Formation of nanocrystals by crystallization of amorphous Fe-Si-B based alloys

The crystallization of amorphous Fe-Si-B based alloys was investigated by means of X-ray diffraction, DSC, and transmission electron microscopy. Crystallization temperatures, phase sequences, and the microstructures of the phases formed are strongly influenced by the chemical composition. In the case of amorphous Fe76.5-xSi15.5B7 Cu1Nbx a reduction of the crystallite size down to 15 nm is found to depend on the Nb content. XRD values of the mean crystallite size calculated from the analysis of line broadening agree well with the TEM results. From in situ XRD observations at high temperature kinetic parameters of the crystallization process could be estimated. The amorphous phase changes its composition due to the primary crystallization and acts, enriched with Nb and B, acts as a diffusion barrier leading to a nanostructured state.