Effect of the welding speed on the microstructure and the mechanical properties of robotic friction stir welded AA7B04 aluminum alloy
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摘要: 針對熔化焊在焊接AA7B04鋁合金時易在焊縫中出現孔洞等缺陷，且接頭性能下降明顯、焊后變形大，以及采用鉚接等機械連接方式會增加連接件的重量等問題，采用集成了攪拌摩擦焊末端執行器的KUKA Titan機器人對2 mm厚AA7B04高強鋁合金進行了焊接，在轉速為800 r·min-1的條件下，研究了焊度對焊接過程中攪拌頭3個方向的受力Fx、Fy和Fz的影響.研究發現，Fz受焊速的影響顯著，隨焊速的增加而降低.利用光學顯微鏡、透射電子顯微鏡、拉伸試驗、三點彎曲試驗和硬度測試等方法，研究了不同焊速下AA7B04鋁合金接頭的微觀組織和力學性能.結果表明：當焊速為100 mm·min-1時，接頭的抗拉強度最高為447 MPa，可達母材的80%，且所有接頭的正彎和背彎180°均無裂紋；接頭橫截面的硬度分布呈W型，硬度最低點出現在熱力影響區和焊核區的交界處，焊速不同會導致不同的焊接熱循環，且隨著焊速的增加接頭的硬度隨之增加；焊核區組織發生了動態再結晶，生成了細小的等軸晶粒，前進側和后退側熱力影響區的晶粒均發生了明顯的變形；前進側熱影響區析出η'相，后退側熱影響區因溫度較高析出η'相和尺寸較大的η相.Abstract: For weld defects such as holes, debasement of the joint properties and large deformations easily appear in fusion welding of the AA7B04 aluminum alloy, and the use of mechanical connections such as riveting increases the weight of the connector. Herein, a 2-mm AA7B04 aluminum alloy was friction stir welded using an industrial KUKA Titan Robot, with a friction stir welding end effector mounted onto the robot. The Fx, Fy, and Fz forces of the tool during welding were recorded, and the resultant mechanical strength and microstructure of the joints were studied. The results show that welding speed imposes a great influence on Fz. The microstructure and mechanical properties at different welding speeds of a friction stir welded joint of an AA7B04 aluminum alloy sheet were investigated via optical microscope observation, transmission electron microscope observation, a tensile test, a three-point bending test, and a hardness test. The results show that the maximum tensile strength of the joint is 447 MPa for a welding speed of 100 mm·min-1, equivalent to 80% of the parent metal. No crack is observed in the joints when bending at 180°. W-shape hardness distribution is observed on the cross-section of all joints; moreover, owing to the lowest hardness in the heat affected zone and the junction of the welding area, different welding speeds lead to different welding thermal cycles, and the hardness of joint increases with the increase in the welding speed. Dynamic recrystallization occurs in the nugget zone, and fine equiaxial grains are produced. The grains of the advancing and retreating sides of the thermo-mechanically affected zone are obviously deformed. The η' phase can be observed in the heat affected zone of the advancing side, and η' phase particles can also be observed in the heat affected zone of the retreating side. Owing to the higher temperature, the larger η phase can also be found in the heat affected zone of the retreating side.
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Key words:
- robot /
- friction stir welding /
- welding speed /
- microstructure /
- mechanical property
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參考文獻
[1] Mishra R S, Ma Z Y. Friction stir welding and processing. Mater Sci Eng R, 2016, 50(1-2):1 [2] Nandan R, DebRoy T, Bhadeshia H K D H. Recent advances in friction-stir welding-process, weldment structure and properties. Prog Mater Sci, 2008, 53(6):980 [3] Zhang Z H, Li W Y, Feng Y, et al. Global anisotropic response of friction stir welded 2024 aluminum sheets. Acta Mater, 2015, 92:117 [4] Zhang Z H, Li W Y, Li J L, et al. Microstructure and anisotropic mechanical behavior of friction stir welded AA2024 alloy sheets. Mater Charact, 2015, 107:112 [5] Threadgill P L, Leonard A J, Shercliff H R, et al. Friction stir welding of aluminium alloys. Int Mater Rev, 2009, 54(2):49 [6] Voellner G, Zaeh M F, Silvanus J. Influence of machine types on FSW seam qualities//Proceedings of 7th International Friction Stir Welding Symposium. Awaji Island, 2008:20 [7] Cook G E, Crawford R, Clark D E, et al. Robotic friction stir welding. Ind Robot Int J, 2004, 31(1):55 [8] Fehrenbacher A, Smith C B, Duffie N A, et al. Combined temperature and force control for robotic friction stir welding. J Manuf Sci Eng, 2014, 136(2):021007-1 [9] Smith C B, Hinrichs J F, Crusan W A. Robotic friction stir welding:state of the art//Proceedings of the Fourth International Symposium of Friction Stir Welding. Waukesha, 2003:14 [10] Bres A, Monsarrat B, Dubourg L, et al. Simulation of friction stir welding using industrial robots. Ind Robot Int J, 2010, 37(1):36 [11] De Backer J, Christiansson A K, Oqueka J, et al. Investigation of path compensation methods for robotic friction stir welding. Ind Robot Int J, 2012, 39(6):601 [16] Liu H J, Zhao Y Q, Hu Y Y, et al. Microstructural characteristics and mechanical properties of friction stir lap welding joint of Alclad 7B04-T74 aluminum alloy. Int J Adv Manuf Technol, 2015, 78(9-12):1415 [17] Wang M, Zhang H J, Zhang J B, et al. Effect of pin length on hook size and joint properties in friction stir lap welding of 7B04 aluminum alloy. J Mater Eng Perform, 2014, 23(5):1881 [18] Chen Y, Ding H, Cai Z H, et al. Effect of initial base metal temper on microstructure and mechanical properties of friction stir processed Al-7B04 alloy. Mater Sci Eng A, 2016, 650:396 [19] Arbegast W J, Hartley P J. Friction stir weld technology development at Lockheed Martin Michoud space system-an overview//ASM International, Trends in Welding Research. Cleveland, 1999:541 [20] Su J Q, Nelson T W, Mishra R, et al. Microstructural investigation of friction stir welded 7050-T651 aluminium. Acta Mater, 2003, 51(3):713 -
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