Critical fictive temperature for plasticity in metallic glasses.

A long-sought goal in metallic glasses is to impart ductility without conceding their strength and elastic limit. The rational design of tough metallic glasses, however, remains challenging because of the inability of existing theories to capture the correlation between plasticity, composition and processing for a wide range of glass-forming alloys. Here we propose a phenomenological criterion based on a critical fictive temperature, T(fc), which can rationalize the effect of composition, cooling rate and annealing on room-temperature plasticity of metallic glasses. Such criterion helps in understanding the widespread mechanical behaviour of metallic glasses and reveals alloy-specific preparation conditions to circumvent brittleness.