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

The ternary phase diagram in the Ni-AI-V system is studied using three dime nsional atom probe (3DAP) analyses and numerical calculations using a mean- field model. Our focus is on the Ni-rich corner of the isothermal section a t 800 degreesC of the ternary phase diagram, where disordered f c.c. matrix coexists with the Ll(2) and DO22 ordered phases. Both the experimental mea surements and numerical calculations showed that the equilibrium compositio ns of the coexisting phases are quite different from those predicted by pub lished phase diagrams. It is demonstrated that the aluminium and vanadium c ompositions in the Ll(2) phase are approximately the same, and there is mor e aluminium in the disordered matrix than that indicated in the existing ph ase diagram. A possible explanation of this disagreement is discussed.