Revisiting the defect structure of MAX phases: the case of Ti₄AlN₃

Abstract

Microstructural study of as-grown Ti₄AlN₃ 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.

Keywords:

• dislocations
• microstructural analysis
• transmission electron microscopy

Acknowledgements

Professor Michel W. Barsoum, Drexel University, Philadelphia, PA, USA, is acknowledged for providing the Ti₄AlN₃ polycrystalline samples.