## 4 Discussion  
This present study evaluated the mechanical properties of as-deposited AA7075 with varying amounts of deposition path overlapping. Deposition hardness and grain size showed only small amounts of variation between samples with no apparent relationship to the overlap region width. The average grain size remained approximately 4 microns in the deposited overlapping region, which is similar to AFSD experiments reported elsewhere [39; 44; 45]. The average deposition hardness, ranging from 120 Hv to 135 Hv, is comparable to work focusing on the repair of AA7075 using AFSD performed by [PERSON] et al. (2022), where a hardness of 130 Hv was reported in the AFSD-repaired region [22], as well as work done by [PERSON] et al. (2020) on the fatigue behavior of as-deposited AA7075, which reported a hardness of 125 Hv after natural aging [32]. The  
Figure 14: (**a**) SEM of tensile specimen fracture surfaces for the specimen with 3.2 mm of overlap (**A**). (**b**) High magnification image of dimpling effect observed in the specimen with \(-\)3.2 mm of overlap (**A**). (**c**) SEM of tensile specimen fracture surfaces for the specimen with \(-\)3.2 mm of overlap (**B**). (**d**) High magnification image of fracture surface geometry observed in the specimen with \(-\)3.2 mm of overlap (**B**).  
hardness gradient observed throughout the TMAZ and HAZ of samples in this present study follows a similar trend documented by [PERSON] et al. (2007) [46], where the hardness decreases significantly outside of the nugget zone due to the excess amount of heat put into the material during friction-stir processes.  
The experimental tensile data shows a range of results that generally follows the trend in which increasing the overlap region width increases tensile strength within the overlap region when all other process parameters are held constant. While the tested specimens performed below the T6 feedstock material's strength and ductility, they did perform similarly to AA7075 material that has undergone FSW [38]. The tensile properties of the specimen with 9.5 mm of overlap (A), which achieved a UTS of 434 MPa compared to the feedstock material (583 MPa), illustrates that while as-deposited material will produce components with inferior mechanical properties when compared to the feedstock material, there was a clear benefit in overlapping the deposition paths to maintain the performance level of friction-stir processed material.  
In order to produce large-scale components using AFSD in practical applications, a minimum amount of material should be overlapped between deposition passes in order to ensure that proper mixing and metallurgical bonding occurs and the desired benefits of the AFSD process are maintained throughout the build. As a near-net shape process, there will still be post-deposition machining and processing to produce a finished component, and the necessary amount of overlapping material will vary from build to build. With an increased overlap region comes improved mixing but less efficient use of material and longer deposition times. Excessive overlap will create diminished returns with respect to material strength while still greatly increasing the cost to produce components. For a relatively large, featureless deposition region, an overlap region width of 6.35-9.53 mm is recommended, assuming that the tool face has similar geometry to the one used in this study, and all other operating parameters are held constant. This overlapping value is equivalent to approximately 25% of the tool face and deposition width, which correlates to the track overlap ratio commonly used in directed energy deposition [47]. This value can be selectively increased as needed to work around potential features in order to reduce machining time, but a reduced overlap width would likely sacrifice the strength of the final component.