The γ' single phase interdiffusion in selected pseudo-binary sections of the Ni3Al-X (X = Cr, Fe, Nb and Ti) ternary alloys was studied at 1173 to 1533K (figures 1 to 6) in order to assess the influence of the site-preference of components upon their diffusion rate. It was observed that a higher fraction of Cr or Fe on the Al sub-lattice led to lower values of DXXNi. Both Ti and Nb, which strongly preferred the Al sub-lattice, exhibited significantly lower interdiffusion coefficients than did Fe and Cr. The equation, DXXNi = DAlAlNi, held for Ti and Nb whereas the relationship, DXXNi > DAlAlNi, was valid for Cr and Fe. The activation enthalpy of Qiij exhibited a systematic decrease with increasing valence electron number of the alloying element. It was noted that Nb exhibited a transient behavior. It had low values of diffusion coefficient as compared with its site occupation, but also a low activation energy.

Interdiffusion in Ternary Ni3Al/Ni3Al-X Diffusion Couples with X = Cr, Fe, Nb and Ti. Cermak, J., Gazda, A., Rothova, V.: Intermetallics, 2003, 11[9], 939-46

Figure 3

Diffusion of Al and Cr in a Ni75.5Al24.5/Ni74.0Al22.0Cr4.0 couple

White circles, i = Cr; black circles, i = Al