Significance of surface layer integrity for sustaining the ductility of gradient-structured nickel

Gradient-structured nickel (Ni) was processed by rotationally accelerated shot peening (RASP). The microstructures and mechanical properties of the RASP-processed samples were studied. Nanostructured layers with a thickness of ~50 μm were formed on the sample surfaces. Beneath the surface layer there is a transition region in the depth range of ~50–150 μm. The transition region contains high densities of dense dislocation walls (DDWs),...