Interdiffusion in Pt-Containing γ-Ni and γ′-Ni<SUB>3</SUB>Al Alloys at 1150°C

Abstract

Ternary interdiffusion coefficients in the γ-Ni and y'-Ni 3 Al 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, ?Ni AlAl , with increasing of Pt content was different for the y and y' phases. In y ?Ni AlAl generally increased with increasing Pt content, but it decreased with increase in Pt in y' phase. By contrast, the main-term coefficients for Pt, ? Ni PtPt apparently increased monotonically with increasing Pt content in both phases, but there was little dependency on Al content. The cross-term interdiffusion coefficients, ? Ni AlPt and ? Ni PtAl , were negative in both y and y', showing that the chemical interaction between Al and Pt in these phases is negative. ? Ni AlPt values were larger than those of ? Ni PtAl ; however, there was no clear dependence of ? Ni AlPt and ? NiPtAl on Pt and Al contents within the composition ranges studied. The cross-term interdiffusion coefficients were comparable to the main-term coefficients in y and within an order of magnitude of each other in y'. The significance of these findings are discussed and quantitatively assessed.