No abstract

In this work a number of cast samples of A356 and A390 were prepared by rheocasting in a specially designed and built furnace unit allowing for the addition of the nano-particles into the molten Al-Si alloy with mechanical stirring. The microstructure features and the mechanical properties of the cast samples were investigated, as well as resistance to wear and corrosion in laboratory tests.The results obtained in this work showed improved wear and corrosion resistance of the nano-dispersed hypereutectic A390 alloys, as well as enhancement in the mechanical strength of the nano-dispersed hypoeutectic A356 alloys, accompanied by significant increase in the elongation percentage, supported by evidence of refined dendrite arms length, and inter-lamellar spacing. The work also shows significant enhancement in the wear and corrosion performance of the nanodispersed alloys.

Improving the strength to weight ratio is a target aimed by many researchers. Metal Matrix Nano Composites (MMNC) have recently emerged as a new generation of composites, where the addition of nano-sized particles leads to an increase in the strength not according to conventional Metal Matrix Composites rules. Aluminium matrix composites reinforced with nano-sized Al 2 O 3 particles are widely used for high performance applications such as automotive, aerospace and electricity industries. In this work a number of cast specimens made from hypoeutectic aluminium silicon alloy (A356) were cast with and without alumina (Al 2 O 3) nanoparticles at different pouring temperatures with stirring during the addition of nano-reinforcement. The microstructure of the new castings was studied using optical microscopy and scanning electron microscopic techniques. Also, the tensile strength, hardness and ductility were evaluated. The significant factors for the tensile strength were analysed using L4 orthogonal array and Analysis of Variance (ANOVA) techniques then building a model by Response Surface Methodology (RSM). The results obtained in this work show that adding alumina nanoparticles and pouring at different temperatures lead to an increase in the tensile strength and the hardness with less change in ductility.