超声波对铝合金激光-电弧复合焊接影响的研究
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摘要
为了解决传统铝合金焊接接头气孔数量多、晶粒粗大及力学性能差的问题,以5083-O铝合金为研究对象,进行了超声振动辅助激光-电弧复合焊接试验。研究了超声振动对铝合金焊缝气孔数量、微观组织及抗拉强度的影响,并探讨了超声波在焊接熔池中对气孔排出和组织细化的作用机理。结果表明,超声辅助焊接的焊缝气孔数量显著降低,主要归功于超声空化效应降低了铝合金熔体中的氢浓度,并促进气泡的快速逸出;超声波的空化效应和声流效应改变了熔体的压力、温度以及流动状态,使熔池的结晶条件发生改变,从而通过提高形核率和破碎枝晶细化了焊缝晶粒组织;施加超声振动后的焊缝平均拉伸强度由242.9MPa提高到270MPa,且断裂位置发生在热影响区,主要是因为焊缝区气孔减少和组织细化。此研究对深入理解铝合金焊接过程中缺陷形成机理及提高接头强度是有帮助的。
In order to solve the problems of large number of gas holes, coarse grain size and poor mechanical properties of traditional aluminum alloy welded joints, laser-arc hybrid welding experiment assisted by ultrasonic vibration was carried out by taking 5083-O aluminium alloy as the research object. The effect of ultrasonic vibration on the number of pore, microstructure and tensile strength of aluminium alloy weld was studied. The mechanism of the effect of ultrasonic wave on pore discharge and microstructure refinement in welding pool was also discussed. The results show that, the number of gas holes in the weld seam of ultrasonic assisted welding decreases significantly. It is mainly attributed to the reduction of hydrogen concentration in aluminium alloy melt by ultrasonic cavitation. It also promotes the rapid escape of bubbles. The cavitation effect and acoustic flow effect of ultrasound change the pressure, temperature and flow state of melt. The crystallization condition of the molten pool is changed. The grain structure of the weld is refined by increasing the nucleation rate and breaking dendrite. The average tensile strength of weld increased from 242.9 MPa to 270 MPa after ultrasonic vibration is applied. The fracture location occurs in the heat-affected zone. It is mainly due to the decrease of porosity and the refinement of structure in the weld zone. This study is helpful to understand the forming mechanism of defects and improve the strength of joints in the welding process of aluminium alloys.
In order to solve the problems of large number of gas holes, coarse grain size and poor mechanical properties of traditional aluminum alloy welded joints, laser-arc hybrid welding experiment assisted by ultrasonic vibration was carried out by taking 5083-O aluminium alloy as the research object. The effect of ultrasonic vibration on the number of pore, microstructure and tensile strength of aluminium alloy weld was studied. The mechanism of the effect of ultrasonic wave on pore discharge and microstructure refinement in welding pool was also discussed. The results show that, the number of gas holes in the weld seam of ultrasonic assisted welding decreases significantly. It is mainly attributed to the reduction of hydrogen concentration in aluminium alloy melt by ultrasonic cavitation. It also promotes the rapid escape of bubbles. The cavitation effect and acoustic flow effect of ultrasound change the pressure, temperature and flow state of melt. The crystallization condition of the molten pool is changed. The grain structure of the weld is refined by increasing the nucleation rate and breaking dendrite. The average tensile strength of weld increased from 242.9 MPa to 270 MPa after ultrasonic vibration is applied. The fracture location occurs in the heat-affected zone. It is mainly due to the decrease of porosity and the refinement of structure in the weld zone. This study is helpful to understand the forming mechanism of defects and improve the strength of joints in the welding process of aluminium alloys.
引文
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[2] LI Zh,WANG T,LIU J,et al.Effect of process parameters on corrosion resistance of aluminum alloy hybrid welded joints [J].Laser Technology,2019,43(2):189-194(in Chinese).
[3] DING J K,WANG D P,WANG Y,et al.Effect of post weld heat treatment on properties of variable polarity TIG welded AA2219 aluminum alloy joints [J].Transactions of Nonferrous Metals Society of China,2014,24(5):1307-1316.
[4] HE Y,TANG X,ZHU C,et al.Study on insufficient fusion of NG-GMAW for 5083 Al alloy [J].The International Journal of Advanced Manufacturing Technology,2017,92(9/12):4303-4313.
