Interdiffusion Between Ti3SiC2–Ti3GeC2 and Ti2AlC–Nb2AlC Diffusion Couples

In this work, we report on the interdiffusion of Ge and Si in Ti₃SiC₂ and Ti₃GeC₂, as well as that of Nb and Ti in Ti₂AlC and Nb₂AlC. The interdiffusion coefficient, D _int, measured by analyzing the diffusion profiles of Si and Ge obtained when Ti₃SiC₂–Ti₃GeC₂ diffusion couples are annealed in the 1473–1773 K temperature range at the Matano interface composition (≈Ti₃Ge_0.5Si_0.5C₂), was found to be given by
D _int increased with increasing Ge composition. At the highest temperatures, diffusion was halted after a short time, apparently by the formation of a diffusion barrier of TiC. Similarly, the interdiffusion of Ti and Nb in Ti₂AlC–Nb₂AlC couples was measured in the 1723–1873 K temperature range. The D _int for the Matano interface composition, viz. ≈(Ti_0.5,Nb_0.5)₂AlC, was found to be given by
At 1773 K, the diffusivity of the transition metal atoms was ≈7 times smaller than those of the Si and Ge atoms, suggesting that the former are better bound in the structure than the latter.