Binding energies and entropies of solute atoms and vacancies in metals. Report 1893.
Year: 1972
Type: report
Abstract: Experimental methods for determining the binding energies and entropies between single vacancies and single substitutional solute atoms are reviewed.The techniques include: (1) combined length and lattice parameter expansion measurements during quasi-equilibrium heating, (2) positron annihilation measurements while holding in thermal equilibrium, (3) vacancy quenching and quenching-annealing experiments, and, (4) measurements of solute and solvent atom diffusion, and vacancy flux-induced solute redistribution.All of these techniques, with the exception of the quenching experiments, indicate small binding energies (<0.05eV) for non-transition element solutes in Al.A somewhat larger values 0vO.2eV) was obtained for the transition solute Mn.Best estimates of the corresponding experimental binding entropies are in the range -2.0k to 1.5k.It is concluded that quenching experiments have generally led to erroneous results because of non-equilibrium clustering effects.Theoretical methods for calculating the binding energy are reviewed and are found to involve various approximations.Improved methods appear to be currently feasible.Nevertheless, the available calculations for non-transition solutes in a trivalent matrix (Al) all yield small values in general agreement with the small values found experimentally.Values of binding entropies have not been calculated on a fundamental basis.However, values in the range found experimentally are expected on the basis of experimental and theoretical determinations of the vacancy formation entropy.
DOI: 10.2172/4589544
Authors: R. Balluffi, P. Ho
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W105624227