Effect of vacuum annealing and heating–cooling cycle annealing on the soft magnetic properties at room- and high-temperatures for nanocrystalline FeCoAlSiBCuNb alloy

Effect of vacuum annealing and heating–cooling cycle annealing on the soft magnetic properties at room- and high-temperatures for (Fe_0.9Co_0.1)_72.7Al_0.8Si_13.5B₉Cu₁Nb₃ alloy was investigated by the temperature dependence of initial permeability (μ_i-T curves). The crystallization behavior and microstructural evolution of alloy with the increase of annealing temperature were studied by means of differential scanning calorimeter (DSC) and X-ray diffraction (XRD). After vacuum annealing at 617 °C for 0.5 h, the µ_i can reach 30,300 and maintain more than 1000 until 640 °C because of larger crystalline volume fraction (V_cry) of 81.9% and smaller intergranular amorphous layer (\(\Lambda\)) of 0.930 nm, which is more excellent than that of other Fe–Co–Al–Si–B–Cu–Nb alloys annealed at their optimum temperatures. In addition, the crystallized interval temperature (∆T_x) of 158 °C, superior to Fe_73.5Si_13.5B₉Nb₃Cu₁ and (Fe_0.9Co_0.1)_73.5Si_13.5B₉Nb₃Cu₁ alloys ever reported, is conducive to precipitating the bcc α-(Fe,Co,Si) and Fe₃(Si,Co,Al) soft magnetic crystalline phases and improving thermostability of alloy.