不同进给速度对铝合金焊接接头的微观组织与力学性能的影响

Effect of Different Welding Speeds on the Microstructure and Mechanical Properties of Aluminum Alloy Welded Joints

摘要: 目的：研究不同进给速度对铝合金搅拌摩擦焊接头组织与力学性能的影响，分析其拉伸行为及断裂机理。方法：采用搅拌摩擦焊对Al-Cu-Mg系铝合金进行对接焊试验，固定旋转速度(1000 r/min)，改变前进速度。利用金相显微镜观察接头微观组织；使用显微维氏硬度仪测试硬度分布；通过拉伸试验机测定接头的常温拉伸性能。结果：微观组织表明：焊核区经历了动态再结晶，形成细小的等轴晶组织。随着前进速度的增加，焊核区晶粒尺寸减小。接头组织呈现显著的非对称性，后退侧热机影响区的晶粒流线更剧烈，边界更清晰。力学性能显示：接头硬度分布呈“W”型，热影响区硬度最低。当前进速度为100 mm/min时，焊核区平均硬度最高(140.85 Hv)，接头抗拉强度达到峰值(413 MPa)，断裂伸长率为8.3%。结论：前进速度通过调控热输入和材料流动，显著影响铝合金FSW接头的微观组织和力学性能。在本研究的参数下，采用1000 r/min的旋转速度和100 mm/min的前进速度，可获得力学性能最优的焊接接头。该研究为优化铝合金搅拌摩擦焊工艺参数提供了理论依据。

Abstract: Objective: To investigate the influence of different welding speeds on the microstructure and mechanical properties of aluminum alloy Friction Stir Welding (FSW) joints, and to analyze their tensile behavior and fracture mechanism. Methods: Butt welding experiments were conducted on Al-Cu-Mg series aluminum alloy plates using friction stir welding, with a constant rotation speed (1000 rpm) and varying travel speeds. The microstructure of the joints was observed using a metallographic microscope; the hardness distribution was tested using a micro-Vickers hardness tester; and the room temperature tensile properties of the joints were determined using a tensile testing machine. Results: The microstructure analysis revealed that the Nugget Zone (NZ) underwent dynamic recrystallization, forming fine equiaxed grains. As the welding speed increased, the grain size in the NZ decreased. The joint structure exhibited significant asymmetry, with more severely deformed grain flow lines and a clearer boundary in the Thermomechanically Affected Zone (TMAZ) on the retreating side. Mechanical properties showed that the hardness distribution across the joint presented a “W” shape, with the Heat-Affected Zone (HAZ) having the lowest hardness. When the welding speed was 100 mm/min, the average hardness of the NZ reached its maximum (125.85 Hv), and the joint achieved its peak tensile strength (413 MPa) with an elongation of 8.3%. Conclusion: The welding speed significantly affects the microstructure and mechanical properties of aluminum alloy FSW joints by controlling the heat input and material flow. Under the parameters of this study, using a rotation speed of 1000 rpm and a welding speed of 100 mm/min resulted in the optimal mechanical properties for the welded joint. This research provides a theoretical basis for optimizing the FSW process parameters for aluminum alloys.