The distribution regularity of residual stress on a metal surface after laser shock marking

Abstract

A metal material surface marking method was developed based on the theory that a larger thickness of the absorption layer can attenuate a laser-induced shock wave. The introduction of surface residual compressive stress is the main feature of this new marking method, which is different from the traditional mechanical processing marking method and is also the key factor leading to the good service performance of the metal material surface. After the laser shock marking (LSM) treatment, the residual stress at different positions on the metal surface was measured, and the change in distribution trend of residual stress and microstructure in the laser shock-treated region was discussed. The results show that for two different marking patterns, the expected deformation areas have a remarkable residual compressive stress distribution, and the relatively large full width at half maximum (FWHM) of the X-ray diffraction peak of the expected deformation areas characterizes significant microstructure changes. The microstructure of the edge region of the formed mark shows a sudden change, while the residual stress changes gradually. This change indicates that the surface's severe plastic deformation is directly related to microstructure changes and indirectly related to residual stress changes.