Structure and properties of modified compocast microsilica reinforced aluminum matrix composite

A356 aluminum alloy reinforced with 7wt.% microsilica composites was produced by the three different processing routes viz. liquid metal stir casting followed by gravity casting, compocasting followed by squeeze casting and modified compocasting route and their properties were examined. Microstructure of liquid metal stir cast Al MMC shows agglomeration of particles leading to high porosity level in the developed material. Adopting new route of compocasting followed by squeeze casting process prevents the agglomeration sites with uniform distribution and dispersion of the dispersoids in the matrix metal. Modified compocasting process reduces the segregation of particles in the final composites thus enhancing the mechanical, tribological and corrosion properties of the composites. Superior wear-resistance properties were exhibited by the modified compocast composite compared to the unreinforced squeeze cast alloy and abrasive type wear mechanism was observed in the case of composite. Increasing the sliding speed resulted in the quick evolution of tribolayer and the wear rate of composite gets reduced. The presence of intermetallic phases like MgAl2O4, NaAlSi3O8 and KAlSi3O8 has a favorable effect on increased corrosion resistance of the composite. Microsilica particles significantly enhanced the compressive strength of modified compocast composites compared to the unreinforced squeeze cast Al alloy. Figure shows (a) SEM photomicrographs of surface treated micro silica particles, (b) A356-7% micro silica (treated) composite synthesized by liquid metal stir casting and gravity cast, (c) A356-7% micro silica (treated) composite processed by compocasting followed by squeeze casting, and (d) recasted final composite by remelting, stirring and squeeze casting. [Display omitted] •Recast compocasting cum squeeze casting provides uniform particle distribution.•Composite microstructure free of segregation, agglomeration and porosity was obtained.•Microsilica particles contribute to enhanced hardness and wear resistance.•Unreinforced alloy and composite show adhesive and abrasive wear mechanism respectively.•Enhanced corrosion resistance and compressive strength were observed in composites.