Thermodynamic approach for determining chemical composition of Fe-Co based amorphous alloys with high thermal stability and glass forming ability

Abstract In this study, possibility of using different thermodynamic parameters, such as: ideal configurational entropy, mixing enthalpy, Gibbs free energy of mixing and mismatch entropy for determining chemical composition of Fe-Co based amorphous alloys was evaluated. The high role of entropy in formation of amorphous phase was confirmed, but maximization of the value of ideal configurational entropy did not allow to obtain fully amorphous alloy. The chemical composition of Fe 35 Co 35 Si 11 B 19 amorphous alloy was determined based on minimization the value of Gibbs free energy of formation of amorphous phase – the new parameter proposed in this study. Herein, this new proposed parameter was also used to describe an influence of different chemical elements on glass forming ability of Zr, Cu and Fe based alloys. It was shown, that the Fe based amorphous alloys with the most negative value of Gibbs free energy of formation of amorphous phase were characterized by high thermal stability. The high thermal stability and glass forming ability of Fe 35 Co 35 Si 11 B 19 amorphous alloy were confirmed by using differential thermal analysis, X-ray diffraction method, Mossbauer spectroscopy and differential scanning calorimetry. Additionally, influence of isothermal crystallization of Fe 35 Co 35 Si 11 B 19 alloy on the structure and magnetic properties was described.