转速对6061铝合金/纯铜异种金属搅拌摩擦焊接头组织与性能的影响

采用搅拌摩擦焊技术对4 mm厚6061-T6铝合金和纯铜进行连接,研究转速对铝铜异种金属接头组织与力学性能的影响。结果表明,当焊接速度为30 mm/min、搅拌头转速在1 200~1 800 r/min的范围内,可以获得表面成形良好、无缺陷的铝铜异种金属接头。大量破碎的铜被搅入焊核区,形成了组织结构复杂的区域。通过EDS和XRD分析,在焊核区内发现了Al_2Cu、Al_4Cu_9和Al Cu金属间化合物。在界面处,铝和铜发生相互扩散形成金属间化合物层,随着转速的提高,化合物层逐渐变厚。由于晶粒细化、固溶强化作用以及金属间化合物的生成,异种接头的焊核区平均显微硬度值高于铝铜两侧平均硬度,并且在焊核区出现硬度峰值点。随着转速的增加,接头抗拉强度呈现先增大后减小的趋势,所得最优接头抗拉强度为183 MPa,达到铜母材的71.8%,断裂位置位于铝侧热影响区,断裂方式为韧性断裂。

Effect of rotation speed on the microstructure and mechanical properties of friction stir welded joints of 6061 aluminum alloy and pure copper dissimilar metals

In this paper,6061-T6 aluminum alloy and pure copper are welded by friction stir welding and the effect of rotation speed on the microstructure and mechanical properties of dissimilar joints is studied.When the welding speed is 30 mm/min and the rotation speed is in the range of 1200 r/min to 1800 r/min,sound joints without defects can be obtained.The complex structures are formed in the nugget zone where a large number of broken Cu particles are stirred into.Al2Cu,Al4Cu9 and AlCu intermetallic compounds are found in the nugget zone.The intermetallic compound layer is formed by mutual diffusion between aluminum and copper at the interface.With the increase of rotation speed,the compounds layer gradually becomes thicker.Due to the grain refinement,solid solution strengthening and the appearance of the IMCs,the average microhardness of the nugget zone is higher than that of aluminum and copper sides,and the microhardness peak appears in the nugget zone.Meanwhile,the tensile strength of the joint firstly increases and then decreases。The tensile strength of the optimal joint is 183 MPa and the joint efficiency is up to 71.8%of Cu BM.The fracture occurs in the heat affected zone of Al side,and the fracture mode is a ductile fracture.