飞机蒙皮铝合金超声辅助搅拌摩擦焊试验分析

针对飞机蒙皮对接时,因搅拌摩擦焊(FSW)工艺窗口狭窄易致底部虚焊、弱连接等缺陷问题,为了探索更适合大飞机蒙皮长程稳定焊接的新方法,设计了超声辅助搅拌摩擦焊(UAFSW)与FSW的蒙皮连接对比试验,采用1.8 mm厚度的2524-T3铝合金进行了同种工艺条件下的UAFSW与FSW焊接,对表面成形良好、内部无缺陷的FSW与UAFSW焊缝,进行了拉伸、金相、扫描电镜观察等对比分析试验。结果表明,与FSW焊缝相比,UAFSW焊缝缺陷率明显降低,工艺窗口扩大;UAFSW焊缝表面纹理更细密,层叠现象消失;UAFSW焊缝的平均抗拉强度略高于FSW焊缝,达到母材强度的90.7%;UAFSW焊缝的平均延伸率则比FSW焊缝高20%左右。研究发现,超声的加入使UAFSW焊缝微观组织更细更均匀,晶粒尺寸变细小,且晶粒沿轧制方向的规律性被打乱,呈现无明显方向的杂序排列。

Test analysis for ultrasonic assisted friction stir welding of aircraft skin aluminium alloy

For the bottom of the weld,weak connection and other defects in the friction stir welding (FSW) of aircraft skin,due to the narrowing of the FSW process window,in order to explore a new method that is more suitable for long-range stable welding of large aircraft skin,skinned contrast test between ultrasonic assisted friction stir welding (UAFSW) and FSW were performed,UAFSW and FSW welding were carried out under the same process conditions using 2524-T3 aluminum alloy with thickness of 1.8 mm.Tensile test,metallographic test,and scanning electron microscopy were implemented for perfect UAFSW and FSW weld joints without internal defects.The results show that,compared with FSW weld joints,the UAFSW weld joint defect rate is significantly reduced,and the process window is expanded;the UAFSW weld surface texture is finer and free from laminations;the average tensile strength of UAFSW weld joints reaches 90.7％ of strength of the base material,slightly higher than that of FSW weld joints;the average elongation of UAFSW weld joints is higher than FSW weld joints by about 20％.The study found that,compared with FSW,the addition of ultrasonic makes finer and more uniform microstructure for UAFSW weld joints,reduces grain size,and disrupts the regularity of the grains along the rolling direction,which makes the grain sequence show no clear direction.