Zone Refining of Aluminum and Its Simulation

Abstract

Ultrahigh-purity aluminum with a residual resistivity ratio (RRR) of 60000­65000 was obtained by the ultrahigh-vacuum melting method. However, it was necessary to reduce the concentration of the elements with distribution coefficient k > 1 to further improve the purity of aluminum. Therefore, we prepared a sample with reduced concentrations of k > 1 elements from an ultrahigh-purity (99.9999%) aluminum material by the zone-refining method, and evaluated its purity by electrical resistance measurement and glow discharge mass spectrometry (GDMS). In addition, the zone-refining process was simulated, and the distribution of the solute atoms after approximately 10 passes of zonerefining was predicted. Moreover, the refining conditions were investigated with the aim of achieving higher purity. In experiments, when the zone width was increased from 60 to 80mm at a zone speed of 60mm/h, the concentrations of the elements with k > 1 in the second half of the material decreased and RRR improved. When the zone speed was decreased to 30mm/h, a marked effect was observed and RRR increased to about 85000. The distribution of the solute atoms determined from the simulation was in good agreement with the results of GDMS analysis, thus confirming the usefulness of the simulation. [doi:10.2320/matertrans.M2013419]