【作者】 徐进；

【导师】 宋玉泉；

【作者基本信息】 吉林大学 ， 材料加工工程， 2005， 硕士

【摘要】 超塑性是具有点阵结构的材料的普遍潜在属性,是材料变形失稳后能重新建立起的稳定的变形过程,其微观物理过程主要是晶界行为,晶界的滑移、迁移和移位。超塑性的实现是材料的内在条件和外在条件相协调的结果。先进的超塑材料,主要包括陶瓷及陶瓷基复合材料、金属基复合材料、金属间化合物、机械合金化合物、功能材料、地质材料、复合材料等。 结构陶瓷具有高强、高韧、低密度、高硬和耐高温抗蠕变、耐磨损、耐腐蚀和化学稳定性好等优异的性能,在电子、机械、冶金、化工等部门得到了广泛的应用,并在宇宙开发、能源技术、海洋技术、航空航天等领域应用前景也愈来愈广阔,已逐步成为尖端技术不可缺少的关键材料。利用结构陶瓷在高温下具有的超塑性进行成形加工是实现复杂形状零件近净成形的重要手段。 结构陶瓷按组分分类,可分为氧化物陶瓷、氮化物陶瓷、碳化物陶瓷等。氧化物陶瓷主要包括氧化铝、氧化锆和莫来石等,原子间主要是以离子键结合,因此具有优异的室温机械性能,高硬度和耐化学腐蚀性。氧化物陶瓷最突出优点是不存在氧化问题,原料价格低廉,生产工艺简单。氮化物陶瓷和碳化物陶瓷的原子间主要是以共价键结合在一起,因而具有较高的硬度、模量、蠕变抗力,并且能把这些性能的大部分保持到高温,这是氧化物陶瓷无法比拟的。但它们的烧结非常困难,生产成本一般比氧化物陶瓷高。 结构陶瓷是由结构比较复杂的离子键或共价键晶体组成的多晶体,离子键的静电作用和共价键的明显方向性,使得陶瓷材料难以满足产生滑移所要求的几何条件和静电条件,滑移系统很少,位错产生和运动很困难,而且陶瓷材料有沿晶界分离的倾向,导致陶瓷材料的本征脆性,加工性能非常差。超塑性加工,包括超塑性成型、连接和烧结锻造等,为结构陶瓷的加工成型提供了可行的途径。本文目的是为后续的结构陶瓷的超塑性研究做前期工作,使超塑性研究的新领域——硬脆性结构材料的研究得以延更多还原

【Abstract】 Superplasticity is the general potential property of materials of lattice structure. It’s a process that materials establish a stable deformation process after they are deformed and become instability. It’s mostly a boundary behavior, i.e. boundary gliding, transferring and shifting occurred as a microcosmic physical behavior. Realization of superplasticity is the result of accomodation between intrinsic and extrinsic qualification of material. Ceramic and ceramic-base-composite, metal-base-composite, intermetallic compounds, mechanical-alloy-compounds, functional materials, geology materials, and composite materials et al, are all advanced materials of superplasticity。The performance of structural ceramics is excellent. Its intensity, tenacity, rigidity, chemistry stability are very superior and its density is lower. The structural ceramics is also able to endure high temperature, abrasion, corrosion, and anti-creep. It is widely used in the field of electronical, mechanical, metallurgical, chemical. And the foreground of applications in the field of cosmic exploitation, technology of energy sources and ocean, aviation and spaceflight are wider increasingly. Step by step, it become the key-material of high-tech which is indispensable. Using the superplasticity of structural ceramics in high temperature processing deformation is the important measurement in the field of realizing the almost-net-deformation of complex shape part.Classified the structural ceramics by component, it is composed of oxide-ceramics, nitride-ceramics, carbide-ceramics, et al. Oxide-ceramics mainly includes alumina, zirconia, et al. Its atoms are almost linked with ion bond. Therefore it is provided with good mechanism performance in room temperature, high rigidity, anti-chemistry-corrosion. No oxidation is the outstanding merit of oxide-ceramics. So the raw material is cheap, andmanufacture of technics is easy. Since the atoms of nitride-ceramics and carbide-ceramics are linked with covalent bonds, the ceramics has anti-creep, high rigidity and module. And they can hold most of the good performance till high temperature. Compared with oxide-ceramics, this characteristic is very excellent. But the sintering of nitride-ceramics and carbide-ceramics is very difficult. So their yielding costs are higher than oxide-ceramic.Structural ceramics is polycrystal, which is made up of ion bonds or covalent bond with complex structure. With the static action of ion bonds and the obvious orientation nature of covalent bond, ceramics cannot satisfy the qualification of geometry and static which is required in causing slip. The slip system is lack. The creation and movement of dislocation are difficult. And ceramics tends to separate along crystal boundary. All of above induce the inbeing brittleness, which causes the poor processing ability. Superplastic processing, including superplastic forming, juncture, sintering, forging, et al, provides feasible approach to process the structural ceramics. To extending the fresh field of superplastic research in rigidity and brittleness structural material, the aim of this paper is the prophase work of superplastic research in structural ceramics latter.In principle, the superplasticity of structural ceramics can be separated into structure superplasticity and phase transformation superplasticity. In the research of structure superplasticity, fined grain superplasticity has been studied much. Most of the conclusion about ceramics superplasticity is obtained in fined structure, and all the superplasticity, which mentioned in this dissertation belong to this.The primary immanent factors affected the fined grain ceramics superplasticity is the size of grain and property of grain boundary. The finer size of grain, the more phase of grain boundary, the easier sliding of grain boundary, and the higher representation extension ratio. The external factors include deformation temperature and strain speed. When temperature rises up, rheo-stress comes down. But it is wrong that the higher temperature, the large extension ratio. At a certain temperature, the maximum will appearance. The deformation rate and deformation temperature restrict each other. There isdifferent optimal deformation rate at different temperature. Simultaneity, there is different optimal deformation temperature with different deformation rate. Superplastic deformation will produce strain which makes grain grow up. When the deformation increases, the size of grain largen, too.There is following same point in structure superplasticity between structural ceramics and metal alloy: 1) strong ability of crystal lattice strain; 2) equal axes shape of grain with small size; 3) stable structure in the deformation term, that is, the size and shape of grain are stable; 4) behave good superplasticity in certain range of strain rate and temperature; 5) the phenomena of grain boundary sliding, grain growing up with strain reinforcing, cavitation between grain.In the process of superplastic deformation, grain boundary sliding is a accepted deformation mechanism. The difference between all kinds of superplastic theory model mainly lies with the different detail of stress centralize caused by corresponding grain boundary sliding. Owing to immanent strong covalent bond and the orientation of bond in ceramics, it could be predicted that, dislocation sliding with relationship with accommodation in ceramic is less effective than diffusion stress.Although the vitreous phase between is not the necessary condition which makes ceramics superplastic, the existence of vitreous phase can improve the superplasticity of structural ceramics remarkably, such as reduce superplastic temperature and deformation stress, increase strain rate, enhance diffuse course of superplastic ceramics and deformation ratio. Notwithstanding, in the course of ceramics superplastic tension, it gained the large extension ratio yet.This dissertation entirely summarizes the research actuality and developing tends of structural ceramics domestic and overseas, sums up the preparation methods of oxide-ceramics, nitride-ceramics, carbide-ceramics, vitreous-ceramics, and expatiate the applications of structural ceramics. Besides, it contrasts and analyzes the experimental procedures and results of superplasticity on oxide-ceramics, obtaining the difference on superplasticity between these oxide-ceramics, and bringing forward the direction for superplastic research for the future. It can be regarded as a background and更多还原