Xing Qingyuan, Wu Xiaohui, Zang Jinxin, Meng Linggang, Zhang Xingguo
AECC Beijing Institute of Aeronautical Materials, Beijing 100095, China.
School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China.
Materials (Basel). 2022 Jan 28;15(3):1040. doi: 10.3390/ma15031040.
In this study, the influence of Er addition on the microstructure, type transformation of second phases, and corrosion resistance of an Al-Zn-Mg-Cu alloy were explored. The results revealed that the added Er element could significantly refine the alloy grains and change the second-phase composition at the grain boundary of the alloy. In the as-cast state, the Er element significantly enhanced the corrosion resistance of the alloy due to its refining effect on the grains and second phases at the grain boundary. The addition of the alloying element Er to the investigated alloy changed the type of corrosion attack on the alloy's surface. In the presence of Er, the dominant type of corrosion attack is pitting corrosion, while the alloy without Er is prone to intergranular corrosion attack. After a solution treatment, the AlCuEr phase was formed, in which the interaction with the Cu element and the competitive growth relation to the AlEr phase were the key factors influencing the corrosion resistance of the alloy. The anodic corrosion mechanism of the AlCuEr and AlEr phases evidently lowered the alloy corrosion rate, and the depth of the corrosion pit declined from 197 μm to 155 μm; however, further improvement of corrosion resistance was restricted by the morphology and size of the AlCuEr phase after its formation and growth; therefore, adjusting the matching design of the Cu and Er elements can allow Er to improve the corrosion resistance of the Al-Zn-Mg-Cu aluminum alloy to the greatest extent.
本研究探讨了添加铒对Al-Zn-Mg-Cu合金微观结构、第二相类型转变及耐蚀性的影响。结果表明，添加的铒元素可显著细化合金晶粒，并改变合金晶界处的第二相组成。在铸态下，铒元素因其对晶粒和晶界处第二相的细化作用而显著提高了合金的耐蚀性。向所研究的合金中添加合金元素铒改变了合金表面的腐蚀类型。在有铒存在的情况下，主要的腐蚀类型是点蚀，而不含铒的合金则易发生晶间腐蚀。固溶处理后，形成了AlCuEr相，其中与铜元素的相互作用以及与AlEr相的竞争生长关系是影响合金耐蚀性的关键因素。AlCuEr相和AlEr相的阳极腐蚀机制明显降低了合金的腐蚀速率，腐蚀坑深度从197μm降至155μm；然而，耐蚀性的进一步提高受到AlCuEr相形成和生长后其形态和尺寸的限制；因此，调整铜和铒元素的匹配设计可使铒最大程度地提高Al-Zn-Mg-Cu铝合金的耐蚀性。
