2219-T87铝合金搅拌摩擦焊接头组织与力学性能

Microstructures and mechanical properties of friction stir welded 2219-T87 aluminum alloy joints

采用搅拌摩擦焊方法对8mm厚2219-T87铝合金进行了焊接.对接头的宏观形貌、微观组织、显微硬度及断口形貌进行了分析.结果表明,焊核区为细小的等轴晶粒,晶粒尺寸远小于母材;热机影响区发生了弯曲变形;热影响区组织出现了明显粗化.前进边热机影响区和焊核区形成明显分界线,后退边相对模糊.搅拌摩擦焊对接头各区域沉淀相分布形态有重要影响.接头室温拉伸强度可以达到母材的70%以上.沿焊缝横截面的显微硬度的分布显示,硬度最低点位于后退侧热影响区区域,断裂位置位于后退侧热影响区处,接头的断裂形式为韧性断裂.

The joint of 2219-T87 aluminum alloy plate in 8 mm thickness was obtained by friction stir welding (FSW),and the microstructures and mechanical properties of the joint were investigated.The results show that the microstructure in the nugget zone (NZ) consists of refined and equiaxed grains,that in the thermal-mechanically affected zone (TMAZ) consists of deformed grains,and that in the heat-affected zone (HAZ) consists of coarse lath grains.There is an obvious interface between NZ and TMAZ at the advancing side,but there is illegibility comparatively at the retreating side.The precipitation phenomena in different zone are affected by friction stir welding.The results of tensile properties show that the transverse tensile strength of FSW joint can reach about 70% of that of the base metal.Hardness measurements show that the FSW joint is soften during welding,heat-affect zone has serious softening,and tensile specimens fracture at the HAZ of retreating side.Fractographs confirm that the fracture of the joint is the mode of ductile fracture.