A novel non-destructive shot peening (NDSP) surface strengthening behavior of a high strength aluminum alloy

Surface strengthening behavior of 7075-T6 aluminum alloy treated by a novel non-destructive shot peening (NDSP) surface strengthening method that employs an austenitic stainless-steel foil as an interlayer to eliminate the micron-scale crater defects and conducted impact stress was investigated based on gradient microstructure characterization, microhardness measurement and residual stress testing. Results show that no micron-scale crater defects left on the specimen surface with roughness decreased to Sa = 0.67 μm treated by NDSP, and a significant residual compressive stress with the peak value & depth of -271.5 MPa & 300 μm was introduced into the surface layer of the specimen. Although conventional shot peening (CSP) can introduce higher residual compressive stress and microhardness to the surface layer under the same shot peening parameters, NDSP eliminates the micron-scale crater defects so as to solve a century long problem for CSP. The surface strengthening mechanism of 7075-T6 aluminum alloy was discussed.