Nanocrystallisation mechanisms in FeCuNbSiB-type alloys from comparative HREM, STM, TGM and calorimetric studies

The process of nanocrystallisation in two alloys (Fe73.5Cu1Nb3S13.5B9 and F e77.5Cu1Nb3Si9.5B9) as a function of their annealing treatments was investi gated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TGM) under magnetic field, conventional transmission elec tron microscopy (TEM), high-resolution transmission electron microscopy (HR EM), electron diffraction (ED) and scanning tunneling microscopy (STM). In addition to information about nucleation and growth of the grains. the two microscopic methods reveal amorphous interfaces between alpha-Fe(Si) nanopr ecipitates. It was shown by means of HREM that during annealing an overlapp ing of the diffusion fields between neighboring alpha-Fe(Si) nanoparticles causes their coalescence into grains, which saturate with the annealing tim e. Scanning tunneling microscopy reveals atomic resolution in the nanocryst als as well as in their grain boundaries. On the basis of these experiments we established annealing conditions which yield the best soft magnetic pro perties. (C) 1999 Elsevier Science S.A. All rights reserved.