Role of Co on microstructure, crystallization behavior and soft magnetic properties of (Fe1−xCox)84Si4B8P3Cu1 nanocrystalline alloys

In this paper, we describe the effects of substituting Co for Fe on the microstructure, crystallisation behaviour, and soft magnetic properties of (Fe1−xCox)84Si4B8P3Cu1 (x = 0.35, 0.5, 0.65) alloys. The results demonstrate that as the Co content in the alloy increases, the heat treatment temperature also improves. When x = 0.35 Co was substituted for Fe in Fe84Si4B8P3Cu1 alloy, there was a significant enhancement in the interval temperature (ΔTx) between the two crystallization temperatures, and this resulted in the largest crystalline volume fraction (Vcry). When annealing at 625–800 K, we observed a dual-phase nanocrystalline structure in all the specimens, which was composed of nanocrystals with average grain size of about 9–28 nm embedded in the residual amorphous matrix. The (Fe0.65Co0.35)84Si4B8P3Cu1 nanocrystalline alloy exhibited a high saturation magnetic flux density, Bs, of 1.68 T; a low coercivity, Hc, of 5.4 A/m; and a high effective permeability, µe, of 29,600 at 1 kHz. Hence, these results indicate that this alloy is promising for use as a soft magnetic material.