Experimental Description of the Al-Cu Binary Phase Diagram

The phase diagram of the Al-Cu binary system was reinvestigated experimentally. The current study was designed to contribute to a better description of those parts of the phase diagram which are disputed in the current scientific literature, and in addition, to study the phase equilibria at 300 °C. The melting behavior of the θ-phase was confirmed to be peritectic. A metastable congruent solidification of the θ-phase was observed from the microstructural examination of as-cast samples. The location of the liquidus curve in this region of the phase diagram was more accurately defined using DSC measurements taken at slow-heating rates (1 °C min −1 ). The temperature stability of the ζ-phase was reevaluated and was found to lie in the range 373–597 °C. The phase boundaries of the γ′ + ε′ two-phase field were experimentally defined. Difficulties in defining the γ′/δ transition were addressed by a combined EDX/XRD investigation of more than ten samples that had been annealed in the temperature range of 500 to 750 °C. The (γ′ + δ) two-phase field was postulated from XRD studies of quenched samples. The temperature of the ordering reaction γ ↔ γ′ within the γ(γ′) + β phase field was experimentally determined to be 779.6 °C. All other parts of the Al-Cu phase diagram studied here were found to be in very good agreement with the most recent previous descriptions.