下扎深度对回填式搅拌摩擦点焊接头断裂行为的影响

发布时间：2018-10-31 17:53

【摘要】：为研究焊接工艺参数对回填式搅拌摩擦点焊(RFSSW)接头断裂行为的影响,以铝合金为例,通过改变焊接过程中套筒的下扎深度对上下板厚度不同的LY12铝合金进行RFSSW试验,从材料流动、原子扩散及接头软化等方面对其接头的断裂机理进行分析,并利用焊点的宏观形貌、显微组织和硬度进行验证。试验及分析结果表明:在RFSSW过程中,当套筒未扎透上板、hook缺陷较平且韧带在整个焊点厚度基本相同时,裂纹主要沿连接强度较弱的搭接面扩展,形成剪切断裂模式;当套筒下扎至下板厚度的15%、hook缺陷向上弯曲且套筒回抽路径产生裂纹缺陷时,裂纹更倾向于沿着原子扩散时间较短的套筒回抽路径扩展,形成剪切塞型断裂模式;随着套筒进一步下扎至下板厚的35%且hook缺陷向下弯曲,裂纹更容易沿着下板中的套筒回抽路径向下扩展;当裂纹扩展到下板的下表面时,形成塞型断裂模式,断口形貌与断裂机理的分析结果相吻合。
[Abstract]:In order to study the effect of welding process parameters on the fracture behavior of backfill friction stir spot welding (RFSSW) joints, the RFSSW tests of LY12 aluminum alloys with different thickness of upper and lower plates were carried out by changing the depth of the sleeve in the welding process, taking aluminum alloy as an example. The fracture mechanism of the joint was analyzed from the aspects of material flow atomic diffusion and joint softening. The microstructure and hardness of the joint were verified by the macroscopic morphology of the solder joint. The experimental and analytical results show that in the process of RFSSW, when the sleeve does not penetrate the upper plate, the hook defects are flat and the thickness of the ligaments is basically the same as the whole solder joint, the crack mainly extends along the weak joint surface, forming a shear fracture mode. When the thickness of the sleeve goes down to the thickness of the lower plate, the hook defect bends upward and the crack defect is produced by the sleeve pumping path, the crack tends to propagate along the sleeve return pumping path with shorter atomic diffusion time, thus forming the shear plug mode of fracture. As the sleeve goes further down to 35% of the thickness of the lower plate and the hook defect bends downward, it is easier for the crack to propagate downwards along the retractive path of the sleeve in the lower plate. When the crack extends to the lower surface of the plate, a stop-type fracture mode is formed, and the fracture morphology is in agreement with the analysis results of the fracture mechanism.
【作者单位】：沈阳航空航天大学航空航天工程学部;北京航空航天大学机械工程及自动化学院;
【基金】：国家自然科学基金资助项目(51204111) 辽宁省自然科学基金资助项目(2013024004)
【分类号】：TG453.9

【参考文献】