Tailoring microstructure and mechanical properties of ?-solidifying TiAl alloy fabricated by laser-engineered net shaping through heat treatment

beta-solidifying TiAl alloy, an advanced gamma-TiAl based alloy, has emerged as a lightweight candidate for high temperature applications in turbine engines. To facilitate the design freedom and manufacturing efficiency, laserengineered net shaping (LENS) is considered as a promising method to fabricate beta-solidifying TiAl alloy components. However, this alloy suffers from cracking during the printing process due to its high brittleness. Hence, grain refinement was introduced to overcome this issue. But, the grain refinement leads to reduction in creep resistance at elevated temperatures. To restore the creep-resistant performance, postproduction heat treatment is required to tailor the mechanical properties of the beta-solidifying TiAl alloy. In the present work, the as-printed TiAl alloy is subject to heat treatment with different processes to maximize the formation of alpha 2/gamma lamellar structure that corresponds to higher creep resistance. Upon characterizations of the heat treated TiAl alloy samples in terms of microstructure, compressive properties at room temperature and creep resistance at 800 degrees C, an optimized two-step heat treatment process comprising of annealing at 1350 degrees C for 1 h followed by air cooling and a subsequent stabilization treatment at 850 degrees C for 6 h is developed. The resultant microstructure consisting of fully lamellar structure with nano-scale lamellar spacing leads to a dramatical increase in the room temperature plasticity of the alloy with respect to the as-printed's, and high creep resistance at 800 degrees C with applied stress of 150 MPa, which is comparable to the alloys fabricated with conventional casting and wrought technologies.