Influence of Ferrotitanium and Silicon Carbide Addition on Structural Modification, Nanohardness and Corrosion Behaviour of Stir-Cast Aluminium Matrix Composites

The use of aluminium based composite is becoming widespread in the industries where enhanced mechanical and improved corrosion resistance properties are required. Microstructural analysis, hardness and corrosion properties of aluminium based composites reinforced with particles of silicon carbide (SiC) and ferrotitanium (TiFe) were investigated. The composites were produced using stir casting technique, with the dispersion of different weight percentages of single and dual reinforced particles within the aluminium matrix. The microstructural evolution, microhardness and nanohardness properties of the as-cast specimens were investigated. Electrochemical testing of specimens was carried out using potentiodynamic polarization and potentiostatic techniques in 3.5 wt.% sodium chloride (NaCl) solution. The microstructural examinations conducted showed a homogeneous dispersion of the SiC and TiFe reinforcements within the aluminium matrix. The hardness (micro and nano) properties of the reinforced specimens were enhanced due factors which include effective load transfer mechanism between the reinforcements and matrix, and an impediment to dislocation movement within the composite. The specimens reinforced with particles of 5% SiC +2% TiFe and 5% SiC exhibited the most improved corrosion resistance from the potentiodynamic polarization and potentiostatic tests conducted. This was confirmed by the surface analysis of corroded specimens carried out using a field emission scanning electron microscope (FE-SEM). The formation of filiform structure on the surface of the unreinforced aluminium alloy and several pits on the surface of the composites was attributed to the aggressive effect of the chloride ions present in the test electrolyte.