Origin of structural heterogeneity in Zr-Co-Al metallic glasses from the point of view of liquid structures

Abstract

To clarify the origin of structural heterogeneity in metallic glasses (MGs), liquid structures upon cooling of Zr-Co-Al alloys were simulated. Being different from Zr10Co85Al5 alloy, the first peak of pair distribution functions (PDFs) for Zr65Co30Al5 alloy exhibits a splitting behavior, which is attributed to the competition between Co-and Zr-centered clusters. The coordination numbers and chemical short-range order (SRO) analysis show that the chemical structural heterogeneity also governs the formation of Zr65Co30Al5 MG. Bond pair analysis reveals the prominence of bond pairs with five-fold symmetry for both MGs, but bond pairs in Zr65Co30Al5 MG exhibit noticeable six-fold symmetric stability. Voronoi polyhedron analysis further confirms the formation of strong chemical SROs in Zr65Co30Al5 MG. Dynamic mechanical experiments (DMA) prove the existence of structural heterogeneity, while Zr65Co30Al5 MG with more pronounced (chemical) structural heterogeneity displays larger ductility. The present work may provide a new insight into the origin of structural heterogeneity in MGs.