Unveiling the time-temperature dependence of metastability of supercooled liquid using nano-calorimetry

There is a lack of understanding of both the conversion of an unstable glass into a metastable supercooled liquid (MSL) upon heating and the metastability of MSLs. In this study, we investigated the time- and temperature-dependent metastability of an MSL using an advanced nano-calorimetric technique. The chosen Au-based metallic glass (AuMG) allowed adequate probing of its MSL in a temperature range between 10 and 70 K above the standard glass transition temperature. We found that the survival time of the MSL state is a quadratic function of temperature. Beyond this duration threshold, the sample undergoes fast crystallization even if it is below the crystallization temperature that is measured using differential scanning calorimetry. Employing transmission electron microscopy, we observed the formation of clusters with a partially ordered lattice structure during relaxation in the AuMG sample fabricated using a nano-calorimeter. The atomic ordering within the clusters was enhanced by increasing time and temperature in the MSL region. Once the as-produced glass entered the MSL stage upon heating followed by a quenching stage at a given rate, the mechanical properties of the quenched glass remained the same regardless of its holding temperature and duration within the MSL region. This work provides insights into the glass-MSL-crystal transformation and offers guidance for designing standard metallic glasses for property characterizations.