Response of copper’s microstructure to laser shock peening

The response of copper’s microstructure to laser shock peening (LSP) was investigated in this study. LSP experiment was conducted with a Spitlight neodymium (Nd)-doped yttrium aluminum garnet laser. Then microstructural observations in the affected zone and substrate were conducted by means of cross-sectional optical microscopy and transmission electron microscopy. The experimental results indicated that the distribution of grain size becomes more uniform near the top surface after LSP treatment, and the average grain size in the top surface is about 5 μm. There are four typical microstructural features along the depth direction due to the ultrahigh plastic strain in the affected zone, and the microstructure changes with the number of LSP impacts. The movement of and interaction between dislocations plays an important role in the evolution of the dislocation structure. Additionally, the grain refinement mechanism of copper along the depth direction, induced by the plastic deformation during multiple LSP impacts, was proposed based on the microstructural observations.