Alloying strongly influences the structure, dynamics, and glass forming ability of metallic supercooled liquids

The addition of a relatively small amount of alloying element(s) can induce major changes in the viscosity, fragility, and glass forming ability of supercooled liquids. A microscopic understanding of this behavior from the structural perspective has been elusive. Through comparisons between Cu-Zr-Al and Cu-Zr supercooled liquids, here we demonstrate the strong effects of Al alloying on the atomic-scale structure, in particular, the evolution of icosahedral local motifs, as well as the resulting dramatic slowing down of relaxation dynamics. The composition-structure-dynamics relationship uncovered for realistic bulk metallic glass forming liquids is important for understanding the glass transition and glass forming ability.