Role of Al in Cu-Zr-Al thin film metallic glasses: Molecular dynamics and experimental study

Abstract

The paper deals with the role of Al in thin film metallic glasses based on Cu and Zr. We employ a combination of molecular-dynamics simulations of the atom-by-atom growth process with magnetron sputtering. We use the previously studied composition Cu0.46Zr0.54 as a starting point, and focus on the effect of Al incorporation into Cu0.46Zr0.54 (simulations) and Cu0.46(Zr + Hf)0.54 (sputtering). We go beyond the state-of-the-art by quantifying the homogeneity, densification, short-range order (bonding preferences and coordination numbers), medium-range order (common neighbor and network ring statistics) and functional properties (hardness, Young's modulus, glass transition temperature and crystallization temperature) in a wide range of Al contents (0to20at.%) and growth conditions. We identify the key building blocks of Cu-Zr-Al: icosahedral clusters (12 vertices) centered around Cu and Al, and supraicosahedral clusters (16 vertices) centered around Zr. The atomic-scale simulations provide a lot of information not accessible experimentally and explain the experimental data. Theresults are important for understanding the structures and properties of this class of metallic glasses, and for optimizing their compositions and pathways for their preparation for various technological applications.