Phase transitions in AU0.5Cu0.5

After having recalled the crystal structures of the three equilibrium phases of stoichiometric Au0.5Cu0.5 alloy, new results are presented in the frame of a general discussion on the transition series (with increasing temperature) : AuCu I(LI0) → AuCu II → disordered AuCu (Al). Both transitions have been followed by in-situ temperature X-ray, confirming earlier electron diffraction studies, and their transition enthalpies have been measured by differential scanning calorimetry. These results are commented, and a possible explanation for the large two-phase hysteresis (35°C) is proposed