气固反应原位生成TiC颗粒增强钛基复合材料
In-situ synthesized TiC particle-reinforced titanium matrix composites prepared by gas-solid reaction
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摘要: 以氢化脱氢钛粉为原料, 经冷等静压成型, 在一定温度下通过CH4和钛粉颗粒间的气固反应在钛粉表面原位生成均匀的TiC颗粒, 采用真空烧结技术制备得到氧含量(体积分数)低于0.2%的TiC颗粒增强钛基复合材料。研究表明, TiC颗粒体积分数比可通过气固反应温度和时间控制, 可获得较高体积分数(> 30%)的TiC颗粒增强钛基复合材料。TiC首先在钛粉颗粒表面形成, 烧结过程中, 钛粉颗粒明显阻碍TiC晶粒长大, 细化TiC晶粒; 同时, 过多的TiC颗粒也阻碍烧结过程中钛的自扩散, 降低烧结相对密度。钛粉压坯在700℃、CH4气氛下发生气固反应(30 min), 再经1300℃烧结后获得的相对密度为98.6%的烧结试样, 试样的综合力学性能较好, 抗拉强度为606 MPa, 延伸率达14.4%, 硬度为HV 442。值得注意的是, 较短时间的气固反应不能够保证压坯内外整体实现原位生成均匀TiC颗粒, 导致烧结试样内外组织的不均性。Abstract: Using hydrogenation-dehydrogenation titanium powders as the raw materials, the in-situ synthesized TiC particles were prepared by gassolid reaction at a certain temperature under the atmosphere of CH4 after cold isostatic pressing, then the TiC particle-reinforced titanium matrix composites were manufactured by vacuum sintering with the oxygen content (volume fraction) less than 0.2%.In the results, the volume fraction of TiC particles can be controlled by adjusting the temperature and time of gassolid reaction, and the TiC particle-reinforced titanium matrix composites with the higher volume fraction of TiC particles (> 30%) can be obtained.TiC is first formed on the surface of titanium powders, and the growth of TiC particles is obviously hindered by Ti powders, resulting in the grain refining of TiC particles; however, the excessive TiC particles also hinder the self-diffusion process of titanium in the sintering process and reduce the relative density.The titanium powder compacts handled by gassolid reaction at 700 ℃ under the atmosphere of CH4 for 30 min are vacuum sintered at 1300 ℃, and the sintered specimens show the better comprehensive mechanical properties, the tensile strength is 606 MPa, the elongation is 14.4%, the hardness is HV 442, and the relative density is 98.6%.However, a relatively short period of gassolid reaction cannot guarantee the uniform distribution of TiC particles, resulting in the inhomogeneity in the internal and external structures of sintered specimens.