Combined Effects of Mg Addition and the Cooling Rate on the Microstructural Evolution and Mechanical Performance in Heat‐Resistant Al–Ce Alloys

Heat‐resistant Al–Ce alloys have attracted considerable attention for high‐temperature applications owing to their excellent castability and intrinsic thermal stability. In this study, the combined effects of Mg addition and the cooling rate on the solidification behavior, microstructural evolution, mechanical properties, and thermal stability of Al–Ce alloys were systematically investigated. Increasing the cooling rate refined the α‐Al grains, produced finer and less segregated eutectic Al 11 Ce 3 , and suppressed the formation of primary Al 11 Ce 3 , leading to simultaneous improvements in strength and ductility. Mg addition altered the solidification behavior through solute‐induced constitutional undercooling, disrupting the coupled growth of α‐Al and eutectic Al 11 Ce 3 and promoting separate eutectic growth and primary Al 11 Ce 3 formation. As a result, Mg significantly enhanced the yield strength (YS) and ultimate tensile strength (UTS), primarily via solid‐solution strengthening after solution treatment, whereas the ductility decreased at high Mg contents. Thermal exposure at 300°C resulted in limited microstructural coarsening and high strength retention, which was attributed to the intrinsic stability of Al 11 Ce 3 and the retained strengthening effect of Mg in the solid solution. Overall, compared with conventional precipitation‐hardened Al–Si and Al–Cu alloys, Al–Ce–Mg alloys demonstrate superior thermal stability, highlighting their strong potential for high‐temperature applications.