Fine tuning in-sync the mechanical and magnetic properties of FeCoNiAl0.25Mn0.25 high-entropy alloy through cold rolling and annealing treatment

In this study, the mechanical and magnetic properties of FeCoNiAl0.25Mn0.25 high-entropy alloy (HEA) were investigated by subjecting as-cast samples to cold rolling and annealing at different temperatures for 1 h. The as-cast and cold rolled HEAs show a single-phase face-centered cubic (FCC) structure. The annealing temperature has a noteworthy influence on the phase composition and microstructure of the cold rolled HEA, and the microstructural evolution is described as follows: heterogeneous microstructure with a FCC matrix and body-centered cubic (BCC) precipitates (750 ℃ and 850 ℃) → recrystallized microstructure with FCC matrix and BCC precipitates (950 ℃) → coarse grains with a single FCC phase (1050 ℃). Though the HEA annealed at 1050 ℃ has the best ductility and lowest coercivity, the yield strength is very low. A good combination of ductility and strength is found in the sample annealed at 850 ℃ (CR+HEA-850), whose microstructure is comprised of BCC precipitates, recrystallized FCC equiaxed grains and a few FCC hard-deformed lamellae. The heterogeneous structure of the CR+HEA-850 resulted in a strong back stress, which contributes to its good mechanical properties. The high yield strength came from the grain refinement, dislocation strengthening, Orowan effect, and twin boundaries. Additionally, its soft magnetic properties are also appealing, showing high saturated magnetization (112.4 emu/g) and good coercivity (8.7 Oe). Compared with the HEAs on other conditions in this study and those previously reported, the CR+HEA-850 displays an interesting combination of magnetic and mechanical performance, which offers a strategy towards a new generation of multifunctional high-entropy alloys.