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本论文采用 TIG 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 TIG 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 TIG 焊缝成形影响显著。200A焊接电流过大，容易焊穿，180A的焊接电流配合60cm/min-70cm/min的焊速难以实现单面焊双面成形。采用双面焊的方法能够实现良好成形，正反两道焊缝能够很好的融合在一起。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。180A电流单面焊试样断口在焊缝区，沿着两对接板的对接面，其抗拉强度只有50～70MPa左右。而180A电流双面焊断裂面位于母材区，接头强度可达到200MPa左右。关键词：AZ31B 镁合金，钨极氩弧焊，焊接接头，微观组织，力学性能8528
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毕业设计说明书（论文）外文摘要
Title: Study on welding process of AZ31B magnesium alloy by TIG welding
Abstract
Butt welding experiments on 4 mm wrought magnesium alloy have been done by TIG 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.200A welding current is too large for AZ31B magnesium alloys that it’s easy to burn through. And 180A welding current with the welding speed of 60cm/min or 70cm/min is difficult to get complete penetration. But With double-sided welding, good welding seam is easy to get. The TIG 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。The 180A current single-sided weld fracture in the weld zone, while the 180A current double-sided weld fracture in the base metal.
Key words: AZ31B Magnesium alloy, TIG welding, welded joint, microstructure, mechanical property
目 次
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 1
1.1.3 镁合金的焊接性 2
1.2 镁及镁合金的焊接研究现状 3
1.3 选题的意义 7
1.4 本课题的主要研究内容 7
2 AZ31镁合金TIG焊工艺试验及工艺参数对焊缝成形的影响 9
2.1 试验材料与设备 9
2.1.1 试验材料 9
2.1.2 焊接设备 9
2.1.3 性能测试设备 9
2.2 工艺试验过程 11
2.2.1 焊前准备 11
2.2.2 焊缝与接头的形式 11