Microstructural evolution and thermal stability of hypoeutectic Al–Ce alloys with Ni and Fe additions

Al–Ce alloy systems are promising for high-temperature applications due to the exceptional thermal stability of the Al11Ce3 eutectic phase. This study examines the effects of Ce, Ni, and Fe additions on the microstructure and mechanical properties of the hypoeutectic Al–9Ce alloy. CALPHAD modeling and experimental casting techniques were used to analyze the alloy systems. Experimental microstructural analysis confirms that adding 3 wt% Ce transforms the hypoeutectic structure into a hypereutectic one, containing primary Al11Ce3 and Al–Al11Ce3 eutectic regions. The addition of 3 wt% Ni promotes Al3Ni phase formation, either independently or in combination with Al11Ce3, while preserving the lamellar structure of Al11Ce3. Meanwhile, the addition of 3 wt% Fe promotes the formation of Al13Fe4, blocky Al10CeFe2 as well as eutectic Al11Ce3 and Al10CeFe2 phases, thereby increasing the volume fraction of strengthening phases and enhancing hardness. Al–9Ce–3Ni exhibits the highest as-cast hardness but undergoes significant coarsening of Ni-rich phases at 400 ◦C, which reduces its hardness. In contrast, Al–9Ce, Al–12Ce, and Al–9Ce–3Fe exhibit superior thermal stability, with Al–9Ce–3Fe emerging as the most promising alloy for high-temperature applications due to its cost-effectiveness and compatibility with recycled aluminum.