Effects of Ir or Ta Alloying Addition on Interdiffusion of L12–Ni3Al

Ternary interdiffusion in L12–Ni3Al with ternary alloying additions of Ir and Ta was investigated at 1473 K using solid-to-solid diffusion couples. Average ternary interdiffusion coefficients were determined from an integration of interdiffusion fluxes calculated directly from experimental concentration profiles. The magnitude of D˜¯NiNi and D˜¯AlAl coefficients was determined to be much larger than that of D˜¯IrIr and D˜¯TaTa coefficients. Ir substituting in Ni-site influenced the interdiffusion of Ni significantly, and D˜¯NiIrAl coefficients were determined to be large and positive. On the other hand, Ta substituting for Al influenced the interdiffusion of Al significantly, and D˜¯AlTaNi coefficients were determined to be large and positive. An excellent agreement was found with ternary interdiffusion coefficients determined by Boltzmann–Matano analysis. Profiles of concentrations and interdiffusion fluxes were also examined to estimate binary interdiffusion coefficients in Ni3Al, and tracer diffusion coefficients of Ir (14.7 × 10−16 ± 1.4 × 10−16 m2/s) and Ta (2.6 × 10−16 ± 2.4 × 10−16 m2/s) in Ni3Al.