Quantitative study on atomic bond proportions and microstructural evolution in Co40Ti60 amorphous alloys via molecular dynamics simulation

This study employed molecular dynamics simulations to systematically investigate the influence of cooling rate on the microstructural evolution and bonding characteristics of Co₄₀Ti₆₀ amorphous alloys. A comprehensive analysis based on pair distribution functions, coordination numbers, atomic bond proportions, Voronoi volume and associated polyhedral features was conducted to elucidate the evolution of heteronuclear and homonuclear bonds under a range of cooling conditions. The results revealed that as the cooling rate increased, the proportion of Co–Ti heteronuclear bonds gradually decreased, whereas the proportions of Co–Co and Ti–Ti homonuclear bonds increased correspondingly. This trend suggests that rapid cooling suppresses the formation of ordered structures, resulting in a more random distribution of bonding types among neighboring atoms. Meanwhile, the overall coordination number decreased, and the average Voronoi volume increased, indicating a transition toward a more open and disordered local structure. In contrast, at lower cooling rates, atoms have more time for rearrangement, leading to the formation of more heteronuclear bonds and characteristic ordered clusters, thereby enhancing structural compactness and short-range order. Overall, the Young's modulus exhibited a decreasing trend with increasing cooling rate, reaching a maximum at 1e13 K/s. This anomaly is attributed to the locally optimized structural synergy induced by a peak number of ordered clusters formed under this specific cooling condition.