The thesis is aimed to study the thermodynamic properties of the melts of the glass-forming four-component Cu–Ni–Ti–Hf system and modeling of phase transformations with their participation. As the main research methods were used: the high-temperature isoperibolic calorimetry for the experimental determination of the mixing enthalpy of liquid alloys, the model of the ideal associate solution for the theoretical study of the temperature-concentration dependence of mixing thermodynamic properties of the melts and the parameters of atomic ordering in them; the CALPHAD-method for modeling of equilibrium and metastable phase transformations with participation of the melts.
The partial enthalpies of the mixing of titanium and hafnium have been investigated for the first time at a temperature of 1873 K by calorimetric method along the cross sections with a constant ratio of components in the corresponding concentration intervals: the Cu–Ni–Hf system – xHf = 0–0,45 for sections xCu/xNi = 3 and xCu/xNi = 1/3; xHf = 0–0,40 for section xCu/xNi = 1; Cu–Тi–Hf system – xTi = 0–0,25 for section xCu/xHf = 3/1, xHf = 0–0,5 for section xCu/xTi = 3/1; Ni–Ті–Hf system – xTi = 0–0,64 for section xNi/xHf = 3/1 and xHf = 0–0,57 for section xNi/xTi = 3/1. It was shown that partial enthalpies of mixing titanium and hafnium in the studied concentration ranges are predominantly negative. The integral enthalpy of mixing of ternary melts also show mainly negative values, which indicate an intensive chemical interaction between the components of the melts.
The obtained experimental data on the mixing enthalpies became the basis for finding the parameters of the associated solution model. Thermodynamic functions of mixing and parameters of chemical short-range order of three- and four-component melts of the Cu–Ni–Ti–Hf system were calculated in the framework of the model in the wide temperature interval for the first time. The composition ranges of amrphisation of liquid alloys by melt quenching were predicted using the empirical rule: 0,25 < xТi < 0,81 for the Cu–Ni–Ti system, 0,20 < xHf < 0,80 for the Cu–Hf–Ni system, 0,17 < xCu < 0,73 for the Cu–Ti–Hf system, 0,24 < xNi < 0,85for the Ni–Ti–Hf system, xCu = 0–0,642 for the section Ni0,33Ti0,33Hf0,33–Cu, xNi = 0–0,762 for the section Cu0,33Ti0,33Hf0,33–Ni, xTi = 0–0,687 for the section Cu0,33Ni0,33Hf0,33–Ti, xHf = 0–0,719 for the section Cu0,33Ni0,33Ti0,33–Hf.
In the framework of the CALPHAD-method, the thermodynamic assessment of the Cu–Ti–Hf system was developed for the first time. The isothermal and polythermal sections, projections of liquidus and solidus surfaces of the phase diagram of the system and its reaction scheme were constructed as a result of the calculations.
In the framework of the CALPHAD-method the database of model parameters of thermodynamic properties of solution phases of the Cu–Ni–Ti–Hf system was developed for the first time. In the framework of the CALPHAD-method the modeling of metastable phase transformations with the participation of supercooled three- and four-component melts of the Cu–Ni–Ti–Hf system was carried out. The concentration regions of the formation of multicomponent amorphous and bulk amorphous alloys were correctly interpreted for the previously investigated systems and also were predicted for unexplored systems on the base of such calculations.
The obtained in the work scientific results can be useful for a wide range of scientists in the fields of physical chemistry, chemical and physical materials science, synthesis of alloys, the theory of metallurgical and foundry processes. The predicted concentration regions of amorphisation form a basis for the directed search for new amorphous alloys.
