Atom probe analyses and numerical calculation of ternary phase diagram in Ni-Al-V system

The ternary phase diagram in the Ni-Al-V system is studied using three dimensional atom probe (3DAP) analyses and numerical calculations using a mean-field model. Our focus is on the Ni-rich corner of the isothermal section at 800°C of the ternary phase diagram, where disordered f.c.c. matrix coexists with the L12 and DO22 ordered phases. Both the experimental measurements and numerical calculations showed that the equilibrium compositions of the coexisting phases are quite different from those predicted by published phase diagrams. It is demonstrated that the aluminium and vanadium compositions in the L12 phase are approximately the same, and there is more aluminium in the disordered matrix than that indicated in the existing phase diagram. A possible explanation of this disagreement is discussed.