Synthesis of TiAl/Nb composites with concurrently enhanced strength and plasticity by powder metallurgy

TiAl-based alloys with high melting point become the promising high temperature structural materials, but the inherent brittleness drawback suppresses their application. Here, we proposed a controllable strategy to concurrently achieve high strength and high plasticity in TiAl/Nb composites that were prepared by introducing fine plastic Nb particulates to disperse around matrix TiAl, followed by powder metallurgy reaction at 1200 °C/50 MPa/1 h. A complex atomic diffusion reaction (ADR) at the interfaces between matrix TiAl and plasticizer Nb was clarified. The results of uniaxial compression of TiAl/Nb composites at room temperature (RT) show the high strength and excellent plasticity, due to the operation of multiple deformation mechanisms of involved phases in the novel structure. Definitely, the prominent deformation mechanism of matrix TiAl was 1/6112¯]111 ss-slip. The plasticizer, such as fresh Nb-based intermetallics (Nb_im) and remained Nb (Nb_r), coordinated the overall migration of matrix particulates in the form of compatible deformation. The strengthening phase O/B2 belonged to the dislocation-mediated deformation and was responsible to propagate stress from the plasticizer to the matrix. Predominantly, the tailoring microstructure that Nb_im/Nb_r was interspersed in the fresh γ_n and O/B2 was conducive to the successive straining of the composites, which in turn facilitated the intersection or entanglement of the proliferating dislocations and thereby resulted in high strength.