Figure 2: Freezing non-equilibrium states.
Heat flow curves are shown after heating the Au70Cu5.5Ag7.5Si17 glass with a rate of 2,000 K s−1 (H1) to Tfreeze(1,2) and cooling with a rate of 5,000 K s−1 (F) and subsequent heating with a rate of 2,000 K s−1 (H2); the upper image illustrates the applied time–temperature regime. The freezing temperature Tfreeze1 (blue curves) was chosen to be just above the formation of the metastable crystalline state (T1), while Tfreeze2 (red curves) was chosen to be within the metastable liquid. No reactions can be seen upon freezing the metastable crystalline state and no glass transition or crystallization is observed after re-heating with a rate of H2=2,000 K s−1 to Tfreeze1. This indicates that the material was mostly crystallized during the first heating step. Upon freezing from Tfreeze2 partial crystallization is observed, and upon re-heating with H2 a small glass transition and crystallization event are seen below Tfreeze2. This provides evidence that a metastable liquid has formed during the endothermic event at Te.
