电磁屏蔽用Mg-Al-Zn合金的制备及组织性能研究

发布时间：2018-01-02 03:07

  本文关键词：电磁屏蔽用Mg-Al-Zn合金的制备及组织性能研究　出处：《西安工业大学》2016年硕士论文　论文类型：学位论文

  更多相关文章： Mg-Al-Zn合金 电磁屏蔽效能 β(Mg_(17)Al_(12))相 Al_2Y相 Al_4Ce相

【摘要】：本文以Mg-Al-Zn为基体,添加不同含量的Y和Ce元素,利用普通铸造法制备出具有优良电磁屏蔽效能的Mg-7Al-1 Zn-0.3Mn-0.9Y-0.6Ce新型镁合金。采用光学金相显微镜(OM)、扫描电子显微镜(SEM)、X射线测试仪(XRD)分析了所制备合金的微观组织,借助电导率仪、法兰同轴测试仪、布氏硬度仪、电子万能试验机等测试手段对所制备的合金进行电磁屏蔽性能和力学性能测试,研究了Y、Ce元素对合金微观组织、力学性能以及电磁屏蔽效能的影响,优化了合金的热处理工艺。合金中Y或Ce的添加量小于等于0.9wt%时,可显著改善合金的显微组织,第二相由较为粗大的枝晶网状逐渐变成弥散分布的块状和颗粒状,并有方块状的A12Y相、针状的Al4Ce相生成,对组织产生了明显的细化作用。但是当合金中Y或Ce的添加量超过0.9wt%时,会对合金组织产生粗化作用。复合添加Y和Ce对合金的显微组织及力学性能均有较大影响。在Al2Y、Al4Ce稀土相的析出强化、Y和Ce的细晶强化的共同作用,使合金的力学性能都得到显著提高,添加0.9wt%Y-0.6wt%Ce的铸态Mg-Al-Zn合金可得到较佳的力学性能,其抗拉强度达到218MPa,延伸率达到了10.5%,布氏硬度达到69.86HB。添加Y、Ce合金元素的合金可以获得良好的屏蔽效能,含0.9wt%Y、0.6wt%Ce时的合金其屏蔽效能为最佳,在测试频率(30-1500MHz)范围内、测试试样厚度为3mm时,最高屏蔽效能值在25MHz达到108.3dB,最低屏蔽效能值在1495MHz为87.13dB,满足军事领域60-120dB的要求。Y、Ce能够改善合金的电导率与电磁屏蔽性能主要依赖于合金中新形成的Al2Y、Al4Ce稀土相化合物,降低了A1在Mg基体中的固溶度,细化了合金组织,从而使合金的电导率与电磁屏蔽效能得到改善。添加过量的稀土元素的添加会使形成的化合物数量增多,晶粒尺寸减小,晶界增多；从而加大了对电子的散射作用,使合金的电导率下降,影响了电磁屏蔽效能。Mg-7Al-1Zn-0.3Mn-0.9Y-0.6Ce合金经固溶后,弥散分布的β-Mg17Al12相发生溶解。在时效时,β-Mg17Al12相又析出,当在200℃效温度时效时,连续的β-Mg17Al12析出相数量较150℃效温度时多；随着时间的延长,β-Mg17Al12析出相的数量增加,且连续析出相的比例增多,组织的这种变化使合金的抗拉强度、硬度值逐渐升高,但合金的延伸率有所降低；最终确定铸造合金最佳热处理工艺为固溶415℃×12h后在80℃温水淬火、时效200℃×12h,空冷。合金的抗拉强度提高到243MPa,布氏硬度达到75.2HB,延伸率为12.3%,达到了电控箱体材料的力学标准。
[Abstract]:In this paper, Y and ce elements with different contents were added in Mg-Al-Zn matrix. A new type of Mg-7Al-1 Zn-0.3Mn-0.9Y-0.6Ce magnesium alloy with excellent electromagnetic shielding efficiency was prepared by ordinary casting method. Optical metallographic microscope was used to fabricate the new magnesium alloy. The microstructure of the alloy was analyzed by means of scanning electron microscope (SEM), SEMU X ray tester (XRD) and Brinell hardness tester (Brinell hardness tester) with the help of conductivity meter, flange coaxial tester and Brinell hardness tester. The electromagnetic shielding properties and mechanical properties of the prepared alloys were tested by means of electronic universal testing machine. The effects of YCe on the microstructure, mechanical properties and electromagnetic shielding efficiency of the alloys were studied. The heat treatment process of the alloy was optimized. When the addition of Y or ce in the alloy was less than 0.9 wt%, the microstructure of the alloy could be improved significantly. The second phase was gradually changed from coarse dendritic network to distributed block and granular, with block A12Y phase and needle-like Al4Ce phase. But when the content of Y or ce in the alloy is more than 0.9 wt%. The composite addition of Y and ce has a great effect on the microstructure and mechanical properties of the alloy. The mechanical properties of Y and ce alloys have been greatly improved by the combined effect of fine grain strengthening. The mechanical properties of the as-cast Mg-Al-Zn alloy with 0.9wt and Y-0.6wt can be obtained. The tensile strength and elongation of the as-cast Mg-Al-Zn alloy are 218MPa and 10.5%, respectively. Brinell hardness reaches 69.86HB.The alloy with YCe alloy can obtain good shielding efficiency, and the alloy containing 0.9wt YCe 0.6wt has the best shielding efficiency. In the test frequency range of 30-1500 MHz, when the thickness of the test sample is 3 mm, the maximum shielding efficiency is 108.3 dB at 25 MHz. The minimum shielding efficiency is 87.13 dB at 1495 MHz, which meets the requirements of 60-120 dB in military field. Ce can improve the electrical conductivity and electromagnetic shielding performance of the alloy mainly depends on the newly formed Al _ 2Y _ 2O _ (4) ce rare earth phase compound, which reduces the solution of Al _ 1 in mg matrix. The structure of the alloy was refined, and the conductivity and electromagnetic shielding efficiency of the alloy were improved. The addition of excess rare earth elements would increase the number of the compounds formed, decrease the grain size and increase the grain boundary. Thus, the scattering of electrons was increased, the conductivity of the alloy decreased, and the electromagnetic shielding efficiency. Mg-7Al-1Zn-0.3Mn-0.9Y-0.6Ce alloy after solid solution. The dispersed 尾 -Mg17Al12 phase dissolves. During aging, the 尾 -Mg17Al12 phase precipitates again, and when aged at 200 鈩，

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