COMPOSITIONAL DEPENDENCE OF CRYSTALLIZATI ON PROCESS IN FE-B-SI AMORPHOUS-ALLOYS

The compositional dependence of the crystallization process at constan t rate heating has been studied for Fe-B-Si amorphous alloys by electr ical resistance measurement and differential scanning calorimetry (DSC ). The crystallization products have been examined by X-ray diffractio n. The relationship between the crystallization process and the amorph ous structure was discussed in terms of the Dubois and Le Caer's struc tural model. A strong compositional dependence was observed in the cha nges in electrical resistivity and DSC curve during the crystallizatio n. Based on the way of the changes in the physical properties, the cry stallization process was classified into five groups. Furthermore, it was found that the crystallization process changed significantly at a critical concentration where the structural change was predicted from the model. Outside the critical concentration amorphous alloys crystal lized at temperatures above 800 K and produced Fe3B and Fe2B as well a s Fe3Si at the initial stage. Inside the concentration alpha-Fe(Si) or Fe3Si appeared as the primary crystalline phase and then Fe-B compoun ds emerged from the remaining amorphous phase. The formation of the me tastable Fe3B phase is considered to be closely related to the order-d isorder transformation in the Fe-Si phase which appears in the initial stage of crystallization.