Hardness and Wear Behaviour of Semi-Solid Cast A390 Alloy Reinforced with Al2O3 and TiO2 Nanoparticles

In this work, a series of castings of hypereutectic aluminium-silicon samples (A390) were prepared by rheo-casting in a specially designed and built furnace unit allowing for the addition of the Al2O3/TiO2 nanoparticles to the Al-Si slurry, with mechanical stirring. The microstructure features and the hardness of the cast samples were investigated, as well as the resistance to wear in laboratory tests. The results obtained in this work show enhancement in the micro-hardness and hardness of the Al2O3/TiO2 nanodispersed hypereutectic A390 alloys, combined with improved wear resistance. The obtained results revealed that the introduction of Al2O3/TiO2 nanodispersions together with the stirring effect induces a refining role, as significant refining was observed in the microstructure of the alloy. The results have also shown that modified intermetallic precipitates have appeared after adding the Al2O3/TiO2 nanoparticles. Evidence for the formation of a combined (TiAlMgSi) oxide has been also presented in this work and its contribution in enhancement of wear resistance cannot be ruled out.