【作者】 刘淑凤；

【导师】 张培萍； 张立功；

【作者基本信息】 吉林大学 ， 材料学， 2006， 硕士

【摘要】 鉴于传统单相材料的缺点,如陶瓷颗粒硬度高,强度大,抗磨损性能好,且高温性能较稳定,但较脆且密度高;而金属材料塑性好,密度低但强度较差,所以本实验选择用氧化铝颗粒和纯金属铝做为起始原料,结合两种材料各自的优点,制备出性能比较优异的复合材料。本文利用X射线衍射、透射电镜、热分析及光谱分析等方法研究了机械处理对纳米氧化铝的相变和电子结构的影响,并探讨了不同粒径的氧化铝颗粒增强铝基复合材料的制备工艺及其对力学性能影响,得出如下结论:1.球磨引起纳米γ-Al2O3—α-Al2O3相变温度降低,相变激活能最大降低210KJ/mol。并在γ-Al2O3纳米粉体上观察到较强的紫外发光,而且发光强度随辐照剂量增加而漂白。初步将它归结为自陷激子或束缚激子以及来自F心和杂质的发光;2.研究了球磨对不同体积比的纳米Al2O3p与Al的复合粉体的微结构和各相分布的影响,并获得了均匀的复合粉体;3.采用两步加压烧结方法,成功制备了不同体积比及不同粒径的Al2O3p增强的Al基复合材料,且其致密度比传统方法有了很大提高,均可达95%。与亚微米增强体相比较,纳米陶瓷增强复合材料的机械性能比基体有了更大的提高;4.15%volAl2O3p(100nm)/Al金属基复合材料(MMC)的屈服强度可达465MPa,且塑性较好。增强相的影响随陶瓷颗粒的粒径减小和体积比的增加而增强。材料的硬度及抗磨损能力随粒径和增强相体积比的变化规律与屈服强度相同。实验结果与Orowan理论和Hall-Petch关系吻合很好。更多还原

【Abstract】 With the development of the modern science and technology, especiallythe progress of aerospace and aircraft industries, more and more advancedmaterials which have excellent properties are desired. These properties such aslower density, high specifc strength and high fracture toughness are hoped, andthe probability of utilization in high temperature, high pressure, highvacuum,intense corrosion or radiation harsh environment is expected. The requirementfor light, strong and stiff materials has extended an interest in metal–matrixcomposites (MMCs) and people have paid more and more attention to thembecause of their improved strength, high elastic modulus and increased wearresistance over conventional alloys during the last 20 years. Ceramics, e.g.boron, carbon, silicon carbide and alumina which have been produced invarious forms such as continuos fibres, short or chapped fibres, whiskers andparticulates or wires have been used as reinforcement in MMCs.Among these metal matrix composites, Aluminum matrix reinforced withAl2O3 particles composites are being considered by aerospace and automotiveindustries for several engine applications such as connecting rods, pistons,gear selector torks and cylinder liners because of their high-strength-to weightratio.In this paper, we discussed the phase transformation and thephotoluminescence of mechanically milled Nano-Sized γ-alumina by XRD,TEM, DSC and PL , and we found that temperature of the phasetransformation was lowered by 210KJ/mol after ball-milling for 100h, andthere was obvious change in the PL with the ball-milling time increasing.Spectral behavior of UV luminescence suggests that the UV band cannot beassigned to F+ or Al+i center, prefer to be self-trapped exciton or bound exciton.The other bands are originated from defect center and impurity.In this paper, the development of the Al matrix composites reinforcedwith Al2O3 particles were summarized. Based on the reviews of the latestdevelopments, a new idea was brought to prepare Al matrix compositesreinforced with different ratios and sizes of Al2O3 particles. The experimentscould be divided primarily three steps: Preparation of composite powders,making green samples and sintering.The XRD and SEM methods were used to character the changes duringthe first stage of mixing composites power, and the composite powders of 5、10、20vol%Al2O3/Al were fabricated well by the high energy ball-milling. Inorder to improve the relative densities of aluminum matrix compositesreinforced with Al2O3 particles, a process of pressing in high pressure(850Mpa) and moderate temperature (230oC) was added to the conventionalpreparation method, powder metallurgy technique. Then we selected the bestmethod for sintering. After sintering, the relative densities of samples for5,10,15,20 (20nm)vol% Al2O3/Al were 99.9%,98.2%,97.2%,95%, and theyield strength was respective to 400Mpa, 503Mpa, 540Mpa and 268Mpa;for5,10,15,20vol(100nm)%Al2O3/Al, the relative densities were99.9%,99.9%,98.2%,96.5%, and the yield strength was respective to 414MPa,449MPa, 465MPa and 532MPa;for 15vol(200nm)%Al2O3/Al and15vol(500nm)%Al2O3/Al, the relative densities were 98.7% and 99.2%, andthe the yield strength was respective to 434MPa and 401MPa;for 15vol%Al2O3(2μm)/Al, the relative density was 99.6%. Dramatic enhancements instrength and hardness are for all the samples. We found that the yield strength,hardness and wear resistance were increased when the smaller size grains forthe Al2O3 were used. To be applied in some field, we regard the15vol%Al2O3p ( 100nm ) /Al as the best one. The mechanism of thereinforcement was analyzed by Hall-Petch and Orowan model.更多还原