A combinatorial assessment of composition-microstructure-magnetic property relationships in magnetic high entropy AlCoxCr1-xFeNi alloy (0 ≤ x ≤ 1) system has been carried out using compositionally graded alloys fabricated via laser additive manufacturing At one end, the AlCoFeNi composition (x = 1) consisted of equiaxed B2 grains, exhibiting very early stages of phase separation (only compositional partitioning) into Ni–Al rich and Fe–Co rich regions within grains of the B2 phase At the other extreme, the AlCrFeNi composition (x = 0) exhibited grains with pronounced spinodal decomposition, resulting in a B2 + bcc microstructure with the degree of spinodal decomposition progressively increasing with Cr content in these AlCoxCr1–xFeNi alloys While the saturation magnetization (Ms) monotonically increases six times from x = 0 to x = 1, the coercivity (Hc) variation is non-monotonic, increasing seven times from x = 0 to x = 04, and subsequently decreasing fourteen times from x = 04 to x = 10 The magnetic phase transition temperature (Tc) for these alloys also increases monotonically with increasing Co content with a second phase transition exhibited in a certain range of compositions between x = 06 to x = 08 Such substantial changes in the magnetization behavior and properties of magnetic high entropy systems opens possibilities of tuning these alloys for specific soft or hard magnetic component applications

A Combinatorial Approach for Assessing the Magnetic Properties of High Entropy Alloys: Role of Cr in AlCoxCr1–xFeNi

Ultrafine microstructure and hardness in Fe-Cr-Co alloy induced by spinodal decomposition under magnetic field

Effect of alloying on magnetic properties of Fe-Cr-12 wt% Co permanent magnet alloys☆

Magnetic properties and microstructures of Fe-Cr-10 wt% Co-M (M=Si/Ti/Ni/Mo/Ge/Ta) permanent magnet alloys

Microstructure and phase transition of Fe-24Cr-12Co-1.5Si ribbons

Four Fe-30/33Cr-11.5/12.5Co-0/1Si alloys (weight fraction) melted in air and treated by alternatively ageing and rolling have been studied by magnetic measurements and electron microscopy. The optimum treatment procedures have been determined and the best obtained magnetic properties are Hc = 54.0 kA m−1, Br = 1.19 T and (BH)m = 29.6 kJ m−1. Transmission electron microscopy proves that rolling after spinodal ageing is effective in elongating and aligning the original isotropic spinodal structures. The extent of elongation is quantitatively related to the amount of area reduction in rolling. Magnetic properties are found to be not very sensitive to slight variations in composition, cooling rates and the temperature of intermediate rolling, and to be tailorable by the exact control of the rolling operation. The rolling-ageing technique as a manufacturing process for Fe-Cr-Co magnets is thought to be promising. Finally, ways of further improvement are discussed.

Tsung Shune Chin

Papers

Electron microscopy and magnetic properties of Fe-Cr-Co-Si permanent magnet alloys manufactured by rolling-ageing technique