Alloy design strategies for sustained ductility in Mg-based amorphous alloys – Tackling structural relaxation

Abstract Mg-based metallic glasses are promising candidates for use in light-weight, high-specific-strength applications, but their low fracture toughness and rapid room-temperature structural relaxation have so far prevented their deployment. In this study we present various design strategies for tackling structural relaxation via studying several Mg-based amorphous alloy systems during room-temperature aging. Our investigations show that relaxation kinetics is strongly affected by solute content, solute type and glass transition temperature T g , and an increase in solvent content generally results in lower relaxation enthalpy, faster relaxation rates, prolonged ductility and a reduction of T g , which increases the alloys' susceptibility to room-temperature crystallization. The results also show that chemical bonding and specific topologies contribute to relaxation kinetics, where alloys with greater mixing enthalpies and greater differences in atomic radii between the constituents exhibit greater relaxation enthalpies and relaxation rates. In conclusion, we present design concepts towards enhancing long-term ductility in Mg-based glasses via a delicate balancing of their chemistry and topology.