The supercooled liquid region span of Fe-based bulk metallic glasses

Abstract

This work presents the results of the study of the magnetically soft, iron-based bulk metallic glasses, from the viewpoint of their ability to deform in the supercooled liquid region and to resist the tendency to crystallise. The calorimetric measurements of glass transition and crystallisation temperatures ( T g and T x1 respectively) were employed, accompanied by the measurements of magnetic properties as the monitor of structural changes after heat treatment. It was found that the widest supercooled liquid region was obtained when zirconium was selected as one of the alloying elements, yielding the T x1– T g span of about 70 °C. Also, it was observed that the values of T g and T x may be controlled by the proportions of the main elements (Fe, Co, Ni), and the glass forming elements (such as B, Nb, Zr). As a guideline, it is suggested that the glassy Fe-based alloys may be maintained in the supercooled liquid state without crystallisation for several minutes, if T x1– T g is wider than 50 °C. Basing on this estimation, calorimetric measurements may be a good indicator of the ability of bulk metallic glasses to be suitable for superplastic compaction into larger shapes.