Cooling-rate-dependent chemical–topological freezing signatures and elastic response of binary amorphous alloys under rapid quenching: a molecular dynamics study

Abstract

Cooling rate strongly influences the structural evolution and structural freezing of amorphous alloys. However, the relationships among chemical short-range order (CSRO), geometrical short-range order (GSRO), and elastic response remain insufficiently understood. In this work, molecular dynamics simulations were performed on four 40:60 binary alloy models under a common nominal cooling protocol. The four systems were Al–Zr, Co–Ti, Ti–Ni and Cu–Zr. The systems were quenched over cooling rates of 1012–1015 K s−1. Atomic bond proportion analysis was used to quantify CSRO. Voronoi cluster analysis was used to characterize GSRO. The lower-cooling-rate configurations are consistent with more extensive atomic rearrangement and higher heteroatomic nearest-neighbour pair fractions. The lower-cooling-rate configurations also exhibit higher populations of fivefold-symmetry clusters, lower mean atomic volumes, and greater local structural ordering. Higher cooling rates suppress atomic rearrangement and preserve more liquid-like local configurations. Among the four alloy-potential models considered in this work, Al–Zr and Co–Ti exhibit relatively pronounced changes in both chemical and topological structures with cooling rate. For Ti–Ni, most structural changes are concentrated within the lower part of the sampled cooling-rate range, with smaller variations at higher nominal cooling rates. In contrast, Cu–Zr exhibits relatively smooth structural variations over the investigated cooling-rate range. The finite-rate apparent tensile modulus generally decreases with increasing cooling rate. This decrease occurs concurrently with less compact local packing and reduced structural order. These findings provide atomistic insight into cooling-rate-dependent chemical and topological freezing and their relationship with the elastic response of rapidly quenched amorphous alloys.