7022铝合金FSJ连接区减薄机理分析

Analysis on the reduction mechanism of 7022 aluminum alloy in the FSJ jointing area

针对10mm厚的7022铝合金进行了FSJ连接实验,并利用工具显微镜对连接区横截面形貌进行分析研究。结果表明,前进侧的连接区塑化金属在搅拌针表面的挤压作用下瞬时针方向流入空腔,后进侧的连接区塑化金属在搅拌针表面的挤压作用下逆时针方向流入空腔。轴肩摩擦软化的塑化金属在搅拌头高速旋转下,形成涡旋流动并在轴肩下压力作用下流入空腔;随着搅拌针的高速旋转,空腔内的塑化金属向四周挤压,致使母材发生塑性变形,同时将底部部分塑化金属挤压到母材上表面,且在轴肩下压力作用下,挤压到轴肩外围形成"飞边";由于涡旋流动,致使连接区中间部位的金属层下凹,形成连接区表面中间部位凹陷。造成了连接区"减薄效应"现象发生。"填充式间接挤压-涡旋流动"模型能准确表达连接区金属塑性流动和减薄形成过程。

Experimental study was carried out on the FSJ of 10mm thick 7022 aluminum alloy. The cross-section of jointing area was analyzed by the tool microscope. The results show that the plastic metal of seam in the ad- vancing side along the surface of the stirring pin was squeezed into the cavity clockwise and the plastic metal of seam in the retreating side along the surface of the stirring pin was squeezed into the cavity counterclockwise. In high rotation speed of the stirring head, the plastic metal soften by shaft shoulder friction stirring was generated vortex flow and squeezed into the cavity under the pressure of shaft shoulder. With the high speed of stirring pin, the plastic metal in the cavity squeezes the base metal to the surrounding, resulting in plastic deformation of base metal. At the same time, the part of plastic metal of the bottom was squeezed to the surface of base metal, which was squeezed to the surrounding and formed the ＂Flash＂ under the action of the pressure of shaft shoul- der. As the vortex flow, the metal layer of the middle was concave, and the middle position of the surface of seam was sunken. ＂Reduction effect＂ phenomenon was occurred in the jointing area. The model of ＂filling indi- rect squeeze - vortex flow＂ can accurately express the flow pattern of the plastic metal of jointing area and reduc- tion formed process.