PHASE CHEMISTRY IN THE TI-SI-N SYSTEM - THERMOCHEMICAL REVIEW WITH PHASE-STABILITY DIAGRAMS

The phase chemistry and thermodynamics of the Ti-Si-N system are reviewed leading to a revision of the ternary phase diagram at 1273 K to include the extended compositional ranges of delta-TiN(x) and Ti5Si3(N(y)) and the compounds Ti3Si, Ti5Si4, and alpha-Ti. This same information is presented in the form of phase stability diagrams which plot the stability criteria for each phase as a function of thermodynamic activity of one component and the relative composition of the other two components. Plots in terms of log a(Si) vs Ti/(Ti + N), log a(N2) vs Si/(Ti + Si), and log a(Ti) vs N/(Si + N) were constructed. All diagrams are consistent with current knowledge of phase compatibility and, therefore, are topologically correct. Further refinement will be possible as more accurate information on thermodynamics and compositional limits of solid solutions becomes available.