Multiscale structures of Zr-based binary metallic glasses and the correlation with glass forming ability

摘要

Thermal behaviors and structures of three Zr-based binary glass formers, Zr50Cu50, Zr64Cu36 and Zr64Ni36, were investigated and compared using differential scanning calorimetry（DSC）, transmission electron microscopy（TEM）, high energy X-ray diffraction（XRD） and small angle X-ray scattering（SAXS）. The high energy XRD results show that the bulk glass former Zr50Cu50 has a denser atomic packing efficiency and reduced mediumrange order than those of marginal glass formers Zr64Cu36 and Zr64Ni36. Based on TEM observations for the samples after heat treatment at 10 K above their crystallization onset temperatures, the number density of crystals for Zr50Cu50 was estimated to be 1023-1024 m-3, which was four-orders higher than that in Zr64Cu36and Zr64Ni36 metallic glasses. SAXS results indicate that Zr50Cu50 has higher degree of nanoscale inhomogeneities than those in Zr64Cu36 and Zr64Ni36 at as-cast state. The observed multiscale structures are discussed in terms of the phase stability and glass-forming ability of Zr-based binary glass formers.