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TiAl/Ti2 AlC composites were prepared by in-situ hot pressing of Ti/Al/C powders mixtures and sintered at different temperatures were investigated by X-ray diffraction (XRD) of samples. The reaction procedure of Ti-Al-C system could be divided into three stages. Below 900°C, Ti reacts with Al to form TiAl intermetallics; above 900°C, C reacts with remain Ti to form TiC triggered by the exothermal reaction of Ti and Al; TiAl reacts with TiC to produce dense TiAl/Ti2 AlC composites. In the holding stage, ternary Ti2AlC develops to layered polycrystal and composites pyknosis in the meanwhile. The mechanism of synthesis and microstructure was especially discussed. [ABSTRACT FROM AUTHOR]

X-ray diffraction (XRD) analysis on different polished surfaces normal to the hot pressing direction reveals that the phase compositions of the polished surfaces from the outside to the inside are pure TiC, Ti3AlC2+TiC, pure Ti3AlC2 and Ti2AlC+Ti3AlC2, no matter elemental powder or TiC is used as raw materials. It is found that ternary-layered carbide Ti2AlC samples synthesized at 1500°C by hot-pressing sintering are inhomogeneous and have a gradient structure. Electron probe X-ray micro-analysis (EPMA) indicates that the Al content along the hot pressing axis is parabolic, it is the highest in the center and the lowest at the both ends, while the Ti content is constant along the axis. The experimental result reveals that the evaporation of Al in samples in an open system during hot pressing sintering results in a gradient structure. [ABSTRACT FROM AUTHOR]