Atomic Force Microscopy and Transmission Electron Microscopy identification of deformation twinning in the Cr2AlC MAX phase

Elementary deformation mechanisms have been investigated in a single-crystalline Cr2AlC MAX phase. Plastic deformation has been induced at room temperature by spherical nanoindentation, with a crystal orientation chosen to minimize basal slip and to promote local crystal reorientation. The combination of Atomic Force Microscopy surface observation, Transmission Electron Microscopy (TEM) characterization and Automated Crystal Orientation Mapping in a same region has provided a full 3D characterization of the deformation microstructure. Localized and isolated deformation twins have been identified below the indents. The whole microstructure consists in interactions between dislocations and {112¯4} twin variants. The TEM analysis also revealed activation of a 13〈112¯0〉{1¯103} slip system never reported before in a MAX phase.