Iron-boron metallic glasses

Abstract

By rapid quenching from the liquid, binary Fe100−xBx glasses are produced over the range 12–28 at.% B. Magnetization measurements in these glasses indicate a compositional dependence of the saturation magnetic moment μs which is consistent with the compositional dependence of the density of the material and reflects electron charge transfer from boron to iron. The extrapolated value of μs for noncrystalline Fe metal is found to be close to that for pure crystalline iron (μs=2.2μB); this is lower than the value of 2.4μB previously estimated for amorphous Fe. Based on x-ray and thermomagnetization data, it is argued that the local atomic arrangements resemble those of bcc iron for the Fe-rich alloys (x<16 at.%) and are similar to those of orthorhombic Fe3B in the vicinity of x=20. For x≳25, the local atomic structure seems like that of tetragonal Fe2B. These structural changes can explain the unexpected decrease of the Curie temperature with decreasing boron content. The decrease of the crystallization temperature with decreasing B content is similar to the compositional trend in the microhardness of the material.