采用挤压铸造技术制备了体积分数为40%的SiC_p/2024Al复合材料,采用TEM对不同尺寸稳定化处理条件下复合材料的微观组织进行了观察,并探讨了尺寸稳定化热处理工艺对复合材料拉伸性能的影响.TEM观察表明:由于SiC颗粒与2024Al基体的热膨胀系数不同,热错配的作用使冷热循环处理后基体中的位错密度增加,为S'相的形成提供了有利的形核部位,促进了S'相的析出,这两种因素都有利于提高复合材料的强度.室温拉伸测试结果表明:零次冷热循环热处理后的SiC_p/2024Al复合材料拉伸强度比较好,两次冷热循环处理后复合材料的强度有所下降,但随着循环次数的增加,复合材料的强度逐渐增加;不同的冷热循环次数对于拉伸断裂方式和断口形貌无显著影响.
The composite of 40%Si_/2024 was fabricated by squeeze casting technology,and the effects of different dimensional stability treatments on its microstructure and mechanical properties were studied by SEM,TEM observation and tensile test machine.TEM observation shows that there exist high-density dislocations,which are caused by the mismatch of CTE between SiC particles and matrixes during thermal-cooling cycling treatment.Therefore,favorable locations are provided for the nucleation of S' phase,which accelerates the precipitation of S' phase.Both effects are beneficial for the increase of composites strength.The results of tensile tests show that SiC_p/2024Al samples without thermal-cooling cycle treatment have high tensile strength,while the strength is decreased after two cycles,and then with the increase of cycles,the strength of composites is increased gradually.Different methods of thermal-cooling cycling treatment have little effect on the fracture behavior and fractography.
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