## 3 Results
### EBM/PBF Additive Manufacturing
#### 3.3.2 Microstructure  
Initial micrographs were taken of the early builds (1-4) in Figure 13 however these are not included as the microstructures revealed that the height of the build was not sufficient to mitigate influence from the build plate including grain size and compositional contamination. Run #5 with the improved parameter set allowed enough sample height to be beyond substrate influence.  
The as-built refined equiaxed microstructure of EBM/PBF run #5 is shown in detail in Figure 14 and is observed throughout the sample. Elemental mapping with EDS confirmed compositional segregation at the grain boundaries; in particular Fe, Al, and Ti had been depleted indicating the formation of the \(\gamma\)-phase (similar to the FCC \(\gamma\)-Fe or Fm\(\overline{3}\)m crystal structure) [6; 32] which is detrimental to magnetic properties and forms upon slower cooling within the EBM/PBF chamber. Suppression of the \(\gamma\)-phase occurs with solutionization and oil quenching, as shown in Figure 15, indicating the as-built EBM/PBF samples still require this step due to the slower cooling rate, similar to traditionally processed alnico. Figure 15 also indicates that grain growth occurs in these Co-lean EBM/PBF samples during the post-build SOQ, consistent with the DED samples as shown in Figure 12.  
As can be seen from the micrograph and the IPF coloring in Figure 16, as well as the IPFs included in Figure 17, there exists slight texturing across the EBM/PBF specimen. However, in the build direction the slight amount of texturing is evident in the \(<\)111\(>\) direction. There is no strong texturing in the desired \(<\)001\(>\) crystallographic orientation for this alnico composition and corresponding set of EBM/PBF processing parameters.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**at.\%** & **Fe** & **Al** & **Ni** & **Co** & **Cu** & **Ti** & **Nb** \\ \hline As-Received Powder CPP & 30.64 & 14.31 & 14.54 & 29.05 & 2.58 & 8.55 & 0.33 \\ As-built, XRF \({}^{+}\) & 29.66 & 7.80 & 18.00 & 32.81 & 0.379 & 9.34 & 1.52 \\ As-built, EDS & 26.52 & 12.14 & 19.33 & 31.07 & 1.41 & 8.89 & 0.55 \\ SOQ, EDS & 26.7 & 12.07 & 19.10 & 31.00 & 1.69 & 8.82 & 0.54 \\ \hline \end{tabular} \({}^{+}\) XRF data accurate to at least \(\pm\) 0.2.  
\end{table}
Table 11: Composition data for the EBM/PBF sample from run #5.  
Figure 14: Micrographs of an as-built transverse section between the magnetic cylinder samples (i.e., build direction is out of the plane). (**A**) Macro image of the entire specimen, where a subtle layered structure variation may be seen in the horizontal direction. (**B**) Magnified region with variations in grain/cellular size apparent. (**C**) Higher magnification micrograph with clear eutectic formation inside cellular boundaries and an elevated amount of the \(\gamma\)-phase at every cell boundary.  
Figure 15: SEM micrograph of one of the cylinder sections after SOQ at 1210 \({}^{\circ}\)C for 30 min and oil quenching.  
Figure 16: SEM micrograph of the ROI as identified in Figure 2 with IPF coloring overlay. Build direction is oriented towards the top of the image. The dark regions forming a “fish-hook” shape is where the EDM wire had removed material before the wire broke.  
Figure 17: _Cont._