摘要稀土镁合金如今作为正在迅速崛起的金属材料，在工业上有着巨大的发展前景。围绕着这一背景，本文综述了稀土镁合金国内外的研究现状，以及稀土镁合金NZ30K激光焊接的根本原理和组织特点。本次试验运用的是对4mm厚的NZ30K稀土镁合金试板进行的激光焊接，在焊后并分析了不同的焊接工艺参数对焊接接头焊缝成形的影响和焊接接头各个区域的显微组织的形成机理，除此之外还对焊接接头的拉伸性能和显微硬度进行了测试，并且分析了在不同的工艺参数条件下的影响。试验结果表明：在焊接参数 （1。4kW焊接功率和1。2m/min 的焊接速度）下，能得到了良好的焊接接头。稀土镁合金焊缝的抗拉强度不是很高，大概是母材的80%，所以NZ30K接头性能一般。金相试验表明，激光功率对于NZ30K焊缝反面熔宽影响比较大,功率越大，反面熔宽也越大； 而焊接速度对焊缝表面熔宽影响比较显著，速度变大，表面熔宽也变大。激光焊接离焦量, 正面保护气流量和背面保护气体流量的变化会引起焊缝的背面熔宽变化。在稀土镁合金的显微组织方面，靠近热影响区的焊缝是柱状晶，焊缝中心主要是等轴晶，焊缝区的晶粒明显比热影响区晶粒致密，但是热影响区的晶粒比焊缝区要大。86153

毕业论文关键词：稀土镁合金；NZ30K；激光焊接；微观组织；接头力学性能

Abstract Rare earth magnesium alloys are now being used as the rapid rise of metallic materials, In the industry has a huge development prospects。 Around this background, This paper summarizes the research status of rare earth magnesium alloy at home and abroad, and the basic principle and characteristics of laser welding, The welding process of NZ30K rare earth magnesium alloy with 4 mm thickness was studied by laser welding, After welding, the influence of different welding parameters on the weld formation and the microstructure of the welded joint are analyzed, and the structure of the energy spectrum analysis and XRD test, At the same time, the tensile properties and microhardness of the joints were tested。 Test results show that, in this paper, the welding parameters (1。4kW and 1。2m/min welding speed), all obtained good welding joints。 The tensile strength of the rare earth magnesium alloy is not very high in the 210-250Mpa。 Laser power has a great influence on the weld width of NZ30K welding seam, and the welding speed has a significant influence on the weld width。 Welding off focus amount, the change of gas flow rate and back protection gas flow rate can cause the change of weld width。 In the microstructure of rare earth magnesium alloy, the weld near the heat affected zone is columnar grain。 the grain size in the weld zone is obviously larger than that of the weld zone, but the grain size of the heat affected zone is larger than that of the weld zone。

Keywords: rare earth magnesium alloy; Laser welding; microstructure; mechanical properties of joint

目  录

第一章  绪论 1

1。1 课题背景 1

1。2 国内外研究现状 2

1。3 镁合金的分类及热处理 3

1。4 镁合金的激光焊接 5

1。4。1镁合金激光焊接工艺及焊缝质量 5

1。4。2镁合金激光焊接接头组织 7

1。4。3镁合金激光焊接接头的力学性能 8

1。4。4镁合金激光焊接的主要缺陷及预防措施 9

1。5本文研究内容 10

第二章  试验材料，设备与方法