Corrosion behavior of as-cast AZ91 magnesium alloy with VN particle additions in NaCl solution
(1. School of Energy and Power Engineering, Changsha University of Science & Technology, Changsha 410114, China;
2. Key Laboratory of Energy Efficiency and Clean Utilization, the Education Department of Hunan Province, Changsha University of Science & Technology, Changsha 410114, China;
3. School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China;
4. Institute of Rare Earth Light Alloys, Hunan Rare Earth Metal Material Research Institute, Changsha 410126, China)
2. Key Laboratory of Energy Efficiency and Clean Utilization, the Education Department of Hunan Province, Changsha University of Science & Technology, Changsha 410114, China;
3. School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China;
4. Institute of Rare Earth Light Alloys, Hunan Rare Earth Metal Material Research Institute, Changsha 410126, China)
Abstract: The microstructures and corrosion behavior of the as-cast AZ91-xVN (x=0, 0.25, 0.5 and 1 in wt.%) alloys were investigated using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. The results showed that VN can significantly refine and modify the microstructures of AZ91-xVN alloys. The corrosion resistance of the AZ91 alloy was first improved and then deteriorated with the addition of VN particles. The superior corrosion resistance of the as-cast AZ91-0.25VN alloy with the lowest corrosion rate (PW=(1.47±0.06) mm/a) was attributed to the additional grain boundaries. With the further increase of VN content, the amount of the lamellar β-Mg17Al12 precipitation phase increased, and thus the galvanic corrosion between β phase and the α-Mg matrix was promoted, resulting in the deteriorated corrosion resistance of the alloys.
Key words: AZ91-xVN alloys; microstructure; grain refinement; corrosion resistance