后热处理对搅拌摩擦加工制备Al-Ti复合材料组织特征的影响

Effects of Post Heat Treatment on Al-Ti Composites Microstructure Prepared by Friction Stir Processing

采用搅拌摩擦加工技术制备Al-Ti复合材料,并对其进行600℃/6h的后热处理,采用SEM、TEM、XRD对搅拌摩擦区热处理前后的微观组织结构及相进行了分析;采用X射线衍射图分析软件TOPAS测量了搅拌区热处理前后的物相晶格常数,研究了后热处理对搅拌摩擦加工制备的Al-Ti复合材料组织特征的影响。结果表明:600℃/6h后热处理后,金属间化合物与铝基结合界面良好;且后热处理可使Ti、Al和Al_3Ti彼此间的扩散速率加快,促进Al_3Ti和新相Al_5Ti_2金属间化合物的产生;此外微观结构中存在位错墙;热处理前后Al_3Ti的轴向比c/a都高于标准数据,但热处理后提高了约0.4%,明显低于热处理前约1.2%的增幅;进行后热处理后,Al-Ti复合材料因搅拌摩擦加工引发的微观缺陷的增殖、再次扩散及缺陷间的互作用,使得原位反应再次进行,促使搅拌区金属间化合物含量提高。

Al-Ti composites were fabricated by friction stir processing （FSP）, and then post-treated at 600 ℃/6 h. The microstructures and phases of the friction zone were analyzed by SEM, TEM and XRD. The lattice constant of the phase before and after the heat treatment was measured by X-ray diffraction analysis software TOPAS. The microstructure of Al-Ti composites prepared by friction stir processing were studied at the effects of post-heat treatment. The results show that the intermetallic compound has a good interface with aluminum base after 600 ℃/6 h post heat treatment; the interdiffusion between Ti, Al and Al 3Ti can be accele- rated by the post-heat treatment, which can promote the formation of Al 3Ti and new phase Al 5Ti 2 intermetallic compounds. In addition, there exists dislocations walls in the microstructure. The axial ratios of Al 3Ti c/a before and after heat treatment are higher than standard data, but the degree of change after heat treatment is about 0.4%, which is obviously lower than that of 1.2% before heat treatment. After the heat treatment, the proliferation, re-diffusion and interaction of the micro-defects caused by the friction stir processing of the Al-Ti composite material cause the in-situ reaction to proceed again, which promotes the increase of the intermetallic compound content in the friction stir zone.