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

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.