Rejuvenation in Hot-Drawn Micrometer Metallic Glassy Wires

We report an enhanced rejuvenation in hot-drawn micrometer metallic glassy wires (MG wires) with the size reduction. Compared to metallic glasses (MGs) in bulk form, the modulus and hardness for the micro-scale MG wires, tested by nanoindentation methods, are much lower and decrease with the decreasing size, with a maximum decrease of \sim 26% in modulus and \sim 17% in hardness. This pronounced rejuvenation is evidenced by the larger sub-T_\rm g relaxation enthalpy of the MG wires. The pronounced rejuvenation is physically related to the higher energy state induced by a combined effect of severely thermomechanical shearing and freezing the shear flow into a constrained small-volume region. Our results reveal that the internal states and properties of MGs can be dramatically changed by a proper modulation of temperature, flow stress and size.