Comparison of structural heterogeneity in Zr- and Pd-based metallic glasses

Abstract

Metallic glasses (MGs) are known to exhibit a nanoscale heterogeneous structure that consists of a weakly bonded region (WBR) and a strongly bonded region (SBR), but its characterization is not yet fully understood. This study investigates the structural heterogeneity of Zr- and Pd-based MGs using a dynamic viscoelastic model. Volume fraction (V) and elastic modulus (Ec) are independently derived from the model to characterize each region. In addition, the structural heterogeneity is evaluated using χ = VEc,WBR/VEc,total. As a result, the strong Zr-based MG is estimated to own approximately 28% of VWBR, approximately 87% of Ec,WBR/Ec,SBR, and χ ∼ 0.241. On the other hand, the fragile Pd-based MG is estimated to own approximately 26% of VWBR, approximately 70% of Ec,WBR/Ec,SBR, and χ ∼ 0.208. Furthermore, a comparison of χ, fragility, and Poisson's ratio shows that as χ increases, fragility decreases and Poisson's ratio increases. Notably, the diversification of constituent elements is inversely related to χ, fragility, and Poisson's ratio in the Zr- and Pd-based MGs. Thus, the existing understanding of the structural heterogeneity inherent in MGs is updated using the constructed dynamic viscoelastic model in this study.