Rare-earth and precious-metal free Cu-based metallic glasses with superior glass-forming ability and processability

Metallic glasses have many fascinating properties such as theoretical-limit approaching strength, high wear and corrosion resistance, and extremely smooth surfaces enabling high-performance thin film diodes. Copper-based metallic glasses are of particular interest due to the low cost and attractive characteristics of the base element, but the copper-based metallic glasses known to date rely on rare-earth or precious metals that have limited supplies and relatively high cost, in order to achieve good glass-forming ability. Here, we report our discovery of a series of rare-earth and precious-metal free copper-based metallic glasses formulated as Cu₄₆Zr_47−xHf_xAl₇ (8 ≤ x ≤ 20, at. %), which possess superior glass-forming ability and processability. Fully amorphous ingots with a large cross section of 15 (all x) to 28.5 mm (x = 13.5) diameter can be readily produced by a simple water quenching method. The Cu₄₆Zr_33.5Hf_13.5Al₇ alloy, in particular, presents the highest glass-forming ability and processability of all known copper-based metallic glasses. The adjustable Hf content in the composition offers a range of physical properties (e.g., density) that can be chosen based on applications. We also discuss the physical origin of the superior glass-forming ability and processability in these copper-based metallic glasses.