Basic Research on the Fracture Phenomena of Ceramics with Particle Dispersion

本研究旨在了解不同微观组织变量对含第二相分散体陶瓷增韧和缓慢裂纹扩展机制的影响。采用模型两相复合材料进行研究。采用热压法制备了分散颗粒热膨胀系数大于基体热膨胀系数的玻璃基/氧化铝颗粒复合材料和玻璃基/氧化镁颗粒复合材料，并对其增韧机理进行了研究。在这两种复合体系中，断裂韧性都随着第二相颗粒的增加而增加，但韧性行为在很大程度上取决于颗粒尺寸、颗粒形态和组成相之间热膨胀失配程度。在研究的复合材料断裂过程中，认为裂纹弯曲和裂纹挠曲机制是主要的增韧机制。此外，对于满足热膨胀失配引起的自发微裂纹形成条件的复合材料体系，微裂纹机制可能有助于韧性的提高。研究了分散颗粒热膨胀系数小于基体热膨胀系数的玻璃基/氧化铝颗粒复合材料和分散颗粒热膨胀系数小于基体热膨胀系数的玻璃基/二氧化硅颗粒复合材料的微裂纹增韧特性。比较了玻璃-氧化铝复合材料与仅存在热膨胀失配的玻璃-二氧化硅复合材料的韧性行为。获得了断裂过程中微裂纹发生条件的基本信息。研究了具有颗粒结构的相分离硼酸铅玻璃压痕微裂纹的缓慢裂纹扩展特性。在试样的抛光表面形成维氏压痕，并在卸载后一段时间内监测残余应力场下诱导裂纹的扩展情况。从微观结构因素对实验结果进行了解释，阐明了湿环境下慢生长过程中裂纹-颗粒相互作用机制。少

The present study was undertaken to obtain a basic information on the effect of various microstructural variables on the toughening and slow crack growth mechanisms in ceramics containing second-phase dispersions. Model two-phase composites were used for study.Glass matrix/alumina particle and glass matrix/magnesia particle composites where thermal expansion coefficient of dispersed particles is greater than that of a matrix were prepared by hotpressing and toughening mechanisms in these composites were investigated. In both composite systems, fracture toughness were found to increase with increasing second-phase particles, but toughness behavior depends strongly on particle size, particle morphology and degree of thermal expansion mismatch between constituent phases. During fracture process of the composites studied, crack bowing and crack deflection mechanisms were considered to act as major toughening mechanisms. In addition, for the composite systems where a condition for spontaneo … More us microcrak formation due to thermal expansion mismatch is satisfied, microcracking mechanism may contribute to toughness increase.Glass matrix/alumina particle and glass matrix/silica particle composites where thermal expansion coefficient of dispersed particles is smaller than that of a matrix were investigated with special reference to microcrack toughening. Toughness behavior of glass-alumina composites were compared with that of glass-silica composites in which only thermal expansion mismatch exists. A basic information on the condition for the occurrence of microcracking mechanism during fracture was obtained.The slow crack growth characteristics of indentation-induced microcracks in phase-separated lead borate glasses with particulate microstructure were investigated. Vickers indentation were made on the polished surface of the specimens and the extension of induced crak under residual stress field was monitored over a time after unloading. Experimental results were interpreted in terms of microstructural factors and crack-particle interaction mechanisms during slow growth wtage under moist environment were clarified. Less