Grain refinement of a TiAl alloy by heat treatment through near gamma transformation

Casting of TiAl alloys is receiving more and more research because of its relatively low cost. One problem with this technology is that the coarse microstructure developed during solidification is harmful to material properties. Thus it is essential to seek an approach to refining the cast microstructure and this approach may also be applicable to cast components. In this study, a novel heat treatment route is proposed to obtain a fine fully lamellar structure from a cast TiAl alloy with a grain size of 1000 m. This route consists of three steps, namely pretreatment to have a feathery structure, annealing in the + region to have a fine near gamma structure and solution treatment to develop a fully lamellar structure with a grain size of 30 m.