A dual-phase FeNiCr_0.8Al_0.8 high entropy alloy with attractive multi-functional thermal and magnetic properties

In this work, the as-cast FeNiCr_0.8Al_0.8 high-entropy alloy was systematically investigated for its multi-functional thermophysical and magnetic properties through microstructure characterization, experimental property analysis, and first-principles calculations. The results indicate that this alloy forms a near equal fraction of two phases with weave-like microstructures. Two phases exhibit the same BCC structure but differ in composition, as confirmed by XRD and microstructure analysis. This alloy exhibits a nearly constant low thermal expansion coefficient of approximately 1.2×10⁻⁵ K⁻¹ over a wide temperature range from 373 K to 973 K, attributed to the constitutional phase microstructure, the temperature-dependent lattice expansion, and Invar effects; high thermal conductivity of up to 37.582 W·m⁻¹·K⁻¹ at 1173 K, surpassing that of the In600 superalloy, due to optimized temperature-dependent electron-phonon transport; and soft magnetic response with a saturation magnetization of 43.2 emu/g and coercivity of 59.2 Oe. The Curie temperature of as-cast FeNiCr_0.8Al_0.8 alloy is determined to be 737 K. The occurrence of secondary order phase transition is further explained by the abrupt property shift of the BCC2 phase under elevated temperature, inducing the alteration of thermophysical and magnetic behavior. The magnetic transition mainly contributes to high magnetic moments and spin polarization of Fe and Ni atoms.