Phase separation and crystallization process of amorphous Fe78B_(12)Si_9Ni_1 alloy

摘要

The influence of the melt heat treatment on the structure and crystallization process of the rapidly quenched amorphous Fe_(78)B_(12)Si_9Ni_1 alloys have been investigated by means of x-ray diffraction, DSC and TEM. Amorphous phase separation has been observed in the alloys quenched after the preliminary high temperature heat treatment of the liquid alloy (heating above 1400°C). Comparative analysis of the pair distribution functions demonstrates that this phase separation accompanied by a changes in the local atomic arrangement. It has been found that crystallization process at heating is strongly dependent on the initial amorphous phase structure - homogeneous or phase separated. In the last case crystallization goes through the formation of a new metastable hexagonal phase [a=12.2849(9), c=7.6657(8)]. At the same time the activation energy for crystallization (Ea) reduces from 555 to 475 kJ mole~(-1).