With the aim of producing metastable precursors for tailoring TiAl based composite, five compositional powder blends of Ti–Al–Si system, i.e. Ti 65Al 17Si 18, Ti 65Al 21Si 14, Ti 72Al 14Si 14, Ti 65Al 14Si 21 and Ti 58Al 21Si 21, were prepared by mechanical alloying (MA). The structural and compositional evolution during MA has been investigated using X-ray diffraction method (XRD), energy-dispersive spectrometer (EDS) and transmission electron microscope (TEM). MA achieved a significant increase in solid solubility limits. Supersaturated solid solution of Ti(Al,Si) was produced with prolonged milling time which was strongly dependent on the starting compositions of blends. No fcc phase or ordered and disordered intermetallics were produced during MA process. With higher and balanced Al and Si contents, for example Ti 58Al 21Si 21 blend, the time required for solid solution formation was reduced drastically. Thermal stability of the mechanically alloyed powders was systematically examined by subsequent annealing process according to the results of differential thermal analyzer (DTA) curves. From XRD patterns of the annealed blends, it was observed that annealing at temperatures just below 600 °C leads to crystalline phases of mainly Al 3Ti and TiSi 2, while more stable Ti 5(Al,Si) 3, (Ti,Si)Al and (Ti,Si) 3Al phases were formed at higher annealing temperatures of above 750 °C.