Microstructural Analyses of Inter-Granular Corrosion Behavior for 6082-T6 Aluminum Alloy

Abstract

The microstructural analyses of the 6082-T6 aluminum alloy were conducted after electro-chemical corrosion tests utilizing the Optical Microscope (OM), Scanning Electrical Microscope (SEM), Transmission Electrical Microscope (TEM), and Electrical Backscattered Spectrum Diffraction (EBSD). In addition, the systematic analysis of the mechanism of intergranular corrosion was carried out by the application of the theory of electro-chemical reaction. It can be concluded that the light-etched zone is a single crystal. Whereas, the deep-etched zone is polycrystalline. Moreover, the fine granulated β"-Mg2Si precipitates are continuously precipitated along grain boundaries, and Precipitate Free Zone (PFZ) are also formed bilaterally along the β"-Mg2Si precipitates with the width of 100∼150nm. The mechanism that causes the inter-granular corrosion is the difference in the micro-electrode potentials between the β"-Mg2Si precipitates and PFZ. In addition, the coarse block-like Mg2Si particles, which were not dissolved when it was subjected to the solid solution treatment, play a certain role in connecting of the corrosion cracks, as a result, the inter-granular corrosion is being accelerated accordingly.