Influence of La on the atomic structure of Al[sbnd]Cu alloy liquid

Abstract

The influence of La element on the atomic structure of AlCu alloy liquid above the liquidus line was investigated through high-energy x-ray diffraction technology on synchrotron facility and constrained reverse Monte Carlo simulation. The addition of La induced a change in nearest neighbor environments and chemical short-range orders of the atoms, which makes the Cu and La atoms dispersed in the liquid and surrounded by Al atoms. The analysis results of atomic topological short-range order show La element does not promote the icosahedral short-range order in the Al86Cu9 liquid, but increases the number of cluster types and reduces the variance of the cluster fraction, leading to a more disordered structure. These results strongly support that the diversity and distribution of clusters are responsible for the glass-forming ability of alloys, not the specific cluster type. Moreover, La element affects the arrangement of clusters in space, enhancing structural heterogeneity of the liquid and the correlation between clusters with high five-fold symmetry, which can also result in an improvement in glass-forming ability. These findings reveal the role of La element in enhancing glass-forming ability, and have implications for understanding the liquid-glass transition mechanism.