CuZr metallic glasses under tensile cyclic loading: inspection of Z cluster networks

Abstract This study investigates the mechanical behavior and structural evolution of CuZr metallic glasses (MGs) under cyclic tensile loading using five compositions ranging from Cu 36 Zr 64 to Cu 64 Zr 36 . The results reveal that the Cu 64 Zr 36 sample consistently exhibits the highest strength and toughness, while also undergoing more pronounced mechanical degradation with cycling. This degradation, manifested by a reduction in Young’s modulus and an increase in Poisson’s ratio, is attributed to plastic softening and the onset of strain localization. Structural analyses based on Voronoi tessellation and network theory emphasize the critical role of icosahedra-like structures, called Z clusters, in deformation behavior. All samples exhibit a decrease in the population and connectivity of Z clusters during cyclic loading, with the Cu 64 Zr 36 MG showing the most significant fragmentation of Z cluster networks. This fragmentation is associated with the development of shear bands, as reflected in the increase in the number of subnetworks and the reduction in both their size and connectivity. In contrast, Cu-poor samples, particularly Cu 36 Zr 64 , Cu 50 Zr 50 , and Cu 56 Zr 44 , display lesser reductions of Z cluster networks, leading to more homogeneous deformation. A combination of both mechanisms is observed in the Cu 60 Zr 40 MG. These findings highlight the importance of atomic structure in determining the mechanical performance and failure mechanisms of MGs under repeated loading.