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摘要本论文以AZ31B镁合金和6061铝合金为研究对象，利用真空扩散焊对镁铝异种金属的焊接进行研究，并对以铜箔作为中间层的真空扩散焊进行了探索性试验。通过工艺参数对接头微观组织及力学性能的影响k，并利用光学显微镜(OM)、扫描电镜(SEM)、能谱(EDX)对接头的组织结构进行了分析，得到了合理的工艺规范和一定强度的镁铝异种金属真空扩散焊接头。
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镁铝直接真空扩散焊试验结果表明：Mg/Al异种材料真空真空扩散焊在加热温度为440℃,压力强度150 MPa,保温时间30min时能得到结合强度最高为33 MPa的真空扩散焊接头。微观组织分析表明，真空扩散焊界面过渡区形成了致密的新相化合物层,随着焊接温度的升高，镁铝真空真空扩散焊的界面过渡区越来越宽，扩散区生成的新相化合物越来越清晰，靠近铝侧出现树枝状条带区，由Mg2Al3和Mg17Al12两种镁铝系金属间化合物组成。断口形貌呈银白色，并伴有一定暗灰色的区域。银白色的断面是界面区的组织残留物，界面区组织残留物呈现树枝状的细小纹理，断口为以解理断裂为主并伴有脆性的混合型断口。
铜中间层镁铝真空扩散焊试验结果表明：Mg/Al异种材料真空真空扩散焊在加热温度为530℃,压力强度10 MPa,保温时间20min时能得到焊缝结合良好、扩散层平直、厚度均匀且较薄，无夹杂、气孔和未焊合等缺陷的接头；接头界面区由Cu/Mg扩散层、铜层、Cu/Al扩散层组成。Cu/Mg扩散层和Cu/Al扩散层显微硬度明显升高且同一扩散区的不同位置硬度存在变化，说明扩散区不同位置生成了不同种类的金属间化合物。6621
关键词 镁合金 铝合金 铜箔中间层 真空扩散焊 异种金属焊接 金属间化合物
毕业设计说明书（论文）外文摘要
Title Vacuum diffusion welding of dissimilar metals aluminum and magnesium Experimental Studies
Abstract
This paper use AZ31B magnesium alloy and 6061 aluminum as the research object, the use of the hot pressure welding of Mg-Al dissimilar metals was exploratory test. Through the research of the middle layer of copper and process parameters influence on the microstructure and mechanical properties of the joint, reasonable technical specifications and a certain intensity of Mg-Al dissimilar metal hot pressure welded joints were got.
The maximum bond strength for 33MPa in the Mg-Al direct hot pressure welded joint were got in heating temperature at 440℃, the pressure strength of 150Mpa and holding time of 30min. A dense layer of new phase compounds was formed in the interfacial transition zone in the pressure welding. With the rising of heating temperature, the interfacial transition zone gets more and more wide, and the new phase compounds generated in the diffusion zone has become increasingly clear. The dendritic band are appeared close to the aluminum side of the interfacial transition zone was formed with Mg2Al3 and Mg17Al12 both Mg-Al intermetallic. The composition of the fracture is to cleavage based, and accompanied by mixed brittle fracture.
The Mg-Al dissimilar metals vacuum diffusion welding with intermediate layer of copper got a good welded and less defect joint in the heating temperature of 530℃, pressure strength of 10Mpa and holding time of 20min. Interface region of welded joints was formed by the Al-Cu diffusion layer, unreacted copper layer, Zn-Mg reaction diffusion layer.The microhardness
Of Al-Cu diffusion layer and Zn-Mg reaction diffusion layer are significantly higher.The hardness in the same diffusion layer is different in different regions.This phenomenon explans that there are different intermetallic compounds in different regions.