Filiform corrosion behaviour on machined AA7150 aluminium alloy
(1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
2. Corrosion and Protection Centre, School of Materials, the University of Manchester, Sackville Street, Manchester, M13 9PL, UK;
3. Hubei Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan 430074, China)
2. Corrosion and Protection Centre, School of Materials, the University of Manchester, Sackville Street, Manchester, M13 9PL, UK;
3. Hubei Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan 430074, China)
Abstract: The microstructure and the filiform corrosion behaviour of machined AA7150 aluminium alloy were investigated using scanning and transmission electron microscopies combined with potentiodynamic polarization and filiform corrosion testing, respectively. It is found that the grain refinement, redistribution of alloying elements, and elements segregation at grain boundaries are evident within the near-surface region on the machined AA7150 aluminium alloy. The corrosion susceptibility of machining introduced near-surface deformed layer is significantly improved caused by the modified microstructure associated with severe deformation. Filiform corrosion resistance on the machined surface is obviously decreased, due to the surface roughness associated with machining tracks and the presence of the electrochemically more active near-surface deformed layer introduced by machining.
Key words: aluminium alloy; near-surface deformed layer; machining; filiform corrosion