摘要:
利用压痕2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。
Abstract:
The R-curve behavior of SiC/ BN multilayered ceramics with different component s in the weak layer wasevaluated using the indentation-st rength-in-bending technique. The influence of the component s of the weak layer onthe R-curve of the SiC/ BN multilayered ceramics was studied. The results show that a rising R-curve behavior isdemonst rated for the laminated SiC/ BN ceramics , and varies with the component s of the weak layer. The SiC/ BNmultilayered ceramic with 30 % Al2O3 addition in the weak layer has a steepest rising R-curve. The above result s areatt ributed to their different toughening mechanisms and interfacial coherent states. I n-si tu toughening is the maintoughening mechanism for the monolithic SiC ceramics , while crack deflection , crack branching and crack delaminating at the SiC/ BN weak interfaces for SiC/ BN multilayered ceramics. The component s in the weak layer have animportant effect on the crack deflection. The interface with a right coherent st ress cont ributes to the crack deflection , and the interface with too weak or very st rong coherent stress does harm to the crack deflection.
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