Investigation of plasma electrolytic oxidation coating formed on two Al–Si–Mg alloys via advanced X-ray computed tomography

In this work, the influence of Si concentration on the microstructure and growth of plasma electrolytic oxidation (PEO) coatings on two types of Al–Si–Mg aluminum alloys were investigated. we utilized a multiscale correlative methodology to analyze the microstructure and micro-defect characteristics of the PEO coatings formed on A357 and 6082 aluminum alloys. The results demonstrate that both coatings exhibit a porous structure and are primarily composed of alumina and amorphous phases. Notably, the PEO coating formed on A357 alloy exhibits lower thickness, higher porosity, and more non-uniform barrier layer compared to that on 6082 alloy due to a higher concentration of Si in the substrate. Advanced X-ray computed tomography effectively characterizes micro-defects with different morphologies within the two coatings. Through microstructural observation and micro-defect characterization, we elucidate the influence of Si on the coating growth.