6061-T651铝合金搅拌摩擦焊接头的显微组织和力学性能

Microstructure and Mechanical Properties of 6051-T351 Aluminum Alloy Friction Stir Welding Joint

通过金相显微镜观察、硬度测试、拉伸试验和扫描电镜观察等试验手段研究分析了6061-T651铝合金搅拌摩擦焊接头的微观组织与力学性能。结果表明,接头处焊核区因剧烈塑性变形和高温循环而发生了动态再结晶,形成细小的等轴晶组织,而热影响区晶粒组织和第二相颗粒均发生一定的粗化。接头的硬度沿着垂直于焊接方向基本呈W形分布,热影响区由于晶粒粗化以及第二相颗粒的聚集长大,其硬度值最低。沿垂直于焊接方向和平行于焊接方向的接头试样强度都比母材低,沿垂直于焊接方向的接头试样伸长率低于母材,而平行于焊接方向的伸长率比母材的高;断口形貌表明断裂方式为典型的韧性断裂。

The microstructure and mechanical properties of 6061-T651 aluminum alloy friction stir welding joint were studied by means of metallographic microscope observation, hardness test, tensile test and SEM observation. The results show that dynamic recrystallization occurs in the nugget zone （NZ） of the welded joint due to severe plastic deformation and high temperature cycle, which results in the formation of fine equiaxed grains. The grains and the second phase particles in the heat affected zone （HAZ） coarsens. The hardness of the joint shows basically W shape along the direction perpendicular to the welding direction. The lowest hardness value appears at the HAZ because of the grain coarsening and the aggregation and growth of the second phase particles. The strengths of the joint specimens along perpendicular and parallel to the welding direction are lower than that of base metal. The elongation of the joint specimen along perpendicular to the welding direction is lower than that of base metal, while it is higher than that of base metal along parallel to the welding direction. The fracture morphologies show that the fracture mode is typical ductile fracture.