## 4 Conclusions  
The main conclusions that can be drawn from this study are as below:  
1. Both pure base metal samples and welded samples have a smaller variation in the fatigue life across trials in the low-cycle regime.
2. At high loading conditions, Al Alloy 7075 has greater fatigue strength than Al Alloy 2024, but there is no noticeable difference at low loads.
3. At log (no. of cycles) 5.0 to 6.5, i.e., the area which carries both the welded sample results and the base sample results, correlate with each other, and the welded samples show better fatigue strength than the base samples. However, the superiority of the welded samples is only scattered in the middle of the horizontal axis, while at the lowest and the highest limits of the number of cycles, base samples have considerable fatigue life, but still less than those of the welded samples.
4. The filler material AA4047 shows higher joint strength in comparison to AA4043 due to high silicon concentration. High silicon concentration leads to low melting temper  
Figure 10: Illustration of the various fracture portions for different samples and loadings (**a**) base sample AA7075 under 245 N (**b**) base sample AA7075 under 335 N-first trail (**c**) base sample AA7075 under 335 N-second trail (**d**) welded sample with filler 4047 under 295 N (**e**) welded sample with filler 4043 under 295 N.  
ature range, hence, giving high resistance to solidification cracking and undercut. It results in low porosity and inclusion, increasing the fatigue strength of AA4047. The melting range of AA4043 is 60 degrees, while that of AA 4047 is 6 degrees. Therefore, 4047 is more crack resistant. Magnesium silicide Mg\({}_{2}\)Si is also present in AA4047 filler material due to the higher concentration of magnesium in it and, hence, increases its tensile strength and bonding forces in the material. Some deviation from the suggested results can be seen in Figure 8 at point 3 and 4, either due to the formation of any welding defect or welding pool instability. One of the reasons could be the absence of magnesium silicide, which reduces crack sensitivity. Although the trend line of AA4047 is higher than AA4043 in all cases, referring to AA4047 as better filler material, it is important to note here that the real-time fatigue testing is carried out in the current study. Generally, fatigue results show high variability in the results, even when identical test pieces are used, so some abnormality in the results is typical in fatigue testing [44; 45; 46].  
Conceptualization, M.H. and T.-u.R.; formal analysis, M.H.; writing--original draft preparation, M.H. and T.-u.R.; review and editing, P.K.; writing--review and editing, M.Y.J.; supervision, C.-W.P. All authors have read and agreed to the published version of the manuscript.  
This study was supported by the National Research Foundation of Korea and funded by the Korean Government (MSIP Grant No. 2020R1A2B5B02002512).  
All the data are reported within the article.  
This study was supported by the National Research Foundation of Korea and funded by the Korean Government (MSIP Grant No. 2020R1A2B5B02002512).  
The authors declare no conflict of interest.