铝合金厚板搅拌摩擦焊焊缝疏松缺陷形成机理

doi:10.7527/S1000-6893.2016.0197

Abstract

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.

Key words: aluminum alloy 7075, friction stir welding (FSW), weld quality, plastic flow, weld defects, formation mechanisms

CLC Number:

V252.2

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.

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

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