【作者】 韩媛媛；

【导师】 李凤珍；

【作者基本信息】 哈尔滨理工大学 ， 材料学， 2004， 硕士

【摘要】 本文建模用材料为挤压铸造方法制备的Al2O3P/2024Al 复合材料和SiCP/2024Al复合材料。利用温度自动测试系统对复合材料试样在固溶淬火以及各种不同冷热循环过程中的温度随时间变化情况进行了测试;通过扫描电子显微镜(SEM)和透射电子显微镜(TEM)等手段对复合材料的显微组织进行观察;利用万能拉伸试验机和热效应自动分析仪测试了SiCP/2024Al复合材料在不同稳定化工艺处理后的微屈服强度和热循环条件下的尺寸稳定性;利用Marc有限元软件建立了热应力分析的平面几何模型,并且对复合材料热处理过程的热应力进行分析,讨论了体积分数、颗粒形状以及稳定化处理工艺对热应力的影响。热残余应力是材料尺寸稳定性的重要影响因素,本文利用有限元法对复合材料稳定化处理过程的热应力进行了数值模拟。模拟结果显示,热处理过程中,由颗粒和基体之间的热错配所造成的微观应力超过基体合金的屈服强度,致使基体发生塑性变形。颗粒体积分数低的Al2O3P/2024Al复合材料的热残余应力场分布比较均匀,随着颗粒体积分数的增加,Al2O3P/2024Al复合材料的局部热残余应力场有相互叠加的现象。球形颗粒和基体的界面附近的热残余应力场分布相对比较均匀;尖角形颗粒和基体的界面附近的热残余应力分布很不均匀,颗粒的尖角处有非常明显的残余应力和应变集中现象。冷热循环可以降低复合材料中的热残余应力,使颗粒尖角处应力集中的现象得到明显改善;冷热循环的下限温度越低,降低热残余应力效果越显著,并且,第一次循环对降低热残余应力起主导作用。不同的稳定化处理工艺对SiCP/2024Al复合材料微屈服强度和热循环条件下的尺寸稳定性的影响不同。在冷热循环工艺处理过程中,上下限温差越大,残余应力释放的越充分,SiCP/2024Al复合材料在无负载热循环条件下的尺寸稳定性越好,与数值模拟结果相吻合。改善SiCP/2024Al复合材料在无负载热循环条件下尺寸稳定性的最佳工艺为160℃~-196℃冷热循环工艺。在负载条件下,随着冷热循环温差的增大,SiCP/2024Al复合材料的微屈服强度呈下降的趋势。更多还原

【Abstract】 The Al2O3P/2024Al composites and SiCP/2024Al composites used in the model were fabricated by squeeze casting method. The temperature changing with the time during quenching and different thermal-cooling cycling treatment was measured by temperature meter. The microstructure was observed by scan electron microscopy (SEM) and transmission electron microscopy (TEM). The micro-yield strength after different stabilized treatment and dimensional stability in thermal cycling conditions of SiCP/2024Al composites were measured by tension test and dilatometer. The planimetric model of composites for thermal stress analysis was established by Marc finite element software. Thermal stress of the composites during different heat treatments was analyzed by Marc software. The effect of volume fraction, particle shape and stabilized treatment technology on the thermal residual stress in the composites was investigated. The thermal residual stress was the important factor of the composites dimension stability. Thermal stress of the composites during stabilized treatment was numerically simulated by finite element method. The result showed that during heat treatment the microstress caused by the thermal mismatch between particle and the matrix. When the microstress was higher than the yield strength of the matrix the matrix would produce plastic deformation. The thermal residual stress of low volume fraction Al2O3P/2024Al composites was found more even. With the volume increased, part of thermal residual stress in composites began to lap each other. The thermal stress field nearing the particle-matrix interface distributed evenly due to the global particles. The thermal stress field nearing the particle-matrix interface distributed unevenly due to the angle particles. There were thermal stress and plastic strain concentration near the particle corner obviously. The thermal residual stress of composites was decreased and the thermal stress concentration near the particle corner was also decreased evidently after thermal-cooling cycling treatment. The <WP=7>lower the lower limit temperature was the smaller thermal residual stress was. The first cycling played the leading role.The micro-yield strength and dimensional stability in thermal-cycling conditions of SiCP/2024Al composite were affected greatly by different dimensional stabilizing techniques. In thermal-cooling cycling, with difference in temperature increasing, the long range residual stress relieved easily, the dimensional stability in thermal-cycling conditions became better, which was accordance with the simulated result. The best technology improving the dimensional stability of SiCP/2024Al composites under no load condition was the technique of 160℃~-196℃ cycling. Under load condition micro-yield strength of SiCP/2024Al composites decreased with difference in temperature increasing.更多还原