Fig. 4
From: Mechanical glass transition revealed by the fracture toughness of metallic glasses
Analogy between the conventional glass transition and the mechanical glass transition based on a crossover of time scales. a The conventional glass transition, probed by the dependence of the enthalpy on T, originates from a competition between the internal structural relaxation time, τSR, and the external time scale set by the cooling rate, \(\tau_{\dot R} \). The glass transition occurs approximately at τSR ≈ \(\tau_{\dot R} \). b In analogy to the conventional glass transition, the mechanical glass transition (probed by the dependence of the fracture toughness on Tf) originates from the competition between the plastic relaxation time scale, τplastic, and the (near notch) deformation time scale, \(\tau_{\dot\varepsilon}\), which is proportional to the applied strain rate. c A ductile-to-brittle transition can also be observed as a function of temperature, as τplastic is also a weak function of T, but it is significantly less pronounced than the toughening transition as a function of Tf
