The development of aluminum-based cladding materials for nuclear fuel confinement is advancing in line with the increasing demand for high-density fuels. Alloying aluminum with magnesium (Mg), iron (Fe), and nickel (Ni) is expected to improve mechanical strength and thermal stability, thereby compensating for the higher hardness associated with high-density fuels. Heat treatment is a proven strategy to further enhance the performance of Al-based alloys in nuclear applications. In this study, Al– Mg–Fe–Ni alloys were fabricated by arc melting, homogenized, rolled, and subjected to heat treatment at 500 °C for 1.5, 3, and 4.5 h. Structural analysis using XRD and GSAS confirmed the formation of a substitutional solid solution with partial preferred orientation. Heat treatment decreased hardness due to recovery and partial recrystallization, but increased bulk density. The sample treated for 1.5 h exhibited the best balance, with a hardness of 82.81± 0.06 HV and a density of 2.7232 ± 0.0002 g/cm³. These results demonstrate that controlled thermal treatment can be used to optimize the structure–property relationship of Al-based alloys, offering valuable insights for the design of advanced cladding materials for high-density nuclear fuels. © 2027 The author(s).