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