Revisiting the defect structure of MAX phases: the case of Ti(4)AlN(3)

Microstructural study of as-grown Ti(4)AlN(3) MAX phase has been performed by transmission electron microscopy. Dislocation walls, dislocation nucleation sites and stacking faults are described. In particular, diffraction contrast analysis combined with high-resolution images give a new insight into the nature of the stacking faults: contrarily to what is usually postulated, it is shown that the stacking faults possess a shear component in the basal plane. The stacking faults are created by the insertion of MX layers in the lattice via diffusion mechanisms. Their possible role on the deformation mechanism of MAX phases is discussed.