Influence of laser treatment on the microstructural evolution and performance of Ti65 alloy

Achieving simultaneous increase in strength and plasticity of metallic materials is a long-term challenge. In this study, we prepared the Ti65 alloy with surface refined structure by laser treatment and studied the evolution of surface and cross-sectional microstructure, as well as its impact on tensile properties. The tensile strength of the Ti65 alloy sheet increases from 1098 to 1136 MPa after laser treatment, and the average fracture strain significantly rises from 6.81% to 10.23%, marking a substantial 50.2% increment. During laser treatment, the fast cooling rate caused the formation of a strengthening layer with fine grains, which leads to an increase in strain hardening rate and non-uniform deformation induced strengthening provided by non-uniform structures. The findings in this work provide a new routine for upgrading mechanical properties of titanium alloy through generating a strengthening layer with fine grains on the surface.