以Al_4C_3、Ti和石墨混合粉体为原料, 采用放电等离子技术原位反应制备了TiC/Ti_2AlC两相复合材料和TiC/Ti_2AlC/Ti_xAl_y三相复合材料. 利用XRD、SEM、TEM研究了复合材料的相组成和微观结构, HRTEM的观察结果显示复合材料的相界面清洁干净, 无非晶相存在. 同时研究了TiC/Ti_2AlC/Ti_xAl_y三相复合材料的原位反应烧结过程, 并对复合材料的导电行为进行了表征. 在室温时TiC/Ti_2AlC材料的电导率大于TiC/Ti_2AlC/Ti_xAl_y三相复合材料,其中TiC/40vol%Ti_2AlC的电导率最高达到8.83×10~5S/m. TiC/Ti_2AlC两相复合材料和TiC/Ti_2AlC/Ti_xAl_y三相复合材料的电导率均随温度的升高而下降, 呈现电导的金属性特征, 同时电导率随温度变化关系符合Arrhenius理论.
TiC/Ti_2AlC and TiC/Ti_2AlC/Ti_xAl_y composites were in-situ fabricated by spark plasma sintering using Ti, Al_4C_3 and graphite powders as starting materials. The phase constitution and microstructures of the composites were analyzed by XRD, SEM and HRTEM. No amorphous phase was detected at the grain boundaries. In-situ reaction and diffusion mechanism were also proposed. Through SEM images and EDS analysis of the starting powder mixtures sintered at intermediate temperatures, the intermediate phases and phase formation sequence in the sintering process can be obtained. The diffusion path in the reaction sintering always occurred along the grain boundaries or crack defects. The electric conductivities of TiC/Ti_2AlC composites were higher than that of TiC/Ti_2AlC/Ti_xAl_y composites at room temperature. The electric conductivity of TiC/40vol%Ti_2AlC was 8.83×10~5 S/m. With the temperature increasing, the electric conductivity of TiC/Ti_2AlC/Ti_xAl_y composites decreased. The temperature dependence of conductivity followed the Arrhenius empirical formula in the measured temperature range.
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