In situ neutron scattering studies of a liquid-liquid phase transition in the supercooled liquid of a Zr-Cu-Al-Ag glass-forming alloy

The presence of a liquid-liquid phase transition in the supercooled-liquid temperature range for a glass-forming Zr-Cu-Al-Ag alloy has been revealed using a suite of in situ neutron scattering techniques, including small-angle neutron scattering (SANS) and total neutron scattering. The SANS data analysis is indicative of the enhancement of nanoscale structural heterogeneities prior to crystallization, which is further supported by the total scattering result that points to an increase in the degree of medium-range ordering during the transition. In addition, a calorimetric anomaly and abnormal thermal expansion behavior were also observed upon heating. As such, this study provides multiscale structural evidence on the liquid-liquid phase transition and helps to gain insight into its underlying mechanism in terms of cluster connectivity.