异种铝合金激光电弧复合焊数值模拟及接头组织性能研究

发布时间：2018-03-16 18:17

  本文选题：异种铝合金　切入点：数值模拟　出处：《西南石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：2A12铝合金和7075铝合金是可热处理高强铝合金,铝合金的材料密度低,比强度较高。这类材料逐渐成为现代高速列车、轿车与小型汽车的理想替代材料。激光-MIG复合焊集合了激光焊和MIG焊两种热源的优势,用于铝合金焊接时,不仅焊接效率高,缺陷少,而且还可以改善焊接接头的组织与性能。本文首先通过数值模拟,得到焊接接头温度场、焊板总变形量、焊缝背宽、熔宽以及焊接接头跟踪点温度、变形量的变化规律,然后以焊板总变形量为主要依据,选择出合适的工艺参数进行实际焊接,并通过实验数据对数值模拟的焊缝背宽、熔宽和焊接接头总变形量进行对比验证;接下来分析激光功率、焊接电流对焊接接头成形性以及焊接接头显微组织的影响,结合EDS和XRD,探究焊接接头中物相的组成;还分析了激光功率、焊接电流对焊接接头显微硬度、抗拉强度、延伸率、冲击韧性等力学性能的影响,并对拉伸断口进行分析。选择综合性能较好的焊接接头进行180℃12h的时效处理,分析时效对焊接接头显微硬度、抗拉强度的影响。具体研究结论如下:数值模拟研究表明:激光功率为3.8 KW、焊接电流为195 A时,数值模拟与实际焊接在焊缝熔宽、背宽方面,对比验证比较符合。在焊接总变形量方面,2A12铝合金侧验证结果比7075铝合金侧好。整体来说,数值模拟对实际焊接有比较大的指导价值。焊接接头成形性研究表明:复合焊焊缝的全透性和铺展性随着激光功率的增加而增加,且焊缝的激光作用区直径和背宽增加,焊缝熔宽变化不大;焊接电流的增加,可以提高复合焊焊缝的全透性,但是其铺展性有所降低;激光焊焊缝熔深随激光功率增加而增加,但焊缝金属元素的烧损加剧。焊接接头显微组织研究表明:2A12铝合金侧热影响区晶粒发生了明显的粗化,固溶区尤为严重;7075铝合金侧晶粒比2A12铝合金侧粗大;随着激光功率和焊接电流的增加,固溶区强化相数量减少,焊缝上部2A12铝合金侧柱状晶减少,7075铝合金侧的柱状晶减少的更加明显,但是焊缝的晶粒却发生了粗化;激光焊接头熔合线附近焊缝的晶粒是典型的柱状晶,焊缝上部的柱状晶更明显。焊接接头力学性能研究表明:接头两侧显微硬度最低位置随着激光功率和焊接电流的增加,距离焊缝中心越远;激光功率对接头抗拉强度和延伸率影响不大;而焊接电流的增加,使得接头的抗拉强度有所下降,延伸率有所增长,断裂位置远离焊缝;激光功率对接头冲击韧性影响并不是很明显;增加焊接电流,接头冲击韧性下降。时效处理可以提高接头的综合力学性能。综上可知,激光-MIG复合焊方法更适合异种铝合金的焊接。激光-MIG复合焊的最佳工艺参数为激光功率3.8 KW,焊接电流195 A。
[Abstract]:2A12 aluminum alloy and 7075 aluminum alloy are heat-treated high-strength aluminum alloys with low density and high specific strength. Laser MIG hybrid welding combines the advantages of laser welding and MIG welding. When used in aluminum alloy welding, it not only has high welding efficiency, but also has less defects. It can also improve the microstructure and properties of welded joints. Firstly, through numerical simulation, the temperature field of welded joints, total deformation of welded plates, weld back width, weld width, temperature and deformation of welding joint tracking point are obtained. Then based on the total deformation of the welding plate, the suitable process parameters are selected for actual welding, and the numerical simulation of weld back width, weld width and total deformation of welded joint are compared and verified by experimental data. Then, the effects of laser power, welding current on the formability and microstructure of welded joints are analyzed, and the phase composition in welded joints is explored by combining EDS and XRD.The microhardness of welded joints is also analyzed by laser power and welding current. The effects of tensile strength, elongation, impact toughness and other mechanical properties on tensile fracture were analyzed. The welding joints with better comprehensive properties were selected for aging treatment at 180 鈩，

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