Structural characterization of Ni-based refractory glassy metals

X-ray scattering patterns of several Ni-based refractory alloy glasses indicated short range atomic order to at least four nearest neighbor shells. Comparisons between diffraction results from a synchrotron source vs. a standard laboratory source showed the necessity for low divergence and high intensity incident radiation in order to distinguish a low concentration of crystallites as small as ≈15 nm, which were present within an amorphous matrix. The divergence of both sources was examined by comparing the diffraction patterns of the same LaB6 standard sample and using this as a reference standard to measure relative grain sizes. The crystallites in these glasses comprised between 0.0% and 7.5% by volume, and were relatively consistent amongst samples of the same composition. These crystalline peaks had potential matches with several metallic elements, compounds and oxides. It is seen that a very small composition range exists for near-perfect bulk metallic glass formers (as defined by a ≈0% crystallinity). Scattering electron microscopy was also performed to understand aspects of individual second phase particles such as size and distribution. Departure of radial distribution results from those predicted by hard sphere models indicated intermediate range order.