Refining the microstructure to strengthen casting titanium alloy by electric pulse

Abstract

Thermal-hydrogen treatment can effectively refine the microstructure and improve the thermoforming, machining performance and superplasticity of titanium alloy. In this study, pulsed electric current is used to replace the traditional heat treatment in the thermal-hydrogen treatment of cast titanium alloy, and the experimental results and strengthening effect of pulsed thermal hydrogen treatment and traditional thermal hydrogen treatment were compared. After pulsed thermal-hydrogen treatment, the lamellar β phase is broken into spherical shape and uniformly distributed in the matrix, and the cast titanium alloy was significantly strengthened. However, the microstructure refinement and strengthening effect of traditional thermal-hydrogen treatment is not as good as that of thermal-hydrogen treatment under electric pulse. The process of thermal-hydrogen treatment is accompanied by the formation of new phases, and the nucleation and growth of new phases are often controlled by atomic diffusion. In addition to the necessary thermal effects, the pulsed electric current also provides athermal effects, and thermodynamically lowering the energy barrier and promoting nucleation, while kinetically promoting the diffusion of atoms and accelerating the solid solution process. Therefore, based on the experimental results and analyses, thermal-hydrogen treatment under electric pulses provides a novel and effective method for refining the microstructure to strengthen cast titanium alloys.