【作者】 胡强；

【导师】 揭小平；

【作者基本信息】 南昌大学 ， 材料加工工程， 2008， 硕士

【摘要】 颗粒增强镁基复合材料由于其密度低、比强度和比刚度高,同时还具有良好的耐高温性、耐冲击性和优良的减震性能等优点,引起了各国学者的广泛关注。本文采用AZ61镁合金作为基体;以SiC颗粒作为增强相,通过搅熔铸造法制备SiCP/AZ61复合材料。利用金相显微镜观察了搅拌铸造法中不同工艺参数的金相组织,分析了搅拌铸造工艺对复合材料微观组织的影响。研究了复合材料中SiC颗粒和AZ61基体合金的复合形成机理。利用拉伸试验机测试了不同工艺参数下SiCp/AZ61镁基复合材料的力学性能。在此基础上采用正交试验法对搅熔铸造法的工艺进行优化,获得了最佳的制备方案。利用机械动态热分析仪（DMA-Q800）测试了AZ61基体合金及搅熔铸造法制备SiC_p/AZ61镁基复合材料的阻尼性能和蠕变性能。通过研究AZ61基体合金和SiC_p/AZ61复合材料的内耗谱,分析应变振幅、频率和温度对AZ61基体合金及SiC_p/AZ61复合材料阻尼性能的影响。基于位错型阻尼机制和界面型阻尼机制的理论,深入分析了SiC_p/AZ61复合材料阻尼性能提高的原因。对室温阻尼-应变振幅的曲线研究表明,SiC颗粒的加入所引起的高密度的位错是室温下SiCp/AZ61复合材料阻尼性能提高的主要原因;并且曲线可以采用G-L位错钉扎模型给予很好的解释。对阻尼-温度-频率曲线的研究表明,高温情况下镁基复合材料阻尼性能提升可以归因于复合材料中大量界面的微滑移。通过研究恒温、恒载下,AZ61基体合金及搅熔铸造法制备的SiC_p/AZ61复合材料的蠕变曲线,可以发现:SiC_P/AZ61复合材料相对于AZ61基体合金,具有较短的初始蠕变阶段、较低的稳态蠕变速率（ε）和较少的总形变量,AZ61基体合金的抗蠕变性能在加入增强相SiC颗粒后得到提高。复合材料抗蠕变性能的提高,主要是因为SiC颗粒在晶界处取代了高温下容易软化的β相(Mg₁₇Al₁₂),SiC颗粒强的钉扎作用阻止了高温下晶界的交滑移和位错攀移的发生。更多还原

【Abstract】 Nowadays,the issue of Magnesium matrix composites has been came into the concern from the researcher’s attention all over the world ,as its low density, high intensity and rigidity, and as well as its excellent propertities such as high temperature resistance and high shocking resistance capability, and good absorbing quality. In this paper, SiCp/AZ61 composite was made by using the magnesium alloy as Matrix,SiC particulate as the enhanced phase,in addition,through three different stir casting technique（such as stirring in a fully liquid condition, stirring in a semi-solid condition, stirr-melting process ）.Moreover, using metallographic phase microscope to observe three different metallographic phase units from three different preparation technique in Stir casting, and the microstructural structure of SiCp/AZ61 composite affected by stir-casting process was analyzed. Forthemore,research on the formation about the theory of SiC particulates and AZ61 matrix of SiCp/AZ61 composite,Stirring-melt casting process was ascertained as a fitting preparing process of SiCp/AZ61 composite. The Mechanical Properties of SiCp/AZ61 magnesium Matrix composite was tested through eletron tensile testing machine with different processing parameters. And in this foudation, optimization result was made by Orthogonal experimental design to get the best fabricating process scheme.The damping property and creep property of matrix alloy AZ61 and SiCp/AZ61 composite prepared by means of stirring-melt casting process were measured by dynamic mechanical thermal analyses （DMA-Q800）. The dependence of the damping capacity of SiCp/AZ61 composite on strain amplitude, frequency and temperature has been analyzed by studying the internal friction spectrum of matrix and composite. On the basis of the interface damping and the dislocation damping, the reason of increasing of damping property on SiCp/AZ61 composite was construed. The results of damping-strain amplitude curve show that dislocation brought by SiC particles play an important role in the increasing of damping property of composites, which can be explained by G-L dislocation pinning theory.The results of damping-temperature-frequency curves show that the improving of damping property of composite in high temperature is due to so much minimal slip of interface in composite. The creep curves of matrix alloy and SiCp/AZ61 composites prepared by stirring-melt casting process at isothermal and were studied.It is found that compared to matrix alloy AZ61, the SiCp/AZ61 composite has shorter initial creep time, lower state-creep velocity and little total transformation. The creeping resistance of Matrix alloy AZ61 was enhaced when mixed with enhanced phase-SiC particles. It is because that the SiC particles substitutes Mg₁₇Al₁₂ phase on grain boundary which will be easliy intenerated at high temperature. The pinning effect of SiC particles prevent dislocation and slipage of grain boundary at high temperature.更多还原