Shaping of metallic glasses by stress-annealing without thermal embrittlement

Thermomechanical shaping of metallic glasses has previously been reported to result in severe thermal embrittlement. This phenomenon is most likely the reason why little effort has been made to exploit the mechanical properties of complex shapes attainable by thermomechanical shaping of metallic glass tapes and ribbons. The present study revealed time-temperature windows in which metallic glasses can be shaped by thermal annealing while remaining fully ductile. These include binary (Fe₈₃B₁₇, Co ₈₀B₂₀ and Pd₈₂Si₁₈), ternary (Fe_81.5B_14.5Si₄ and Cu₆₀Zr ₃₀Al₁₀) and more complex quaternary Zr₇₀Ni ₁₆Cu₆Al₈ glassy alloys of both metal-metalloid and metal-metal types. All showed full bending ductility after shaping. The thermomechanical processing leading to full shaping without thermal embrittlement was successfully modeled using the approach of A.I. Taub (Acta Metallurgica 1981) based on the free-volume model of structural relaxation. The results are of direct interest for applications of metallic glasses as springs.