Crystallization behavior and temperature dependence of the initial permeability of an FeCuNbSiB alloy

The crystallization behavior of an Fe_73.5Cu₁Nb₃Si_13.5B₉ alloy was studied by differential scanning calorimetry. Two crystallization peak temperatures at infinitesimal heating rate were obtained to be 769 K (T_x1) and 910 K (T_x2), respectively. The associated activation energies by means of Kissinger’s peak shift method were obtained to be 340 and 428 kJ/mole, respectively. Initial permeability (μ_i) and Q values versus temperature was in situ investigated in the range from 300 to 873 K by a specially designed setup on toroid ribbon cores. Their variations with temperature reveal corresponding changes in magnetization and nanocrystallization, etc. Anomaly μ_i peaks at 428 K in the cooling curve instead of at room temperature. By isothermal annealing at 823 K, precipitous maxima in μ_i and Q appear at about 50 min. This in situ method may be too powerful to work out optimal annealing processes for a specific nanocrystalline alloy.