The effects of alloying composition on plasticity and strength of notched metallic glasses

Abstract

Using notch geometry in the metallic glass (MG) samples, it is possible to improve the homogeneous plasticity and mechanical properties. In this work, the molecular dynamics (MD) simulation was performed to indicate how the alloying composition of MGs can tune the mechanical properties of notched samples. For this purpose, CuZr MGs were constructed through atomic-scale simulation with alloying compositions of Cu₆₄Zr₃₆, Cu₆₀Zr₄₀, Cu₅₄Zr_46, and Cu₅₀Zr₅₀, while a symmetrical surface notch was produced at the waistline of samples by removing certain atoms and relaxing the new free surfaces. The tensile loading was also carried out to characterize the plastic deformation and strength in the CuZr MGs. According to the results, Cu₆₄Zr₃₆ and Cu₆₀Zr₄₀ alloys exhibited a localized plastic deformation in the notch region, while the decrease in Cu content, i.e. Cu₅₄Zr₄₆, led to the generation of nanoscale shear events outside the notch region and extended the deformation area in the body of the sample. The results also indicated that the change in the mechanism of plastic deformation in the notched samples strongly depended on the type and population of polyhedrons rearranged in the backbone structure. Moreover, it was found that the Voronoi volume in the Cu₅₄Zr₄₆ alloy exhibited a gentle increment under the tensile loading in both the notched and un-notched regions, while the Cu-rich MGs, i.e. Cu₆₄Zr₃₆ and Cu₆₀Zr₄₀, showed a sudden increment of Voronoi volume at the center of the notch region, which was indicative of strain localization in the atomic system.