Effect of stress shot peening on the residual stress field and microstructure of nanostructured Mg-8Gd-3Y alloy

Abstract

The effects of stress shot peening on the residual stress, microstructure and mechanical property of nanostructured Mg-8Gd-3Y alloy were systematacially investigated by the X-ray diffraction stress analysis, modified Williamson–Hall method, transmission electron microscopy and hardness tester. The results indicated that conventional shot peening led to a gradient nanostructured Mg-8Gd-3Y alloy with a size of 60–100 nm at the top surface layer. The formation of nanograins was primarily ascribed to the dynamic rotation recrystallization. Compared with conventional shot peening, stress shot peening significantly improved the residual stress distribution with a maximum value of −215 MPa and the affected depth. In parallel, stress shot peening conferred superior microstructures at the deformation layer, with smaller domain size, more severe lattice distortion and higher-density dislocations. Owing to inducing finer microstructures and higher compressive residual stresses, stress shot peening produced a stiffer deformation layer. It is concluded that stress shot peening was more potent in promoting the surface layer characteristics of nanostructured Mg-8Gd-3Y alloy than conventional shot peening.