# An Additively Manufactured Fe-3 Si Stator for a High-Performance Electrical Motor
## 3 Results and Discussion
### DC Magnetic and Electrical Properties  
Thin induction rings (ID: 44.63 mm (1.757 in. ), OD: 54.81 mm (2.158 in. ), thickness: 1.40 mm (0.05512 in.)) were machined from a hollow cylinder that was printed for DC magnetic and electrical property measurements. Figure S2 shows the test specimen used for both high- and low-field DC magnetic measurements and to study the influence of heat treatment on the magnetic properties of Fe-3 Si. For this study, two sets of required rings were annealed under H\({}_{2}\) atmosphere in a horizontal furnace at 750 \({}^{\circ}\)C and 800 \({}^{\circ}\)C for 2 h. The as-printed and heat-treated rings were stacked in a core box and wound with multistrand Litz wires to measure DC and AC magnetic properties. High-field DC magnetization measured in a randomly chosen cut piece equivalent to an isotropic direction was conducted using a superconducting quantum interference device (SQUID) magnetometer at room temperature. The measured saturation induction value of 2.1 T is consistent with conventional Fe-3 Si steel products. Although too small to see on the hysteresis image due to the large scale of the magnetizing field values, the coercivity of the material is approximately 0.5 Oe. Figure 5 shows the DC electrical resistivity measured using a conventional, four-probe resistance measurement system. The room temperature resistivity is approximately 50 \(\upmu\)\(\Omega\) cm, which is comparable to cold-rolled, non-grain-oriented Fe-3 Si resistivity [29]. The magnetic hysteresis loops were measured for the ring samples magnetized up to a low-magnitude DC applied field of approximately 32 Oe, as shown in Figure 6 (left). The corresponding low-field, DC-relative permeability is presented in Figure 6 (right). The coercivity is approximately 0.5 Oe, which is within the range of conventional laminations \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample Number** & **Yield Tensile Strength (MPa)** & **Yield Tensile Strain** & **Ultimate Tensile Strength** & **Ultimate Tensile Strain** & **Young’s Modulus (MPa)** \\  & & **(\%)** & **(MPa)** & **(\%)** & **Young’s Modulus (MPa)** \\ \hline
1 & 573.6 & 2.157 & 613.5 & 17.9 & 29,317.1 \\ \hline
2 & 518.8 & 2.270 & 598.7 & 14.9 & 25,068.1 \\ \hline
3 & 629.2 & 2.361 & 638.3 & 11.0 & 29,117.1 \\ \hline
4 & 553.3 & 2.326 & 645.5 & 15.8 & 26,019.6 \\ \hline
5 & 550.3 & 2.292 & 631.9 & 16.3 & 26,303.4 \\ \hline
6 & 524.2 & 2.185 & 611.5 & 16.3 & 26,404.3 \\ \hline
7 & 539.6 & 2.100 & 630.5 & 24.7 & 27,836.6 \\ \hline Average (\(\pm\)SD.) & 555.6 (\(\pm\)37.35) & 2.200 (\(\pm\)0.09) & 624.3 (\(\pm\)16.72) & 16.7 (\(\pm\)4.12) & 27,152.3 (\(\pm\)1629.02) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mechanical properties of the Fe-3 Si alloy using ORNL SS-3 standard samples. Figure 4: (a) ORNL SS-3 standard sample specification with a thickness of 0.03 in. for the samples shown in the inset of (b); and (b) tensile properties of SLM-printed Fe-3 Si. Color represents the data for different samples. (25 to 50 A/m, or 0.314 to 0.628 Oe). Again, note that Figure 6 (left) is the low-field magnetization hysteresis loop of the material. The maximum relative permeability of 7479 at an applied field of approximately 1 Oe is comparable to that of the rolled, non-oriented electrical steel [30]. Figure 7 presents the comparison of the saturation magnetization and relative permeabilities of the as-printed and annealed samples, where both the saturation magnetization and maximum relative permeability increase with heat treatment temperatures under a low applied magnetic field (0 to 60 Oe). The annealed samples were heated for 2 h in H\({}_{2}\) at elevated temperatures. Some of these samples were heated at 750 \({}^{\circ}\)C, while others were heated at 800 \({}^{\circ}\)C. The left-hand graph in Figure 7 compares the magnetic induction curves of the three sample types. The right-hand graph in Figure 7 compares the relative permeability curve of the three sample types.