alloy

Functional thin-walled aluminum alloys were the main production materials for the outer wall of novel light-weight flight power. The harsh service conditions of power had put forward strict requirements on the me-chanical properties and functional characteristics of thin-walled parts. The functional surface produced by the traditional process was difficult to overcome the functional-mechanical properties trade-off. The feasibility and productivity of complex curved components was another issue. How to efficiently manufacture functional structures with excellent mechanical properties was the key technical bottleneck that needed to be broken through in current engineering field. A novel strategy called multistage laser shock peening (MLSP) was proposed to manufacture microstructures with functional and excellent mechanical properties. The mechanical properties, surface wettability, electrochemical behavior and tribological behavior of MLSP samples were systematically discussed and analyzed. A series of micro-pits filled with abundant micro and nano structures were shown on the surface of the enhanced MLSP sample, which constituted functional microstructures across scales. Due to the decrease of the shock pressure, the hardness of the material presented a gradient distribution in the horizontal and vertical directions. Effective synergistic plastic deformation was achieved in MLSP-induced multistage heterogeneous gradient structures, which increased the yield strength of the material by 214% from 21 MPa to 66 MPa while the ductility was slightly reduced from 26% to 25%. Compared with the traditional laser shock technology, the MLSP samples had more balanced structural properties. MLSP strategy could provide a new way to manufacture high reliability functional metal surfaces.