Al composition dependence of Pt, Mn and V diffusion in L1(2)-type ordered Ni3Al

The Al composition dependence of diffusion coefficients of Pt (substituting for Ni atoms on face centered sites in the Ni3Al, referred to as alpha-sit es), Mn (for Al atom on corner sites, beta-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 increas ing Al composition of Ni3Al. These composition dependences are consistent w ith that of vacancy concentrations at alpha-sites in Ni3Al calculated by Ki m. The activation energy of V diffusion is by about 110 kJ/mol higher than those of Pt and Mn. This high activation energy includes the increase in th e total bond energy due to the jump of V atom from beta- to alpha-sites. Th e above results verified that the V atom jumps to an adjacent vacant alpha- site and then it diffuses randomly through alpha-sites until it jumps to a vacant beta-site.