Abstract: For the sake of analyzing the flow behavior of plastic metal in extruded zone around tool pin-tip and its effect on formation quality of the weld, friction stir welding (FSW) experiments were carried out, taking thick copper foils with thickness of 0.02 mm as insert tracer material and 2024 aluminum alloy sheets with thickness of 1 mm and 2 mm as base metal, adopting different stacking methods. It could be found during FSW process that the plasticized metal on upper part of the weld continuously migrated towards the tool pin-tip along the pin thread groove direction, grew up and form an extruded zone around the pin-tip. The extruded zone generally consisted of an expanded zone located on both sides of the pin and a deformed zone under the pin-tip surface. Moreover, the metals in the deformed zone included two parts, one came from the plasticized metal migrated from the weld top, and the other came from the deformed metal of original base material suffered from the rotation frictional force. The flow patterns of plastic metals in the extruded zone were divided into three types: axial-extruding flow, horizontal-friction flow and bypassing flow. For FSW of thick plate, the plastic metals in the extruded zone tended to transfer around the pin in the bypassing flow way, which leaded to the formation of loose zone or cavity defect inside the weld.
毛育青, 柯黎明, 江周明. 搅拌针端部挤压区内塑性金属的流动行为[J]. 材料导报, 2018, 32(20): 3612-3617.
MAO Yuqing, KE Liming, JIANG Zhouming. Flow Behavior of Plastic Metal in Extruded Zone Around Tool Pin-tip. Materials Reports, 2018, 32(20): 3612-3617.
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2018, Vol. 32 
