Experimental investigation and thermodynamic modeling of the V-Ga system

Phase equilibria and thermodynamic properties of the V-Ga system were investigated through experiments and thermodynamic modeling. In the experimental part, eight alloys with different phase constituents were prepared by arc melting. The annealed alloys were analyzed by X-ray diffraction, scanning electron microscopy, electron probe microanalysis and differential scanning calorimetry. The homogeneity ranges of V3Ga and V6Ga5 at 873 K and 1173 K were determined. Six invariant reactions were confirmed and the reaction temperatures were measured. Based on the experimental phase diagram and thermodynamic data from the present work as well as those from literature, the V-Ga system was assessed by means of CALPHAD approach. The intermetallic compound V6Ga7 was described with a four-sublattice model (V)2(V)3(V, Ga)2(V, Ga)6, while V6Ga5 and V3Ga were described with a two-sublattice model according to their crystal structures and solubility ranges. A set of self-consistent thermodynamic parameters were obtained, and all calculations are in satisfactory agreement with the experimental observations.