摘要本论文采用熔化极气体保护焊弧焊对4mm厚的AZ31B镁合金薄板进行对接接头焊接，分别采用脉冲MIG焊、MIG焊和脉冲CMT焊接工艺。选择合理的工艺参数，在不开坡口不留间隙的情况下实现了单面焊双面成形，得到的成形良好的焊缝。在焊接试验的基础上，研究了镁合金焊接接头的组织及力学性能，探讨了焊接工艺规范参数对焊接接头组织和力学性能的影响规律。
通过试验发现AZ31B镁合金的焊接接头包括焊缝区、热影响区和母材区。AZ31B镁合金母材和焊缝的相结构均为镁固溶体(α-Mg)和金属间化合物(γ-Mg17Al12)。焊缝区以初生的α(Mg)为主，析出的γ(Mg17Al12)相主要弥散分布于晶界。进行硬度测试，发现母材硬度较高，热影响区硬度稍低，焊缝由于存在析出相导致测试时硬度值上下波动。拉伸试验断裂面位于热影响区，说明该区域抗拉强度较低，热影响区是焊接接头的薄弱部位。7138
关键词：AZ31B镁合金  脉冲MIG焊  脉冲CMT焊  微观组织  力学性能
毕业设计说明书（论文）外文摘要
Title  Study on metal gas welding process of Magnesium Alloys                   
Abstract
Butt welding experiments on 4mm wrought magnesium alloy have been done by metal gas welding process in this thesis. The experiment adopts the method of pulse MIG welding and Non-pulse welding and plus CMT welding process. Experiments have been done by choosing proper welding parameters combination on metal gas welding with single wire, we can get good shape of welding seam. In the case of choosing square groove and no-gap welding, we can get one-side welding with back formation. On the basis of the welding test to study the microstructure and mechanical properties of welded joints of magnesium alloy, and investigate how welding parameters affect the welded joint microstructure and mechanical properties.
The experiment results show that welding joint of magnesium alloy  including the weld zone, heat affected zone and base metal. In the AZ31B magnesium, the phase structure of base metal and weld seam are both magnesium solid solution (α-Mg) and intermetallic compounds (γ- Mg17Al12).It is mainly primary α(Mg) phase in the welding seam area and the precipitated γ(Mg17Al12)phase is mainly distributed over the crystal boundary.The microstructure and properties of welding joint will change with the changes of process parameters.
Keywords  AZ31B magnesium alloy  Pulsed MIG Welding  The pulse CMT welding  Microstructure    Mechanical properties
目次

1  绪论    1
1.1  镁及镁合金概述    1
1.1.1  纯镁及镁合金    1
1.1.2  镁合金分类和牌号    1
1.1.3  镁合金中的合金元素及其作用    4
1.1.4  镁合金的焊接性    5
1.2  镁及镁合金的焊接研究现状    6
1.3  镁合金熔化极惰性气体保护焊    11
1.4  选题意义    12
1.5  本课题主要研究内容    12
2  AZ31B镁合金熔化极气体保护焊试验    14
2.1  试验材料    14
2.2  试验设备    14
2.2.1  焊接设备    14
2.2.3  性能测试设备    14
2.3  焊接过程    16
3  AZ31B镁合金熔化极气体保护焊焊缝成形分析    17
3.1  脉冲MIG焊    17
3.2  直流MIG焊    18
3.3  脉冲CMT焊    19 镁合金气体保护焊工艺研究+文献综述:http://www.youerw.com/cailiao/lunwen_4935.html