Atomic-scale simulation to study the dynamical properties and local structure of Cu-Zr and Ni-Zr metallic glass-forming alloys.

Abstract

Molecular dynamics simulation with well-developed EAM potentials was carried out to investigate the transport properties and local atomic structure of Cu-Zr and Ni-Zr metallic glasses and supercooled liquids. It is found that Cu or Ni atoms have much faster dynamics than Zr atoms in relaxation timescales, while Zr atoms display faster dynamics in the Cu-Zr system than in the Ni-Zr system. A dynamical crossover phenomenon from Arrhenius to super-Arrhenius behavior in the transport properties was observed for the Cu65Zr35 system at Tx ≈ 1250 K and the Ni65Zr35 system at Tx ≈ 1500 K, respectively. Further structural analysis suggests that the dominant interconnected clusters in Cu65Zr35 and Ni65Zr35 systems are 〈0, 0, 12, 0〉, 〈0, 1, 10, 2〉, 〈0, 2, 8, 2〉 and 〈0, 3, 6, 4〉. To directly characterize and visualize the correlated dynamics, we regard the full icosahedra as the microscopic origin responsible for the formation of metallic glasses in the Cu65Zr35 system, while the metallic glass formation in the Ni65Zr35 system can be attributed to the slow dynamics of 〈0, 3, 6, 4〉, 〈0, 2, 8, 2〉 and 〈0, 1, 10, 2〉 Ni-centered Voronoi polyhedra. The local atomic order and dynamics for Cu65Zr35 and Ni65Zr35 systems are remarkably different, and these differences are presumed to hinder crystal nucleation and growth, hence promoting the largely different bulk glass-forming ability.