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Analysis of bubble behavior and microstructure of aluminum alloys welded by electron beam

铝合金电子束焊接气泡行为及显微组织分析

基本信息

批准号：
12650713
负责人：
FUJII Hidetoshi
金额：
$ 2.05万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650713/
关键词：
Microgravity Electron beam Welding Aluminum alloys Bubble Oxide film Surface tension Connection Microstructure

项目摘要

Aluminum alloys were welded by electron beam under both microgravity and terrestrial conditions to investigate the beam stability, the effects of welding parameters on the convection in a molten pool, microstructure and bubble behavior. First, a small-sized electron beam welding system was developed to be loaded in the capsule for the drop shaft type microgravity facility at JAMIC. The distance between the filament and the sample is just 370 mm. The beam diameter was set to be 3 mm to perform a thermal conductive welding as in arc welding.By performing transmission X-ray analyses, it is found that the number of bubbles decreases under microgravity. Butt-welding of 5NAl and Al-6 %Cu alloy was performed in a horizontal direction under both microgravity and terrestrial conditions and consequently, the convection due to surface tension is found to be very weak and even weaker that that due to gravity, although it is thought to be largest. This fact causes the number of bubbles to decrease under microgravity. When atomic oxygen is irradiated to the aluminum surface, the thickness of the oxide film increases, and consequently, the number of bubbles increases in the bead. These all results do not contradict the hypothesis that bubbles are generated due to the reaction between molten aluminum and Al_2O_s, producing Al_2O gas phase.When horizontal welding performed under terrestrial conditions, the molten pool falls downward, the solidification rate decreases in the middle and lower parts of the bead, and hence, a feather crystal structure is easily formed and the grain size becomes larger.

在微重力和陆地条件下对铝合金进行了电子束焊接，研究了电子束稳定性、焊接工艺参数对熔池对流、焊接组织和气泡行为的影响。首先，开发了一个小型电子束焊接系统，用于装载在日本原子能机构落轴式微重力设施的密封舱中。灯丝与试样之间的距离仅为370 mm，为了进行与电弧焊接相同的热传导焊接，光束直径设定为3 mm。通过透射X射线分析，发现微重力下气泡的数量减少。在微重力和陆地条件下，对5 NAl和Al-6%Cu合金进行了水平对接焊接，结果表明，尽管表面张力引起的对流最大，但表面张力引起的对流很弱，甚至弱于重力引起的对流。这一事实导致微重力下气泡的数量减少。当原子氧照射到铝表面时，氧化膜的厚度增加，因此，珠粒中的气泡数量增加。在地面条件下进行水平焊接时，熔池福尔斯向下倾斜，焊道中下部的凝固速度降低，容易形成羽毛状结晶组织，晶粒尺寸变大。