Phase formation during mechanical alloying in the Ti–Si system

Mechanical alloying of Ti–Si powder mixture or TiH1.924–Si powder mixture was performed by high-energy ball milling, in which the Ti to Si mole ratio was 1:2. The phase formations in both mixtures during milling were investigated by X-ray diffraction. Mechanical alloying a mixture of elemental powders led to the formation of TiSi2 equilibrium compound, while when starting from Si + TiH1.924, a metastable phase was formed. The metastable phase completely transforms to TiSi2 when the mechanically alloyed powder is annealed at temperatures above 800 °C. Two different pathways of phase transitions during mechanical alloying are attributed to the existence of hydrogen atoms, i.e., when starting from Si + TiH1.924 compared to Si + Ti, the kinetics for the formation of the TiSi2 intermetallic compound slows down. The kinetics related to the different phase transitions depending on the starting powder mixture are discussed.