Alloying Elements Effects on Electrical Conductivity and Mechanical Properties of Newly Fabricated Al Based Alloys Produced by Conventional Casting Process

Abstract

The present investigation deals with a comprehensive study on the production of aluminum based alloys with the incorporation of different alloying elements and their effect on its electrical conductivity and mechanical properties. Casting of pure aluminum with different concentration and combinations of alloying additives such as cupper (Cu), magnesium (Mg) and silver (Ag) were carried out using a graphite crucible. The as-cast microstructure was modified by hot rolling followed by different heat-treated conditions viz., annealing, normalizing, quenching, and age hardening. The mechanical properties and electrical conductivity of the produced heat-treated alloys sheets under various processing conditions were carried out using tensile testing, hardness, and electrical resistivity measurements. It was found that by increasing the alloying elements content, yield strength results increased significantly by more than 250% and 500% for the as rolled and 8 h aged Al-Cu-Mg alloy, respectively. On the other hand, the electrical conductivity reduces slightly with −14.6% and −16.57% for the as rolled and 8 h aged of the same Al-Cu-Mg alloy, respectively. From the last four decades, due to the increase in demand from the electricity transmission lines, copper is being replaced by Al because of its light weight and relatively low cost. In addition, among the engineering conductor materials, aluminum has a very good electrical conductivity due to lower specific gravity (almost in the second rank after copper). The replacing of copper by aluminum for electricity transmission by overhead ACSR (aluminum conductor steel-reinforced) conductors, power cables, etc. has increased all over the world. Moreover, substitution of copper by aluminum also takes place in countries which have enough resources from copper, since it shows a good economical advantage as serious competitor against copper. Practically, by adding alloying elements to pure aluminum, aluminum’s strength can be significantly improved. However, on the other hand a great reduction in the electrical conductivity takes place due to the solute atoms and impurities generated by substitution of alloying elements. Another process affecting the electrical conductivity of aluminum is the heat treatment process, since elements in the solid solution phase represent a higher resistance than non-dissolved elements. That is why it is a great challenge to play with the strength of the pure aluminum in such a way that the decrease in its electrical conductivity will be still acceptable and valid for the selected application.