Interdiffusion in Pt-Containing γ-Ni and γ′-Ni3Al Alloys at 1150°C

Ternary interdiffusion coefficients in the γ-Ni and γ′-Ni3Al phases of the Ni-Al-Pt system at 1150°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, \\ ildeDAlAlNi, with increasing of Pt content was different for the γ and γ′ phases. In γ \\ ildeDAlAlNi generally increased with increasing Pt content, but it decreased with increase in Pt in γ′ phase. By contrast, the main-term coefficients for Pt, \\ ildeDPtPtNi, apparently increased monotonically with increasing Pt content in both phases, but there was little dependency on Al content. The cross-term interdiffusion coefficients, \\ ildeDAlPtNi and \\ ildeDPtAlNi, were negative in both γ and γ′, showing that the chemical interaction between Al and Pt in these phases is negative. \\ ildeDAlPtNi values were larger than those of \\ ildeDPtAlNi; however, there was no clear dependence of \\ ildeDAlPtNi and \\ ildeDPtAlNi on Pt and Al contents within the composition ranges studied. The cross-term interdiffusion coefficients were comparable to the main-term coefficients in γ and within an order of magnitude of each other in γ′. The significance of these findings are discussed and quantitatively assessed.