THERMODYNAMIC ANALYSIS OF Ti, Zr, V AND Cr IMPURITIES IN ALUMINUM MELT

摘要

Aluminum is widely used as the main material for overheadrnpower cable because of its good electrical conductivity and lightrnweight. Metal impurities, in particular Ti, Zr, V and Cr in thernsolution, affect the electrical conductivity of aluminumrnsignificantly. Industrially, boron treatment has been used tornremove these impurities through the formation of borides.rnHowever, studies have shown that solution thermodynamics andrnthe detailed reaction mechanisms of the borides formed inrnaluminum melts are not well understood. In the present work,rnthermodynamic analysis has been carried out to investigate thernrelative stability and to elaborate on the preferential formation ofrnvarious borides in aluminum melt. It is shown that diboridesrn(MB2) are the most thermodynamically stable boride compoundsrnof these impurities in the given working conditions. The ZrB_2,rnTiB_2 and VB2 phases are more stable compared to AlB2 and CrB_2rnhence do not dissolve readily. It is also shown that the relativernstability of the boride phases is affected by the presence of otherrnmetal diborides.