New thermodynamic parameter describing glass forming ability of bulk metallic glasses

The key step in exploiting a new type of bulk metallic glass (BMG) is to judge quickly the glass forming ability (GFA) of the alloys. The mole melting enthalpies of BMGs are calculated using the weighted averages principle. The reliability and limitation of the T _rg criterion for GFA are discussed, and the reason why the T _rg of BMGs presently is more than 0·5 is also discussed. In addition, two new criteria, ΔH _mg and ΔG _g, for GFA are presented. The GFA sequence of BMGs is calculated using the ΔH _mg criterion, the result agrees with that of Inoue and Shibata and R _c criterion. Furthermore, as an example, the R _c of the alloys developed by Dong Chuang et al. are calculated using ΔH _mg and ΔG _g. The ascending sequence of these alloys calculated by the ΔH _mg criterion agrees with that of Dong Chuang et al. In contrast, the result using the ΔG _g criterion is contrary to that of Dong Chuang et al., indicating that the ΔH _mg criterion is better and more convenient than the ΔG _g criterion. The optimum ΔH _mg was found to be −15·16 kJ mol⁻¹.