Achieving Superior High-Temperature Strength and Oxidation Resistance of TiAl Nanocomposite through In Situ Semicoherent MAX Phase Precipitation.

Increasing the service temperature of TiAl intermetallics is the main challenge for the development of next-generation aircraft. Dispersion-strengthening, an effective means to further improve the high-temperature performance of metals, fails to implement in TiAl intermetallics due to difficulties in interface optimization. Here, we successively fabricate a TiAl naocomposite with fully lamellar microstructures and homogeneously dispersed Ti2AlC nanoprecipitates via spark plasma sintering. The composite consisted of semicoherent interfaces among γ-TiAl/Ti2AlC precipitates/α2-Ti3Al, in addition to continuous polysynthetic nanotwins. Strong pinning effects as well as strain-induced nanoscale TiCr2 precipitation uplift the operation temperature of TiAl nanocomposites by more than 50 °C. Furthermore, we experimentally proved that semicoherent interfaces among in situ Ti2AlC precipitates and its surrounding matrix serve as oxygen diffusion barrier during isothermal oxidization and significantly drop down the mass gain of TiAl nanocomposites during operation, making the present nanocomposite a highly potential candidate for use as light-weight structural materials in automotive and aerospace industries.