Ultrahigh strength and high plasticity in TiAl intermetallics with bimodal grain structure and nanotwins

Nanostructured intermetallics generally exhibit high strength but limited plasticity due to the covalent nature of their bonding. In this study, high-pressure torsion followed by annealing was used to produce TiAl intermetallics with two microstructural features: (i) bimodal microstructure composed of nanograins and submicrometer grains; and (ii) nanotwins. An exceptional performance, combining ultrahigh yield strength, ∼2.9 GPa, and high strain to failure, ∼14%, was achieved with micropillar compression tests. Twinning, dislocation slip and grain boundary sliding appear to be active under compressive stress.