Study On Toughening-strengthening Mechanisms And Thermal Shock Resistance Of Advanced Ceramic Materials

Residual thermal stress, toughening-strengthening mechanisms and thermal shock resistance of nanocomposite ceramic tool materials as well as thermal shock resistance of functionally gradient materials with different shapes were investigated as the main content of this thesis, which are of great importance for the design and development of functionally gradient ceramic tool materials and nanocompsite ceramic tool materials with high toughening and strengthening as well as high thermal shock resistance.The theoretical model for studying the micro residual thermal stresses in nanocomposite ceramic tool material was established, by which the values and the distribution of residual thermal stresses induced by the nano inclusions were obtained. The effect of plasticity deformation on residual thermal stress was investigated. The residual thermal stresses in the intra and the inter granular of nanocompsite ceramic tool materials were analyzed.The toughening and strengthening mechanisms of nanocompsite ceramic tool materials were thoroughly researched. The contributions of several toughening and strengthening mechanisms were analyzed. The optimal content and critical size formulas of nano granule were educed. The relation between nanocompsite ceramic strength and residual thermal stresses was established. The microstructure of ceramic composite material Al₂O₃ and Si₃N₄ reinforced by TiC_nano particles as well as the toughening and strengthening mechanisms were analyzed in detail.The critical temperature difference of nanocompsite ceramic materials was researched. The relationship between thermal shock resistance and toughening and nano particle size of nanocompsite ceramic materials was analyzed. The thermal shock resistances of Al₂O₃/TiC and Si₃N₄/TiC nanocomposite ceramic tool materials were researched.Based on the critical stress fracture theory of ceramic materials, the thermal shock behaviors of functionally gradient infinite ceramic cylinder and functionally gradient ceramic sphere were investigated respectively by the calculations of transient...