铝合金厚板搅拌摩擦焊焊缝疏松缺陷形成机理

发布时间：2019-04-28 08:20

【摘要】：采用圆锥形搅拌头焊接20mm厚的7075-T6铝板,分析焊接过程中焊缝内部疏松缺陷的形成过程及原因。研究表明,焊缝表面成形良好,无明显缺陷。但是,在焊缝轴肩区和焊核区之间出现了疏松缺陷。分析认为,焊缝上、下部金属温度差太大,导致其塑性流动行为发生变化是疏松缺陷形成的主要原因。搅拌摩擦焊(FSW)过程中,焊缝上部金属温度较高,而底部温度仍然很低,脱离搅拌针端部的塑化金属在周围冷金属巨大的变形抗力作用下转而沿搅拌针表面往上迁移。到达轴肩区下方汇聚区时,由于轴肩区金属温度高,向下的挤压力太小,导致回迁上来的塑化金属继续往上迁移并冲破轴肩区而沿轴肩边缘溢出形成飞边。汇聚区内没有足够的塑化金属填充、焊缝无法被压实而产生疏松孔洞。通过建立疏松缺陷形成的物理模型,可以更直观地反映出焊缝金属流动形态及缺陷形成过程。
[Abstract]:A conical agitator was used to weld 7075-T6 aluminum plate with thick 20mm. The forming process and causes of loose defects in the weld during welding were analyzed. The results show that the weld surface is well formed and there is no obvious defect. However, there is a loose defect between the shoulder and the core of the weld shaft. It is considered that the change of plastic flow behavior is the main cause of loose defect formation due to the large temperature difference between the lower part of the weld and the lower part of the weld. In the process of friction stir welding (FSW), the temperature of the upper part of the weld is higher, but the temperature of the bottom is still very low. The plasticized metal separated from the end of the stirring pin moves upward along the surface of the stirring needle under the action of the great deformation resistance of the surrounding cold metal. When reaching the convergence area below the shoulder region, due to the high temperature of the metal in the shoulder area, the downward extrusion pressure is too small, resulting in the plastic metal moving back up and breaking through the shoulder area and forming a flying edge along the shoulder edge. There is not enough plasticized metal filling in the convergence area, and the weld can not be compacted to produce loose holes. By establishing the physical model of loose defect formation, the flow pattern of weld metal and the process of defect formation can be reflected more intuitively.
【作者单位】：南昌航空大学轻合金加工科学与技术国防重点学科实验室;西北工业大学凝固技术国家重点实验室;
【基金】：国家自然科学基金(51265043,51265042) 江西省高等学校科技落地计划(KJLD13055,KJLD12074)~~
【分类号】：TG453.9

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