Revealing interface-assisted plastic anisotropy via in situ transmission electron microscopy tension of lamellar TiAl

Assembling functional units into specific orientation organizations based on functional unit and organization (FUO) paradigm can maximize utilizing mechanical property anisotropy of lamellar-structured materials. However, the origin of their anisotropic deformation behaviors has not been clearly understood. Taking the fully lamellar γ-TiAl/ α2-Ti3Al dual-phase single crystal as an example, we decouple the interface functional units governed anisotropic plastic deformation through in situ transmission electron microscopy tensile testing and multiscale microstructural characterizations. The orientation organization-dependent slip continuity across the γ/α2 interface and interface strength play a determinant role in plastic anisotropy beyond intrinsic dislocation activities within the lamellae. Consequently, translamellar stress transfer or interface delamination prevails under the tension parallel or perpendicular to the lamella, elaborating the strong anisotropy in strength and ductility. These mechanistic insights hold general implications to understanding the anisotropic plastic deformation of lamellar-structured materials, benefiting the structural design of high performance alloys.