Reaction of boron to transition metal impurities and its effect on conductivity of aluminum
(Department of Materials Engineering,Dalian University of Technology,
Dalian 116023, China)
Dalian 116023, China)
Abstract: The effects of boron on electrical conductivity of aluminum and the action mechanism have been investigated. The results indicate that, by combining with the trace amounts of transition elements Ti, V and Zr to form two kinds of insoluble borides, boron can significantly improve the electrical conductivity of commercial aluminum. One of the borides contains 54.42％ B, 13.70％ Al and 23.39％(mole fraction) transition elements (including Ti, V, Zr and Fe) and is in the form of fine particles. The other one, in hexagonal shape, contains 78.59％ B, 14.97％ Al and 2.56％(mole fraction) transition elements (including Ti, V and Fe). Neither Cr nor Mn is found in these borides. The conversion of some transition metal impurities from solid solution state to the boride precipitates form leads to a decrease in electrical resistivity, and this decrease constitutes 86.2% of that can be achieved by complete removal of transition element impurities from aluminum melts.
Key words: boron; electrical conductivity; commercial aluminum