Fabrication, microstructure and high-temperature strengthening mechanism of multi-scale Ti2AlC/TiAl composite

The multi-scale Ti 2 AlC/TiAl composites were fabricated. Micro-Ti 2 AlC particles are obtained in-situ at the grain boundaries of the full lamellar TiAl matrix by vacuum arc melting. The targeted precipitation of submicro-Ti 2 AlC at the lamellae TiAl/Ti 3 Al phase boundary and directional precipitation of nano-Ti 2 AlC within TiAl crystals are achieved by heat treatment. And the best high-temperature tensile properties are obtained when the graphite powder is added at 2 at.%, resulting in a tensile strength of 561 MPa and an elongation of 3.6%. These findings underscore the multifaceted role played by the multi-scale Ti 2 AlC: micro-Ti 2 AlC effectively inhibits grain boundary softening and hinders dislocation motion, while submicro-Ti 2 AlC prevents twin propagation and obstructs dislocation motion. Nano-Ti 2 AlC, on the other hand, not only hinders dislocation movement but also fine-tunes the lamellar microstructure.