## 4 Conclusions  
This paper investigated the influence of minor additions of La or/and Ce on the microstructural components and forming properties of Al-1.4 Fe alloys. Samples underwent homogenization treatment under various conditions, whereby the optimum homogenization process was defined, followed by detailed microstructure analyses. The alloy with the best forming properties was then chosen. Our main conclusions are as follows:  
When homogenizing the Al-1.4 wt.% Fe alloys at 580 \({}^{\circ}\)C, the majority of the homogenization process was completed after 6 h; at 600 \({}^{\circ}\)C, after about 5 h; and at 620 \({}^{\circ}\)C the homogenization process is mostly completed after about 4 h. After that, only the diffusion process of the chemical composition takes place. In the as-cast Al-1.4 wt.% Fe samples, very fine spherical particles and rod-like phases are present, representing the metastable Fe-based phases. A stable Al\({}_{13}\)Fe\({}_{4}\) phase is also present, which is darker and sharper. During homogenization, the stable Al\({}_{13}\)Fe\({}_{4}\) phase in the interdendritic region grows noticeably. After 6 h at 580 \({}^{\circ}\)C, the amount of fine spherical particles from the metastable phase significantly decreases and disappears after 10 h of homogenization at 580 \({}^{\circ}\)C; only a stable Al\({}_{13}\)Fe\({}_{4}\) phase is present in a more agglomerated form. Ce and La integrate into the Al-Fe eutectic, and also form (\(\alpha\)-Al + Al\({}_{11}\)Ce\({}_{3}\)) and  
Figure 8: Stress-strain curves of experimental alloys homogenized at a temperature of 580 \({}^{\circ}\)C (**a**,**b**) and 600 \({}^{\circ}\)C (**c**,**d**) for 6 h (**a**,**c**) and 10 h (**b**,**d**). (\(\alpha\)-Al + Al\({}_{11}\)La\({}_{3}\)) eutectic structures. Claw-like Al-Fe-Ce ternary intermetallic compounds and short rod-like Al-Fe-Ce phases (possibly Al\({}_{13}\)Fe\({}_{3}\)Ce phase [21; 32]) also form. These phases are unevenly distributed in the alloy; while the completion of the homogenization process cannot be predicted from micrographs after 6 h, it can be predicted after 10 h of homogenization. The proportion of homogenized Fe-phases is higher after 6 h of homogenization at 600 \({}^{\circ}\)C than at a homogenization temperature of 580 \({}^{\circ}\)C; homogenization is rather complete already after 6 h and certainly complete after 10 h at 600 \({}^{\circ}\)C.  
After homogenization at 580 \({}^{\circ}\)C and 600 \({}^{\circ}\)C for 10 h, the Al\({}_{13}\)Fe\({}_{4}\) phase is thermodynamically more stable than the metastable particles in these conditions. The Ce- and La-bearing phases are also agglomerated and tend to have rounded edges, whereas the La-bearing phases are more spherical than the Ce-bearing phases, which tend to appear in the form of rods and claws. In the samples homogenized at 580 \({}^{\circ}\)C for 6 h, alloy K3 (with 0.15 wt. La and Ce) shows the most favorable forming properties, which even improve slightly with a longer (10 h) homogenization time. A homogenization temperature of 600 \({}^{\circ}\)C worsens the forming properties of all RE-containing alloys. Due to the grain refining effect on the \(\alpha\)-Al grains and formation of discontinuous eutectic structures of the various Fe intermetallics that form in Al-Fe alloys, it was expected that the addition of Ce and La would have a favorable influence on the alloys' mechanical properties. Uniform homogenization transforms the lamellar metastable and stable Al\({}_{x}\)Fe\({}_{y}\) phases into short rods. The formation of Al\({}_{11}\)Ce\({}_{3}\) can reduce the refinement effect of the mixed RE combination, which harms the mechanical properties of the alloy. The addition of La was shown to be advantageous as a micro-addition to Al-Fe alloys. The analysis of the forming properties of these alloys shows that the combination of Ce and La is the most favorable addition. Conceptualization M.V. and K.O. ; methodology, M.V. ; validation, M.V. ; formal analysis, M.V., J.M., D.B. and K.O. ; investigation, M.V. and K.O. ; data curation, D.B.