Microstructural Evolution and Thermal Stability of Hypoeutectic Al-Ce Alloys with Ni and Fe Additions

Al-Ce alloys have significant potential for high-temperature applications because of their many advantageous characteristics, notably the exceptional stability of the Al₁₁Ce₃ eutectic at high temperatures. This study examines how adding Ni, Fe and Ce affects the microstructure and mechanical properties of hypoeutectic Al-9Ce alloys. The introduction of 3 wt.% Ce transitions the hypoeutectic microstructure to a hypereutectic one, characterized by primary blocky Al₁₁Ce₃ phases and binary eutectic regions of αAl/Al₁₁Ce₃. In contrast, the incorporation of Ni leads to in the formation of an additional eutectic phase, αAl/Al₃Ni, while maintaining the lamellar structure of Al₁₁Ce₃. On the other hand, the addition of 3 wt.% Fe induces the formation of primary Al₁₀CeFe₂ phases, along with eutectic regions of αAl/Al₁₁Ce₃ and αAl/Al₁₀CeFe₂. The development of these additional phases significantly increases the volume fraction of strengthening phases, thereby enhancing the hardness of the base alloy. However, the Al-Ce-Ni alloy displays reduced resistance to coarsening due to the accelerated growth of Ni-rich phases. In contrast, both the binary Al-Ce alloys (Al-9Ce and Al-12Ce) and the ternary Al-9Ce-3Fe alloy demonstrate superior thermal stability, attributable to the coarsening-resistant phases of Al₁₁Ce₃ and Al₁₀CeFe₂. Among these, the Al-9Ce alloy with 3 wt.% Fe is particularly promising for high-temperature load-bearing applications, offering both exceptional performance and cost-effectiveness.