Alignment of the TiAl/Ti3Al lamellar microstructure in TiAl alloys by directional solidification

By using an appropriately oriented seed from the TiAl–Si system, the TiAl/Ti3Al lamellar microstructure was aligned parallel to the growth direction for ingots having compositions of Ti–47Al, Ti–43Al–3Si, and Ti–46.5Al–3Nb–0.5Si (at.%). Directional solidification was performed in a floating zone furnace at growth rates between 5 and 40 mm h−1. In addition, some ingots were directionally solidified in 16 mm diameter ceramic crucibles. Evidence for the solidification of the β-phase can be observed for some Ti–47Al ingots grown at 40 mm h−1 and different possible growth morphologies are discussed to explain the observed microstructures. Preliminary results from room temperature tensile tests and high temperature compression tests are also presented.