## 3 Results and Discussion
In the fully precipitated state (highest strength state), no dynamic precipitation was observed under cyclic loading in these aluminum alloys. This, however, was achieved in the HiperFer and HiperFer\({}^{\text{AM}}\) type alloys. Process-induced pores that are contained in additively manufactured materials can act like notches and cause an accumulation of plastic strain in the surrounding material under cyclic loading. In steels of the HiperFer type, this induces thermomechanically induced precipitation [28; 32] of Laves phase particles at these dislocations at high temperature, which strengthen the vicinity of pores and actively obstruct crack propagation. Within the scope of this study, it was investigated to which degree microstructure characteristics (grain size, particle number, size, etc.) can be influenced \"in-build\" by varying the AM process parameters. For this purpose, the area-specific laser powers of 195 and 1050 W/mm\({}^{2}\) were chosen. HiperFer\({}^{\text{AM}}\) manufactured with a specific laser power input of 195 W/mm\({}^{2}\) in the following is referred to as the low-power-density (LPD) variant, while an energy input of 1050 W/mm\({}^{2}\) was the high-power-density (HPD) variant. Further AM parameter variations are summarized in Table 2.  
The typical microstructure of recrystallized and quality heat-treated ferritic, Laves-phase-strengthened steels consists of globular grains with particle-free zones (varying from 200-2000 nm in width, depending on the chemistry and temperature/stress history) along  
Figure 5: Microstructural features of LMD-manufactured HiperFer\({}^{\text{AM}}\) (LPD variant, further process parameters, cf. Table 2). HAGbs (Figure 6). Near the PFZ (\"IG\({}_{\text{Centerior}}\)\" region in Figure 6), the particles were usually slightly smaller. Gradual particle dissolution was argued to be the reason for this particular feature. The elements dissolving into the matrix diffuse toward the grain boundary and gradually coarsen the Laves phase particles located there. Accordingly, the particles in the grain interior (\"IG\({}_{\text{Center}}\)\" region in Figure 6) were found to be larger [11]. Large, aligned, rod-shaped grains were predominantly observed in the LPD-manufactured HiperFer\({}^{\text{AM}}\), while only a small area of aligned, even smaller rod-shaped grains was encountered in the HPD variant (Figure 7) where the globular grain shape prevailed (Figure 7b). This demonstrated that the grain size could readily be adjusted by varying the AM processing parameters. Conventionally processed HiperFer 17 Cr2 typically prevails in a grain size of approx. 500 \(\upmu\)m, while both applied AM parameter sets resulted in predominantly globular grains in the size region of approx. 200 \(\upmu\)m and less (Figure 8). However, incompletely melted tungsten clusters were observed (cf. Figure 7). An additional processing-related issue was SiO\({}_{2}\) particles. These particles tended to be larger and more numerous in the LPD variant than in the HPD variant (cf. Figure 7). Finley-distributed SiO\({}_{2}\) particles were also observed in LPBF-manufactured 316L [9]. Figure 6: Schematic representation of the typical microstructure of recrystallized and quality heat-treated ferritic Laves-phase-strengthened steel [30]. Figure 7: SEM micrographs of LMD-manufactured HiperFer\({}^{\text{AM}}\) in the as-built state: (**a**) LPD and (**b**) HPD variants. In the future, this can be prevented via the preparation of a master alloy from which the AM powder will be produced. Moreover, the change in power density resulted in a different number and size of Laves phase particles (cf. Figure 9). In the LPD material, the area-specific total number of particles in the as-built state was more than twice that of the HPD variant (cf. Figures 9 and 10a). The particle size classification demonstrated a clear tendency toward larger particle diameters in the HPD variant. The proportion of particles below 20 nm was lower by more than a factor of 5 in the HPD variant (Figure 10b).