Calculations of mixing enthalpy and mismatch entropy for ternary amorphous alloys : Special issue on bulk amorphous, nano-crystalline and nano-quasicrystalline alloys

Abstract

Chemical mixing enthalpy (ΔH chem ) and mismatch entropy normalized by Boltzmann constant (S σ /k B ) corresponding to the three empirical rules for the achievement of high amorphous-forming ability (AFA) were calculated with thermodynamical functions for the gross number of 6450 alloys in 351 ternary amorphous systems. The temary amorphous alloys have ΔH chem of -86 to 25 kJ/mol and S σ /k B of 1.0 × 10 -3 to 5.7. The average values of ΔH chem and S σ /k B are calculated to be -33 kJ/mol and 0.33, respectively. The 30 alloys in 9 ternary amorphous systems including 10 alloys in Ag-Cu-Fe system have positive values of ΔH chem . Most of the ternary amorphous alloys have the values of ΔH chem and S σ /k B inside a trapezoid regicn in ΔH chem - log(S σ /k B ) chart except mainly for the H- and the C-containing alloys. Si-W-Zr system and the 32 alloys having positive values of ΔH chem . The analysis of AFA was carried out for typical five ternary amorphous systems. The following four results are derived. 1) Al-La-Ni and B-Fe-Zr alloys have high AFA in accordance with the concept of the three empirical rules. 2) The further multiplication of alloy components causes an increase in the AFA of Al-B-Fe alloys. 3) Thermodynamical factors represented by melting temperature and viscosity at the melting temperature are required for evaluation of AFA for Mg- and Pd-based amorphous alloys. 4) A tendency for log(S σ /k B ) to increase with decreasing ΔH chem is recognized in each alloys system, implying the stabilization of an amorphous phase against solid solution and intermediate phase.