Synthesis of nanocrystalline equiatomic nickel-cobalt-iron alloy powders by mechanical alloying and their structural and magnetic characterization

Mechanically alloying equiatomic Ni, Co, and Fe powder blends for 9 h resulted in the formation of nanocrystalline equiatomic NiCoFe alloy powders comprised of. gamma-phase. The crystallite size and the lattice parameter was similar to 20 +/- 5 nm and 0.3597 +/- 0.0005 nm, respectively. The mode of the powders was 3-7 mu m. The saturation magnetization (M-S) and the intrinsic coercivity (H-CI) of the alloy, at 300 K, was similar to 136 +/- 5 Am-2/kg and similar to 2.0 +/- 0.2 kA/m, respectively. Both M-S and H-CI, irrespective of the milling media and milling atmosphere, decreased with increase in temperature from 60 K to 300 K. At elevated temperatures (400 K to 880 K), the alloy powders maintained the gamma-phase up to 640 K, thereafter it was comprised of gamma-phase and alpha-Fe. In the temperature regime 300-640 K, the percentage decrease in M-S and H-CI was similar to 12% and similar to 30%, respectively. The M-S and H-CI at 300 K, after the magnetization versus applied magnetic field (M-H) run at 640 K, was similar to 136 Am-2/kg and similar to 1.5 kA/m, respectively; while the same after the M-H run at 880 K was similar to 154 Am-2/kg and similar to 1.0 kA/m, respectively. Annealing of the nanocrystalline alloy powders is likely to improve its soft-magnetic properties.