Nanoindentation-induced deformation twinning in MAX phase Ti₂AlN

Plastic deformation mechanisms have been investigated in the MAX phase Ti2AlN. Nanoindentation has been used to induce plastic deformation in a single grain, and a Transmission Electron Microscopy (TEM) lamella has been extracted in cross section through the indent by using Focused Ion Beam (FIB) technique. By combining TEM observations and automated crystal orientation mapping (ACOM), highly misoriented domains (HMD) have been revealed below a nanoindentation imprint. Thanks to a careful analysis of the relative crystal orientations between these HMD, {11-22} and {11-21} deformation twins have been identified for the first time in a MAX phase. Complex structures, involving secondary twinning or different {11-22} twin variants have also been characterized.