Thermodynamic Analysis of Ti, Zr, V and Cr Impurities in Aluminum Melt

Aluminum is widely used as the main material for overhead power cable because of its good electrical conductivity and light weight. Metal impurities, in particular Ti, Zr, V and Cr in the solution, affect the electrical conductivity of aluminum significantly. Industrially, boron treatment has been used to remove these impurities through the formation of borides. However, studies have shown that solution thermodynamics and the detailed reaction mechanisms of the borides formed in aluminum melts are not well understood. In the present work, thermodynamic analysis has been carried out to investigate the relative stability and to elaborate on the preferential formation of various borides in aluminum melt. It is shown that diborides (MB2) are the most thermodynamically stable boride compounds of these impurities in the given working conditions. The ZrB2, TiB2 and VB2 phases are more stable compared to AlB2 and CrB2 hence do not dissolve readily. It is also shown that the relative stability of the boride phases is affected by the presence of other metal diborides.