Experimental techniques for obtaining reliable enthalpies of formation and migration of vacancies in pure metals were critically considered. Emphasis was placed on studies which were based upon the quenching-in of so-called thermal vacancies. From measurements of the residual electrical resistance introduced into high-purity Al foils (0.1mm) by ultra-fast quenches (initial quenching rate of about 2 x 106K/s) from between 800 and 530K, and from published data on high-temperature differential dilatometry, the enthalpy (0.65eV) and entropy (0.76k) of monovacancy formation - as well as the resistivity (1.9µΩm) per unit atomic concentration of vacancies - were derived. By combining these results with Al self-diffusion data deduced from nuclear magnetic resonance results, it was possible to deduce a migration enthalpy of 0.61eV and a pre-exponential factor of 6 x 10-6m2/s for monovacancy diffusivity. The divacancy binding enthalpy was found to be 0.17eV. This was in full agreement with some earlier determinations, but differed markedly from others.

Quenching Studies of Lattice Vacancies in High-Purity Aluminium. A.Khellaf, A.Seeger, R.M.Emrick: Materials Transactions, 2002, 43[2], 186-98