## 2 Materials and Methods
### Fracture Toughness and Resistance Curves Determination Procedure  
Above-mentioned rectangular test specimens were used for determination of fracture toughness and resistance curves as well. This experiment was conducted according to [23]. To achieve faster crack initiation, a straight notch was cut using wire saw K.D. Unipress Saw WS-22. Measuring scale was drawn on both polished sides of test specimens in the crack growth direction to enable easier monitoring of crack growth. Two microscope cameras were used for monitoring and measuring crack growth on both sides of the specimen as presented in Figures 6 and 7, and the mean crack growth value was calculated. \begin{table}
\begin{tabular}{c c c c c c c} \hline \(\Delta K_{\text{s}}\) & \(\mathbf{d}a/\mathbf{d}N_{\text{s}}\) & \(a\), mm & \(N_{\text{s}}\) - & \(R\), - & \(\Delta M_{\text{s}}\) Nm & \(M_{\text{m}}\), Nm \\ \hline
13 & 0 & 2.011 & 12,542 & 0.1 & 13.79 & 8.43 \\ \hline
12.54 & 804.794 & 2.047 & 27,878 & 0.1 & 13.17 & 8.05 \\ \hline
12.34 & 618.045 & 2.063 & 27,904 & 0.1 & 12.9 & 7.88 \\ \hline
12.05 & 418.945 & 2.087 & 27,949 & 0.1 & 12.53 & 7.66 \\ \hline � & � & � & � & � & � & � \\ \hline
9.34 & 93.277 & 2.267 & 30,997 & 0.1 & 9.26 & 5.66 \\ \hline
9.24 & 73.037 & 2.278 & 31,148 & 0.1 & 9.13 & 5.58 \\ \hline
9.14 & 47.136 & 2.289 & 31,375 & 0.1 & 9.01 & 5.51 \\ \hline � & � & � & � & � & � & � \\ \hline
7.38 & 10.214 & 2.382 & 44,671 & 0.1 & 7.1 & 4.34 \\ \hline
7.3 & 14.362 & 2.392 & 45,372 & 0.1 & 7.01 & 4.28 \\ \hline
7.23 & 8.162 & 2.402 & 46,611 & 0.1 & 6.92 & 4.23 \\ \hline � & � & � & � & � & � & � \\ \hline
5.42 & 1.392 & 2.691 & 185,318 & 0.1 & 4.82 & 2.95 \\ \hline
5.36 & 0.907 & 2.702 & 197,320 & 0.1 & 4.75 & 2.9 \\ \hline
5.31 & 0.801 & 2.712 & 209,809 & 0.1 & 4.7 & 2.87 \\ \hline � & � & � & � & � & � & � \\ \hline
4.63 & 0.064 & 2.852 & 866,415 & 0.1 & 3.95 & 2.41 \\ \hline
4.58 & 0.045 & 2.862 & 1,089,085 & 0.1 & 3.9 & 2.38 \\ \hline
4.53 & 0.001 & 2.872 & 2,460,570 & 0.1 & 3.85 & 2.35 \\ \hline \end{tabular}
\end{table} 
Table 2: Parameters recorded during \(\Delta K_{\text{th}}\) determination for SLM-produced alloy. Specimen loading in this experiment consisted of three steps: initial fatigue loading, stable crack growth, and final fatigue loading of the specimen. Fatigue loading prior to and after stable crack growth was performed using Rumul Cracktronic device. Maximal bending moment was defined for first fatigue loading using the criterion that the ratio of maximal stress intensity factor to elasticity modulus \(K_{\text{max}}/E\) must not exceed \(1.5\times 10^{-4}\) m\({}^{0.5}\)[24]. After the first loading step, knives for CMOD gauge were glued on the notched side of test specimens, as presented earlier, and a stable crack growth step was performed. For this step, universal testing machine Instron 1255 was used. The test specimen was positioned for a three-point bending test, as presented in Figure 8. Measurement scale on the test specimen was used to allow crack growth monitoring and measurement. Each line on the scale represents 0.5 mm difference from the adjacent line, with the first line on the bottom starting at 2.5 mm from the bottom of the specimen. Figure 6: Monitoring and measurement of crack growth using two microscopes. Figure 7: Microscopic view at 10x magnification of crack on test specimen with measurement scale. The crack mouth opening displacement extensometer was calibrated and mounted onto pre-glued knives to measure the CMOD. The load increased continuously until the maximum force value was reached, at which point loading stopped and unloading began, representing the final part of this step of the experiment. This process ensures that the data is recorded during stable crack growth. The purpose of this experiment was to determine the force vs. crack mouth opening displacement (F-CMOD) and force vs. load line displacement (F-LLD) relationships, which serve as input data for determination of resistance curves.