Investigation on the properties of anodic oxides grown on aluminium-silicon alloys irradiated by pulsed electron beam

Abstract

Al-Si alloys are among the most common aluminium based materials for cast products due to theirhigh strength-to-weight ratio, excellent processability and relatively low cost. The presence of Si inthe molten Al phase improves the castability and decreases the solidification shrinkage. Hard anodicoxidation 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 makethe process challenging or even not possible. The surface pretreatment of Al-Si alloys with intensepulsed electron beams (EB) can effectively overcome the aforementioned limitations. Electron beamsources can be employed to reduce Si content and to refine and disperse Si particles, and effectivelycreate an Al substrate that is more prone to oxidization. In the present work, two electron beamunits were used, RITM-SP and SOLO, to modify the surface properties of hypoeutectic, eutectic andhypereutectic Al-Si alloys, by investigating the effect of energy density and number of pulses. Theelectron beam treated substrates were hard anodized and characterized in term of microstructure,elemental distribution, corrosion resistance and surface mechanical properties.