Interdiffusion in Pt-containing γ-Ni and γ′-Ni3Al alloys at 1150°C

Tertiary interdiffusion coefficients in the gamma-Ni and gamma'-Ni3Al phases of the Ni-Al-Pt system at 1150 degrees C were experimentally determined by applying a Boltzmann-Matano method at a common composition in the time-invariant diffusion paths for a given two couples. The variation of the main-term interdiffusion coefficients of Al, (D) over tilde (Ni)(AlAl), with increasing of Pt content was different for the gamma and gamma' phases. In gamma (D) over tilde (Ni)(AlAl) generally increased with increasing Pt content, but it decreased with increase in Pt in gamma' phase. By contrast, the main-term coefficients for Pt, (D) over tilde (Ni)(PtPt), apparently increased monotonically with increasing Pt content in both phases. but there was little dependency on At content. The cross-term interdiffusion coefficients, (D) over tilde (Ni)(AlPt) and (D) over tilde (Ni)(PtAl), were negative in both gamma and gamma'. showing that the chemical interaction between Al and Pt in these phases is negative. (D) over tilde (Ni)(AlPt) values were larger than those of (D) over tilde (Ni)(PtAl); however, there was no clear dependence of (D) over tilde (Ni)(AlPt) and (D) over tilde (Ni)(PtAl) on Pt and Al contents within the composition ranges studied. The cross-term interdiffusion coefficients were comparable to the main-term coefficients in gamma and within an order of magnitude of each other in gamma'. The significance of these findings are discussed and quantitatively assessed.