Influence of Si content on microstructure of TiAl alloys

A systematic study of four ternary TiAl-based alloys with constant Ti content of 52.2at.% and variable Si content ranging from 0.3 to 2.7at.% (Al in balance) was conducted. The alloys were prepared from elemental powders via a route including powder mixing, precompaction, cold extrusion, and reactive hot-isostatic pressing. All investigated alloys contain the intermetallic compounds γ-TiAl, α2-Ti3Al, and ζ-Ti5(Si,Al)3. The microstructure can be described as a duplex structure (i.e., lamella γα2 regions distributed in a γ matrix) containing ζ precipitates. With increasing Si content, the number of primary ζ precipitates increased and the γ grain size became finer while the lamellar volume fraction decreased slightly.