Effect of Bismuth and Lead on the Mechanical Properties of Aluminium-4%Copper Alloy

Abstract

This study investigated the effect of Bismuth and Lead on the mechanical properties of aluminium-4wt% copper alloy. The doping elements were added in amounts of 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, and 4.0% by weight, mixed, and cast using gravity die casting method. The samples were then machined. Percentage elongation, ultimate tensile strength, hardness, and impact strength of the developed alloys were determined for each specimen. The microstructure of the samples was also studied using metallurgical microscope. Results obtained from the research showed that bismuth and lead improved percentage elongation of the alloy significantly. The highest value was achieved at 4.0wt% bismuth, followed by 4.0wt% lead. These values were 15.9% and 15.1% for bismuth and lead respectively; a very significant improvement beyond the 10.0% elongation observed from the control specimen (Al-4%Cu). Such specific data was not seen in available literatures as at the time of carrying out this study. The hardness values and Impact strength of the alloys doped with lead and bismuth significantly reduced as the percentage weight of the dopants increased, while a relatively slight decrease in tensile strength was observed. It was also observed that beyond 2.0wt% Bi, there was a significant drop in the strength and hardness of the alloy, which is not good for engineering applications. Results from this research also show that bismuth would be a better, and more environmentally friendly, substitute to lead when improved machinability, weldability, or workability of Al-4wt%Cu alloy is desired.