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

The kinetics of copper clustering and primary crystallization of FINEMET ty pe alloys with the compositions Fe74.5-xSi13.5B9Nb3Cux and Fe77Si11B9Nb3-xC ux have been studied by small-angle neutron scattering (SANS) and high-sens itivity differential scanning calorimetry (DSC) in order to explain the dif ferent optimized Cu contents, x, for obtaining the highest permeability in these two alloys. SANS results have shown that the alloys with the optimize d Cu contents have the finest nanocrystalline microstructures. Kinetic anal yses of Cu clustering prior to primary crystallization have shown that the number density of Cu clusters becomes highest at the crystallization stage of alpha -Fe primary crystals in the alloy containing an optimized amount o f Cu. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. Al l rights reserved.