Analysis of icosahedra in rapid solidification of Pd<sub>82</sub>Si<sub>18</sub> amorphous alloy under high pressure

Compared with traditional glasses, metallic glasses (MGs) have excellent properties, such as high strength, high hardness, high fracture toughness, good soft magnetic properties and corrosion resistance due to their unique structure. Such properties enable them to be used in optics, electronics, construction and other fields, making them a highly promising new material with great application potential. As the properties of amorphous alloys are closely linked with their local structure, microstructure characteristics have always been a research focus in the amorphous field. Previous studies showed that the onset temperature of heredity and hereditary fraction of characteristic clusters could effectively evaluate the glass forming ability of an amorphous alloy. In order to figure out the relationship between the microstructure characteristics and cluster evolution of amorphous alloys on the one hand, and the formation of glass on the other hand, the glass transition processes of the Pd₈₂Si₁₈ alloy under different pressure conditions were simulated by using the molecular dynamics method, and the heredity and evolution of the Pd₈₂Si₁₈ amorphous alloy were analyzed by using the cluster-type index method and the reverse tracking method. After the simulation, it was found that the glass transition temperature of the Pd₈₂Si₁₈ alloy could be increased when the pressure was higher, and a large number of icosahedra were formed in the solidified alloy when the pressure was sufficiently high. Icosahedra is a kind of structure widely exists in amorphous materials and has been studied for quite a long time. This paper conducted a detailed comparative analysis on two icosahedra and investigated the heredity ability of clusters with different chemical components under high pressures. The results showed that it was easier for icosahedra with central atom Pd and those with central atom Si to form a medium-range order in the Pd₈₂Si₁₈ amorphous alloy. An increase in pressure could bring a higher onset temperature of heredity and stage hereditary fraction. Combined with the results of cluster heredity analysis under 0 GPa, this meant Si-centered clusters had stronger heredity ability than Pd-centered clusters, thus the former ones had a greater impact on glass forming ability. These findings are of significance in understanding the relationship between microstructure evolution and glass formation, as well as providing certain guidance on the design of amorphous alloys.