【作者】 苏畅；

【导师】 李建波； 陈先华；

【作者基本信息】 重庆大学 ， 材料科学与工程， 2022， 硕士

【摘要】 随着电子科学技术的快速发展,电子设备越来越多,其产生的电磁污染已经是一个不可避免的问题。电磁屏蔽是一种有效的保护措施,其重要性日益凸显,发展出高性能的屏蔽材料已成为重要的研究热点。镁合金作为一种电磁屏蔽材料,与传统金属材料相比,具有密度低、质量轻、比强度高的优势,在电磁屏蔽方面具有很高的应用潜力。然而普通商用镁合金的电磁屏蔽性能较低,需要进一步提升。同时,传统的镁合金耐热性能差,导致其制成的电磁屏蔽零部件在高温环境下无法满足特殊设备的使用要求,这严重制约了镁合金作为电磁屏蔽材料的发展。利用合金化的方法,可以改善镁合金的组织,生成不同类型的第二相,不仅有利于提升力学性能,还能增加合金中反射电磁波的界面,提高电磁屏蔽性能。因此,通过探索合金化对镁合金电磁屏蔽性能和力学性能的影响与内在机制,进一步提升镁合金的电磁屏蔽性能,改善镁合金的强度和耐热性能,开发出高性能电磁屏蔽镁合金材料。这对促进镁合金功能特性和力学性能一体化,推动镁的发展有重要意义。本文在Mg-Gd-Y合金成分的基础上分别添加Sn、Nd元素,通过改变元素含量制备出Mg-12Gd-3Y-x Sn合金和Mg-12Gd-3Y-x Nd合金。系统研究了元素种类和含量的变化对镁合金组织、力学性能、电磁屏蔽性能的影响。通过不同的热处理工艺和变形加工工艺来改善合金的电磁屏蔽性能和力学性能,分析组织与性能的关系,找到组织影响性能的机理,扩宽镁合金的应用范围。得到的主要研究结果如下:铸态Mg-12Gd-3Y-x Sn合金中主要存在α-Mg基体、Mg₂₄（Gd,Y）₅相和Mg₅（Gd,Y）相,添加Sn元素可以促进Mg₂Sn相的生成。合金的电磁屏蔽性能随着Sn元素的添加而提高,时效和轧制可使得合金的电磁屏蔽性能进一步提升,在1500 MHz时最高可达90 d B。Sn元素有利于细化挤压态合金的晶粒尺寸,提升合金的强度,改善合金的高温力学性能,其中Mg-12Gd-3Y-1.0Sn合金的晶粒尺寸最小,平均晶粒直径为1.5μm。时效过后Mg-12Gd-3Y-1.0Sn合金在常温下抗拉强度为476 MPa,屈服强度为319 MPa,在200℃、250℃时的抗拉强度分别为415 MPa和383 MPa。铸态Mg-12Gd-3Y-x Nd合金中主要存在α-Mg基体、Mg₂₄（Gd,Y）₅相和Mg₅（Gd,Y）相,添加Nd元素可以促进Mg₄₁Nd₅相的生成,同时Nd元素有利于降低Gd和Y元素在镁基体中的固溶度,使得第二相的数量增多。铸态合金的电磁屏蔽性能随着Nd元素的添加而提高。随着轧制压下量的增加,轧制态合金的电磁屏蔽性能逐渐提升,在1500 MHz时最高可达88 d B。Nd元素细化了挤压态合金的晶粒,其中Mg-12Gd-3Y-1.0Nd合金晶粒尺寸最小,平均晶粒直径为1.7μm。Nd元素提升了合金的强度,并有效降低了高温下合金强度的下降速度。挤压时效态Mg-12Gd-3Y-1.0Nd的性能最好,常温下抗拉强度和屈服强度分别为440 MPa、312 MPa,在200℃、250℃的抗拉强度则可分别达到405 MPa和382 MPa。更多还原

【Abstract】 As an electromagnetic shielding material,magnesium alloy has the advantages of low density,lightweight,and high specific strength compared with traditional metal materials.As a result,it has high application potential in electromagnetic shielding.However,the electromagnetic shielding performance of ordinary commercial magnesium alloys is low and needs to be further improved.At the same time,the traditional magnesium alloy has poor heat resistance,so the electromagnetic shielding parts made of it cannot meet the requirements of special equipment in a high-temperature environment.These shortcomings seriously restrict the development of magnesium alloys as electromagnetic shielding materials.Alloying can improve the structure of magnesium alloys and generate different types of second phases.It is not only beneficial to improve the mechanical properties but also increases the interface for reflecting electromagnetic waves in the alloy,thereby improving the electromagnetic shielding performance.Therefore,exploring the influence and internal mechanism of the electromagnetic shielding properties and mechanical properties of magnesium alloys by alloying is necessary.Improve the strength and heat resistance to develop high-performance magnesium alloys.It is of great significance to promote the integration of functional properties and mechanical properties to promote the development of magnesium alloys.Based on the composition of Mg-Gd-Y alloy,Sn and Nd are added respectively to prepare Mg-12Gd-3Y-x Sn and Mg-12Gd-3Y-x Nd alloys.The effects of Sn and Nd elements on the microstructure,mechanical properties,and electromagnetic shielding properties of magnesium alloys are systematically studied.At the same time,improve the electromagnetic shielding properties and mechanical properties of alloys through different heat treatment processes and deformation processing processes.Analyze the relationship between organization and performance,and explore how the organization affects performance.The main results are as follows:The as-cast Mg-12Gd-3Y-x Sn alloy mainly contains Mg₂₄（Gd,Y）₅ and Mg₅（Gd,Y）phases.Adding Sn element can promote the formation of the Mg₂Sn phase.The electromagnetic shielding performance of the alloy increases with the addition of the Sn element.And the electromagnetic shielding performance can be further improved by aging and rolling,which can reach up to 90 d B at 1500 MHz.Sn is beneficial to refine the grain size of the as-extruded alloy,enhance the strength of the alloy,and improve the high-temperature mechanical properties.Among them,the grain size of Mg-12Gd-3Y-1.0Sn alloy is the smallest.After aging,the tensile strength and yield strength of Mg-12Gd-3Y-1.0Sn alloy at room temperature are 476 MPa and 319 MPa,respectively.The tensile strengths of the alloys at 200°C and 250°C are 415 MPa and 383 MPa,respectively.The as-cast Mg-12Gd-3Y-x Nd alloy mainly contains Mg₂₄（Gd,Y）₅ and Mg₅（Gd,Y）phases.Adding Nd element can promote the formation of the Mg₄₁Nd₅ phase.Nd element is beneficial to reducing the solid solubility of Gd and Y elements in the magnesium matrix and promoting the increase of the second phase.The electromagnetic shielding performance of the as-cast alloy increases with the addition of the Nd element.With the increase in rolling reduction,the electromagnetic shielding performance of the alloy gradually improved,reaching a maximum value of 88 d B at 1500 MHz.The Nd element refines the grains of the extruded alloy,and the Mg-12Gd-3Y-1.0Nd alloy has the smallest grain size with an average grain diameter of 1.7μm.The Nd element can improve the strength of the alloy and inhibit the decreased rate of strength at high temperatures.Aged Mg-12Gd-3Y-1.0Nd has the best performance,and the tensile strength and yield strength at room temperature are 440 MPa and 312 MPa,respectively.The tensile strength at200°C and 250°C can reach 405 MPa and 382 MPa,respectively.更多还原