Formation and fracture of Mg88Al6Zn6 MGs analyzed by topologically close-packed cluster correlation

The microstructure of metallic glasses (MGs) significantly impacts glass transition and mechanical properties, but the current research on this topic is still not comprehensive enough. Therefore, the rapid solidification and tensile processes of Mg88Al6Zn6 MGs have been investigated in this paper by molecular dynamics simulations and their microstructure has been analyzed by the Largest Standard Cluster Analysis (LaSCA). The results show the transformation of other clusters to topological close-packed (TCP) and defective TCP (D-TCP) clusters during the rapid solidification process. The transformation rate slows down significantly near the glass transition temperature (Tg) 530 K, and the two finally reach 39.19%. These clusters can be divided into five groups (c1-c5) based on their correlation indexes, and their dynamic behavior and hereditary are discussed. Clusters with strong correlations tend to form larger-sized medium-range ordered nanoclusters, which serve as the "structural skeleton" of MGs. During the tensile process, TCP and D-TCP clusters with a lower average atomic potential energy (-0.57 eV) exhibit a higher packing density and structural stability, consequently enhancing the strength of MGs (3.29 GPa). Furthermore, the larger-sized nanoclusters formed by strongly correlated clusters also contribute to the strength of local regions, thereby improving the overall tensile performance of MGs. These findings offer valuable insights into the microstructural mechanisms involved in the formation and fracture of MGs.