Creep and Creep Fracture of Oxide Ceramics

微结构（颗粒大小、第二阶段等）对高温变形的影响，如蠕变和蠕变断裂已被研究用于某些氧化物陶瓷;具有且不具有跨粒度玻璃相位，可显示出精细颗粒的、稳定的四环氮基亚超塑性、β-孢子虫玻璃陶瓷和精细颗粒的、单相位多聚体（3Al_2O_3·2SiO_2）。通过压力解决方案，玻璃相位和玻璃陶瓷增强了蠕变应变率。However，他们是洞穴的起源，在谷物边界上进行微裂纹的结果。现代陶瓷通常有非常好的微结构，没有玻璃相位，有时在高温下显示高导电性（某些情况下的超塑性），并导致塑料成型的应用。在另一方面，这些陶瓷产品的抵抗力有限，以适应高温结构应用中的变形。许多人被认为在它的细粒度（1.5毫米）上具有很高的爬行抵抗力，并在爬行结构上具有很高的强度。在谷物大小的多块腿上，在谷物边界上捕捉到了这种增加的裂缝压力，被观察到在Y-TZP。“对Cavitation的启动的准则是很难确定的，而这是这项研究的下一步。

The effects of microstructures (grain size, second phase, etc) on high temperature deformation such as creep and creep fracture were studied for some oxide ceramics; magnesias with and without an intergranular glass phase, a fine-grained, yttria stabilized tetragonal zircoenia exhibiting superplasticity, a beta-spodumene glass ceramic and fine-grained, single phase mullite (3Al_2O_3・2SiO_2). Glass phases in the magnesia and the glass ceramic enhanced the creep strain rates by pressure solution. However, they were the origins of cavitation, resulting in microcracking at grain boundaries. Modern ceramics often have very fine microstructures without apparent glassy phases, thus show sometimes high ductility (superplasticity in some cases) at high temperatures, leading the application to plastic forming. On the other hand, these ceramics show limited resistance to deformation in high-temperature structural application. The mullite was shown to have high creep resistance in spite of its fine grain size (1.5 mum) and to have high strength in creep fracture. The increase in grain size of the mullite led to cavitation at grain boundaries and thus lowered the creep fracture stress, as observed in Y-TZP. The criterion for initiation of cavitation was difficult to determine, which is the next step of this study.