Through-thickness inhomogeneity of localized corrosion in 7050-T7451 Al alloy thick plate
来源期刊：中南大学学报(英文版)2015年第7期
论文作者：FENG Lei PAN Qing-lin WEI Li-li HUANG Zhi-qi LIU Zhi-ming
文章页码：2423 - 2434
Key words：aluminium; polarization; electrochemical impedance spectroscopy (EIS); intergranular corrosion; exfoliation corrosion; stress corrosion
Abstract: The through-thickness corrosion inhomogeneity of 7050-T7451 Al alloy thick plate was studied using immersion tests, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), slow strain rate testing (SSRT) technique combined with optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the through-thickness corrosion resistance is ranked in the order of T/2>surface>T/4. And the 75 mm-thick 7050 alloy plate presents better corrosion resistance than the 35 mm-thick plate. The results are discussed in terms of the combined effect of recrystallization and cooling rate in quenching. Alloy with lower volume fraction of recrystallization and smaller grain aspect ratio displays better corrosion resistance. The lower corrosion resistance caused by the slower cooling rate results from the higher coverage rate of grain boundary precipitates and larger width of precipitate free zone.
FENG Lei(丰雷)1, PAN Qing-lin(潘清林)1, WEI Li-li(韦莉莉)1, HUANG Zhi-qi(黄志其)2, LIU Zhi-ming(刘志铭)2
(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Guangdong Fenglu Aluminium Co. Ltd., Foshan 528133, China)
Abstract:The through-thickness corrosion inhomogeneity of 7050-T7451 Al alloy thick plate was studied using immersion tests, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), slow strain rate testing (SSRT) technique combined with optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the through-thickness corrosion resistance is ranked in the order of T/2>surface>T/4. And the 75 mm-thick 7050 alloy plate presents better corrosion resistance than the 35 mm-thick plate. The results are discussed in terms of the combined effect of recrystallization and cooling rate in quenching. Alloy with lower volume fraction of recrystallization and smaller grain aspect ratio displays better corrosion resistance. The lower corrosion resistance caused by the slower cooling rate results from the higher coverage rate of grain boundary precipitates and larger width of precipitate free zone.
Key words:aluminium; polarization; electrochemical impedance spectroscopy (EIS); intergranular corrosion; exfoliation corrosion; stress corrosion
