R-CURVE BEHAVIOR AND THERMAL SHOCK RESISTANCE FOR Al2O3 CERAMIC MATRIX COMPOSITES
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摘要: 采用压痕-弯曲强度法获得了Al2O3-SiCW和Al2O3-TiCP陶瓷基复合材料的裂纹扩展阻力曲线(R-曲线),并测试了材料的抗热震性能,分析了材料的阻力曲线行为与其抗热震性能之间的内在联系。结果表明:材料的阻力曲线行为与抗热震性之间存在明显的相关性。热震引起材料强度的下降幅度与其阻力曲线的陡峭程度及上升幅度有关。阻力曲线越陡峭,上升幅度越大,抗热震性也越好。其中Al2O3-SiCW复合材料显示出更为优越的抗裂纹扩展能力与抗热震性能。扫描电镜观察及理论分析显示:晶须的拔出与桥联补强增韧机制是产生这一现象的主要原因。Abstract: The crack growth resistance behaviors(R-curve ) of Al2O3-SiCW and Al2O3-TiCP ceramic matrix composites were determined by the indentation-strength method. The properties of the thermal shock resistance of the two materials were also estimated. The relationship between the R-curve and the thermal shock resistance of the materials was discussed. The properties of the thermal shock resistance increased with the increasing steepness of the R-curve gradient. Both materials exhibited rising R-curve behavior and improved thermal shock resistance. The Al2O3-SiCW composite showed better damage tolerance and higher thermal shock resistance than Al2O3-TiCP composites. SEM observation and theoretical analysis indicate that these phenomena can be attributed mainly to the principle toughening mechanism of pull-out and bridging of the SiC whiskers.
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