Material Engineering and Mechanical Manufacturing

Formation mechanism of weld loose defect in friction stir welding thick plates of aluminum alloy

  • MAO Yuqing ,
  • KE Liming ,
  • LIU Fencheng ,
  • CHEN Yuhua
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  • 1. National Defence Key Discipline Laboratory of Light Alloy Processing Science and Technology, Nanchang Hangkong University, Nanchang 330063, China;
    2. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China

Received date: 2016-04-26

  Revised date: 2016-06-16

  Online published: 2016-06-22

Supported by

National Natural Science Foundation of China (51265043, 51265042); Landed Plan of Science and Technology in Colleges and Universities of Jiangxi Province (KJLD13055, KJLD12074)

Abstract

20 mm thick 7075-T6 aluminum alloys are joined by friction stir welding (FSW) using a tapered pin, and the formation process and reason of loose void defect are investigated during FSW. The results show that the weld surfaces are good without any defects. However, the loose defect is found in all welds between the shoulder zone and the nugget zone. The main reason is that the metal is stirred abnormally to cause the change in the plastic flow behavior due to high temperature difference on the top and bottom of the weld. During FSW, the temperature on the top is high while low on the bottom of the weld, the plastic material fallen off the pin-tip suffers from large deformation constraining force of the surrounding cold metal, and then moves upwards along the surface of the pin to reach the shoulder zone. The extruding force to plastic material is small because the temperature is too high, and the plastic material continues to migrate upwards and traverses the shoulder zone to flow along the edge of tool shoulder and form the flash finally. There is not enough plasticized metal to fill the cavity, and the loose zone is thus formed in the weld. By establishing the physical model for loose defect formation, the flow behavior of the plastic material and the formation process of loose defect in FSW can be directly reflected.

Cite this article

MAO Yuqing , KE Liming , LIU Fencheng , CHEN Yuhua . Formation mechanism of weld loose defect in friction stir welding thick plates of aluminum alloy[J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2017 , 38(3) : 420367 -420367 . DOI: 10.7527/S1000-6893.2016.0197

