Small-angle neutron scattering and differential scanning calorimetry studies on the copper clustering stage of Fe–Si–B–Nb–Cu nanocrystalline alloys

Abstract The kinetics of copper clustering and primary crystallization of FINEMET type alloys with the compositions Fe 74.5− x Si 13.5 B 9 Nb 3 Cu x and Fe 77 Si 11 B 9 Nb 3− x Cu x have been studied by small-angle neutron scattering (SANS) and high-sensitivity differential scanning calorimetry (DSC) in order to explain the different optimized Cu contents, x , for obtaining the highest permeability in these two alloys. SANS results have shown that the alloys with the optimized Cu contents have the finest nanocrystalline microstructures. Kinetic analyses of Cu clustering prior to primary crystallization have shown that the number density of Cu clusters becomes highest at the crystallization stage of α-Fe primary crystals in the alloy containing an optimized amount of Cu.