铝合金超声辅助搅拌摩擦焊接接头组织性能研究

目的探究超声振动对铝合金搅拌摩擦焊的作用效果。方法分别采用普通搅拌摩擦焊和超声辅助搅拌摩擦焊方法,对7075铝合金进行焊接试验,并对焊接接头的微观组织、力学性能、断口形貌进行分析。结果普通搅拌摩擦焊焊缝中生成了隧道型缺陷,施加超声振动后,缺陷消失,形成了无缺陷的良好接头,且与普通搅拌摩擦焊相比,超声辅助搅拌摩擦焊焊缝热影响区晶粒长大程度较小,焊核晶粒细化。接头强度明显提高,达到铝合金母材强度的71.5%,接头断裂模式为韧窝和准解理的混合断裂形式。结论超声振动促进了塑性金属的流动,能有效抑制孔洞、隧道型缺陷等的形成,同时超声振动能在提升金属塑性的同时,降低焊缝的热输入。

Microstructure and Properties of Aluminium Alloy Welding Joint by Ultrasonic-assisted Friction Stir Welding

The paper aims to explore effects of ultrasonic vibration on friction stir welding of aluminum alloy. Microstructure, mechanical property and fracture surface of 7075-T6 aluminum alloy were analyzed through ordinary friction stir welding and ultrasonic-assisted friction stir welding respectively. A tunnel-type defect was generated in the ordinary friction stir welding. After the ultrasonic vibration was applied, the defect disappeared and a good joint without defect was formed. Compared with the ordinary friction stir welding, the degree of growth of heat affected zone grains welded by ultrasonic-assisted friction stir welding was small, the grain size of the weld nugget was refined, the joint strength was obviously improved, and it reached 71.5% of the strength of the aluminum alloy base metal. The joint fracture mode was a mixed fracture mode of dimple and quasi-cleavage. Ultrasonic vibration promotes the flow of plastic metal, which can effectively inhibit the formation of holes, tunnel-type defects, etc. At the same time, ultrasonic vibration can increase the plasticity of the metal and reduce the heat input of the weld.