Local Atomic Structure Analysis of Zr-Ni and Zr-Cu Metallic Glasses Using Electron Diffraction

Abstract

Local atomic structures in Zr_66.7Ni_33.3 and Zr_66.7Cu_33.3 metallic glasses were examined by using nanobeam electron diffraction (NBED), energy-filtered selected area electron diffraction (SAED) and high-resolution electron microscopy (HREM). Locally ordered regions of atomic medium range order (MRO) were observed in both of the specimens by NBED, although it was difficult to recognize the regions using HREM. Statistical analyses for NBED patterns revealed such a difference in the extended MRO regions between the specimens that the MRO structure in Zr_66.7Ni_33.3 is more complex with a large dispersion of interplanar spacings than those in Zr_66.7Cu_33.3. To understand nearest-neighbor atomic coordination, we performed electron intensity analyses using energy-filtered SAED patterns and constructed structure models including about 5000 atoms with the help of reverse Monte Carlo simulation. The nearest-neighbor atomic environments around Ni atoms in Zr_66.7Ni_33.3 are also different from those around Cu atoms in Zr_66.7Cu_33.3, consistent with the NBED study. The local structural difference between the two glasses was discussed in relation to their glass-forming abilities.