【作者】 邹晓强；

【导师】 刘生发； 黄尚宇；

【作者基本信息】 武汉理工大学 ， 材料加工工程， 2006， 硕士

【摘要】 镁合金具有密度小、比强度和比刚度高、阻尼性能好及电磁屏蔽等优点，在汽车、电子等领域得到越来越广泛的应用。 本文以目前使用最广泛的AZ91镁合金为对象，研究了电磁搅拌和合金元素Ce、Sr、Ca的复合作用对其显微组织及性能的影响，并对其组织细化机理进行了探讨。采用金相显微镜、扫描电子显微镜和X射线衍射仪等对合金的组织结构进行了观察与分析，测量了合金晶粒尺寸及硬度值，并对两者之间的关系进行了回归分析。结果表明：电磁搅拌和三种合金元素的复合作用都具有细化铸态AZ91镁合金晶粒的作用。当电磁搅拌电压一定(100V)并加入0.2％～0.8％Ce，发现加入0.8％Ce的合金晶粒尺寸最小，硬度值最大。加入0.1％～0.3％Sr也可细化合金组织，Sr加入量为0.2％时，晶粒尺寸最小，硬度值达到最大。加入0.1％～0.3％Ca同样能细化合金晶粒，Ca加入量为0.2％时，晶粒尺寸最小。回归分析表明，晶粒尺寸与硬度之间的关系符合Hall-petch公式。此外，利用差热分析探讨了电磁搅拌和Ce、Sr、Ca对AZ91镁合金的晶粒细化机制。 利用静态失重法、X射线衍射仪等手段研究了电磁搅拌和Ce、Sr、Ca复合对AZ91镁合金在3.5％NaCl水溶液中的腐蚀规律。结果表明，电磁搅拌加0.2％～0.8％Ce可显著降低合金的腐蚀速度，其中电磁搅拌电压为100V，加入0.5％Ce对合金的腐蚀速度降低幅度最大。电磁搅拌(电压100V)加0.1％～0.3％Sr可改善合金的腐蚀性能，其作用远不及稀土元素Ce。Ca(0.1％～0.3％)元素的加入对合金的腐蚀性能产生不利影响。更多还原

【Abstract】 The application for magnesium alloys in the automotive, electronics and communication industries has been expanding at a high rate due to their low density, high strength-to-weigh, rigidity-to-weigh ratio, good damping capacity and good electromagnetic shielding properties.In this thesis, the effect of combined electromagnetic stirring and Ce、Sr、Ca on microstructure and corrosion performance for AZ91 magnesium alloy, which is the most widely used magnesium alloy, was studied. In addition, grain refinement mechanism was discussed. Microstructures of alloys were observed and studied by means of optical microscope(OM)、scanning electron microscope(SEM)、differential thermal analyzer(DTA) and X-ray diffract analyzer(XRD)and so on. Grain size and alloy hardness was measured, the linear relation was presented between grain size and hardness by regression analysis. The experimental results showed that the effect of combined electromagnetic stirring and Ce、Sr、Ca could all refine grain size. When electromagnetic stirring voltage is 100V, 0.2%～0.8%Ce added to AZ91, 0.8%Ce addition could get the finest grain and maximum hardness value. 0.1%～0.3%Sr addition to AZ91 could refine grains too. 0.2%Sr addition could get the finest grain and maximum hardness value. 0.1%～0.3%Ca addition to AZ91 could also refine grains. 0.2%Ca added to AZ91 could get the finest grain. Regression analysis showed that the relationship between grain size and hardness is in agreement with Hall-petch expression. Besides, grain refinement mechanism of combined electromagnetic stirring and Ce、Sr、Ca on AZ91 was discussed by differential thermal analyzer.The effect of combined electromagnetic stirring and Ce、Sr、Ca on the corrosion property and corrosion mechanism in 3.5%NaCl solution were studied by means of static weight-loss test and X-ray diffract analyzer. The experimental results showed that electromagnetic stirring and 0.2%～0.8%Ce could reduce corrosion rate remarkably. When electromagnetic stirring voltage is 100V, 0.5%Ce addition could get the minimum corrosion rate. Electromagnetic stirring and 0.1%～0.3%Sr could improve corrosion property too, but the effect is inferior to Ce. 0.1%～0.3%Ca更多还原