Thermodynamics of binary and ternary melts of the 3d transition metals (Cr, Mn, Fe, Co and Ni) with boron

Abstract

The thermodynamic functions (Gibbs energy, entropy) of mixing in the binary FeB, CoB and NiB systems were determined using experimental activity data from the literature and the enthalpy data of the alloy formation measured earlier by the author. The excess entropies of mixing were found to be largely negative, indicating the existence of short-range ordering in these liquid alloys. A short description of the experimental method for a ternary system and an example of the original values measured in a separate experiment are given. The partial and integral enthalpies of formation of the ternary CrFeB, MnFeB, CoFeB and NiFeB melts were measured directly using a high-temperature isoperibolic calorimeter. The large negative enthalpies of mixing in all the studied ternary systems reflect the strong interaction of the alloy components. The existence of attractive forces between unlike atoms of the 3d transition metals in the ternary alloys causes a decrease in the absolute values of the partial enthalpy of mixing of boron. Comparing the experimental data with the data interpolated from the binary boundary systems using well-known models, it was shown that these models in most cases are incorrect for the ternary Cr(Mn,Co,Ni)FeB melts. Using the measured data, the glass-forming ability of the ternary melts is discussed.