On the structure and aging behavior of rapidly quenched Fe-B alloy

The crystallization of amorphous Fe-B alloy containing less than 15 at. % of boron occurs by two-stage reaction, the precipitation of α-solid solution phase, and the formation of crystalline Fe3B. But the boron content in the α-solid solution and in the remnant amorphous phase is not clear. In case of the thin amorphous foils quenched from the melt, the surface exerts complicated influence on the crystallization process of the amorphous alloy and the structure of as-quenched specimens. In this study, these problems were clarified. The amorphous and crystalline specimens were prepared, and the nominal composition was Fe90B10, Fe87B13, Fe85B15 and Fe80B20. The measurement of the lattice parameters was performed by a step-scanning method. In the Fe90B10, the amorphous phase was not able to be produced. Instead, the coexistence of α-Fe and orthorombic Fe3B was obtained. In the Fe87B13, the formation of γ-Fe phase in the as-quenched specimens was discovered on and near the surface. The γ-Fe phase was more stable thermally than the amorphous phase. In the continuous heating of the Fe85B15, the X-ray profile showed the first and second stages. In the Fe80B20, the formation of the solid solution near the surface did not occur, and the crystallization initiated even inside the specimens. (Kako, I.)