铸造am60镁合金tig焊接头组织性能研究（本科毕业论文设计）.doc
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铸造am60镁合金tig焊接头组织性能研究（本科毕业论文设计）,摘要镁合金作为现有的最轻的商用金属结构材料，具有比重轻、高比强度、高比刚度，减振吸噪能力强，以及良好的电磁屏蔽能力和铸造性能和易于再生利用等一系列独特的优点，被誉为“21世纪的绿色结构材料”，在国防军工、航空航天、交通工具、3c产品及手动工具等领域有着极为广阔的应用前景。本文对3.0mm厚的am60镁合金薄板（压铸态）...
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摘 要
镁合金作为现有的最轻的商用金属结构材料，具有比重轻、高比强度、高比刚度，减振吸噪能力强，以及良好的电磁屏蔽能力和铸造性能和易于再生利用等一系列独特的优点，被誉为“21世纪的绿色结构材料”，在国防军工、航空航天、交通工具、3C产品及手动工具等领域有着极为广阔的应用前景。
本文对3.0mm厚的AM60镁合金薄板（压铸态）的钨极氩弧焊工艺进行了试验，采用金相显微镜分析测试手段研究了焊接接头各区域的显微组织，并进行了硬度测试等。
试验结果表明：采用TIG焊焊接压铸AM60合金时，焊缝成形不佳。微观组织分析表明：AM60 镁合金TIG 焊时，焊缝区为细小的等轴晶组织，晶界和晶粒内部存在析出相, 热影响区晶粒较粗大，且热影响区较宽。焊接接头的主要缺陷是气孔，气孔产生的主要原因是：压铸态的母材中存在微孔等缺陷；焊接过程中由于氢在镁中的溶解度急剧下降和焊缝凝固很快不利于气体溢出导致较多氢气孔出现；镁合金中低熔点高蒸汽压镁元素的蒸发也是气孔的来源之一。硬度测试表明：焊缝硬度相对较高，而热影响区硬度明显下降，是由于焊缝的晶粒细小，热影响区晶粒粗大、且存在疏松等缺陷。
关键词：AM60镁合金，钨极氩弧焊，组织，性能，气孔
ABSTRACT
Magnesium alloys, as the lightest structural material at present , have many advantages, such as high specific strength, high specific rigidity, good casting capability and easy to recycle. As a result, magnesium alloys are named with “Green structural material of the 21th century”, and have a huge potential in mass application in road vehicles, aircrafts, space shuttles, communication and electronic goods.
In this thesis, the processing of gas tungsten arc (TIG) welding of magnesium alloy AM60 plates with 3.0 thickness were studied. The microstructure was investigated with optical microscopy.
The result indicated that the quality of the welding is not good. It’s found that the large number of pores in the joint seriously impact the mechanical property of the joint，the pores may be reduced by adjusting the parameters and eliminating the factors of gas，but they can’t be entirety avoided. Magnesium has higher hydrogen solubility in liquid than in solid. The difference in the solubility between the solid and liquid phase was major cause of the porosity of magnesium alloys during welding. The low melting element of magnesium alloy was easily to vaporize and the presence of porosity in the base metal coalesced and expanded，which was another cause. The hardness test indicate that the structure in weld is harder than other areas.
