Quantifying microstructural heterogeneity and its link to dynamic fragility in CuZr metallic glasses

Abstract

The absence of effective parameters to describe structural heterogeneity impedes the investigation into its correlation with the physical properties of materials. Here, we introduce the use of Moran's index, typically employed in geographical studies to characterize spatial heterogeneity, for the depiction of structural heterogeneity in metallic glasses. By employing molecular dynamics simulations in conjunction with Moran's index, we quantitatively assess the degree of microstructural heterogeneity in Cu50Zr50 and Cu64Zr36 metallic glasses and examine its connection to dynamic fragility. Our findings reveal that the spatial structural heterogeneity in the Cu50Zr50 system is significantly lower than that in the Cu64Zr36 system, with a more gradual decrease observed as temperature is reduced, suggesting that Cu50Zr50 possesses a more stable liquid structure. Our study indicates that lower levels of heterogeneity and a diminished temperature dependence of this heterogeneity correlate with stronger dynamic fragility. Furthermore, our methodology demonstrates the potential to be an effective tool for elucidating structural heterogeneity in metallic glasses.