Enhanced glass forming ability and plasticity in Mg-based bulk metallic glasses

In the present study, the effect of small substitution in Mg₆₅Cu₂₅Gd₁₀ (at.%) alloy has been investigated for two purposes, i.e.: (1) for improvement of glass forming ability (GFA) and (2) for enhancement of compressive plasticity possibly. The Mg₆₅Cu_7.5Ni_7.5Ag₅Zn₅Y₅Gd₅ bulk metallic glass (BMG) with diameter of 14 mm is successfully fabricated by conventional copper mold casting method in air atmosphere, which is the highest GFA among those previously reported for Mg-based alloys. The significantly improved GFA of the Mg-Cu-Ni-Zn-Ag-Y-Gd alloys can be properly represented by T_rg, γ and ε parameters. Although general Mg-based BMG show a little and no plasticity under compressive loading, the addition of element having positive enthalpy of mixing with constitutive element such as Be, Ag and Y increases the plasticity in a limited composition range.