This study explores replacing ceriumCerium (Ce) with mischmetalMischmetal (MM) in cast Al–MM alloys, focusing on their microstructureMicrostructure, hardness, and resistance to creep and coarsening. Al–MM alloys with varying MM compositions (Ce, CeLa, 2CeLa, 54Ce27La19Nd) exhibit an Al–Al11MM3 microstructureMicrostructure which is eutectic for Al-9MM and hyper-eutectic for Al–12MM, with similar as-cast hardness (~525 MPa). The consistent mechanical and microstructural properties across these compositions indicate the flexibilityFlexibility of MM composition in alloy designAlloy design. Al-9MM shows excellent Al11MM3 coarsening resistance, with minimal hardness reductionReduction after 11 weeks at 300 and 350 °C, and only a 15% reductionReduction after 8 weeks at 400 °C, outperforming eutectic alloys like Al–12.6Si and Al–6.4Ni. Additionally, Al-9MM demonstrates better creep resistanceCreep resistance at 300 °C compared to most precipitatePrecipitate-strengthened Al–Sc–Zr and solid-solution-strengthened Al–Mg/Mn alloys, but Al-9MM is outperformed by the eutectic-strengthened Al–6.4Ni and Al–10Ce–5Ni. The use of MM in place of Ce allows to maintain comparable mechanical propertiesMechanical properties while offering environmental and sustainabilitySustainability benefits, highlighting the potential of MM as a viable alternative to pure Ce in Al alloysAl alloy.