The influence of Ag substitution for Cu on glass-forming ability and thermal properties of Mg-based bulk metallic glasses

A group of pseudo-ternary Mg–(Cu–Ag)–Dy bulk metallic glasses (BMGs) was developed by copper mold casting. The glass-forming ability (GFA) is significantly improved by the coexistence of similar elements of Ag and Cu. The critical diameter for glass formation increases from 10 mm for ternary Mg56.5Cu32Dy11.5 alloy to 18 mm for pseudo-ternary Mg56.5Cu27Ag5Dy11.5 alloy. Thermal stability, crystallization and melting behaviors of the Mg-based BMGs were evaluated. The decrease of Gibbs free energy difference between undercooled liquid and crystalline phases caused by similar element substitution with optimal amount can be responsible for the increase in GFA of the resulting alloys.

► Glass-forming ability of Mg–Cu–Dy alloys is improved by substituting Ag for Cu.
► The crystallization thermodynamics is analyzed during similar element substitution.
► Gibbs free energy change is responsible for the increase in glass-forming ability.