Effects of Ag addition on crystallization, microstructure and mechanical properties of Zr-Cu-Ni-Al-Ag bulk metallic glasses

The composition dependences of crystallization, microstructure and mechanical properties have been investigated. When the Ag content is in the range of 0-8 at%, the BMGs with two or three-step of crystallization process exhibit remarkable plasticity, of which primary phase is an icosahedral phase. However, when the Ag concentration reaches 12-16 at%, the BMGs with single-step of crystallization mode display relatively limited plasticity, whose precipitation phase is Zr₂Cu and/or Zr₂Ni intermetallic compounds. Structural analyses reveal that the presence of icosahedral medium-range order clusters, which, in turn leads to the heterogeneity of free volume distribution, is responsible for the improvement of plasticity. The present results suggest that, under appropriate microstructural design by the introduction of icosahedral medium-range order clusters, BMG has extensive application prospect as structural material.