## 3 Results and Discussions
This is mainly attributed to the heat being accumulated during the deposition due to its scanning characteristics, leading to higher peak temperature and thermal stress than other cases. The figure also shows that the raster pattern case has higher stress than the alternate case. The scanning strategies of the raster and the alternate are not significantly different. The only difference is that the alternate pattern has intervals between each deposition, which promotes more heat transfer to the surroundings. The results present that the type of deposition pattern significantly affects the thermal gradient and, thus, residual stress generation. Figure 5: The evolution of temperature contours for the different deposition patterns (unit: \({}^{\circ}\)C). (**a**) Alternate, (**b**) in-out spiral (**c**) out-in spiral, and (**d**) raster. The inhomogeneous thermal gradient in AM deposition could lead to excessive distortion. Therefore, warpage was investigated to ensure structural integrity of AM parts. In this work, the AM deposition layer is built up in the z-direction. Figure 8 shows the displacement distributions for different deposition patterns. Overall, the maximum warpage is found at the corner of the substrate, while the minimum displacement is located in the center for all types of patterns considered. This overall trend results from the compressive residual stress generated during deposition. Considering the heat transfer throughout the thickness of the substrate during the deposition, the temperature at the top surface is higher than the one at the bottom. As the substrate is clamped, the heat expansion generates compressive thermal stress. The higher thermal stress is applied at the top and the lower stress is applied at the bottom due to the temperature difference throughout the thickness. Such stress gradients lead to the bending of the substrate and the deposition layer. This explains the overall distortion trends of the substrate and deposition layer, which are  
Figure 6: The temperature at the center of the deposition layer for the different scanning patterns. (**a**) Alternate, (**b**) in–out spiral, (**c**) out–in spiral, and (**d**) raster. Refer to Figure 3 for the point of investigation. Figure 7: The Mises stress along the diagonal direction of different patterns. observed in Figure 8. Similar trends of distortion are also observed in other works, which show experimentally measured warpage, for example, single welding pass [38]; WAAM multi-layer depositions [39, 40, 41]; and a thin-walled rectangle deposited by multi-layered WAAM [42]. [PERSON] et al. [38] investigated the distortion in the welding of 9 Cr-1 Mo steel. Maximum distortion after removal of clamping was measured as 2.1 mm. It was reported that this was mainly because of the compressive residual stress near the welding line. [PERSON] et al. [39] measured the welding distortion of multi-layer WAAM depositions. In their works, the distortion of the specimens was observed in the z direction (thickness direction) with a concave-up curvature. A comparative study of numerical and experimental results on the distortion of HSLA S460 WAAM was also reported [40], which presented angular distortion in the multilayer of WAAM depositions. [PERSON] et al. [42] analyzed the distortion of the thin-walled rectangular component fabricated by twenty-five layers of WAAM depositions. Their comparison results between simulation and experiment demonstrate the concave distortion of samples, which is the same as in the present study. It is interesting to note that the line-type patterns (i.e., alternate and raster) exhibit similar contours for warpage, while the spiral-type patterns (i.e., in-out and out-in) have different trends in the displacement distribution. Although the same level of heat source energy is applied to the substrate for all pattern cases, the amounts of cumulative heat in the center of the deposition layer are different depending on the type of pattern.