摘要本文采用 CMT 焊对4mm厚的AZ31B 镁合金进行了对接试验，采用了光学显微镜、硬度测试仪等现代分析测试手段，研究了 AZ31B 镁合金焊接接头的微观组织及力学性能，并探讨了焊接工艺参数对焊接接头组织和力学性能的影响规律。我们得出结论：AZ31B 镁合金 CMT 焊焊接接头主要由焊缝区、热影响区和母材区组成，母材和焊缝的相结构主要为α-Mg固溶体和β-Mg17Al12金属间化合物。焊接工艺参数对 AZ31B 镁合金 CMT 焊缝成形影响显著。155A焊接电流过大，容易焊穿，145A的焊接电流配合70cm/min的焊速以实现单面焊双面成形达最佳效果。经硬度测试，发现焊接接头母材区的硬度最大，热影响区硬度略小，而焊缝区硬度值波动较大。经拉伸实验，发现焊接接头的断口形貌有明显的韧窝，呈现韧性断裂的特征。145A电流单面焊试样断口在焊缝区，沿着两对接板的对接面，其抗拉强度195MPa左右。67493

毕业论文关键词：AZ31B 镁合金，CMT冷金属过渡焊，焊接接头，微观组织，力学性能

毕业设计说明书（论文）外文摘要

Title Study on welding process of AZ31B magnesium alloy by

 CMT welding                                        

Abstract

Butt welding experiments on 4 mm wrought magnesium alloy have been done by CMT welding process in this thesis. The optical microscope, hardness tester and other modern test measurement were applied. Microstructures and mechanical properties of welded joints of AZ31B magnesium alloys have been studied. And the influence of welding parameters on the microstructures and mechanical properties of welded joints has been discussed as well. The experiment results show that the adjusting range of welding current and welding speed is very narrow.155A welding current is too large for AZ31B magnesium alloys that it’s easy to burn through. And 145A welding current with the welding speed of 60cm/minis the best process to get complete penetration.The CMT welding joints of AZ31B magnesium alloy are composed of weld zone, heat affected zone and base metal zone. The phases of both base metal and weld are mainly α-Mg solid solution and γ- Mg17Al12 intermetallic compound. The hardness of the base metal is the highest，and the heat-affected district is slightly lower. The hardness of welding zone is undulating and irregular, but the average hardness value of this zone is the lowest of these zones. There are obvious dimples which have tough broken feature in the fracture of welding join.

Key words AZ31B Magnesium alloy, CMT welding, welded joint, microstructure, mechanical property

目    录

1  绪论 1

1.1  镁及镁合金概述 1

1.1.1  纯镁的特性 1

1.1.2  镁合金的分类与特性 2

1.1.3 镁合金中的合金元素及其作用 3

1.1.4  镁合金的焊接性 4

1.2  镁及镁合金的焊接研究现状 5

1.3  选题意义 10

1.4  本课题主要研究内容 11

2 AZ31镁合金CMT焊工艺试验研究 11

2.1  AZ31镁合金CMT焊试验材料与设备 11

2.2  AZ31镁合金CMT焊工艺试验过程 13

2.2.1 AZ31镁合金CMT焊焊接工艺