## 2 Materials and Methods  
The addition of rare earth elements (Ce and/or La) to Al-1.4 wt.% Fe alloys was planned and simulated using Thermo-Calc 2022b software and the TCAL6 database. The findings from these simulations are detailed in [24], wherein the experimental alloys were produced using the same methodology. The alloys were melted in an induction furnace, cast into steel molds to form bars with dimensions of 22 mm in diameter and 15 mm in length, and analyzed to confirm their chemical composition. The process involved heating the alloy to 750 \({}^{\circ}\)C before adding and mixing the rare earth elements, then casting the mixture into bars. The chemical compositions of the test alloys are provided in Table 1.  
Differential scanning calorimetry (DSC) homogenization simulations were conducted using the DSC 404 F1 Pegasus instrument from the NETZSCH Group, Selb, Germany. During these tests, as-cast samples were placed in an empty corundum reference pan, whereby scans were carried out in a dynamic argon atmosphere. The homogenization regime was determined based on the results of the Thermo-Calc simulations presented in [24], where the homogenization temperature was set at 20 \({}^{\circ}\)C below the solidus temperature and continued with heating at a rate of 20 K/min to a temperature of 580 \({}^{\circ}\)C, 600 \({}^{\circ}\)C, or 620 \({}^{\circ}\)C and a holding time of 12 h. Cooling was then carried out at a rate of 20 K/min. The tangent method was used to determine the change in the slope of the DSC curves due to changes during homogenization. Based on these results, the homogenization time at the tested temperature was estimated.  
The specimens for the microstructural and forming properties tests were cut from the bars in their as-cast state and trimmed to cylinders with a diameter of 10 mm and length of 15 mm. The single-stage solution annealing (homogenization treatment) was carried out in an electric chamber furnace that had previously been calibrated. The test samples were homogenized at 580 \({}^{\circ}\)C and 600 \({}^{\circ}\)C for 4, 5, 6, 7, 8, 9, 10, 11, and 12 h, followed by quenching in air. Based on the DSC homogenization simulation and the microstructural analysis, samples were selected for further analysis of their forming properties.  
All metallographic examinations were performed on as-cast samples and after homogenization annealing at 580 \({}^{\circ}\)C and 600 \({}^{\circ}\)C for 4, 5, 6, 7, 8, 9, 10, 11, and 12 h, respectively, with the samples ground and polished (no etching) according to the standard metallographic procedure for aluminum alloys. Microscopic examinations were conducted using an Olympus BX61 microscope (Olympus Europa SE and Co. KG, Hamburg, Germany) at 100\(\times\) and 1000\(\times\) magnifications. SEM images and EDS maps were captured using a Thermo Fisher Scientific Quattro S FEG SEM equipped with an Oxford Instruments Ultim(r) Max EDS SDD analyzer (ThermoFisher Scientific, Waltham, MA, USA).  
Forming properties were analyzed using uniaxial hot compression tests. Before performing the hot compression tests, the samples were homogenized at 580 \({}^{\circ}\)C and 600 \({}^{\circ}\)C for 6 h and 10 h. After homogenization, the samples were cooled in air and machined into cylindrical hot compression samples with a diameter of 10 mm and a length of 15 mm. The Gleeble 3800 thermomechanical simulator with a Hydrawedge II (Dynamic Systems Inc., New York, NY, USA) was used for uniaxial hot compression tests. The cylindrical samples were heated in a vacuum at a rate of 10 K s\({}^{-1}\) to the soak temperature of 500 \({}^{\circ}\)C and held for 300 s before being hot compressed at a strain rate of 1 s\({}^{-1}\) to a true deformation of 1.1. After deformation, the deformed samples were cooled with compressed air to preserve the developed microstructure.