This study aims at developing novel Full-Heusler high entropy intermetallic compounds (FH-HEICs). To this end, the formation of Heusler-type intermetallic structures and their thermal stability are studied in three systems with (CoFeNiCuV)2MnAl, Co2(FeMnNiCuTi)Al and Co3(FeMnNiCu)Al chemical compositions, where one sublattice composed of multi-component elements. The results indicated that (CoFeNiCuV)2MnAl crystallizes in a pure FH-HEIC type phase consisting of ordered L21 and disordered A2 structures, and it remains stable after 5 h annealing at 900 °C. Annealing could effectively suppress segregation of elements in (CoFeNiCuV)2MnAl, but it did not trigger substantial disorder-to-order phase transition. Co2(FeMnNiCuTi)Al crystallized in a mixture of B2 and FCC phases, in which the ordered B2 structure undergoes a transition to disordered A2 type structure upon annealing at 900 °C. On the other hand, Co3(FeNiMnCu)Al exhibited a A2+FCC two-phase structure in both as-cast and annealed states. (CoFeNiCuV)2MnAl exhibited higher microhardness value (589 HV) compared to Co2(FeMnNiCuTi)Al (474 HV) and Co3(FeMnNiCu)Al (417 HV) FH-HEICs, consisting with its higher degree of ordering. Finally, all the samples exhibited ferromagnetic behavior with relatively high magnetic saturation and coercivity in the range of semi hard magnetic materials.
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