As inductor technology advances, greater efficiency and smaller components demand new core materials. With recent developments of nanocrystalline magnetic materials, soft magnetic properties of these cores can be greatly improved. FeCo-based nanocrystalline magnetic alloys have resulted in good soft magnetic properties and high Curie temperatures; however, magnetoelastic anisotropies persist as a main source of losses. This investigation focuses on the design of a new Fe-based (Fe,Ni,Co)88Zr7B4Cu1 alloy with reduced magnetostriction and potential for operation at elevated temperatures. The alloys have been processed by arc melting, melt spinning, and annealing in a protective atmosphere to produce nanocrystalline ribbons. These ribbons have been analyzed for structure, hysteresis, and magnetostriction using X-Ray diffraction, vibrating sample magnetometry (VSM), and a home-built magnetostriction system, respectively. In addition, Curie temperatures of the amorphous phase were analyzed to determine the best performing, high-temperature material. Our best result was found for a Fe77Ni8.25Co2.75Zr7B4Cu1 alloy with a 12 nm average crystallite size (determined from Scherrer broadening) and a 2.873 Å lattice parameter determined from the Nelson-Riley function. This nanocrystalline alloy possesses a coercivity of 10 A/m, magnetostrictive coefficient of 4.8 ppm, and amorphous phase Curie temperature of 218°C.

In all previous studies of soft magnetic alloys, magnetic softness is obtained through forming a completely amorphous state via rapid solidification, such as by melt spinning at a high cooling rate followed by annealing, typically at 600 °C, to develop a magnetically isotropic nanostructure. Fine powdering of the annealed alloy via ball milling is then required for manufacturing, net shaping, and 3D printing. However, the soft magnetic properties are susceptible to the subsequent processing conditions, characterized by significantly increased coercivity. Herein, nanoscale crystallites are obtained directly from the melt‐spun Fe77Ni5.5Co5.5Zr7B4Cu ribbon (i.e., not through annealing of a completely amorphous ribbon) that exhibits structural stability during the annealing and ball‐milling processes. The melt‐spun ribbon annealed at high temperatures (700 °C) remains magnetically soft with Hc of ≈0 Oe, which is a key property for high‐temperature applications. Ball milling of the annealed melt‐spun samples results in fine powders with low Hc values over a wide temperature range up to 427 °C. It is shown that the rapidly solidified crystalline ribbon provides an ideal precursor for the manufacture of high‐temperature soft magnetic materials. This new approach provides a straightforward method of making soft magnetic alloy powders.

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