【作者】 杜赵新；

【导师】 刘志光；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2009， 硕士

【摘要】 SiC连续纤维增强Ti基复合材料(TMC)的比强度和比刚度高、使用温度高、疲劳和蠕变性能好、减重效果显著,在航空发动机上有广阔的应用前景。由于Ti的化学活性大,在复合材料的SiC纤维/Ti界面处仍存在着严重的界面反应,极大的损害SiC/Ti基复合材料的力学性能,制备工艺对复合材料的性能也有很大影响。本文通过扫描电镜、X射线衍射和电子背散射等分析手段,对用FFF法制备的以Ti-6Al-4V合金以及Ti基体复合材料的界面反应以及性能影响因素进行了分析;本文还对液态复合工艺制备SiC连续纤维增强Ti基复合材料进行了探索研究。该实验所用纤维为国防科技大学提供的细纤维和西北工业大学提供的粗纤维,利用扫描电镜观察分析了复合材料的界面反应与断口形貌,发现由FFF法制备的复合材料中无涂层纤维与基体之间、基体与涂层之间有明显的界面反应层,SiC纤维中的元素向基体扩散,在界面生成脆性产物,加大了界面的脆性,使材料呈现脆性断裂。在复合材料中还发现“耳状”空洞等组织缺陷,本实验通过在纤维层中添加钛粉解决了此问题,但是钛粉的加入方法与加入量还有待深入研究。实验采用离心铸造法作为液态复合工艺制备复合材料的方法,研究发现,液态复合工艺的最大缺点是金属液与纤维在高温下会发生严重的界面反应,从而影响到复合材料的性能。在相同的制备条件下,无涂层纤维与基体的界面反应层厚度可达到110μm左右,而TiN与C涂层纤维与基体的反应厚度为5～10μm,约为无涂层纤维复合材料的十分之一,说明纤维表面的障碍涂层对金属液与纤维的反应有很好的阻碍作用,如果采用理想的涂层,提高冷却速度,减少金属液与纤维之间的界面反应时间,则液态复合工艺将是一种方便、低成本的SiC/Ti基复合材料制备工艺。更多还原

【Abstract】 Continuous SiC fiber reinforced titanium matrix composites (TMC) has high specific strength and stiffness, high service temperature, good anti-fatigue and creep-resistant performance and significant weight reduction effect. These advantages give it a wide prospect of application on aeroengine. But due to the high chemical activity of titanium, there is serious interface reaction between SiC fibers and titanium matrix which will cause severe damage on the mechanical properties of SiCf/Ti composites. Some elements of the SiC fiber diffuse into the matrix and give birth to some brittle products, these brittle products will increase the brittleness of the interface which makes the fracture mechanism of the material become brittle fracture. On the other hand, the manufacture process has a great impact on the mechanical properties of SiCf/Ti composites too. By means of SEM microstructure observation, X-ray diffraction and electron backscatter diffraction analysis, we analyzed the interface reaction of SiCf/Ti and SiCf /Ti-6Al-4V interface in SiCf/Ti and SiCf /Ti-6Al-4V composites made though FFF method respectively. Beside that, factors influencing mechanical properties were also studied in this thesis. The liquid composite process of SiCf/Ti composites was studied in this thesis too.Fibers used in this thesis are domestic fibers, including thick fibers come from National University of Defense and Technology and thin fibers come form Northwestern Polytechnical University. By the way of SEM, we observed and analyzed the interface reaction and fracture morphology of the composites made by FFF method and significant interfacial reaction layers were observed between fibers and matrix, matrix and coatings. Also, some defects as“earring”holes were observed in the microstructure. These problems were solved with the method of adding titanium powder into fibers layer. But how to adding and how much titanium powder should be added still need further research.By using centrifugal casting method as liquid composite technology of the preparation of SiCf/Ti matrix composites found that,the drawback of liquid composite process is there will be a serious interfacial reaction between liquid metal and the fiber at high temperature, this reaction will damage the mechanical properties of Sic/Ti composites. Preparation in the same conditions, the interfacial reaction layer’s thickness between the uncoated fiber and the matrix is 100μm, but TiN-coated and C-coated fibers’ reaction layer’s thickness is 5-10μm only, less than one-tenth of uncoated fiber composites,it indicate that Barrier coatings on the surface of Sic fibers can prohibit this kind of reaction effectively. If we can find an ideal coating and reduce the reaction time between Sic fibers and titanium slurry by rise the cooling speed, we will make liquid composite process becomes a convenient and low cost process.更多还原