Thermodynamic Properties of the Glass-Forming Ternary (Fe, Co, Ni, Cu)–Ti–Zr Liquid Alloys I. Mixing Enthalpies of Liquid Alloys

Data on the mixing enthalpies of liquid alloys in ternary Me–Ti–Zr (Me = Fe, Co, Ni, Cu) systems and boundary binary systems are summarized. The partial mixing enthalpies of titanium and zirconium and the integral mixing enthalpy of liquid Co–Ti–Zr alloys were investigated for the first time by high-temperature calorimetry at 1873 K along the x_Co/x_Ti =3 section at x_Zr = 0–0.57 and x_Co/x_Zr = 3 section at x_Ti = 0–0.54. It was shown that the investigated partial and integral functions were characterized by significant negative values. The isotherms of the integral mixing enthalpy of liquid Fe–Ti–Zr alloys at 2173 K and liquid Co–Ti–Zr alloys at 1873 K are described using the Redlich–Kister–Muggianu polynomial. A new description for the liquid Cu–Ti–Zr alloys at 1873 K is also presented. The negative values and composition dependence of the ∆_mH function for liquid alloys of each ternary system are determined by the predominant influence of MeTi and MeZr pair interactions, in which iron, cobalt, nickel, and copper are electron acceptors, while titanium and zirconium are donors. In the considered series of the binary Me–Ti and Me–Zr systems and ternary Me–Ti–Zr systems, the absolute values of the integral mixing enthalpy of liquid alloys increase in the transition from the iron systems to the nickel systems and are minimal in the systems with copper.