Thermodynamic and topological modeling and synthesis of Cu-Zr-Ti-Ni based bulk metallic glasses by mechanical alloying

Abstract

In the present investigation, thermodynamic and topological concepts have been used together to understand the formation of bulk metallic glasses. The article attempts to develop a parameter that combines chemical mixing enthalpy (ΔH _chem), mismatch entropy normalized by Boltzmann constant (ΔS _σ /k_B), and configurational entropy (ΔS _config/R), which can be effectively used to identify the best bulk glass forming compositions in multicomponent systems. The ΔH _chem for multicomponent systems has been calculated by extending the Miedema's macroscopic model, and ΔS _σ /k_B was obtained from Mansoori's approach. The iso-ΔH _chem, iso-ΔS _σ /k_B, and iso-ΔS _config/R contours have been developed. The product of ΔH _chem and ΔS _σ/k_B in the ΔS _config/R range of 0.9 to 1.0 can be correlated strongly to glass forming ability. This has been demonstrated in the case of the quaternary Cu-Zr-Ti-Ni bulk glass forming system to determine the bulk metallic glass forming compositions. Mechanical alloying is used to prepare the bulk amorphous powder at the compositions predicted by the model in order to validate the model.