Are hints about glass forming ability hidden in the liquid structure?

Despite intense interest, identifying the structural origin of glass forming ability in metallic alloys remains a challenge due to the difficulty of describing the evolution of the long-range disordered structure from the liquid. Here, we report the cluster variance in the liquid as a potential parameter to predict glass formation based on our investigation of the structural and cluster evolution in the ternary Al-Ni-Zr system using molecular dynamics simulations. The glass forming ability is greatest where the variance of cluster fractions in the liquid is minimized, which was verified by the experimental glass forming range identified using a high-throughput alloy processing technique. Experimentally, glass formation was found over a wide compositional range centered on Al_21.4Ni_23.9Zr_54.7, and is in excellent agreement with simulations. Because the variance of cluster fractions at temperatures above the liquidus temperature is independent of quench rate as well as any particular cluster type, we believe this method could be extended to any alloy system, including those of higher complexity.