7020铝合金水下搅拌摩擦焊接头组织和力学性能

Microstructure and Mechanical Properties of Underwater Friction Stir Welded Joints of 7020 Aluminum Alloy

摘要: 采用水下搅拌摩擦焊技术对厚度为5 mm的7020铝合金板材进行焊接，对接头的微观组织和力学性能进行了研究。结果表明：焊核区通过动态再结晶形成了细小的等轴晶，大部分沉淀相固溶到铝基体中。与常规的空冷接头相比，水冷接头焊核区微观组织更加细小，热机影响区沉淀相较多，热影响区的沉淀相细小，其软化区变窄。水冷接头的抗拉强度为（418.5±7.4）MPa，达到母材的90%，与空冷接头相比有较大的提高。

Abstract: 7020 aluminum alloy plate with a thickness of 5 mm was welded by underwater friction stir welding(UFSW), and the microstructure and mechanical properties of the welded joint were studied.The results show that the microstructure of nugget zone consists of fine equiaxed grains due to dynamic recrystallization, and most of precipitates dissolve into the Al matrix. Compared with that of the air-cooling FSW joint, the microstructure of the nugget zone of the UFSW joint are finer, more precipitates exsit in thermo-mechanically affected zone and finer precipitates exists in heat affected zone, the soft region becomes narrow. The ultimate tensile strength of the UFSW joint reaches (418.5±7.4) MPa, equivalent to 90% of the base metal, which is greatly improved compared with that of the air-cooling FSW joint.