Accessing thermoplastic processing windows in metallic glasses using rapid capacitive discharge

摘要

The ability of the rapid-capacitive discharge approach to access optimal viscosity ranges in metallic glasses for thermoplastic processing is explored. Using high-speed thermal imaging, the heating uniformity and stability against crystallization of Zr₃₅Ti₃₀Cu_7.5Be_27.5 metallic glass heated deeply into the supercooled region is investigated. The method enables homogeneous volumetric heating of bulk samples throughout the entire supercooled liquid region at high rates (~105?K/s) sufficient to bypass crystallization throughout. The crystallization onsets at temperatures in the vicinity of the “crystallization nose” were identified and a Time-Temperature-Transformation diagram is constructed, revealing a “critical heating rate” for the metallic glass of ~1000?K/s. Thermoplastic process windows in the optimal viscosity range of 100–104?Pa·s are identified, being confined between the glass relaxation and the eutectic crystallization transition. Within this process window, near-net forging of a fine precision metallic glass part is demonstrated.