Influence of Grain Boundary Precipitates on Intergranular Corrosion Behavior of 7050 Al Alloys

Coatings

Haitao Chi¹  Linchi Zou²  Rongying Liu³  Binshu Wang³  Yuxiao Qiu³  Chen Wang³  Junfeng Chen³ 

[1] Fujian Xiangxin Co., Ltd., Fuzhou 350119, China;School of Materials Science and Engineering, Fujian University of Technology, Fuzhou 350118, China;School of Materials Science and Engineering, Fuzhou University, New Campus, Fuzhou 350116, China;

关键词: 7050 Al alloys;    intergranular corrosion;    grain boundary precipitate;    precipitation free zone;    alloy element;   

DOI  :  10.3390/coatings12020249

来源: DOAJ

【 摘 要 】

The effects of the grain boundary precipitation on intergranular corrosion behavior were investigated by exfoliation tests and complementary techniques like scanning electron microscope (SEM), optical profilometry (OP), transmission electron microscope together with energy dispersive spectroscopy (TEM-EDS), and atomic force microscope (AFM). The results reveal the influencing mechanism of intergranular corrosion behavior from grain boundary precipitates (GBPs). The potential discrepancy between GBPs and adjacent areas induces corrosion cavity germination along the grain boundary. Furthermore, the increase of both active Mg and Zn content in GBPs improve the potential difference, which aggravates the intergranular corrosion cavity germination. However, the increment of noble Cu content in GBP is beneficial to reduce the potential difference. On the other side, the distribution of the continuous precipitates in the grain boundary region helps the initial corrosion cavities to connect, which improves the growth of intergranular corrosion cracks. Additionally, discontinuous GBPs and precipitation free zone (PFZ) hinder the spread and connection of intergranular corrosion cavities. Therefore, 7050 aluminum alloy forming different grain boundary precipitation characteristics after different aging treatments shows different resistance to intergranular corrosion: peak-aging < under-aging < over-aging.

【 授权许可】

Unknown