In-situ synthesis of alumina-matrix oxide/oxide composites and performance enhancement by multiple toughening

采用反应烧结的方法原位合成了六铝酸钡和氧化锆基增强铝基复合材料。原位合成的复合材料具有细长的六铝酸钡和等轴氧化锆颗粒的微观结构特征。具有拉长形貌的Ba-β-Al_2O_3相的形成可能归因于Ba离子沿基面的优先扩散。TZP或Y_2O_3的加入促进了复合材料的致密化和四方氧化锆的形成，这是由于在烧结过程中氧化铝和锆酸钡发生反应而产生的氧化钛向单斜氧化锆的扩散。由于裂纹偏转、裂纹桥联和氧化锆从四方相向单斜相转变等多种增韧作用，合成的氧化铝基复合材料具有较高的断裂韧性。

Alumina matrix composites reinforced with barium hexaluminate and zirconia were synthesized in situ through reactive sintering of alumina and barium zirconate powder mixtures. The in-situ synthesized composites exhibited a microstructural feature of the elongated barium hexaluminate and equiaxed zirconia particles. The formation of Ba-beta-Al2O3 phase with an elongated morphology is likely to be attributed to preferred diffusion of Ba cations along the basal planes. The incorporation of TZP or Y2O3 promotes densification of the composites and formation of tetragonal zirconia due to diffusion of yttria to monoclinic zirconia, which is generated through reaction between alumina and barium zirconate during sintering. The synthesized alumina matrix composites showed high fracture toughness, as a result of multiple toughening effects including crack deflection, crack bridging, and martensitic transformation of zirconia from tetragonal to monoclinic phases.