Silicide precipitation in a γ-based Ti-47Al-2W-0.5Si alloy

The microstructures of the Ti47A12W alloys containing 0.28 to 0.59 at.%Si were analyzed. Noncoherent primary silicide particles were found in the interdendritic zones of the alloys containing more than 0.4 at.%Si due to strong segregation of Si. Secondary Ti5Si3 particles were observed in the α2-Ti3Al, β and γ-TiAl phases of the alloy, precipitating preferentially at the interfaces and growing into α2 and β, which are richer in silicon. The orientation between Ti5Si3 and β matrix phase was identified as [2¯113]Ti(5)Si(3)//[010]β and (01 1¯0)Ti(5)Si(3)//(10 1¯)β. The observed moire fringe spacing of secondary silicides in the α2-Ti3Al, β and γ-TiAl phases are consistent with calculated values.