The effect of hydrostatic pressure on the stability of precipitates in the Al-Li and Cu-Be alloy systems has been examined using a first-principles method. The solid-phase portion of the Cu-Be and Al-Li phase diagrams has been computed from first-principles. In the case of Cu-Be no adequate description of the thermodynamics could be obtained, and consequently no realistic phase diagram could not be computed. However, an analysis of a Calphad type calculation indicates why the current method fails. For Al-Li a good cluster expansion could be obtained and the computed zero pressure phase diagram exhibited excellent agreement with the experimental data. A high pressure phase diagram was computed as well. It is predicted that phase equilibria in the Al-Li system are little affected by compression. Compression does not affect the Al - AlaLi metastable phase equilibria but the calculated equilibrium isothermal solubility of Li in Ä1 is decreased, in agreement with recent measurements.
- Al-Li alloys
- Cluster variation method
- Cu-Be alloys
- Enthalpies of formation
- Pressure dependence of phase equilibria
- Theory of alloy phase stability
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