弱层成分对SiC/BN层状陶瓷阻力行为的影响

Influence of the component of weaklayer in the SiC/BN multilayered ceramics on its resistance behavior

利用压痕-强度法测定了不同弱层成分的SiC/BN层状陶瓷的阻力曲线行为,研究了BN弱层成分对SiC/BN层状陶瓷的阻力曲线行为的影响,并与SiC块体陶瓷作对比。结果表明:与SiC块体陶瓷相比,SiC/BN层状陶瓷具有更为明显的升值阻力曲线行为,且其阻力曲线行为受弱层成分的影响。其中,BN弱层中加入30%Al2O3的SiC/BN层状陶瓷显示出更为优越的抗裂纹扩展能力,其阻力曲线上升最陡,上升幅度最大。分析认为,这与它们不同的增韧机制和界面的结合状态有关。原位增韧是SiC块体陶瓷韧性提高的主要原因。裂纹遇到弱界面时发生偏转、分叉以及脱层等是层状陶瓷材料抗裂纹扩展能力提高的主要原因。而弱层成分又影响着裂纹的偏转,适当结合强度的界面有利于裂纹的偏转,结合强度太弱太强的界面都不利于裂纹的偏转。

The R-curve behavior of SiC/BN muhilayered ceramics with different components in the weak layer was evaluated using the indentation-strength-in-bending technique. The influence of the components of the weak layer on the R-curve of the SiC/BN multilayered ceramics was studied. The results show that a rising R-curve behavior is demonstrated for the laminated SiC/BN ceramics, and varies with the components of the weak layer. The SiC/BN multilayered ceramic with 30% Al2O3 addition in the weak layer has a steepest rising R-curve. The above results are attributed to their different toughening mechanisms and interracial coherent states. In-situ toughening is the main toughening mechanism for the monolithic SiC ceramics, while crack deflection, crack branching and crack delaminating at the SiC/BN weak interfaces for SiC/BN muhilayered ceramics. The components in the weak layer have an important effect on the crack deflection. The interface with a right coherent stress contributes to the crack deflection, and the interface with too weak or very strong coherent stress does harm to the crack deflection.