Microstructural characterization of layered ternary Ti2AlC

Microstructures of Ti2AlC were investigated by means of X-ray diffraction, transmission electron microscopy, and analytical electron microscopy. The as-synthesized Ti2AlC is predominantly single phase and free of amorphous grain-boundary phases. High-resolution imaging reveals that the stacking sequence of Ti and Al atoms along the [0 0 0 1]Ti2AlC direction is ABABAB. Two intergrown structures, i.e., Ti3AlC2–Ti2AlC and Ti2AlC–TiC–Ti2AlC, were determined using high-resolution imaging and energy dispersive X-ray analysis. Ti3AlC2 and TiC share close crystallographic relationships with Ti2AlC, which opens up the possibility of tuning the properties of Ti–Al–C carbides by controlling the microstructures. Investigation of the microstructure of TiAl-containing Ti2AlC revealed that Ti2AlC preferentially forms at TiAl twins.