铝合金电子束焊接工艺分析

铝合金电子束焊接工艺分析

摘要

6082-T6铝合金属于AI-Mg-Si系可热处理强化铝合金，由于具有轻质高强、良好的挤压成型性和耐腐蚀性等特点，近年米在轨道交通行业尤其是在高速列车车体上得到了广泛应用。由于该铝合金在实际生产中大多作为焊接结构使用，采纳传统的焊接方法如TIG、MIG

等进行焊接时，易造成接头焊缝组织粗大、焊缝气孔率高以及产生热裂纹等缺陷，导致难以获得高质量的焊接接头，在一定程度上限制了其使用。相比较而言，真空电子束焊(EBW)具有能量密度高、热输入小、焊接变形小等特点，用于6082-T6等铝合金的焊接具有较大优势。基于此，本文对厚度分别为8mm和15mm的6082-T6铝合金的EBW焊接工艺及其接头的组织与性能进行研究，并与厚度为8mm的MIG焊接头的组织与性能进行对比,分析研究在不同焊接工艺条件下获得接头的微观组织、力学性能及耐蚀性能的差别及其原因。

接头显微组织观察表明，EBW接头焊缝组织为细小的等轴晶和树枝晶，具有明显的二次枝品，在晶界和枝晶界分布着大量的共晶组织，且分布均匀:电子束焊接时采纳圆形扫描方式能够明显细化晶粒，这是由于圆形扫描对熔池金属具有猛烈的搅拌作用，可提高熔池金属中溶质元素的流动性，减少合金元素的偏析:MIG焊接头焊缝组织为较粗大的等轴晶和树枝晶，二次枝晶不明显。对接头焊缝进行XRD物相分析，所获接头焊縫金属主要为a-Al基体相,同时含有少量的β(Mg2Si强化相及单质Si,在相结构组成上EBW接头和MIG焊接头基本相同。进一步通过TEM观察分析，证明了接头焊缝中的强化相主要为β(MgzSi)相。

接头显微硬度分布测试表明，EBW接头焊缝的硬度值低于热影响区和母材本身，热影响区的宽度较窄，其软化程度较轻，并且采纳圆形扫描方式获得接头焊缝区的硬度值最高，直线扫描的次之，未添加扫描方式获得接头焊缝的硬度值最低。而MIG焊接头的热影响区宽度相对较大，存在一个明显的软化区域，是焊接接头最薄弱的区域。

接头拉伸性能测试表明，几种接头的焊接质量均良好，可以满足实际工程结构对其强度要求。其中EBW接头的抗拉强度最高达到母材本身强度的84.1%，

而MIG焊接头的强度则相对较低，其抗拉强度只达母材本身强度的68.6%。拉伸断口扫描观察显示，接头拉伸断口呈明显的延性断裂特征，在断口表面存在着大量的韧窝，韧窝的大小、深浅各异，并且在韧窝的底部可以清楚地观察到第二相粒子，进一步的EDS分析表明，这些第二相粒子主要为(Mg2Si)相。

采纳静态失重法及电化学测试方法评价接头焊缝的耐腐蚀性能，结果表明，对于8mm厚6082-T6铝合金焊接接头来说，采纳圆形扫描方式获得接头A5的耐蚀性能最好:相比较而言，MIG焊接头焊缝的耐蚀性要差些。

综上所述，在本文中试验条件下，8mm厚6082-T6铝合 金EBW接头的整体性能高于MIG焊

接头,并且其最佳工艺参数为:电子束流I=105mA,焊接电压U=50kV,焊接速度v=1500mm:

min' ,圆形扫描; 15mm厚6082-T6铝合

金的最佳I艺参数为:电子東流I=205mA，焊接电压U=50kV,焊接速度v=1500mm-min',采纳圆形扫描方式。

关键词: 6082-T6 铝合金，电子束焊，MIG焊，显微组织，力学性能，耐腐蚀性

Abstract

The 6082-t6 aluminum alloy belongs to ai-mg-si heat-treatable aluminum alloy. Due to its light weight,

high strength, good extrusion molding and corrosion resistance, it has been widely used in the rail transit

industry in recent years, especially in the body of high-speed trains. As this aluminum alloy is mostly used

as a welding structure in practical production, the use of traditional welding methods such as TIG and MIG

will easily lead to defects such as thick weld structure, high porosity of weld seam and thermal crack, which

makes it difficult to obtain high-quality welded joints and limits its use to a certain extent. In comparison,

vacuum electron beam welding (EBW) has the characteristics of high energy density, small heat input,

small welding deformation, etc., and has great advantages for welding of 6082-t6 aluminum alloys. Based

on this, in this paper, the thickness of 8 mm and 15 mm respectively 6082 - T6 aluminum alloy EBW

welding process and the joint microstructure and properties was studied, and the thickness of 8 mm,

comparing the microstructure and properties of MIG welding head analysis under the condition of different

welding technology for joint microstructure, mechanical properties and corrosion resistant properties of

difference and its reason.

Weld joint microstructure observation showed that the EBW joint organization for small isometric and

dendrites, has obvious secondary branch, with a large number of grain boundary distribution in grain

boundary and branches eutectic organization, and evenly distributed: using circular scanning of electron

beam welding way can significantly refine the grain size, this is due to the circular scanning has strong

stirring effect of molten pool of metal, and can improve the mobility of solute elements in molten pool of

metal, reduce the segregation of alloying elements: the weld microstructure of MIG welding head for a

bulky isometric and dendrites, secondary dendrite is not obvious. XRD phase analysis of the joint weld shows that the metal of the joint weld is mainly a-al matrix phase, and contains a small amount of (Mg2Si

strengthening phase and elemental Si. In terms of phase structure, EBW joint and MIG welding joint are

basically the same. By TEM observation and analysis, it is confirmed that the strengthening phase is mainly

(MgzSi) phase.

Joint distribution of microhardness tests show that the EBW joint weld hardness value is lower than

the heat affected zone and base itself, heat affected zone width is narrower, the softening to a lesser degree,

and adopts circular scanning method to obtain the highest hardness value of joint weld area, line scan times,

did not add to scan for joint weld hardness value is the lowest. However, the width of heat affected zone of

MIG welding joint is relatively large, and there is an obvious softening zone, which is the weakest area of

welding joint.

The test results show that the welding quality of several joints is good, which can meet the strength

requirement of practical engineering structure. Among them, the tensile strength of EBW joint is up to

84.1% of the strength of the base metal itself, while the strength of MIG welding joint is relatively low, and