Superior strength-plasticity synergy in a heterogeneous lamellar Ti2AlC/TiAl composite with unique interfacial microstructure

Abstract

Improving the plasticity of TiAl alloys at room temperature has been a longstanding challenge for the development of next-generation aerospace engines. By adopting the nacre-like architecture design strategy, we have obtained a novel heterogeneous lamellar Ti2AlC/TiAl composite with superior strength-plasticity synergy, i.e., compressive strength of ∼2065 MPa and fracture strain of ∼27%. A combination of micropillar compression and large-scale atomistic simulation has revealed that the superior strength-plasticity synergy is attributed to the collaboration of Ti2AlC reinforcement, lamellar architecture and heterogeneous interface. More specifically, multiple deformation modes in Ti2AlC, i.e., basal-plane dislocations, atomic-scale ripples and kink bands, could be activated during the compression, thus promoting the plastic deformation capability of composite. Meanwhile, the lamellar architecture could not only induce significant stress redistribution and crack deflection between Ti2AlC and TiAl, but also generate high-density SFs and DTs interactions in TiAl, leading to an improved strength and strain hardening ability. In addition, profuse unique Ti2AlC(11¯03¯)/TiAl(111) interfaces in the composite could dramatically contribute to the strength and plasticity due to the interface-mediated dislocation nucleation and obstruction mechanisms. These findings offer a promising paradigm for tailoring microstructure of TiAl matrix composites with extraordinary strength and plasticity at ambient temperature.