高温等静压后处理液相烧结SiC陶瓷的强化与增韧机理

研究了高温等静压（ＨＩＰ）后处理对液相烧结ＳｉＣ陶瓷的强化与增韧机理。通过讨论ＨＩＰ后处理对材料显微结构与力学性能的影响，建立了实验模型，深入分析了ＨＩＰ氮化后处理通过中，起主导作用的物理化学过程，并将此过程分为Ｎ２的扩散、表面氮化反应及进一步的致密化三个阶段。结果表明，ＨＩＰ后处理通过受液相烧结ＳｉＣ陶瓷显微结构的影响非常显著，当ＳｉＣ的液相烧结温度较低，晶粒尺寸较小时，将有利于Ｎ２沿ＳｉＣ晶界

STRENGTHENING AND TOUGHENING MECHANISM OF POST-HOT ISOSTATIC PRESSING OF LIQUID PHASE SINTERED SiC

The strengthening and toughening mechanism of liquid phase sintered SiC followed by post-hot isostatic pressing(HIP)was studied. Based on the analysis of the microstructure and mechanical properties of SiC by post-HIP treatment, the experimental model is proposed and the dominant physico-chemical process during N 2-HIP treatment is discussed. The HIP nitridation process is divided into three stages, the diffusion of N 2,surface nitridation reaction and further densification. The results indicate that post-HIP treatment is affected by the microstructure of liquid phase sintered SiC significantly. When the sintering temperature is relatively low and the grain size is small, it will benefit to the diffusion of N 2 along SiC grain boundaries, promote the reaction between SiC and N 2,enhance the sliding of SiC grains along grain boundaries and rearrangement of grains, so that the effects of post-HIP treatment are strengthened. The strengthening and toughening mechanism of post-HIP treated liquid phase sintered SiC can be ascribed to:(1)the formation of dense and homogeneous microstructure; (2) the elimination of open pores and surface defects; (3) the production of surface compressive stress. As a result, the bending strength and fracture toughness are increased.