CRYSTALLIZATION PROCESS OF FE80P20-XSIX AMORPHOUS-ALLOYS

The crystallization process of Fe80P20-xSix amorphous alloys has been studied by electrical resistivity, X-ray diffraction, neutron diffract ion, and transmission electron microscopy. This process is classified into two different patterns with a boundary of 6 at%Si. In the alloys containing less than 6 at%Si, alpha-Fe and Fe3P, both of which are sta ble phases, precipitate from the amorphous matrix directly. In the cry stallization of the amorphous alloys containing over 6 at%Si, two comp lex phases are observed in the early stages. We found that these two p hases are isostructural with the alpha-Mn type and beta-Mn type phase. After these two metastable phases disappear, another metastable phase which is probably Fe2P appears. In the final stage of the crystalliza tion, however, existing crystalline phases are stable alpha-Fe (or ord ered Fe3Si) and Fe3P. In the isothermal crystallization process of the Fe80P14Si6 amorphous alloy, only the alpha-Mn type phase is observed as the metastable phase at high temperatures such as 683, 703 and 723 K; however, at a lower temperature such as 668 K, no metastable phase is observed. The precipitation of the metastable alpha-Mn type and/or beta-Mn type phases, which consist of the Frank-Kasper coordination po lyhedra, can be closely related to the local structure in these amorph ous alloys.