Cu clustering stage before the crystallization in Fe-Si-B-Nb-Cu amorphous alloys

The Cu clustering stage before the crystallization of Fe-Si-B-Nb-Cu amorpho us alloys have been studied by three dimensional atom probe (3DAP) small-an gle neutron scattering (SANS) and high sensitive differential calorimetry ( DSC). Cu clustering occurs prior to the onset of the primary crystallizatio n reaction. The number of the clusters estimated by 3DAP is large enough to provide heterogeneous nucleation sites to all bcc/D0(3) Fe-Si crystals whi ch appear at higher temperatures. This fact indicates that the distribution of nanocrystalline Fe-Si is strongly affected by that of the Cu-enriched c lusters. The average diameter and interparticle distance of the Cu-enriched clusters have also been estimated by SANS. An exothermic reaction is obser ved above the Curie Temperature in the DSC curves of the Fe-Si-B-Nb-Cu allo ys. The onset temperature of the exothermic reaction is shifted to lower te mperature with increasing Cu content. (C) 1999 Acta Metallurgica Inc.