Effect of annealing on mechanical and thermoelectric properties of a Al₂CoCrFeNi high-entropy alloy

In this study, a relatively light and high strength high entropy alloy thermoelectric material (Al₂CoCrFeNi) for extreme service conditions was prepared by arc melting method. We find that the microstructure of the high entropy alloy (HEA) can be changed by annealing. By the tuning of proper annealing process, the microstructure evolution of the HEA can be adjusted to improve its mechanical and TE properties. Ultimate compressive strength can reach about 1.3 GPa after 1000 ℃ annealing. Fine-grain and precipitation strengthening are the main reasons for the improvement of the mechanical properties. The conductivity, Seebeck coefficient and thermal conductivity are all affected by grain size, precipitates, structural complexity and so on. The present work provides an effective means of preparing and regulating microstructures for the energy-conversion technique, and also supplies a feasible reference for the future development of lightweight, high-strength HEA TE materials.