Prediction of glass-forming ability and characterization of atomic structure of the Co-Ni-Zr metallic glasses by a proposed long range empirical potential

Abstract

An interatomic potential is constructed for the Co-Ni-Zr ternary metal system under long range empirical formalism and applied to conduct molecular dynamics simulations and Voronoi tessellations. Using solid solution models with varying solute concentrations, the simulations reveal that the physical origin of metallic glass formation is the crystalline lattice collapsing while solute concentration exceeding the critical solid solubility and determine a series of critical values. In the composition triangle, the determined critical solid solubilities define a quadrilateral region, in which the formation of Co-Ni-Zr ternary metallic glasses is favored and could therefore be considered as the quantitative glass-forming ability of the system. Voronoi tessellations indicate that the atomic structure of the Co-Ni-Zr ternary metallic glasses is obviously affected by the concentration of the component metals and that the differences of the atomic radii play the key role in influencing the atomic structure of the metallic glasses, e.g., for the Co50 − x/2Ni50 − x/2Zrx (15 < x < 80) metallic glasses, the {0, 0, 12, 0} icosahedrons are the most popular polyhedrons, and they are almost Co- or Ni-centered. With increasing Zr concentration, the average coordination numbers of Co, Ni, or Zr decrease. When the Zr concentration is greater than 50 at. %, the fractions of {0, 0, 12, 0} icosahedrons and {0, 1, 12, 0} icosidihedrons decrease and the fraction of {0, 2, 8, 1} octadecahedrons remarkably increases. It turns out that the predicted glass-forming ability is well supported by the experimental observations so far reported in the literature.