Classification of Crystallization Process of Fe–B–Si Amorphous Alloys by Electrical Resistivity and Calorimetric Measurements

Abstract

The crystallization characteristics of Fe-B-Si amorphous alloys at constant rate heating are studied by differential scanning calorimetry (DSC) and electrical resistivity measurements. The crystallization products are examined by X-ray diffraction and transmission electron microscopy. The compositional dependence of crystallization process is discussed in relation to amorphous structure. It is shown that the crystallization process is classified into six groups based on the way of the changes in electrical resistivity and DSC curves during the crystallization. Moreover, a critical concentration exists where the crystallization process significantly changes. Amorphous alloys with the B and Si content beyond the critical concentration crystallize at temperatures above 800 K and produce Fe 3 B and Fe 2 B as well as Fe 3 Si at the initial stage. At the alloy content below the critical concentration, α-Fe(Si) or Fe 3 Si appears as the primary crystalline phase and then Fe-B compounds emerge from the remaining amorphous phase. The appearance of the metastable Fe 3 B phase is closely related to the order-disorder transformation in the Fe-Si phase which forms at the initial stage of crystallization. The dependence of the crystallization temperature on average electron concentration is observed only in the alloys below the critical concentration.