Key word: magnesium alloy AM60，TIG，microstructure，property，porosity
目 录
中文摘要 Ⅰ
ABSTRACT Ⅱ
1绪论 1
1.1 引言 1
1.2镁合金在我国的应用现状 1
1.3镁合金的焊接特性及研究现状 3
1.3.1 镁合金的焊接特性 3
1.3.2 镁合金焊接的研究现状 4
1.4 本论文的研究内容和意义 8
2 试验 9
2.1 试验设计 9
2.1.1 试验目的 9
2.1.2 试验原理 9
2.1.3 试验条件 13
2.2 试验过程 13
2.2.1 焊接试验 13
2.2.2 金相试样制备及观察 14
2.2.3 硬度测试 14
3 试验结果及分析 15
3.1 焊缝成形观察 15
3.2 金相试验结果及分析 16
3.2.1 金相组织分析 16
3.2.2 缺陷分析 21
3.3 硬度试验结果及分析 24
4 结论 25
4.1 结论 25
4.2展望 25
致谢 26
参考文献 27
镁合金作为现有的最轻的商用金属结构材料，具有比重轻、高比强度、高比刚度，减振吸噪能力强，以及良好的电磁屏蔽能力和铸造性能和易于再生利用等一系列独特的优点，被誉为“21世纪的绿色结构材料”，在国防军工、航空航天、交通工具、3C产品及手动工具等领域有着极为广阔的应用前景。
本文对3.0mm厚的AM60镁合金薄板（压铸态）的钨极氩弧焊工艺进行了试验，采用金相显微镜分析测试手段研究了焊接接头各区域的显微组织，并进行了硬度测试等。
试验结果表明：采用TIG焊焊接压铸AM60合金时，焊缝成形不佳。微观组织分析表明：AM60 镁合金TIG 焊时，焊缝区为细小的等轴晶组织，晶界和晶粒内部存在析出相, 热影响区晶粒较粗大，且热影响区较宽。焊接接头的主要缺陷是气孔，气孔产生的主要原因是：压铸态的母材中存在微孔等缺陷；焊接过程中由于氢在镁中的溶解度急剧下降和焊缝凝固很快不利于气体溢出导致较多氢气孔出现；镁合金中低熔点高蒸汽压镁元素的蒸发也是气孔的来源之一。硬度测试表明：焊缝硬度相对较高，而热影响区硬度明显下降，是由于焊缝的晶粒细小，热影响区晶粒粗大、且存在疏松等缺陷。
关键词：AM60镁合金，钨极氩弧焊，组织，性能，气孔
ABSTRACT
Magnesium alloys, as the lightest structural material at present , have many advantages, such as high specific strength, high specific rigidity, good casting capability and easy to recycle. As a result, magnesium alloys are named with “Green structural material of the 21th century”, and have a huge potential in mass application in road vehicles, aircrafts, space shuttles, communication and electronic goods.
In this thesis, the processing of gas tungsten arc (TIG) welding of magnesium alloy AM60 plates with 3.0 thickness were studied. The microstructure was investigated with optical microscopy.
The result indicated that the quality of the welding is not good. It’s found that the large number of pores in the joint seriously impact the mechanical property of the joint，the pores may be reduced by adjusting the parameters and eliminating the factors of gas，but they can’t be entirety avoided. Magnesium has higher hydrogen solubility in liquid than in solid. The difference in the solubility between the solid and liquid phase was major cause of the porosity of magnesium alloys during welding. The low melting element of magnesium alloy was easily to vaporize and the presence of porosity in the base metal coalesced and expanded，which was another cause. The hardness test indicate that the structure in weld is harder than other areas.
Key word: magnesium alloy AM60，TIG，microstructure，property，porosity
目 录
中文摘要 Ⅰ
ABSTRACT Ⅱ
1绪论 1
1.1 引言 1
1.2镁合金在我国的应用现状 1
1.3镁合金的焊接特性及研究现状 3
1.3.1 镁合金的焊接特性 3
1.3.2 镁合金焊接的研究现状 4
1.4 本论文的研究内容和意义 8
2 试验 9
2.1 试验设计 9
2.1.1 试验目的 9
2.1.2 试验原理 9
2.1.3 试验条件 13
2.2 试验过程 13
2.2.1 焊接试验 13
2.2.2 金相试样制备及观察 14
2.2.3 硬度测试 14
3 试验结果及分析 15
3.1 焊缝成形观察 15
3.2 金相试验结果及分析 16
3.2.1 金相组织分析 16
3.2.2 缺陷分析 21
3.3 硬度试验结果及分析 24
4 结论 25
4.1 结论 25
4.2展望 25
致谢 26
参考文献 27
