Computational assisted design of the favored composition for metallic glass formation in a Ca–Mg–Cu system

Abstract

To well predict the favored composition for metallic glass formation in a Ca–Mg–Cu system, a realistic interatomic potential was first constructed for the system and then applied to Monte Carlo simulations. The simulation not only predicts a hexagonal composition region for metallic glass formation, but also provides a favored sub-region within which the amorphization driving force is larger than that outside. The simulations show that the physical origin of glass formation is the solid solution collapsing when the solute atom exceeds the critical solid solubility. Further structural analysis indicates that the 1551 bond pairs (icosahedral-like) dominate in the favored sub-region. The large atomic size difference between Ca, Mg, and Cu extends the short-range landscape, and a microscopic image of the medium-range packing can be described as an extended network of pentagonal bipyramids entangled with four-fold and six-fold disclinations, together fulfilling the space of the metallic glasses. The predictions are well supported by the experimental observations reported to date and can provide guidance for the design of ternary glasses.