Al-Zn-Mg-Sc-Zr合金搅拌摩擦焊接接头的显微组织、力学性能及局部腐蚀性能

摘要

The mechanical properties and localized corrosion of Al-Zn-Mg-Sc-Zr alloy friction stir welded joint were investigated by hardness testing, polarization curve testing, corrosion immersion testing and slow strain rate tensile testing. Moreover, the microstructure of the welded joint was characterized by optical microscopy and the transmission electron microscopy. The results show that the hardness curve of the welded joint exhibits “W” shape, and the lowest hardness appears in the transition zone between heat affected zone(HAZ) and thermo-mechanical affected zone (TMAZ). Compared with the base material, the localized corrosion resistance of the welded joint decreases, and the stress corrosion cracking susceptibility increases. The TMAZ exhibits the lowest corrosion potential, the highest current density, the largest intergranular corrosion depth and the lowest corrosion resistance. During welding, mostη′phase dissolves and a number ofη phase is located at grain boundaries in the grains of TMAZ, which leads to the decrease of hardness and corrosion resistance.%通过硬度测试、极化曲线测试、腐蚀浸泡和慢应变速率拉伸方法研究Al-Zn-Mg-Sc-Zr合金板材搅拌摩擦焊接接头的力学性能和局部腐蚀性能，并利用金相显微镜和透射电镜对焊接接头的显微组织进行分析。结果表明：焊接接头的硬度曲线呈现 W 型，硬度最低值出现在热影响区与热机影响区的交界处；和母材相比，焊接接头的局部抗腐蚀性能降低，应力腐蚀敏感性增大。热机影响区的腐蚀电位最低，腐蚀电流密度最高，晶间腐蚀深度最大，抗腐蚀性能最差。热机影响区的硬度和腐蚀性能的降低，主要是由于该区的晶粒发生变形，大部分η′沉淀强化相溶解，晶界上分布着大量的η相。