High-temperature lattice parameters of copper-aluminium alloys

Abstract Lattice parameters of α γ2, δ, and θ-phase alloys from the copper-aluminium system have been measured by X-ray diffraction in the temperature range 20 to 850°C. The results have been used, along with values for the pure metals, to evaluate volume changes on alloying which have been found to correlate well with previously measured enthalpies and excess entropies of formation of the same alloys. The results also tend to confirm the view that alloys in the region of 40 at.- % aluminium exist as a separate phase (δ) with a γ-brass structure containing 50 atoms and two vacancies, instead of the normal 52 atoms, per unit cell.