| The binding energy for a Sc atom-vacancy couple was determined in an Al-0.0087 at%Sc alloy by the resistivity measurements. For pure Al, the formation energy of a vacancy was determined to be 0.79 eV, being in good agreement with those in the literature. The apparent vacancy formation energy in a dilute Al-0.0087 at%Sc alloy was 0.65 eV. Clearly it is somewhat lower than that for a pure Al which suggests the presence of a vacancy as a vacancy-solute couple in the Al-Sc alloy. On the basis of semi-emprical calculation using the vacancy formation energies in pure Al and in the dilute Al-Sc alloy and using the relationship proposed by Lomer(IOM series, no.23(1958)p.85), the vacancy-Sc binding energy for Sc was found to be 0.35 eV. The value, 0.35 eV, obtained in this study is larger than those observed for other transition elements in Al. This high vacancy-Sc binding energy is considered to affect the precipitation behaviors in Al-Sc alloys. |
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