Features of a nano-twist phase in the nanolayered Ti3AlC2 MAX phase

Complex intermetallic materials known as MAX phases exhibit exceptional properties from both metals and ceramics, largely thanks to their nanolayered structure. With high-resolution scanning transmission electron microscopy supported by atomistic modelling, we reveal atomic features of a nano-twist phase in the nanolayered Ti3AlC2. The rotated hexagonal single-crystal is encompassed within basal symmetric twist interfaces similar to grain boundaries. In particular, we show that air-oxidation at 1000 ∘C can form a twisted phase that leads to the formation of interfacial dislocation networks with screw characters or to severe interfacial reconstructions. Additionally, we explore the contribution of disclinations to the representation by continuum models of the stress field generated by such nano-twist defect in the Ti3AlC2 bulk phase. The occurrence of this unexpected defect is foreseen to impact the physical response of this nanolayered-based material and, as such, supports property-by-design approaches.