Heat contents of the intermetallics V 3Ge and V 5Ge 3 and thermodynamic modeling of the Ge–V system

Abstract

Fourteen alloys were prepared by arc-melting the pure elements and annealing the alloys at 850 °C for 30 days. The annealed alloys were examined by X–ray diffraction (XRD), scanning electron microscope with energy dispersive X-ray analysis (SEM/EDX), differential scanning calorimetry (DSC) and drop calorimeter. The major experimental results are as follows. (I) The heat contents of V 3Ge and V 5Ge 3 were measured by drop calorimeter from 400 to 900 °C. (II) The microstructure analysis of as-cast alloy V 87.1Ge 12.9 indicates that the eutectic composition of liquid ↔ (V) + V 3Ge is above 12.9 at.% Ge, and that of V 2.9Ge 97.1 shows that the eutectic composition of liquid ↔ V 17Ge 31 + Ge is close to 97.1 at.% Ge. (III) The invariant reaction temperatures of liquid + V 11Ge 8 ↔ V 17Ge 31 and liquid ↔ V 17Ge 31 + Ge are at 960.0 ± 2 °C and 930.7 ± 2 °C, respectively. Based on the experimental results in this study and in the literature, the Ge–V system was modeled by CALPHAD approach.