ABSTRACT
The effect of chromium and manganese on the mechanical properties and corrosion resistance of Al-Si-Fe alloy was investigated. Alloys of varying percentages of Chromium and Manganese from 0.1 to 0.5% (0.1, 0.2, 0.3, 0.4, and 0.5%) with the percentages of iron and silicon kept constant were sand cast into cylindrical test bars of dimension 20mm by 300mm. The mechanical properties (Tensile strength, Hardness and impact energy) of the as-cast and age-hardened alloy samples were determined. Also the corrosion characteristics of the two categories of alloys (as-cast and age-hardened) in 0.5M HCl solutions at room temperature (280C) over period of 480hrs were investigated by weight loss method. The results obtained showed an increase in the tensile properties and hardness for the two different alloys with increased Cr and Mn addition. However, the age-hardened samples have improved tensile strength, ductility, hardness, impact energy and corrosion resistance than the as-cast. For example, the highest tensile strength value obtained in the as-cast and age-hardened conditions for Cr is 79.90N/mm2 and 100.44N/mm2, Mn is 77.34 N/mm2 and 98.18 N/mm2, and MnCr is 82.81 N/mm2 and 103.23 N/mm2 respectively. Lowest corrosion rate in the as-cast and age-hardened conditions was at 0.5% (Cr, Mn, MnCr) additions. However, it was also observed that the corrosion rate decrease with increase in the number of days of exposure time for all the alloys. These could be attributed to the corrosion products, formed which tends to shield up corroding surface resulting to a decrease in corrosion rate of the samples investigated.