【作者】 许坤；

【导师】 王志；

【作者基本信息】 济南大学 ， 材料学， 2004， 硕士

【摘要】 Ti与Al₂O₃均具有质轻、耐高温、耐腐蚀等优异性能,以及良好的物理化学相容性和相近的热膨胀系数。因此,研究和开发集金属陶瓷优异性能与一体的Ti/Al₂O₃体系复合材料,以期在梯度飞片中间层材料、新型刀具和汽车发动机零部件等方面得以应用。利用放电等离子烧结技术（SPS）的快速、低温等特点,通过调整材料的组成比例和添加适当的金属元素,抑制强烈的界面反应,制备出结构致密、性能优异的Ti/Al₂O₃系复合材料。利用XRD、EDS及EPMA等分析手段研究了Ti/Al₂O₃界面反应特性,结果表明Ti/Al₂O₃存在界面化学反应:Al原子和O原子扩散进入金属Ti中,在界面处生成Ti₃Al、TiAl等产物,O原子固溶于金属Ti中。金属Nb能有效的控制界面反应,避免脆性的Ti₃Al相生成,生成的AlNb₂能减少Al原子向金属Ti中扩散距离和O原子在Ti中固溶量。利用超声波脉冲回波法对Ti/Al₂O₃系复合材料的声学性能和弹性力学参量进行测量,结果发现所制备材料的波阻抗值为25～30（×109g/m2s）,介于高波阻抗的金属W、Mo和低波阻抗的Al、Mg之间,并且与金属Mo和金属Al具有良好的界面焊接性,可以作为波阻抗梯度飞片中间层材料。对Ti/Al₂O₃系复合材料的微观结构分析发现,界面处Ti₃Al相的存在是导致材料性能恶化的主要原因。研究了不同Nb掺量对Ti/Al₂O₃系复合材料性能影响规律,结果表明当Nb掺量为1.5vol%时,20vol%Ti/Al₂O₃和40vol%Ti/Al₂O₃复合材料的相对密度、弯曲强度、断裂韧性和显微硬度达到最大;Nb掺量为2.0vol%时,60vol%Ti /Al₂O₃复合材料力学性能则最佳;80vol%Ti/Al₂O₃复合材料的力学性则随Nb掺量的增加而增大。探讨了Nb对Ti/Al₂O₃系复合材料的强韧化机制的影响,研究发现Nb的掺入细化了材料的晶粒,并使材料的断裂模式由沿晶断裂转变为以穿晶断裂为主的混合断裂模式,以及形成的位错环等使得复合材料强度大幅度提高;裂纹的偏转和桥联是提高复合材料韧性的主要原因。更多还原

【Abstract】 It was necessary to fabricate the Ti/Al₂O₃ composites on applying to graded flier- plate, reamer and engine parts because Ti and Al₂O₃ had high strength with light mass, well thermal stability and high the module of elasticity, and what’s more, it can also stand high temperature and wear.The full dense and excellent composites were obtained by spark plasma sintering on the base of controlling interfacial reaction by means of suitable metal elements. Studying on Ti/Al₂O₃ interfacial reaction by XRD, EDS and EPMA showed that alumina decomposed firstly and then aluminum atom reacted with titanium forming Ti₃Al in the further titanium and poor aluminum and TiAl in the titanium and further aluminum, and O dissolved into titanium, niobium, however, not only hold back interfacial reaction and forming Ti₃Al, but also decreased aluminium diffusing from Al₂O₃ to Ti, at the same time, reduced the ability of O into titanium.The acoustics and mechanical properties of Ti/Al₂O₃ by ultrasonic pulse-echo method were measured and results indicated that wave impedance was 25～30（×109 g/m2s） between W, Mo and Al, Mg. The Mo-Ti/Al₂O₃ flier-plate with good parallelism, planeness and high densification was prepared by using diffusion welding method （under certain welding parameters such as temperature, pressure, time and atmosphere, etc）. The microstructure showed that Ti₃Al was major reason resulting in decreasing the mechanical of Ti/Al₂O₃ composite.Influencing of niobium on properties disciplinarian of Ti/Al₂O₃ composites indicated that the relative density, bending strength, fracture toughness and micro- hardness of 20vol% Ti/Al₂O₃ and 40vol%Ti/Al₂O₃ composites were best adding 1.5vol%Nb. 60vol%Ti/Al₂O₃ composites, however, required 2.0vol%Nb and 80vol%Ti /Al₂O₃ composite increased with niobium increasing. Based on niobium controlling interfacial reaction, the fracture mode of the Ti/Al₂O₃ composites changed from interganular to a mixing fracture of interganular and transgranular, and simultaneously dislocation strengthened the mechanical properties. The crack propagating was mainly deflection and bridging the prolonged the crack propagating path and advanced the fracture critical stress which was main cause of enhancing toughness of composites.更多还原