Structure and magnetic properties of Ni5(Fe0.5Co0.5)68.5Si13.5Nb3B9Cu alloy

Structure and magnetic properties of as-quenched and annealed Ni5(Fe0.5Co0.5)68.5Si13.5Nb3B9Cu samples were investigated. Structure has been studied by x-ray diffraction and transmission electron microscopy, while magnetic properties including initial permeability (μi) and saturation magnetism (Ms) have been performed by induction methods. When annealing at 510–600 °C, a dual-phase nanocrystalline structure was observed, which was composed of nanocrystals with average grain size about 13–14 nm embedded in the residual amorphous matrix. It was found that the substitution of 50 at% Co for Fe in Ni5Fe68.5Si13.5Nb3B9Cu alloy significantly enhanced the Curie temperature of amorphous phase (Tcam) and interval temperature (ΔTx) between the two crystallization temperatures. Moreover, the substitution was clearly efficient for improving the high-temperature magnetic properties. Especially, even annealing at 600 °C, the Ni5(Fe0.5Co0.5)68.5Si13.5Nb3B9Cu alloy still exhibited larger μi value at elevated temperatures above Tcam. The evolution of μi with temperature was systematically analyzed in terms of random anisotropy model. - Highlights: ► Co-doping in Ni5Fe68.5Si13.5Nb3B9Cu alloy raised high-temperature magnetic softness. ► High-temperature initial permeability μi was improved with Vcry increasing. ► When annealing above 570 °C, μi exhibited larger value at elevated temperatures above Tcam. ► The evolution of μi was systematically analyzed in terms of random anisotropy model.