Silicon Addition Influence on Properties of Anodised Al-Si Alloy Surface

This work presents the influence of the anodizing method and parameters on the properties and microstructure of the anodic layer produced on AlSi8 and AlSi9Cu3 cast aluminium alloys, in particular the effect on size and morphology of primary Si precipitates and the homogeneity of the resulting oxide coating.For investigations there were applied light microscope techniques, moreover hardness and wear resistance was examined in order to evaluate the obtained surface quality.The microstructure of the obtained surface layer was analysed by taking into account the primary silicon precipitates.The results of the hardness and abrasive wear test also show the influence of anodizing and electrolyte parameters on the structure and properties of the tested aluminium alloys.In case of the AlSi9Cu3 alloy the obtained alumina layer is of lower thickness -13.3 µm, about 50% less compared to the AlSi8 one, however the AlSi8 layer is more homogeneous and more uniform.The results of the wear test show that both anodised alloys show ca.35% lower mass loss compared to non-anodized alloys, so structure of the Al2O3 layer increases the abrasion resistance.