The impact of fragility on the calorimetric glass transition in bulk metallic glasses

The glass transition of bulk metallic glasses with various fragilities as well as strong oxide glasses is studied using differential scanning calorimetry (DSC). It is found that the liquid fragility determined from equilibrium viscosity measurements is very well correlated with the scaled maximum slope of the DSC heat flow during the glass transition. We compare the correlation found in this work and those correlations with fragility from previous studies on other classes of glass-formers and find that the slope, which describes the curvature of the enthalpy on a reduced temperature scale, is a quantity better correlated with fragility, as it reflects the timescale of the non-equilibrium relaxation and the distribution of relaxation times in the glassy state. The present findings are supported by a recent theoretical report for calculated enthalpy curves with different fragilities from a model of selenium using the enthalpy landscape approach. (C) 2014 Elsevier Ltd. All rights reserved.