Determination of interdiffusion coefficients of Si and Al in Ti3SiC2–Ti3AlC2 diffusion couple at 1373-1673 K

Abstract

In the diffusion couple of Ti3SiC2 and Ti3AlC2, only interdiffusion of Si and Al occurred during diffusion treatment process. Based on the concentration profiles of Si and Al measured by electron probe microanalysis (EPMA), the interdiffusion coefficients of Si and Al at 1373-1673 K in Ti3SiC2–Ti3AlC2 diffusion couple were determined by both the Boltzmann-Matano (B-M) method and the Saucer-Freise (S-F) method. At the position of Matano plane with the composition of Ti3Al0.5Si0.5C2, the interdiffusion coefficient could be expressed as Dint (m2/s) = 5.6 × 10−4⋅exp [−246 ± 14 (kJ/mol)/RT]. Based on the two methods, the calculated interdiffusion coefficients increased with increasing temperature, and the magnitudes of their absolute values were on the order of 10–13-10–11 m2/s at 1373-1673 K. At 1373-1573 K, the calculated interdiffusion coefficients decreased monotonously with the increase of Si concentration, that is, xSi/(xAl + xSi). But at 1673 K, the variation trend of interdiffusion coefficients with xSi/(xAl + xSi) was no longer monotonous, probably due to the presence of Ti5Si3 phase and voids on Ti3AlC2 side.