THE THERMODYNAMIC FUNCTIONS OF MONOBORIDES XB (X=Ti, Mn, Fе, Co)

In the paper the physical properties and thermodynamic functions of monoborides ХВ (Х=Ti, Mn, Fe, Co) are studied with accounting for fluctuation processes. The research was performed for alloys with boron content of 9,0-15,0 % (wt.), the rest is metal Х (Х=Ti, Mn, Fe, Co). We use the microstructure analysis, the X-ray structural and the durometric analyses to determine the physical properties of alloys. In the paper it is determined the phase composition of Ti-B, Mn-B, Fe-B and Co-B alloys and physical properties of monoborides. In this paper for the first time it is determined the thermodynamic functions of monoborides using the Hillert and Staffansson model with accounting for the first degree approximation of high-temperature expansion for the free energy potential of binary alloys. We obtain the temperature dependences for such thermodynamic functions as Gibbs free energy, entropy, enthalpy and heat capacity Ср along with their values at the formation temperature for ХВ monoborides (Х=Ti, Mn, Fe, Co). The approach under consideration enables to give more thorough from the thermodynamic point of view description of monoborides formed from the liquid. The outcomes of the thermodynamic function calculation for TiB, MnB, CoB та FeB monoborides are in good agreement with experimental data and results of other authors.