The effect of microstructure on mechanical and magnetic properties of FeCoNiAl0.75Nb0.25 high-entropy alloy†

This work systematically investigated the relationship between the microstructure, and mechanical and magnetic properties of FeCoNiAl_0.75Nb_0.25 high-entropy alloy. Our results indicated that the microstructure of the alloy comprised a BCC solid solution phase along with a eutectic mixture of FCC and intermetallic phases. The application of heat treatment resulted in a significant evolution of the microstructure. The precipitation of the needle-like intermetallic phase occurred rapidly with increasing annealing temperature, reaching a maximum proportion at 825 °C, and decreased quickly upon further increase to 1000 °C. Correspondingly, the hardness and compressive yield strength of the alloy increased rapidly, attaining maximum values of approximately 600 HV and 2000 MPa, respectively. However, the precipitation adversely affected magnetic properties. The best values in the as-cast state for saturation magnetization, and coercive force are 0.67 T and 716 A m⁻¹, respectively, while the hardness remains 493 HV. Therefore, it is very suitable for magnetic parts requiring superior mechanical properties.