## 4 Discussion
Once the stable preheating parameter set was identified, the melting parameters for run #5 were able to generate a dense sample, \(\sim\)99.9% according to optical measurements and 7.17 \(\pm\) 0.001 g/ccas measured by helium pychrometry. The high temperature required for preheating and for the subsequent melting step probably contributed to the observed equiaxed microstructure, as well as to the significant loss of aluminum and copper due to volatilization, significantly altering the composition. This change in composition appears to have led to changes in the expected solidification kinetics and solid-state phase transformations, e.g., the spinodal decomposition, as well as the magnetic properties. Any alteration of the spinodal decomposition phenomena during the MA and the concentration of the diffusing species during the lower temperature draw cycles will ultimately impact the magnetic properties. The loss of both Al and Cu was likely a contributor to the observed drop in coercivity as both elements act to separate the Fe-Co rods in the nanostructure; without a high enough concentration of Al and Cu, the Fe-Co rods will no longer be substantially isolated and the coercivity will decrease due to magnetic spin coupling between them [11; 12; 34; 35]. The main objective was to obtain a dense, EBM/PBF build of alnico, thus, unlike the DED samples, EBM/PBF AM processing parameters were not explored. However, minor modifications in the AM processing parameters may have caused the subtle \"layered\" microstructure (Figure 16) consisting of large and fine grains with a minor \(<\)111\(>\) and \(<\)101\(>\) texture. However, this \"layered\" microstructure was eliminated upon SOQ in which accelerated, uniform grain growth occurred with preliminary indications of a preferred texture. Similar to the DED, the accelerated grain growth observed in EBM/PBF samples during the SOQ is likely a product of residual stresses. The higher cooling rate at the interface of the build and build environment in DED vs. EBM/PBF could be exacerbating this effect for the DED samples. Unlike the DED samples, the coercivity was much lower in the EBM/PBF samples in comparison, especially, to the Co-lean DED samples. As mentioned above, the increased grain size of the post-SOQ EBM/PBF samples usually suppresses the formation of \(\gamma\)-phase and promotes coercivity. Although EBM/PBF and DED as-built samples did not result in a strong \(<\)001\(>\) texture, minor texturing is evident upon printing, that may be accentuated by SOQ. Thus, texturing in the \(<\)001\(>\) with an EBM/PBF AM approach may be possible if more analysis and parameter studies are conducted to promote such a texture. Additionally, similar to the DED, there should be more focus in utilizing the residual stress for alignment purposes during the SOQ process. If a \(<\)001\(>\) texture can be obtained, EBM/PBF could be an attractive processing route for alnico magnets as long as the compositional losses could be mitigated via strategic alloying. The alnico magnet microstructure is most likely constant during the MA and FHT process since the temperatures are significantly below the SOQ temperatures (830-870 \({}^{\circ}\)C and 650-580 \({}^{\circ}\)C, instead of 1210 \({}^{\circ}\)C /1215 \({}^{\circ}\)C) [28]. The highest coercivity values for AM builds were achieved by the DED samples, well above the EBM/PBF samples of similar composition. Again, the loss of Al and Cu in the EBM/PBF samples cannot be ignored as a significant factor in this coercivity loss. The highest remanence was achieved by the EBM/PBF samples at lower MA temperatures (830 \({}^{\circ}\)C and 850 \({}^{\circ}\)C) and was relatively MA time independent. However, by the same token as coercivity, composition shifts likely contributed to the higher remanence, since remanence can depend on the final chemistry of alnico [11; 13].