## 3 Results  
Figure 5 shows representative cross-sections of three different builds with schematics of the tool face position superimposed on the deposition cross-section to illustrate the location of the tooling relative to the final depositions. These cross-sections are scaled to the same proportions, and it can be observed that as the overlap value increases, the width of  
Figure 4: (**a**) Representative AFSD overlap build with a tensile specimen layout schematic. (**b**) Dimensioned model of the tensile specimen. the build decreases, similar to the observations made from the builds in Figure 3. Figure 5a shows the tool face schematic for a build with a 6.4 mm gap, corresponding to Build A from Table 1 and Figure 3a. This build can be clearly seen as two distinct depositions with their own TMAZ and HAZ that appear to be the most intense beneath the 'nugget zones' of the deposition paths. The boundary between the TMAZ and HAZ can be observed in the microscopy image as there is a clear distinction between the refined grains undergoing recrystallization within the TMAZ and the much larger grains of the base material within the HAZ. The material between the depositions is flash material that makes contact between the deposition paths but does not experience any mixing. Figure 5b shows the schematic for a build with a 6.4 mm overlap, corresponding to Build E from Table 1 and Figure 3e. In Figure 5b, there is not a clear boundary in the deposited material between the two passes, but there is instead a central interface region where there is a large amount of mixing between the two passes. Figure 5c shows the schematic for a build with a 19.1 mm overlap, corresponding to Build I from Table 1 and Figure 3i. In this build, the mixing zone of the overlapped region follows the flow pattern of the retuning deposition pass, giving a more distinct interface boundary of the mechanically affected zones for each deposition pass. Figure 6 shows the overlap interface regions for each build, where the two regions of deposited material are mixed and bonded together. Figure 6a-i correspond to the build parameters detailed in Table 1. Using optical microscopy on the etched cross-sections of each build, the material flow at the overlap boundary interface can be visualized clearly. In Figure 6a (\(-\)6.4 mm overlap), 6b (\(-\)3.2 mm overlap), and 6c (0.0 mm overlap), distinct swirling patterns are present in the flash material as the depositions are pressed together. Figure 5: (**a–c**) Representative etched cross-sections with tool profile schematics of the AFSD overlap builds. There was minimal mixing in these builds, so a clear boundary between deposition passes can be observed. In Figure 6d-i, the interface material was mixed during the deposition of the return pass, so the flash material, as well as a portion of the initial deposition layer, was mixed with the new material. This makes a defined boundary between the deposition passes difficult to identify and causes the swirling pattern to become blended and deformed within the cross-section. The cross-sections show an increasing level of mixing between deposition layers and passes because while the swirling pattern is still visually present in each cross-section, the boundary becomes less distinct as the overlap distance increases. A build with a large overlap region will have to force more pre-existing material outward as new material is deposited. Additionally, the interface boundary at the edge of the initial deposition pass is consumed as part of the TMAZ of the return pass. This means the interface is subjected to high amounts of shear force and plastic deformation as new material is deposited, eliminating any distinct interface boundary and creating a more homogeneous material. In addition to mixing between deposition passes, substrate deformation can be seen in many of the cross-sections shown in Figure 6. As the substrate material near the surface interacts with the tool face, a portion undergoes dynamic recrystallization, creating a gradient region within the TMAZ.