The thermodynamic assessment of the Ti-Si-N system and the interfacial reaction analysis

A consistent thermodynamic data set for the Ti-Si-N ternary system is obtained by means of calculation of phase diagrams (CALPHAD) technology. The sublattice model is used to describe the ternary solid solution phases: (Ti,Si)1(N,Va)0.5 for (αTi), (Ti,Si)1(N,Va)3 for (βTi), (Ti,Si)1(N,Va)1 for TiN and (Si,Ti%)2(Si%,Ti)3Ti3(N,Va)1 for Ti5Si3Nx. The intermetallic compounds, Ti3Si, Ti5Si4, TiSi, TiSi2, Si3N4 and Ti2N are treated as stoichiometric compounds. The liquid solution phase and the diamond-Si phase are assumed to be substitutional solutions with Redlich-Kister formula for the expression of the excess Gibbs energy. The gas phase is treated as an ideal mixture. Based on the present optimized data, the interfacial reactions of Ti/Si3N4 and TiN/Si couples are analysed and the phase formation sequences are predicted. The calculation results agree well with experiments.