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 = 0.4, and subsequently decreasing fourteen times from x = 0.4 to x = 1.0. 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 = 0.6 to x = 0.8. 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.
Owing to excellent mechanical properties, such as high strength, high elastic modulus and large elastic as well as fracture strain, carbon nanotubes (CNTs) are attracting significant interests as reinforcements in metallic coatings. In the present investigation, CNT reinforced nickel composite coatings were deposited on a stainless steel substrate using pulse electrodeposition process employing a nickel Watts bath. The presence of CNTs in the composite coating prohibited the columnar growth of the nickel grains resulting in random/weak texture and smaller thickness of the composite coatings. The Ni-CNT composite coatings exhibited significantly improved microhardness (580¡15 HV) compared to pure nickel coatings (320¡15 HV). The ball-on-disc wear testing data indicated that the reinforcement of CNTs significantly improved wear resistance of the composite coatings compared to pure nickel coatings.
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