Cluster Heredity and Evolution Dominate theComposition-Dependent Glass-Forming Ability of Cu-Ag Alloys

The rapid solidification process of liquid Cu_100-xAg_x (5 ≤ x ≤ 25) alloy was simulated using molecular dynamics (MD) method, and the microstructure and its evolution were characterized by combining the pair distribution function, Honeycutt-Andersen (H-A) bond type index, and cluster type index method (CTIM). The results indicate that at the cooling rate of 1 × 10¹² K/s, the critical composition for the formation of amorphous Cu_{100 x}Ag_x alloy is x ≈ 7, and the reduced glass transition temperature T_rg increases with the increase of x (≥ 10). When the composition is x ≤ 6, the system mainly forms FCC crystals and a small amount of HCP clusters, with (13 3/1441 6/1551 4/1661) and (14 4/1441 4/1551 6/1661) clusters acting as precursors for the system crystallization; Within the range of 10 ≤ x ≤ 25, a large number of highly localized five-fold symmetric defect icosahedra, (12 12 12/1551) regular icosahedra, and their extended clusters are formed in amorphous alloys, and the number of these clusters significantly increases with the increase of Ag content. Further hereditary tracking analysis revealed that as the Ag content increased, the stage  hereditary  fraction and onset temperature of the heredity of (12 12/1551) icosahedral clusters in the rapid solidification alloy also increased, indicating that the heredity  and evolution of clusters dominated the compositional dependence of glass-forming ability (GFA) in Cu-Ag alloys.