Investigation on the Properties of Anodic Oxides Formed on Aluminium–Silicon Alloys Irradiated by Pulsed Electron Beam

Al–Si alloys are among the most common aluminium based materials for cast products due to their high strength-to-weight ratio, excellent processability and relatively low cost. The presence of Si in the molten Al phase improves the castability and decreases the solidification shrinkage. Hard anodic oxidation is largely employed to improve their surface mechanical properties and corrosion resistance. However, the presence of high Si contents (>3%) and the size of Si particles in the alloy make the process challenging or even not possible. The surface pretreatment of Al–Si alloys with intense pulsed electron beams (EB) can effectively overcome the aforementioned limitations. Electron beam sources can be employed to reduce Si content and to refine and disperse Si particles, and effectively create an Al substrate that is more prone to oxidization. In the present work, two electron beam equipment were used, RITM-SP and SOLO, to modify the surface properties of hypoeutectic, eutectic and hypereutectic Al–Si alloys, by investigating the effect of energy density and number of pulses. The electron beam treated substrates were hard anodized and characterized in term of microstructure, elemental distribution, corrosion resistance and surface mechanical properties.