Relationship between surface residual stress and dislocation configuration after laser shock processing of TC4 titanium alloy

Abstract

Through the combination of simulation and experiment, this paper explored the correlation between residual compressive stress and loading pressure in the range of 2800 MPa to 11,000 MPa. The experimental results showed that the surface residual compressive stress increased first and then decreased with the increase of loading pressure. When the surface residual compressive stress decreased, the surface nanocrystallization appeared. With the increase of loading pressure, the form of energy dissipation changed. When the loading pressure was greater than 2800 MPa, which is equal to the Hugoniot elastic limit, the residual compressive stress layer was formed on the surface of material. When the loading pressure was greater than 5600 MPa, which is slightly more than the double Hugoniot elastic limit, the residual compressive stress layer was formed and the dislocation configuration changed. When the loading pressure was greater than 8500 MPa, which is slightly more than the triple Hugoniot elastic limit, the residual compressive stress decreased and the surface nanocrystallization occurred, accompanied by surface damage. For the new grains and sub grains formed by surface nanocrystallization, the atomic arrangement direction in the grains was consistent with the propagation direction of laser shock wave.