Classification of crystallization process of Fe-B-Si amorphous alloys by electrical resistivity and calorimetric measurements

The crystallization characteristics of Fe-B-Si amorphous alloys at constant rate heating are studied by differential scanning calorimetry (DSC) and el ectrical resistivity measurements. The crystallization products are examine d by X-ray diffraction and transmission electron microscopy. The compositio nal dependence of crystallization process is discussed in relation to amorp hous structure. It is shown that the crystallization process is classified into six groups based on the way of the changes in electrical resistivity a nd DSC curves during the crystallization. Moreover, a critical concentratio n exists where the crystallization process significantly changes. Amorphous alloys with the B and Si content beyond the critical concentration crystal lize at temperatures above 800 K and produce Fe3B and Fe2B as well as Fe3Si at the initial stage. At the alloy content below the critical concentratio n, alpha-Fe(Si) or Fe3Si appears ast the primary crystalline phase and then Fe-B compounds emerge from the remaining amorphous phase. The appearance o f the metastable Fe3B phase is closely related to the order-disorder transf ormation in the Fe-Si phase which forms at the initial stage of crystalliza tion. The dependence of the crystallization temperature on average electron concentration is observed only in the alloys below the critical concentrat ion.