Thermodynamic and kinetic interpretation of the glass-forming ability of Y-containing Cu-Zr-Al bulk metallic glasses

Abstract

In the present study, the glass-forming ability (GFA) of (Cu50Zr43Al7)100-xYx (x = 0, 2, 4 and 6 at.%) bulk metallic glasses (BMGs) was investigated from thermodynamic and kinetic viewpoints. The amorphous structure of the alloys was confirmed using several techniques including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and differential scanning calorimetry (DSC). The thermal characteristics obtained through DSC and differential thermal analysis (DTA) were employed to establish a correlation between the GFA and thermodynamics/kinetics factors. The (Cu50Zr43Al7)98Y2 BMG has a promising GFA of 15 mm diameter, i.e. a 50% increase in GFA compared to the base alloy. Several GFA indicators (ΔTx, Trg, γ and K) confirm the excellent glass-forming capability of 2 at.% Y-doped BMG. The role of the optimum yttrium content in improving the GFA was scrutinized considering atomic, topological, and thermodynamics concepts. The interpretations imply that Y enhances the GFA through two main ways including promoting a more densely packed atomic configuration and also through scavenging oxygen as an undesirable element in glass-forming systems.