论文总字数：23036字

摘 要

21世纪以来，镁合金铝合金复合结构已经广泛应用于很多领域，例如汽车制造行业、冶金业、船舶与海洋工程业、铁道交通等等。镁合金与铝合金给我们的生活带来了极大的便利，对于镁铝异种金属激光焊接的研究也越来越得到了重视。

众所周知，镁铝合金都属于活泼金属，极容易在表面形成致密的氧化膜，氧化膜的存在使原子间的相互扩散发生了问题，当使用传统的熔焊方法焊接镁铝合金时，焊接接头处极容易产生一些焊接缺陷，例如裂纹、气孔、夹杂等，这些焊接缺陷大大影响到生产质量和实际应用。采用固相焊接方法虽然可以有效减少上述的焊接缺陷，但是焊接镁铝合金时极易生成脆性镁铝系金属间化合物，从而造成接头的质量达不到预期的要求。研究表明，通过添加合适的中间层可以阻止镁铝金属间化合物的产生，镁铝异种金属的焊接通常会采用此种方法来抑制金属间化合物。

本文主要研究内容和结论如下：

（1）激光功率对于镁铝异种金属激光焊接的焊缝成形有一定的影响，当激光功率增加时，更加容易焊透试样，功率过大则会直接烧穿。其中焊接功率为1.5kW，焊接速度为1.5m/min，送丝速度为1.8mm/min，离焦量为 5mm时的焊缝表面成形较好。

（2）对比添加锌锡复合中间层与未添加中间层的接头成形情况，可以发现，添加了锌锡复合中间层后，在不同的焊接工艺参数条件下，焊接接头的表面成形明显优于未添加中间层时的接头表面成形。

（3）添加了锌锡复合中间层后，试样焊缝区域的显微硬度相较于母材区域有很大的提高，查阅相图可知，中间层的加入使得焊缝区域的相组成发生了改变，这也是显微硬度提高的原因。

关键词：镁/铝合金 异种金属 激光焊接 中间层

Effect of Interlayer on Laser Welding of Aluminum/Magnesium Dissimilar Metal

ABSTRACT

窗体顶端

窗体顶端

窗体顶端

窗体底端

Since the 21st century, magnesium alloy and aluminum alloy composite structures have been widely used in many fields, such as automobile manufacturing, metallurgy, ship and Marine engineering, railway transportation and so on. Magnesium alloy and aluminum alloy have brought great convenience to our life, and more and more attention has been paid to the study of laser welding of magnesium and aluminum alloy.

As is known to all, magnesium aluminum alloy are active metal, extremely easy in the density of the surface oxide film and oxidation film of the problems happened to the interdiffusion between the atoms, when using the traditional method of fusion welding when the welding of magnesium alloy, the welding joint is extremely easy to produce some weld defects, such as cracks, porosity, inclusions and so on, these weld defects greatly affect the production quality and practical application. Use although solid-phase welding method can effectively reduce the weld defects, but when the welding of magnesium alloy easily generate brittle magnesium aluminium intermetallic compounds, resulting in the quality of the joint can not meet the expected demand. The results show that the formation of mg-al intermetallic compounds can be prevented by adding suitable intermediate layer.

The main research contents and conclusions of this paper are as follows:

(1) the laser power has certain influence on the formation of welding seams welded by magnesium and aluminum heterologous metal laser. When the laser power increases, it is easier to weld through samples, and if the power is too high, it will burn through directly. The welding power is 1.5kw, the welding speed is 1.5m/min, the wire feeding speed is 1.8mm/min, and the weld surface is well formed when the off-focus is 5mm.

(2) compared to add zinc tin composite joint forming situation of middle layer and not add the middle layer, can be found that added zinc tin compound after the middle layer, under the condition of different welding process parameters, the surface of the welding joint forming is better than not to add the middle tier of joint surface forming.

(3) added zinc tin compound after the middle tier, microhardness of weld area compared with parent metal sample area has a lot to improve, refer to phase diagram, the middle tier to join makes weld area of phase composition changed, that is why microhardness increase.

Key words: Magnesium/aluminum alloys；Dissimilar metals；Laser welding；Intermediate layers

目录

摘 要 1

ABSTRACT 2

第一章 课题研究目的和研究内容 6

1.1课题研究的意义与背景 6

1.2激光焊接的原理 6

1.3激光焊接的优点 7

1.4激光焊接的发展过程和重要应用 7

1.5铝/镁异种材料激光焊接的问题 8

1.6铝/镁焊接工艺国内外研究现状及分析 9

1.7添加锌锡复合中间层的作用 10

1.8本课题的研究内容 10

第二章 实验材料、设备和方法 11

2.1实验材料 11

2.2激光焊接试验 11

2.3.1焊缝组织分析实验 13

2.3.2显微硬度试验 15

第三章 镁/铝激光焊接头宏观成形特征 16

3.1.1未添加中间层焊缝表面形貌 16

3.1.2焊接接头成形特征分析 16

3.2.1添加中间层焊缝表面形貌 17

3.2.2焊缝截面宏观形貌 17

3.2.3焊接接头成形特征分析 18

3.3本章小结 18

第四章 镁/铝激光焊接接头微观组织及显微硬度分析 19

4.1添加锌锡复合中间层的接头微观组织 19

4.2接头微观组织比较 27

4.3接头显微硬度分析 28

4.4镁/铝激光焊经济性分析 30

4.5本章小结 30

第五章 结论 31

参考文献 32

致谢 34

请支付后下载全文，论文总字数：23036字