Al-Ti-B_4C体系熔体内燃烧合成TiC-TiB_2颗粒局部增强钢基复合材料

COMBUSTION SYNTHESIS OF TiC-TiB_2 PARTICULATES LOCALLY REINFORCED STEEL MATRIX COMPOSITES FROM AN Al-Ti-B_4C SYSTEM DURING CASTING

利用Al-Ti—B4C体系通过燃烧合成辅助铸造法成功制备了TiC-TiB2颗粒局部增强钢基复合材料，研究了Al含量对局部增强复合材料的组织及耐磨性的影响．结果表明，不同Al含量（0～50％，质量分数）的Al-Ti—B4C压坯在约1873K钢液浇注下都能原位反应生成TiC和TiB2陶瓷颗粒，而且钢液都向预制块发生了不同程度的浸渗．压坯内Al含量的变化不仅影响了合成产物的相组成及陶瓷相的分布、尺寸和数量，而且还影响了局部增强区和钢基体界面处陶瓷颗粒的分布状况．随Al含量的增加，合成陶瓷的颗粒大小、数量以及颗粒间的孔隙均变小，产物中形成的金属间化合物的种类和数量增多，且陶瓷颗粒在界面处的梯度分布趋势减弱并最终消失．磨损测试结果表明，复合材料局部增强区的耐磨损性比钢基体显著提高，而且在Al含量为0时为最好，然后依次为含30％Al，10％Al和50％Al的复合材料．

From the point of view of the application, the service life of component usually relies on the wear resistance of local region, and it is desirable that the local region of component rather than the whole component is reinforced by ceramic particulate to offer high-wear resistance. In this study, the TiC-TiB2 particulates locally reinforced steel matrix composites were fabricated by an SHS-casing route using an Al-Ti-B4C system. The effects of the Al content on the microstructure and wear resistance of the composites were investigated. The results show that the TiC and TiB2 particulates were formed in all the preforms with various Al contents （0-50%, mass fraction） after the high temperature （about 1873 K ） steel melt was poured into the mold and the molten steel, to the different extents, penetrates into the synthesized samples. The Al content in the preforms has a large effect on the constitute of the synthesized products and the quantity, size and distribution of the ceramic phases in both the reinforced region and the transition region. With the increase of the Al content, the quantity and average size of the ceramic particles as well as holes decrease, the type and quantity of the intermetallic compounds in the products increase and the gradient distribution of the ceramic particles in the transition region weakens and finally disappears. The wear resistance of the locally reinforced composites is much superior to that of the unreinforced steel matrix, and the best appears in the sample free of Al composition, and then followed by the samples of 30%Al, 10%Al and 50%Al in turn.