Study of wire fabrication of aluminum treated with diboride particles

Abstract

The present thesis focuses on the fabrication of aluminum wires by adding XB2 nanoparticles into an aluminum matrix, where X is a transition metal: Nb, Mg and Zr. The incorporation of aluminum in the XB2 particles is normally a complex process due to lack of enough affinity between the components. Liquid aluminum has a high surface tension, combined with the unavoidable oxide layer that is formed externally on the diboride prevents proper contact between the particle and liquid aluminum at the fabrication temperatures. An alternative process is then needed for proper inoculation of Al with the diborides. Diboride nanoparticles were obtained by fragmentation in a high energy ball mill and then mechanically alloyed with pure aluminum powder to form nanocomposite pellets. High energy ball milling was selected as the key process to achieve appropriate mixing and homogenization between components. The XB2/Al pellets were then sintered in a reduced vacuum atmosphere in order to increase the homogenization of the pellets and enhance the strength of diboride/ aluminum interface. The pellets of XB2/Al were added into the molten aluminum and mixed. The treated melt was then poured into a cylindrical mold to produce cylindrical ingots, which were subsequently cold-rolled to obtain wires with 1 mm diameter with a cross area reduction of 91%. The wire specimens were mechanically characterized and their electrical resistivity was measured and compared with pure aluminum. The results obtained in this thesis clearly demonstrated the feasibility of improving the mechanical properties of the material without significantly affecting its electrical resistivity of the wires.