Synthesis and mechanism of ternary carbide Ti_3AlC_2 by in situ hot pressing process in TiC-Ti-Al system

摘要

Ti_3AlC_2 is successfully synthesised by in situ hot pressing process from 2TiC/xAI/Ti (x= 1,1-2) raw powders. The phases and microstructure of the samples are identified by X-ray diffraction and scanning electron microscopy. It is found that aluminium content influences on the generating content of Ti_3AlC_2 significantly. High purity Ti_3AlC_2 can be obtained from a compacted cylinder composed of TiC-Ti-1.2AI at 1350°C for 2 h, and the purity of Ti_3AlC_2 is nearly 96.9 wt-%. The corresponding density and compressive strength are 3.93 g-cm~(-3) and 377.34 MPa respectively. Ti_3AlC_2 grain exhibits typical plate-like structure. When aluminium melts, a mass of Al atoms diffuse to Ti grain rapidly, and Ti-Al intermetallic compounds generate. Then, Ti-Al intermetallic compounds react with TiC to form Ti_3AlC_2 directly. Using TiC powders as the raw materials provides Ti_6C octahedra directly. At elevated temperature, a part of aluminium will evaporate and lose. This will result in that every two layers of Ti_6C octahedra are linked by aluminium planes directly and Ti_3AlC_2 can be formed.