LF21超声搅拌摩擦焊接头组织及性能分析

利用超声波对金属塑性成形作用对LF21铝合金进行了超声搅拌摩擦焊接试验,并对常规搅拌摩擦焊与超声搅拌摩擦焊接头的微观组织、断口形貌进行了对比分析.结果表明,超声能量通过搅拌头有效地导入焊缝底部,在增加焊缝底部搅拌强度的同时,提高了搅拌针周围金属原子的运动和扩散能力,焊核区的金属组织有明显的晶粒细化和组织均匀化.超声搅拌摩擦焊断口韧窝数量与深度均不及常规搅拌摩擦焊,撕裂棱不明显;超声搅拌摩擦焊可以提高接头力学性能,但平均断后伸长率相比常规搅拌摩擦焊有所下降.

Ultrasonic friction stir welding of LF21 aluminum alloy

According to the principle of the role of ultrasound on metal plastic forming, the self-developed ultrasonic friction stir welding machine was used to weld LF21 aluminum alloy plates.The microstructures and fracture appearance of aluminum alloys were studied.Experiments show that the ultrasonic energy can inject into the weld joint effectively.It can not only increase the intensity of the bottom of weld joint, but also improve metal atoms motion and diffusion ability around mixing needle.The grain in microstructure of WNZ(weld nugget zone) is refined and homogenized obviously.The tensile fracture of ultrasonic friction stir welded joint appears to be a dimple pattern.The depth of dimple is shallower and the number of dimples is less than that in the fracture of friction stir welding.The result shows that ultrasonic welding can improve the mechanical properties of the joint, but the elongation decreases a little compared to that of friction stir welding.