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采用挤压铸造法制备了Al2O3p/40Cr表层复合材料,研究了复合材料在热震过程中裂纹萌生和扩展的机理。复合层厚度为5mm,Al2O3颗粒体积分数为56%;热震试验采用650℃保温5min、20℃水冷,反复循环。结果表明,在弱机械结合情况下,由于空气中的氧气和铁生成的氧化物与基体在热膨胀系数和弹性性能上不匹配,裂纹首先在氧化层中萌生,随着氧化层厚度增加,会加速裂纹的生长;从各个方向生长的裂纹相遇时会搭接在一起,形成比较大的宏观裂纹。此机理与WC等其他颗粒增强复合材料的热震失效机理有着显著差异。热震15次后,试验材料在复合层和基材的宏观界面出现大裂纹。
The Al2O3p / 40Cr surface composites were prepared by squeeze casting method and the mechanism of crack initiation and propagation during thermal shock was investigated. The thickness of the composite layer is 5mm and the volume fraction of Al2O3 particles is 56%. The thermal shock test is carried out by using 650 ℃ for 5min and 20 ℃ for water cooling. The results show that in the case of weak mechanical bonding, cracks originate in the oxide layer due to the mismatch between the thermal expansion coefficient and the elastic properties of oxygen and iron in the air and the matrix. As the oxide layer thickness increases, it accelerates Crack growth; crack growth in all directions will meet when the encounter lap, the formation of larger macroscopic cracks. This mechanism is significantly different from the thermal shock failure mechanism of WC and other particulate reinforced composites. Thermal shock 15 times, the test material in the composite layer and the substrate macroscopic interface cracks.