Calculation and measurement of the A1-V-N phase diagram

A thermodynamic evaluation of the V-N system is developed and combined with previous assessments of the Al-N and Al-V systems to describe the Al-V-N system. It is shown that the direct extrapolation from the binary edges can describe the experimental isothermal section at 1000°C from the literature. For the isothermal section 1300°C, however, the extrapolation does not reproduce the reported AlN+bcc+hcp phase equilibrium. In order to solve this discrepancy, thin film diffusion couples V/AlN were prepared by electron beam evaporation. The couples were annealed at 1000 and 1300°C for 144 and 69h. respectively, and then analyzed by X-ray diffraction (XRD). It is found that the phase assemblage data resulting from the fully reacted samples support the present calculation.