Thermodynamic modeling of the Ge–Ti system supported by key experiment

A complete thermodynamic investigation of the Ge–Ti system was performed in this study. Seven samples were prepared by arc-melting the pure elements in order to check the literature data on phase diagram and enthalpy of formation of Ti5Ge3. The samples were annealed at certain temperatures for extended periods of time, and then quenched. Both the as-cast and annealed samples were examined by X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) technology. The phase transformation temperatures were measured by differential thermal analysis (DTA). The measurement on enthalpy of formation for Ti5Ge3 was performed using the Kleppa-type HTRC with the calorimeter temperature set at 1100 ± 2 °C. Based upon the literature data and current experimental results, the Ge–Ti system was critically assessed by means of CALPHAD approach. The calculated phase diagram and thermodynamic properties agree well with the literature data and the present experimental results.

► All of the experimental phase diagram and thermodynamic data available for the Ge–Ti system have been critically evaluated.
► The general feature of the Ge–Ti system and enthalpy of formation of Ti5Ge3 have been checked via experiment. The annealed samples are characterized by X-ray diffraction, scanning electron microscope and differential thermal analysis.
► An optimum thermodynamic data set for the Ge–Ti system was obtained. The comprehensive comparison shows that the calculated phase diagram and thermodynamic properties are in good agreement with the experimental data.