Ab initio-based prediction and TEM study of silicide precipitation in titanium

Abstract

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