Effects of electroshock treatment on microstructure evolution and texture distribution of near-beta titanium alloy manufactured by directed energy deposition

摘要

Electroshock treatment (EST) can influence the microstructure of a material in a short time through the coupling of the thermal and nonthermal effects of a high-density pulsed current. In this study, a Ti-55531 near-beta titanium alloy manufactured by a laser-based directed energy deposition was processed via EST, and the microstructure was characterized via scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). After the EST, small subgrains were precipitated in the large columnar beta grains. With an increase in the EST time, the alpha phase precipitated along the grain boundary tended to grow, the curvature radius of the alpha tips increased, and distinct spheroidization occurred. The EBSD results indicated that after the EST, the maximum texture intensity of the beta phase decreased from 23.18 to 13.15, and the texture intensity exhibited a uniform distribution. The foregoing results were attributed to the thermal and nonthermal effects of the EST, which led to an energy concentration on the tips of the needle-like alpha phase and the phase transformation of the tips. When the high current passes through the sample, both the thermal and nonthermal effects are introduced, the thermal effect cause the increase of samples temperature, and the nonthermal effect shows as the form of special forces such as the electrostatic and electronic wind forces, which can influence the movement of dislocation. This work is expected to provide a new method for optimizing the microstructure of the near-beta titanium alloys manufactured by a laser-based directed energy deposition.