Effect of rare earth samarium addition on the kinetics of precipitation in Al-Cu-Mn casting alloy

The mechanical properties of Al-Cu-Mn casting alloy mainly depend on the morphology, distribution, size, and number of θ′(Al₂Cu) precipitates. In this study, we have analyzed the effect of rare earth samarium (Sm) addition on the kinetics of precipitation in the Al-Cu-Mn casting alloy by using differential scanning calorimetry (DSC) and high-resolution transmission electron microscopy. Thermal effect peaks that are attributed to the formation and the dissolution of Guinier-Preston (GP) zone and θ′ phase were identified from the DSC curves. The activation energy of θ′ formation was calculated by using both the Kissinger method and the analytical model, and the corresponding results were compared. Results suggest that the activation energy of θ′ formation in Al-Cu-Mn alloy is dramatically higher than that in Al-Cu-Mn-Sm alloy. Accordingly, it is concluded that the addition of rare earth Sm decreases the activation energy of θ′ formation and promotes the formation of θ′ precipitates.