Composition dependence in glass-forming ability of Cu-Ag binary alloys

Alloys around eutectic points are thought to be good glass formers. However, the glass-forming ability (GFA) as a function of composition from pure metals to the eutectic alloy has not been quantified and the underlying microstructural and dynamical origins are unclear. In this work, the GFA of Cu-Ag alloys at various compositions was thoroughly investigated by using molecular dynamics simulations. According to the results, the critical cooling rate for glass formation Rc (K/s) varies with solute content x ' (at%), following R-c asymptotic to Aexp(kx') where A = 4.61 x 10( 12) and k =-0.25 on the Cu side and A = 4.43 x 10(12) and k =-0.19 on the Ag side. The R(c )of the eutectic alloy is about 5 orders of magnitude lower than that of the pure metals. Structurally, the number of densely packed icosahedral-like clusters in Cu-Ag metallic glasses increases with increasing solute content, resulting in the most densely packed structure at the eutectic composition. The dynamical properties of Cu-Ag melts are basically independent on composition at high temperatures, but obviously change with composition at low temperature. Besides the largest reduced glass transition temperature, the highest five-fold symmetry (FFS) local structure and more importantly the retarded dynamics of liquid atoms below the liquidus temperature around the eutectic composition impart the eutectic alloy with the best glass-forming ability. (C) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study thoroughly investigated the glass-forming ability of Cu-Ag alloys at different compositions using molecular dynamics simulations. The results showed that the eutectic alloy exhibited the best glass-forming ability, with a critical cooling rate significantly lower than that of pure metals. The number of densely packed icosahedral-like clusters increased with increasing solute content in the alloy. While the dynamical properties of Cu-Ag melts were composition-independent at high temperatures, they clearly changed with composition at low temperatures.