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

Abstract Thermal behaviors and structures of three Zr-based binary glass formers, Zr 50 Cu 50 , Zr 64 Cu 36 and Zr 64 Ni 36 , 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 Zr 50 Cu 50 has a denser atomic packing efficiency and reduced medium-range order than those of marginal glass formers Zr 64 Cu 36 and Zr 64 Ni 36 . Based on TEM observations for the samples after heat treatment at 10 K above their crystallization onset temperatures, the number density of crystals for Zr 50 Cu 50 was estimated to be 10 23 –10 24  m −3 , which was four-orders higher than that in Zr 64 Cu 36 and Zr 64 Ni 36 metallic glasses. SAXS results indicate that Zr 50 Cu 50 has higher degree of nanoscale inhomogeneities than those in Zr 64 Cu 36 and Zr 64 Ni 36 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.