Investigation of microstructure and tribological property of Ti-6Al-4V alloy by laser shock peening processing

Laser shock peening (LSP) is a process that introduces compressive residual stresses in order to improve the surface properties of materials. In this study, we investigated the effects of LSP on the microstructure and tribological properties of Ti-6Al-4 V alloy. Our examinations of both surface and cross-sectional microstructures of the samples reveal that the shape of the β phase changes from a long strip to a short bar or granular after the LSP treatment. As laser intensity increases, both surface roughness and surface microhardness gradually increase. While LSP treatment weakens the original high-peak bump structure, it also produces a large number of scattered small flat bumps. We found that the maximum hardness is on the surface, and with an increase in depth, the hardness decreases until it stabilizes to 339.4 HV which is the microhardness of the matrix. The thickness of the high-microhardness layer is approximately 350 µm. LSP treatment can reduce the wear depth and wear volume of Ti-6Al-4 V alloy, effectively improving its tribological property. Additionally, the higher the laser intensity, the better the wear resistance. Our findings provide insights for further studying and applying the LSP process to improve the tribological properties of Ti alloys.