摘要镁合金具有密度低，强度高，导热性能好，抗震性能好，电磁屏蔽性能优势以及应用在汽车，航空航天，电子信息产业，有广阔的发展前景。

然而，在室温下，用紧密堆积的六方晶系结构的镁，滑系统，塑性变形。

这些属性导致生产困难和昂贵的方法制备的镁合金部件的结构复杂。

因此，使用镁合金结构简单焊接方法连接成一个复杂的结构，在镁合金结构件制造，不仅节省成本，而且还减少过程的复杂性的有效措施之一。

在本文中，AZ31和AZ61变形镁合金的研究，通过调整不同的焊接工艺，金相组织分析和力学性能测试，系统的研究，不同的镁合金激光焊接和TIG焊接热输入量和焊接速度焊接参数接头的组织和力学性能的影响，阐明组织演变，并获得焊接接头的力学性能之间的关系;强化机理模型预测了镁合金的高功率激光焊接接头的屈服强度增强机制。

的实验事实的基础上的理论分析，得出以下结论：1、间增加的能量不仅会导致增加的TIG焊接接头的AZ31镁合金热影响区，热影响区和熔合区的晶粒粗化，连续减少β-相的热影响区和熔合区的颗粒或不连续β相增加。

然而，如果该行的能量太低，将导致在焊缝中的未焊透和孔隙度，从而降低了在焊接接头的拉伸强度。

2、较小功率的前提下，AZ31镁合金激光焊接熔深增加线能量增加。

焊缝的表面上的等离子体有利于激光焊缝的深度增加。

随着焊接线能量在AZ31镁合金激光焊接熔合区，呈现胞状晶→胞状树枝晶→树枝晶→等轴晶的转变。

此外，适度的提高线能量可以降低镁合金的激光焊接头的应变速率，降低焊接凝固裂纹的形成的概率。

关键词：镁合金;激光焊;钨极氩弧焊;微观组织;力学性能ABSTRACTMagnesium alloys have low density, high specific strength, good thermal conductivity, excellent seismic performance, and good electromagnetic shielding performance and other advantages, has broad application prospects in the automotive, aerospace and electronic information industry. However, magnesium has the close-packed six party crystal structure at room temperature, slip, plastic deformation capacity low. These properties result in the complex structure of magnesium alloy production and preparation of difficult and high cost. Therefore, the use of welding method for magnesium alloy is simple structure will be connected with a complicated structure becomes magnesium alloy structural parts manufacturing industry not only cost savings,but also one of effective measures to reduce the complexity of the technology. Based on the AZ31 and AZ61 magnesium alloy as the research object, through the welding parameters under different process adjustment, and combined with the microstructure analysis and mechanical properties testing, a systematic study of the different welding speed and the welding line energy effect of microstructure and mechanical properties of joint of magnesium alloy laser welding and TIG, clarification the relationship between the microstructure evolution and mechanical properties of the welded joint; and the strengthening mechanism model to forecast the yield strength enhancement mechanism of high power laser welding of magnesium alloy joints. Based on the experimental facts, combined with theoretical analysis, the main conclusions are the following:1, line energy not only leads to AZ61 magnesium alloy gas tungsten arc welding HAZ width increases, heat affected zone and Fusion Zone grain coarsening, and make continuous β - heat affected zone and fusion zone of reduced and granular or discontinuous beta phase increased. Low line energy will lead to lack of penetration and porosity in weld appearance, and the ultimate tensile strength of the welded joint reduction 2, in the condition of low power, AZ61 wrought magnesium alloy laser weld penetration increases with the increase ofwelding line energy. Plasma welding on the surface of thin and stable in favor of laser weld penetration increase. With the increase of welding line energy, influenced by constitutional undercooling degree of change,the fusion zoneof AZ61 magnesium alloy laser welding deformation, microstructure evolution of the critical region near the partially melted zone are presented in the cellular crystal and cellular dendrite, dendritic, equiaxed grains. In addition, appropriately increasing the line energy can reduce the magnesium alloy laser welding joint strain rate, thereby reducing the possibility of the formation of weld solidification cracks in the line, but the high energy will lead to weld HAZ liquation crack increase.Keywords : magnesium alloy; laser welding; TIG welding; microstructure; mechanical properties目录中文摘要.......................................................... ............................................................ (I)英文摘要.......................................................... ............................................................ .. (II)第1章绪论.......................................................... ............................................................ .. (1)1.1 镁合金得简介 ......................................................... . (1)1.1.1 镁合金得发展.......................................................... . (1)1.1.2 镁合金得分类.......................................................... . (2)1.2 镁合金焊接得国内外研究现状 ......................................................... (2)1.3 本文得主要研究内容 ......................................................... . (6)第2章研究内容与方法 ......................................................... .. (7)2.1 实验材料 ......................................................... ............................................................ (7)2.2 焊接设备 ......................................................... ............................................................ (7)2.2.1 交流钨极氩弧焊焊机.......................................................... . (7)2.2.2 小功率激光脉冲焊接机 ......................................................... .. (8)2.2.3 大功率激光器.......................................................... . (8)2.3 性能检测设备 ......................................................... . (8)2.3.1 焊接接头试样得制备.......................................................... . (8)2.3.2 扫描电子显微镜.......................................................... (8)2.3.3 万能材料试验机(SANS XYA105C) ................................................... . (9)2.3.4 显微硬度计.......................................................... .. (9)第3章镁合金钨极氩焊接接头微观组织和力学性能得关系 (11)3.1 线能量得变化对镁合金钨极氩弧焊接接头微观组织得影响 (11)3.1.1 镁合金钨极氩弧焊焊接接头得微观组织特征 (11)3.1.2 线能量得变化对焊接接头热影响区微观组织得影响 (12)3.1.3 线能量得变化对焊缝熔合区微观组织得影响 (13)3.2 线能量得变化对焊接接头力学性能得影响 ......................................................... .. (15)3.2.1 拉伸强度.......................................................... . (15)3.2.2 显微硬度.......................................................... (17)3.3 本章小结.......................................................... . (19)第4章焊接线能量得变化对镁合金小功率激光焊接性能得影响 (20)4.1 焊接线能量对焊缝熔深得影响.......................................................... . (20)4.2 焊接线能量变化对焊缝熔合区微观组织得影响 (22)4.3 线能量得变化对热裂纹形成得影响.......................................................... .. (25)4.4 线能量得变化对微气孔形成得影响.......................................................... .. (27)4.5 本章小结.......................................................... . (29)第5章结论.......................................................... ............................................................ (30)致谢.......................................................... ............................................................ . (31)参考文献.......................................................... ............................................................ (32)第1章绪论1.1 镁合金得简介1.1.1 镁合金得发展20世纪初期镁合金作为结构材料在是军事需求带动下，镁合金的需求生产开始快速增长。