高能缺陷和第二相对新型超高强铝合金腐蚀行为的影响

Corrosion behavior of a new ultra high strength aluminum alloy due to high energy defects and secondary phases

采用等径角挤压(ECAP)和固溶时效处理获得超高强铝合金,并采用透射电子显微镜、扫描电镜以及电化学工作站等测试手段对其微观结构演变以及电化学腐蚀行为进行研究。结果表明:等径角挤压变形后晶粒细化至亚微米(9.68→1μm),大变形诱导的溶质原子偏析和不连续脱溶效应造成第二相长大(53→416 nm)和晶界偏聚;大塑性变形材料经固溶时效处理后,部分第二相的晶界偏析现象减弱,呈细小颗粒状弥散分布于铝基体中。细晶组织和高能缺陷有利于形成附着力良好且致密稳定的氧化膜,晶界偏析的减弱和弥散细小的第二相抑制了点蚀对晶间腐蚀的促进作用,最终显著优化超高强铝合金的耐腐蚀性能。

Ultrahigh strength aluminum alloys were prepared by equal channel angular pressing (ECAP) and solution aging treatment. The microstructure evolution and electrochemical corrosion behavior of the alloy were studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electrochemical workstation. The results show that grains are refined to submicron level after ECAP. Solute segregation and discontinuous dissolution caused by severe plastic deformation lead to the coarsening of secondary phases particles and segregation at grain boundary. Partial secondary phase particles in Al-Zn-Mg-Cu alloy are refined and dispersed in aluminum matrix after the process of severe plastic deformation and solution aging, which demonstrates the decrease of secondary phase segregation at grain boundary. The dense and stable oxide films, as well as the fine secondary phase particles with diffused distribution, have beneficial influence on the improvement of corrosion resistance of ultra-high strength aluminum alloy. The dense and stable oxide films with high adhesion are formed by fine grain structure and high energy defects. Intergranular corrosion is depressed by dispersed fine secondary phase and decrease of grain boundary segregation.