APT characterization of some iron-based bulk metallic glasses

A microstructural characterization was performed on 3 iron-based bulk metallic glasses. These alloys were an arc cast Fe61Y2Zr8Co6Al1Mo7B15 A2 alloy, a twin roll cast Fe68Y2Zr2Nb2Cr1.5V4.5B20 DarpaQ21 alloy and a vacuum induction melted Fe50.7Y1.5Cr14.5Mo13C14.8B5.5 Darva101-Y alloy. The alloys were characterized by scanning electron microscopy and atom probe tomography in the as-cast condition. Some micrometer and nanometer scale precipitates were observed in all 3 alloys indicating that the alloy compositions are not fully optimized in the as-cast state. The Darva101-Y alloy was also characterized after annealing above the onset of crystallization temperature for 1 h at 610 °C. This annealing treatment produced a mixture of crystalline phases: M6(BC) and Fe14Y2B in addition to a high temperature M23C6 phase that is indicated from XRD and previous research.