7050高强铝合金激光焊接接头的组织性能

Microstructures and Mechanical Properties of 7050 Ultrahigh-Strength Aluminum Alloy Joints by Laser Welding

采用光纤激光对3mm厚的7050铝合金板进行了对接焊,分析了焊接工艺对焊缝成形的影响,并对接头的微观组织、化学成分、力学性能及断口特征进行了研究。结果表明,当激光功率为3kW,焊接速度为4m·min^(-1),光斑直径为0.2mm时,能够得到性能良好的焊接接头。焊缝中心以等轴晶组织为主,晶界处弥散分布着Al-Cu金属间化合物,焊缝边缘为柱状晶组织,热影响区(HAZ)较窄。焊缝中无强化相析出,热影响区的强化相有所熔解。接头硬度分布不均匀,焊缝处硬度最低,热影响区发生明显软化。焊接接头抗拉强度为307 MPa,接头拉伸后断于焊缝,断口处有小韧窝,呈沿晶脆性断裂特征。

The butt welding of 3 mm thick 7050 aluminum alloy plates by using fiber lasers is conducted. The effect of welding process on weld forming is studied, and microstructures, chemical compositions, mechanical properties and fracture characteristics of joints are also investigated. The results show that well joints can be obtained when laser power of 3 kW, welding speed of 4 m · min^- 1, and spot diameter of 0.2 mm are chosen. There exist mainly equiaxed grains in the weld center, AI-Cu intermetallic compounds are dispersed in the grain boundaries, there are mainly columnar dendrite grains in the weld edge, and the heat affected zone （HAZ） is relatively narrow. No precipitation is found in the weld and the strengthening phase in the HAZ melts slightly. The microhardness distribution of weld joints is non-uniform, the hardness at the weld is the lowest, and there exists obvious softening in the HAZ. The tensile strength of welded joints is 307 MPa, the joints fracture along the weld after tensile, and there exist small dimples in the fractures, which shows a character of intergranular brittleness fracture.