A study of microstructure and mechanical properties of (CoCrNi)82Al9Ti9 high entropy alloy by electrical-thermal-mechanical coupled rapid post-treatment

Abstract

In this work, we have creatively used electrical-thermal-mechanical coupled rapid post-treatment to improve the properties of (CoCrNi)82Al9Ti9 high entropy alloy (HEA). The effect of the electrical-thermal-mechanical coupled field on the phase, microstructure, microhardness, fracture toughness, and compression properties of SLM specimens are investigated. The results show that the SLM specimen exhibits face-centered cubic (FCC) and body-centered cubic (BCC) phases and the microstructure is a dendrite structure. The SLM specimens exhibit imperfections, including porosity and cracks, as well as low densification. After electrical-thermal-mechanical coupled rapid post-treatment, the FCC phase decreases while the BCC phase increases in the SLM specimen, and the microstructure changes from dendritic to recrystallized. The created specimens are healed of defects and the densification is increased to 99.6%. It can be attributed to the combination of the electrical (Electron wind) and thermal effects (Joule heat) of pulse current. Electron wind promotes the diffusion of atoms and expansion of the movement of dislocations, providing the material basis for defect healing and recrystallization. Joule heat provides the substance conditions. The (CoCrNi)82Al9Ti9 HEA has a remarkable improvement in strength and ductility.