纳米金刚石含量对网状结构钛基复合材料组织与性能的影响

Effect of Nanodiamond Contents on Microstructure and Properties of Titanium Matrix Nanocomposites with Network Microstructure

通过对钛粉表面修饰聚乙烯醇,利用交联反应使纳米金刚石(NDs)均匀分布在球形钛粉末表面,然后采用放电等离子烧结技术成功制备了网状结构分布的纳米金刚石增强钛基复合材料。研究了不同NDs含量对复合材料组织结构、导热性能与压缩性能的影响。结果表明,部分NDs与Ti原位反应生成了Ti C,其与残留的NDs呈三维网络状分布在TA1纯钛基体中,网络尺寸为100~200μm。导热测试结果表明,随着增强相含量的增加,复合材料的热导率呈下降趋势;压缩实验表明:Ti-1.0%NDs(质量分数)复合材料有较优异的性能,强度提高的同时仍然保持了高塑性。材料断裂时主要是沿网状结构界面处断裂,几百微米尺寸的网状结构起到加固梁的作用,而网络状内部存在着大量纯钛晶粒仍保持较低的硬度和良好的塑性,从而有效的调和了钛基复合材料强度和塑性的矛盾。

Nanodiamonds(NDs) reinforced titanium(Ti) matrix composites with network microstructures were prepared by spark plasma sintering technique. Spherical Ti particles were modified with polyvinyl alcohol and then crosslinked with the NDs. Finally, the NDs were distributed uniformly on the surface of the spherical Ti particles. The effects of ND contents on the microstructures, thermal conductivity and compression performance of the Ti nanocomposites were studied. The results show that Ti C particles are in-situ formed due to the reaction between the Ti and NDs but some NDs are still preserved in the nanocomposites, the NDs/Ti C hybrid reinforcements have a three-dimensional network distribution in the Ti matrix and the size of network is 100~200 μm. The results of thermal conductivity test show that the thermal conductivity of the nanocomposites decreases with the increase of the content of the reinforcing phases. The compressive tests show that the Ti-1.0 wt% NDs composites have excellent mechanical properties;the ductility of the composites remains high enough while the hardness and strength are greatly improved. The fracture surfaces of the composites show that the cracks propagate along the network-structured boundary. The network microstructures with hundreds of microns play the role of reinforcing beams, while the internal matrix of the network still maintains low hardness and high ductility of the pure Ti. Eventually, the contradiction between strength and ductility of the Ti matrix composites is reconciled effectively.