Al-TiO2系XD合成Al3Ti的形貌及其影响因素分析

本文主要研究了Al-TiO2系XD合成铝基复合材料的反应产物Al3Ti的形貌及其演变的影响因素.研究表明Al-TiO2系反应产物由Al2O3和Al3Ti组成,Al2O3为细小颗粒,与铝液不润湿,偏聚于基体颗粒的界面;Al3Ti呈棒状,优先生长方向为<110>;随着增强相体积分数的增加,反应温度提高,活性Ti原子的扩散能力增强,扩散路程变短,有利于Al3Ti择优生长,但Al2O3颗粒的浓度增加,使Ti原子的扩散阻力和Al3Ti的生长阻力同步增大,Al3Ti的择优生长倾向反而减弱,其形貌由棒状向块状演变;在纯铝液中Al3Ti的生长形貌为细长棒状,而在真空中则为薄片状;随着保温时间的延长,其轴向尺寸明显增大,径向尺寸增加不明显.

Analysis of Al3Ti Morphology and Its Influence Factors of the Composites Fabricated by XD Method in Al-TiO2 System

The Al_3Ti morphology and its influence factors of the composites fabricated by XD (exothermic dispersion) method in Al-TiO_2 reaction system are studied in the paper. The studied results indicated that reacted products of the Al-TiO_2 system were consisted of Al_3Ti and Al_2O_3. The Al_2O_3 phase with particulate shape segregated at the aluminum matrix regions due to its bad wetting with the matrix. The other phase Al_3Ti in the stick shape was formed by Al and active Ti atoms that were produced by the reaction between liquid aluminum and TiO_2, and its preferential growing direction was <110>. With increase of reinforcement volume fraction, the diffusion distance and diffusion ability of the active Ti atoms became shorter and stronger respectively. But owing to increase of concentration of Al_2O_3 phase, the diffusion resistance of Ti atoms and growing resistance of the Al_3Ti became higher. Therefore, the preferential growing tendency of Al_3Ti phase became weaken and its shape changed from stick to block. The morphology of Al_3Ti phase also changed with its growing circumstance, it was in the shape of slender stick and slice with growing in the pure liquid aluminum and vacuum state respectively. With the increase of keeping time, the length of Al_3Ti stick became longer in evidence, but the radical dimension increased indistinctively.