[5] SONG X H,JIN X Zh,CHEN Sh Q,et al.Progress of laser-arc hybrid welding and its applications in automotive body manufacture [J].Laser Technology,2015,39(2):259-265(in Chinese).
[6] WANG H Y,SUN J,LIU L M.Formation and control mechanism of porosity in 6061-T6 aluminum alloy laser arc hybrid high speed welding [J].Chinese Journal of Lasers,2018,45(3):0302001(in Chinese).
[7] XU G X,ZHANG W W,LIU P,et al.Numerical analysis of fluid flow in molten pool of laser GMAW composite heat source welding [J].Journal of Metals,2015,51(6):713-723(in Chinese).
[8] XU Ch Y,LIU Sh Y,ZHANG H,et al.Droplet transfer characteristics and force analysis of laser arc composite welding process [J].Journal of Mechanical Engineering,2018,54(6):154-161(in Chinese).
[9] YANG Y D,LIU J,SHI Y,et al.Effect of nozzle shape on forming quality of aluminum alloy composite welding joint [J].Laser Technology,2018,42(2):222-228(in Chinese).
[10] LIU J,LI Zh,SHI Y,et al.Effect of laser-arc distance on surface flow of laser-GMAW hybrid welding molten pool[J].Chinese Journal of Lasers,2018,45(10):1002004(in Chinese).
[11] XIE W,FAN C,YANG C,et al.Effect of acoustic field parameters on arc acoustic binding during ultrasonic wave-assisted arc welding [J].Ultrasonics Sonochemistry,2016,29:476-484.
[12] ROSTAMIYAN Y,SEIDANLOO A,SOHRABPOOR H,et al.Experimental studies on ultrasonically assisted friction stir spot welding of AA6061[J].Archives of Civil & Mechanical Engineering,2015,15(2):335-346.
[13] JIAN X,XU H,MEEK T T,et al.Effect of power ultrasound on solidification of aluminum A356 alloy [J].Materials Letters,2005,59(2):190-193.
[14] LIU C,CHEN D,HILL M R,et al.Effects of ultrasonic impact treatment on weld microstructure,hardness,and residual stress [J].Materials Science & Technology,2017,33(12):1-9.
[15] XU H,JIAN X,MEEK T T,et al.Degassing of molten aluminum A356 alloy using ultrasonic vibration[J].Materials Letters,2004,58(29):3669-3673.
[16] LI H X.Study on corrosion resistance of aluminum alloy composite welded Joint by welding process [D].Changchun:Changchun University of Science and Technology,2017:5-10 (in Chinese).
[17] LI Y J,WANG J.Principle and application of welding [M].Beijing:Chemical Industry Press,2009:18-21(in Chinese).
[18] TUCKER J D,NOLAN T K,MARTIN A J,et al.Effect of travel speed and beam focus on porosity in alloy 690 laser welds [J].Journal of Metals,2012,64(12):1409-1417.
[19] GAO M Zh.Study on interface microstructure of ultrasonic assisted brazing joint of AZ31B magnesium alloy/6063 aluminum alloy [D].Lanzhou:Lanzhou University of Technology,2017:20-25(in Chinese).
[20] KANG J,ZHANG X,WANG S,et al.The comparison of ultrasonic effects in different metal melts[J].Ultrasonics,2015,57:11-17.
[21] XU H,JIAN X,MEEK T T,et al.Degassing of molten aluminum A356 alloy using ultrasonic vibration [J].Materials Letters,2004,58(29):3669-3673.
[22] MA G,YAN S,WU D,et al.Microstructure evolution and mechanical properties of ultrasonic assisted laser clad yttria stabilized zirconia coating [J].Ceramics International,2017,43(13):9622-9629.
[23] BURKE J E,TURNBULL D.Recrystallization and grain growth [J].Progress in Metal Physics,1952,3(3):220-292.
[24] MA L,SHU G,CHEN F.Study on solidification of metal melt in ultrasonic field [J].Materials Science and Engineering,1995(4):2-7.
[25] GE H L.Study on microstructure change and influence mechanism of aluminum alloy with ultrasonic impact welding [D].Harbin :Harbin Institute of Technology,2016:32-47 (in Chinese).