Determination of vacancy-Sc interaction energy by electrical resistivity measurements

In order to obtain the binding energy between Sc solute and atomic vacancy, electrical resistivity measurements on the quenched specimens were carried out of high purity Aland a dilute Al-0.0087at%Sc alloy. Vacancy formation energy in pure Al was determined to be 0.79eV, which is in good agreement with those previously reported. The apparent vacancy formation energy in the dilute Al-0.0087at%Sc alloy was determined to be 0.65eV, which is somewhat lower than that in pure Al, suggesting the presence of the vacancy-solute interaction in the alloy. On the basis of the experimentally determined vacancy formation energy in pure Al and in the dilute Al-Sc alloy, the vacancy-Sc binding energy was calculated to be 0.35eV using the relationship proposed by Lomer. The value, 0.35eV, obtained is rather large in comparison with those for other transition elements in Al. This high vacancy-Sc binding energy is considered to be responsible for the characteristic effects of Sc on the precipitation behaviors in Al alloys.