The mismatch entropy for bulk metallic glasses: A thermodynamic approach

摘要

Based on the thermodynamic fragility model, a new parameter (S_δ/k_B)/M is proposed to evaluate the glass-forming ability (GFA) of metallic glasses, where M and S_δ/k_B are the fragility of the superheated melts and the mismatch entropy normalized by the Boltzmann constant, respectively. A positive relationship between (S_δ/k_B)/M and glass forming ability is observed for both bulk metallic glasses and marginal metallic glasses, and an eutectic alloy with (S_δ/k_B)/M larger than 0.17 can be selected as a bulk glassy forming candidate. As most alloys can obtain the temperature dependence of viscosity above liquidus temperature, (S_δ/k_B)/M can be used as a prediction parameter for high GFA. Although both high and low M values can work in determining GFA, the high GFA of bulk metallic glasses is primarily due to the large mismatch entropy (S_δ/k_B > 0.17).