摘要本文以 6061-T6 铝合金为研究对象，利用 YLS-6000W 光纤激光+GMAW 复合热 源焊接设备对铝合金进行焊接。利用 VHX-900E 显微镜、扫描电子显微镜（SEM）、 X 射线能谱分析（EDS）、X 射线衍射仪（XRD）、显微维氏硬度测试以及电化学阻 抗等测试技术，研究激光+GMAW 复合热源焊不同焊接工艺下 6061-T6 焊接接头微观 组织及其在 3。5%NaCl 溶液中腐蚀行为。

结果表明，随着激光功率的增大，焊缝成形性提高，熔深和熔宽均增加，同时晶 粒粗化，枝晶间距增大。电弧在前时，整个焊缝处组织均匀化程度较高，熔滴的补充 增加了焊缝表层硬度；激光在前时，整个焊缝处呈现出较为明显的层次结构组织，同 时组织较电弧在前时粗化，但焊缝成形性优异，并且可以消除激光倾斜影响，提高焊 缝底部硬度。81352

6061-T6 在 3。5% NaCl 溶液中的腐蚀过程分为点蚀诱导期、点蚀发展期和腐蚀产 物膜生长阶段，EIS 阻抗中 Nyquist 图显示，由高频容抗—低频感抗体系转变为高频 容抗—低频 Warburg 阻抗。对于焊接接头，随着激光功率的增加，腐蚀加剧；激光在 前时，焊缝点蚀孔数目较多；而电弧在前时，点蚀坑直径较大，低功率时 Mg2Si 相优 先发生腐蚀，高功率时 Al-Fe-Si 相周围的基体优先发生腐蚀；浸泡 480h 后材料表面 的腐蚀产物以 Al2O3 和 Al(OH)3 为主；

毕业论文关键词：6061 铝合金，腐蚀，焊接接头，电化学

Abstract In this paper, the research object is 6061-T6 aluminum alloy welded by laser + GMAW hybrid welding equipment。 The effect on microstructure and corrosion behavior of 6061 aluminum welding joints in solutions of 3。5%NaCl was carried out using VHX-900E digital microscope, SEM, EDS, XRD, Vickers hardness and EIS test。

The results showed that the formability, penetration depth and weld width increased with increasing laser power。 The grain coarsening and the dendrite arm spacing growth at the same time。 As arc leading, the microstructure of the weld showed high uniformity and the addition of droplet increases the hardness of the weld surface。 As laser leading, the microstructure of the weld showed unity structure and the coarsening microstructure。 However, the formability were better than those of that condition and the influence of bias laser beam were eliminated。 At this condition, the hardness of welding bottom was improved。

The corrosion process of 6061-T6 can be pided into pitting sprouting period, pitting developing period and the growth of corrosion production period。 EIS study system changed from high frequency capacitive reactance- low frequency inductive impedance condition to high frequency capacitive reactance- low frequency Warburg impedance condition。 For welded joints, corrosion became serious with the increase of laser power。 When laser leads, the number of pitting was more than arc leading。 When arc leads, the pitting is larger。 At lower laser power, the Mg2Si phase was firstly corroded and Al-Fe-Si phase corroded first at the condition of high laser power。 After soaking 480h, the mainly corrosion products on the surface of the material were composed of Al2O3 and Al(OH)3。

Keywords: 6061 aluminum, corrosion, welding joint, electrochemical

目 录

第一章 绪论 1

1。1  铝合金的概述 1

1。1。1  铝合金的特点 1

1。1。2  铝合金的分类 1

1。2  铝合金焊接技术 3

1。2。1  铝合金焊接的特点 3

1。2。2  激光+熔化极气体保护复合焊