Reinforcement of TiAl alloy by evenly distributed micron-/nano-Y2O3 particles

TiAl alloy has attracted widespread attention as an alternative material to aero-engine turbine blades. Because the obvious brittleness of TiAl alloy, TiAl alloy reinforced with nano-sized reinforcement is a feasible pathway to improve its mechanical properties due to the nano-sized reinforcement does not easily cause stress concentration and crack initiation while strengthening the alloy matrix. However, since the high specific surface energy and van der waals attraction of nanoparticles, they tend to agglomerate to form unevenly distributed micron-sized particles in alloy melt, which makes it difficult to fabricate TiAl alloys reinforced with nano-sized reinforcements by low-cost casting method. In this work, a TiAl alloy reinforced with evenly distributed micron−/nano-Y2O3 was successfully fabricated by casting method and subsequent heat treatment based on an innovative strategy of stepwise dispersion combined with solid solution-precipitation. Micron-Y2O3 in as-cast TiAl alloy "inherits" the uniform distribution state of Y-rich particles in Al-based master composite; the subsequent heat treatment and furnace cooling process make the nano-Y2O3 uniformly precipitated in the TiAl matrix. Nano-Y2O3 particles (~ 50 nm) were uniformly distributed in both α2/γ lamellae and lamellar colony boundaries. The ultimate compressive strength and fracture strain of TiAl alloy reinforced with micron−/nano-Y2O3 particles are 1970 MPa and 29.5%, respectively.