7449铝合金激光电弧复合焊工艺及焊后热处理对接头组织性能的影响

发布时间：2018-04-26 02:41

  本文选题：7449铝合金 + 激光电弧复合焊　； 参考：《中南林业科技大学》2017年硕士论文

【摘要】：7449铝合金是由法国Alcan公司研制生产的新型Al-Zn-Mg-Cu-Zr系合金,具有较高的强度、断裂韧性及抗疲劳裂纹扩展能力,已应用在Air Bus公司最新研发的民用客机A350上,但国内外关于7449铝合金的激光电弧复合焊接头的性能方面的研究工作很少。论文在大飞机用铝合金研究项目背景下,以7449铝合金薄板为实验研究对象,借助金相显微镜(OM)、扫描电子显微镜(SEM)等微观组织分析手段,并通过显微硬度测试、拉伸性能测试、晶间腐蚀实验和剥落腐蚀实验等方法,探讨并研究了激光电弧复合焊工艺及焊后热处理工艺(固溶处理、单级时效)对7449铝合金激光电弧复合焊接头组织及性能的影响,并取得了如下主要研究成果:(1)在激光束偏转轴线角度10°与电弧焊枪旁轴复合、15 L/min的高纯氩气作为保护气体、电弧焊枪与母材的夹角为54°及光丝间距为3mm等条件下,7449铝合金较优的激光电弧复合焊的工艺参数为:激光功率为2.3 KW,焊接速度为40mm/s,离焦量为0mm,送丝速度为7 mm/s。此时复合焊接头的抗拉强度为256.73 MPa,延伸率为2.87%,焊缝的硬度值为112.75 HV。接头各区域的硬度值从焊缝区、熔合区到热影响区逐渐增大。(2)对7449铝合金激光电弧复合焊接头进行475℃/1h固溶处理后,抗拉强度和延伸率分别为430.70 MPa、3.80%,焊缝硬度为117.38 HV。与固溶处理前相比,抗拉强度提高了 67.76%,延伸率增大了 32.40%,硬度提高了 4.11%。(3)对7449铝合金激光电弧复合焊接头进行120℃/24h单级时效处理后,抗拉强度和延伸率分别为542.90 MPa、3.96%,焊缝硬度为140.65 HV,比固溶处理后的接头分别提高了 26.05%、4.0%和19.82%。热影响区硬度水平恢复到与母材相当。复合焊接头的塑性略有恢复。(4)7449铝合金激光电弧复合焊接头固溶处理前、后的抗腐蚀能力基本一致,焊缝区、热影响区、母材区的抗腐蚀能力依次减小;而单级时效后,焊缝区、热影响区、母材区的抗腐蚀能力依次提高。焊后热处理对接头的晶间腐蚀性能和剥落腐蚀性能的影响是相同的。
[Abstract]:7449 aluminum alloy is a new type of Al-Zn-Mg-Cu-Zr alloy developed and produced by Alcan Company of France. It has high strength, fracture toughness and anti-fatigue crack propagation ability. It has been applied to the newly developed A350 of Air Bus Company. However, there is little research on the properties of 7449 aluminum alloy laser arc composite welding joint at home and abroad. Under the background of the large aircraft aluminum alloy research project, taking 7449 aluminum alloy thin plate as the experimental object, by means of metallographic microscope, scanning electron microscope (SEM) and other means of microstructure analysis, microhardness test, tensile property test, etc. The effects of laser arc composite welding process and post welding heat treatment (solid solution treatment, single stage aging) on the microstructure and properties of laser arc composite welding joint of 7449 aluminum alloy were discussed and studied by means of intergranular corrosion test and exfoliation corrosion test. The main research results are as follows: (1) High purity argon, which is composed of laser beam deflection axis angle of 10 掳and arc welding torch side axis for 15 L/min, is used as protective gas. When the angle between the arc welding torch and the base metal is 54 掳and the optical wire spacing is 3mm, the optimum parameters of laser arc composite welding are as follows: laser power is 2.3 KW, welding speed is 40 mm / s, defocus is 0 mm, wire feeding speed is 7 mm / s. The tensile strength of the joint is 256.73 MPA, the elongation is 2.87 and the hardness of the weld is 112.75 HV. The hardness of 7449 aluminum alloy laser arc composite welding joint increased gradually from weld zone, fusion zone to heat affected zone. The tensile strength and elongation of 7449 aluminum alloy laser arc composite welding joint were 430.70 MPA / 1 h and 117.38 HV, respectively. The tensile strength, elongation and hardness of 7449 aluminum alloy laser arc composite welding joint were increased by 67.76%, 32.40% and 4.11% respectively, compared with those before solution treatment. After 120 鈩，

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