## 3 Results and Discussion
To evaluate whether high residual stress was the root cause for the low ambient temperature fracture strain, additively manufactured (HPD) tensile specimens were heat-treated at 650 \({}^{\circ}\)C for 90 min and subsequently tensile tested at ambient temperature. This heat treatment increased the fracture elongation by an approximate factor of 3 to a value of \(\sim\)5%, while the UTS further increased to about 800 MPa (cf. Figure 11 and Table 3). A conclusive assessment of the high level of residual stress as the reason for the low ambient temperature ductility was not possible because any heat treatment for stress reduction potentially led to the precipitation of additional strengthening Laves phase particles. \begin{table}
\begin{tabular}{c|c|c|c|c|c|c|c} \hline \multirow{2}{*}{**Material**} & \multicolumn{3}{c|}{**Hardness, As-Built State (HV1)**} & \multicolumn{3}{c|}{**Hardness, After Creep Compression Test (HV1)**} \\ \hline  & **Mean** & **Min.** & **Max.** & **Range** & **Mean** & **Min.** & **Max.** & **Range** \\ \hline HiperFerAM LPD-L & 199 & 193 & 209 & 16 & 211 & 197 & 222 & 25 \\ \hline HiperFerAM HPD-L & 226 & 217 & 233 & 16 & 248 & 239 & 252 & 13 \\ \hline HiperFerAM LPD-Q & 196 & 186 & 201 & 15 & 218 & 206 & 226 & 20 \\ \hline HiperFerAM HPD-Q & 233 & 217 & 244 & 27 & 252 & 240 & 272 & 32 \\ \hline \end{tabular}
\end{table} 
Table 4: Hardnesses of LPD and HPD HiperFer\({}^{\rm AM}\) in the as-built state and after compression creep testing. Figure 12: HiperFer\({}^{\rm AM}\) (**a**) LPD and (**b**) HPD EBSD mappings taken perpendicularly to the fracture surfaces after the tensile experiments at ambient temperature. \begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Material**} & **Heat-Treatment** & **Area-Specific** & **Test** & & \\  & **Treatment** & **Laser Power** & **Temperature** & **UTS (MPa)** & **A\({}_{\rm t}\) (\%)** \\  & **State** & **(Wmm\({}^{-2}\))** & **(\({}^{\circ}\)C)** & & \\ \hline HiperFer & 650 \({}^{\circ}\)C/120 & - & 20 & 653 & 19.2 \\
17 Cr2 & - & - & 650 & 235 & 17 \\ \hline HiperFer\({}^{\rm AM}\) & As-built & 1050 (HPD) & 20 & 760 & 1.6 \\ \hline HiperFer\({}^{\rm AM}\) & As-built & 195 (LPD) & 20 & 667 & 1 \\ \hline HiperFer\({}^{\rm AM}\) & 650 \({}^{\circ}\)C/90 min & 1050 (HPD) & 20 & 804 & 4.8 \\ \hline HiperFer\({}^{\rm AM}\) & As-built & 1050 (HPD) & 650 & 290 & 33.5 \\ \hline HiperFer\({}^{\rm AM}\) & As-built & 195 (LPD) & 650 & 280 & 16.3 \\ \hline \end{tabular}
\end{table} 
Table 3: UTS (20 and 650 \({}^{\circ}\)C) values and A\({}_{\rm t}\) of HiperFer 17 Cr2 compared with the HiperFer\({}^{\rm AM}\) LPD and HPD variants. However, in view of the tensile properties at 650 \({}^{\circ}\)C, this assumption was reasonable. At 650 \({}^{\circ}\)C, HiperFer\({}^{\text{AM}}\) (HPD) reached UTS/fracture elongation values of 290 MPa/33.5%, which constituted a remarkable improvement over conventionally produced HiperFer 17 Cr2 sheet material (UTS: 235 MPa, A\({}_{\text{t}}\): 17%, cf. Figure 11 and Table 3). Concerning the UTS, no significant difference existed when applying the LPD parameters (cf. Figure 11 and Table 3), but the total fracture elongation diminished to about 16%, which still correlated well with the conventionally rolled sheet material. In the LPD HiperFer\({}^{\text{AM}}\), localized sub-grain formation was observed (Figure 13a), while global sub-graining occurred in the HPD variant (Figure 13c). Since the deformation conditions in the tensile test were identical, a higher stacking fault energy (i.e., the ability of dislocations for transversal slip) in the HPD variant caused by the adjusted AM parameters could have been responsible for the global subgrain formation. Effective grain refinement caused by the high degree of global sub-grain formation obviously yielded higher plastic deformability (Figure 13d) in the case of the HPD variant.