Assessment of Ce-rich intermetallics formation in Al-Cu-Mg-xCe alloys using thermal analysis cooling curves

The computer-aided cooling curve analysis (CA-CCA) was employed to investigate the solidification behavior of Al-Ce-Mg-xCe (x = 0, 0.5, 1.0, 1.5, and 3.0 mass %) alloys. Field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) techniques were used, along with the liquidus projection of ternary Al-Cu-Mg and Al-Cu-Ce phase diagrams, to evaluate the microstructure and predict the sequence of main reactions involved in the solidification of alloys. According to the results, Al₂CuMg, Al₂Cu, Al₁₅(CuFeMn)₃Si₂, and Mg₂Si were found to be the main compounds present in the microstructure of Al 2024 alloy. The addition of Ce up to 1.5 mass % resulted in the formation of AlCeCuSi, Al₈CeCu₄, and Al₂₄Cu₈Ce₃Mn compounds in the microstructure. Further addition of Ce up to 3.0 mass % promoted the formation of a new Ce-rich phase (Al₄Ce) in the microstructure. The formation temperature (range) and reactions during which the Ce-rich compounds are formed were also suggested. The formation of Al₄Ce compound in the microstructure of 3 mass % Ce-containing samples suppressed the nucleation and growth temperatures of the Al₂Cu eutectic, prolonged the solidification time, significantly reduced the solidification end temperature, and increased the alloy solidification range.