Characterisation of stir-cast ferrotitanium and silicon carbide reinforced aluminium matrix composites

Ph.D. (Metallurgical Engineering)Abstract: The superior qualities offered by aluminium matrix composites (AMC) over the years as compared with the conventional aluminium alloys has made it a widely used material for fabrication of various components in the engineering sector. This has led to a decline in the use of monolithic materials in the engineering industry. The fabrication of stir cast aluminium matrix composite reinforced with silicon carbide (SiC) and ferrotitanium (TiFe) particles was carried out after a preliminary analysis was conducted to determine the optimum parameters at which improved properties would be achieved. Locally sourced aluminium-silicon (Al-Si) alloy was melted in a crucible furnace at a temperature ranging between 670-7500C, and different weight percentages of single and combined particles of SiC and TiFe reinforcements were added. Rigorous stirring of the molten composite was manually done in the furnace for 10 min, while the pouring temperature was regulated to 6900C to prevent cracking and brittleness of composites after cooling. The chemical composition of the cast Al-Si ingot was determined using a mass spectrometer, while the morphologies of SiC and TiFe starting powders were examined under a field emission scanning electron microscope (FESEM) equipped energy dispersive X-ray (EDX). Prior to determination of chemical composition, the phase analysis powders were assessed using X-ray diffractometer (XRD) technique. The microstructural properties of the as-cast aluminium alloy and composites were investigated using optical microscope (OM), FESEM and XRD, while the mechanical properties were evaluated from the tensile, hardness, tribology and nanoindentation tests conducted. The corrosion resistance of the specimens was further determined in 3.5 wt.% NaCl solution using potentiodynamic polarization and potentiostatic techniques. Microstructural observations from OM, FESEM and XRD confirmed an adequate dispersion of the reinforcement particles within the aluminium alloy matrix. The composites reinforced with 5 wt.% SiC + 2 wt.% TiFe..