Mixing enthalpy measurements of liquid Ti‐Zr, Fe‐Ti‐Zr and Fe‐Ni‐Zr alloys

Abstract

The mixing enthalpies of liquid Ti‐Zr, Fe‐Ti‐Zr and Fe‐Ni‐Zr alloys were measured by levitation alloying calorimetry. The mixing enthalpy of Ti‐Zr alloys is slightly exothermic and symmetric with an extreme value of −5.2 kj mol−1. It can be described according to the regular solution model. Experimental investigations of the mixing enthalpies of the strongly non‐ideal binary systems Fe‐Ti, Fe‐Zr and Ni‐Zr had already been subject of earlier works. Based on experimental data temperature dependent descriptions of the mixing enthalpies were calculated with a regular associate model. From the model parameters of the binary subsystems the mixing enthalpy of the respective ternary system can be predicted. Model calculations of the mixing enthalpies of liquid Fe‐Ti‐Zr and Fe‐Ni‐Zr alloys were performed along different concentration sections and compared with experimental data, respectively. A good accordance was observed. The mixing enthalpies of liquid Fe‐Ti‐Zr and Fe‐Ni‐Zr alloys are given at T = 2152 K and T = 1892 K in form of isoenthalpy diagrams, respectively. Moreover, with help of the temperature dependence of the mixing enthalpy the excess heat capacities of the alloys were calculated.

Thermodynamic assessment of the Cu-Ti-Zr system. II. Cu-Zr and Ti-Zr systems

“…Three experiments were also conducted between 2337 and 2347 K in the zirconium-rich region in the range of concentrations x Zr = 0.418-1. The data obtained in [59] and presented in Fig. 6 are indicative of the exothermic formation of Ti−Zr melts.…”

“…The thermodynamic assessments of the titaniumzirconium system presented in [62] and [63] are based on the data of [53−55] and [53−58], respectively. Figure 6 compares the experimental values of integral mixing enthalpy of Ti−Zr melts [59] and respective values based on [62] and [63] and demonstrates what errors may be committed in calculations using these models. It is obvious that the inadequate description of the thermodynamic properties of melts is a serious shortcoming in the thermodynamic assessments of the titanium-zirconium system [62,63] notwithstanding the good agreement between the experimental and calculated data on phase equilibria.…”

“…The results of both papers show that the melt behavior is close to ideal. 2260 K [59] 2347 K [59] 2112 K [59] 2337 K [59] 2336 K [59] 2111 K [59] This study, calculation [62], calculation [63], calculation The enthalpies of the phase transformation (βTi, βZr) → (αTi, αZr) ( Table 4) were studied in [57,58] between 853 and 993 K with calorimetric methods for five alloys at x Zr = 0.2−0.8. The results of these papers agree satisfactorily with each other and are indicative of exothermal process.…”

“…Levitation calorimetry was used in [59] to study the thermodynamic properties of liquid alloys in the Ti−Zr system. The integral mixing enthalpy in the system was examined over the entire range of compositions.…”

Thermodynamic assessment of the Cu-Ti-Zr system. I. Cu-Ti system

“…The merits and demerits of the results obtained in [11] were detailed in [12]. New experimental data on the mixing enthalpy of Cu−Ti−Zr melts [13], phase transformations in the system [7], the mixing enthalpy of Ti−Zr melts [14], and the temperature dependence of the integral mixing enthalpy of Cu−Ti [15] and Cu−Zr [16] melts provide the basis for new thermodynamic assessment.…”