The Al composition dependence of diffusion coefficients of Pt (substituting for Ni atoms on face centered sites in the Ni3Al, referred to as α-sites), Mn (for Al atom on corner sites, β-sites) and V (for both the atoms) atoms in the Ni3Al phase was studied by using the diffusion couple method. The diffusion coefficients of Pt, Mn and V elements increase with increasing Al composition of Ni3Al. These compositional dependences were consistent with that of vacancy concentrations at α-sites in Ni3Al calculated by Kim. The activation energy of V diffusion was by about 110kJ/mol higher than those of Pt and Mn. This high activation energy included the increase in the total bond energy due to the jump of V atom from β- to α-sites. The above results confirmed that the V atom jumped to an adjacent vacant α-site and then diffused randomly through α-sites until it reached a vacant β-site.

Al Composition Dependence of Pt, Mn and V Diffusion in L12-Type Ordered Ni3Al. Minamino, Y., Yoshida, H., Hirao, K., Yamane, T., Jung, S.B.: High Temperature Materials and Processes, 1999, 18[5], 337-50