References

[1] BALASUBRAMANIAN V, RAVISANKAR V, MAD-HUSUDHAN R G. Effect of postweld aging treatment on fatigue behavior of pulsed current welded AA7075 aluminum alloy joints[J]. Journal of Materials Engineering and Performance, 2008, 17(2):224-233.
[2] FULLER C B, MAHONEY M W, CALABRESE M, et al. Evolution of microstructure and mechanical properties in naturally aged 7050 and 7075 Al friction stir welds[J]. Materials Science and Engineering:A, 2010, 527(9):2233-2240.
[3] BAHEMMAT P, HAGHPANAHI M, GIVI M K B, et al. Study on dissimilar friction stir butt welding of AA7075-O and AA2024-T4 considering the manufacturing limitation[J]. The International Journal of Advanced Manufacturing Technology, 2012, 59(9):939-953.
[4] MAO Y Q, KE L M, LIU F C, et al. Effect of tool pin eccentricity on microstructure and mechanical properties in friction stir welded 7075 aluminum alloy thick plate[J]. Materials and Design, 2014, 62:334-343.
[5] SIVARAJ P, KANAGARAJAN D, BALASUBRAMANIAN V. Effect of post-weld heat treatment on tensile properties and microstructure characteristics of friction stir welded armour grade AA7075-T651 aluminium alloy[J]. Defence Technology, 2014, 10:1-8.
[6] CABIBBO M, FORCELLESE A, SIMONCINI M, et al. Effect of welding motion and pre-/post-annealing of friction stir welded AA5754 joints[J]. Materials and Design, 2016, 93:146-159.
[7] HU Z L, WANG X S, PANG Q, et al. The effect of postprocessing on tensile property and microstructure evolution of friction stir welding aluminum alloy joint[J]. Materials Characterization, 2015, 99:180-187.
[8] DORBANE A, MANSOOR B, AYOUB G, et al. Mechanical, microstructural and fracture properties of dissimilar welds produced by friction stir welding of AZ31B and Al6061[J]. Materials Science and Engineering:A, 2016, 651:720-733.
[9] MIRONOV S, ONUMA T, SATO Y S, et al. Microstructure evolution during friction-stir welding of AZ31 magnesium alloy[J]. Acta Materialia, 2015, 100:301-312.
[10] QIAN J W, LI J L, SUN F, et al. An analytical model to optimize rotation speed and travel speed of friction stir welding for defect-free joints[J]. Scripta Materialia, 2013, 68(3-4):175-178.
[11] 李宝华, 唐众民, 鄢江武, 等. 5A06铝合金厚板搅拌摩擦焊工艺研究[J]. 热加工工艺, 2011, 40(11):152-154. LI B H, TANG Z M, YAN J W, et al. Research on friction stir welding parameters of thick 5A06 aluminum alloy[J]. Hot Working Technology, 2011, 40(11):152-154(in Chinese).
[12] 赵衍华, 林三宝, 吴林. 2014铝合金搅拌摩擦焊接头缺陷分析[J]. 焊接, 2005(7):9-12. ZHAO Y H, LIN S B, WU L. Analysis of friction stir welding defects in 2014 aluminum alloy[J]. Welding & Joining, 2005(7):9-12(in Chinese).
[13] 王磊, 谢里阳, 李兵. 铝合金搅拌摩擦焊焊接过程缺陷分析[J]. 机械制造, 2008, 46(522):5-9. WANG L, XIE L Y, LI B. Analysis of welding defect in friction stir welding aluminum alloy[J]. Machinery, 2008, 46(522):5-9(in Chinese).
[14] SHRIVASTAVA A, DINGLER C, ZINN M, et al. Physics-based interpretation of tool-workpiece interface temperature signals for detection of defect formation during friction stir welding[J]. Manufacturing Letters, 2015, 5:7-11.
[15] KIM Y G, FUJII H, TSUMURA T, et al. Three defect types in friction stir welding of aluminum die casting alloy[J]. Materials Science and Engineering:A, 2006, 415:250-254.
[16] XU W F, LIU J H, LUAN G H, et al. Temperature evolution, microstructure and mechanical properties of friction stir welded thick 2219-O aluminum alloy joints[J]. Materials and Design, 2009, 30(6):1886-1893.
[17] MAO Y Q, KE L M, LIU F C, et al. Investigations on temperature distribution, microstructure evolution, and property variations along thickness in friction stir welded joints for thick AA7075-T6 plates[J]. The International Journal of Advanced Manufacturing Technology, 2016, 86(1):141-154.
[18] CANADAY C T, MOORE M A, TANG W, et al. Through thickness property variations in a thick plate AA7050 friction stir welded joint[J]. Materials Science and Engineering:A, 2013, 559:678-682.
[19] HEURTIER P, JONES M J, DESRAYAUD C, et al. Mechanical and thermal modeling of friction stir welding[J]. Journal of Materials Processing Technology, 2006, 171:348-357.
[20] 柯黎明, 潘际銮, 邢丽, 等. 搅拌针形状对搅拌摩擦焊焊缝截面形貌的影响[J]. 焊接学报, 2007, 28(5):16-20. KE L M, PAN J L, XING L, et al. Influence of pin shape on weld transverse morphology in friction stir welding[J]. Transaction of the China Welding Institution, 2007, 28(5):16-20(in Chinese).
[21] KE L M, XING L, INDACOCHEA J E. Material flow patterns and cavity model in friction-stir welding of aluminum alloys[J]. Metallugical and Materials Transactions:B, 2004, 35(1):153-160.
[22] PRANGNELL P B, HEASON C P. Grain structure formation during friction stir welding observed by the ‘stop action technique’[J]. Acta Materialia, 2005, 53(11):3179-3192.
[23] DAS B, BAG S, PAL S. Defect detection in friction stir welding process through characterization of signals by fractal dimension[J]. Manufacturing Letters, 2016, 7:6-10.
[24] LIU X C, WU C S, PADHY G K. Improved weld macrosection, microstructure and mechanical properties of 2024Al-T4 butt joints in ultrasonic vibration enhanced friction stir welding[J]. Sciences and Technology of Welding and Joining, 2015, 20(4):345-352.
[25] 柯黎明, 潘际銮, 邢丽, 等. 搅拌摩擦焊焊缝金属塑性流动的抽吸-挤压理论[J]. 机械工程学报, 2009, 45(4):89-94. KE L M, PAN J L, XING L, et al. Sucking-extruding theory for the material flow in friction stir welds[J]. Journal of Mechanical Engineering, 2009, 45(4):89-94(in Chinese).

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