Effect of Multiple Shot Peening on Residual Stress and Microstructure of CNT/Al−Mg−Si Alloy Composite

In this study, multiple shot peening was performed on a carbon nanotubes−reinforced aluminum matrix composite, of which residual stress fields and tissue structure evolution were investigated. It is shown that the multiple shot peening could significantly increase the magnitude of compressive residual stress field, modify surface morphology of the specimens, and further refine the grain sizes of the near surface layer. Dislocation density in the near−surface layers were also elevated by multiple shot peening. Moreover, enhanced microhardness with more even distribution were obtained in the modified peened layers ascribed to the raised compressive residual stress field and microstructure which could give rise to the strain−hardening effects.