The literature contains many contradictory data about the most thermodynamically favorable structure of precipitates in α-Ti matrix of the hypoeutectoid Ti-Si alloys. In this work we applied our recently developed thermodynamic model to predict the structure of Ti-Si precipitates in α-Ti matrix of the Ti-Si alloy with total Si concentration of 0.7 wt.%. We considered all prominent Ti-Si phases such as Ti3Si,Ti5Si3,Ti5Si4,TiSi and two TiSi2 phases and discovered that formation of the Ti5Si3 phase is more favorable than that of the Ti3Si in contradiction with the known phase diagrams. Theoretical result was confirmed by experimental investigation of microstructure and phase composition of the model Ti-0.7Si alloy annealed at 873 K for 10 h. Indeed, the only observed phase has hexagonal Ti5Si3 structure. To ensure the completeness of the results we calculated ab initio elastic constants for all considered Ti-Si phases.
- Density functional theory
- Titanium silicides
- Transmission electron microscopy