PSI - Issue 68

T.N. Examilioti et al. / Procedia Structural Integrity 68 (2025) 756–761 T.N. Examilioti et al./ Structural Integrity Procedia 00 (2025) 000–000

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Fig. 3. Quality map based on the quality index ! of post welded heat treatment AA2198 specimens and under different (a) different filler materials; (b) different thicknesses. The application of PWHT results in a noticeable increase in the quality index for both AA4047 and AA2319 filler materials, transitioning from the AW condition to 3 h and 170 o C and UA condition ( Fig. 3a ). However, with increasing ageing times, there is continuous improvement in quality, reaching 48 h and PA condition. The overall quality index is decreased for both filler materials at 98 h and OA condition. For the case of different material thicknesses under PWHT and AA4047 filler material, both thicknesses present similar quality index with higher quality in the PA condition ( Fig. 3b ). The overall quality index shows a slight decrease in the OA condition, reflecting a reduction in yield stress accompanied by a slight increase in ductility. 5. Conclusions The effect of different filler materials and nominal thicknesses of AA2198 joints on the mechanical properties under different artificial ageing conditions was investigated. The AA4047 filler material shows a continuous increase in yield stress by about 45 % up to 48 h of ageing at 170 o C, while AA2319 filler material shows slightly lower results in the case of PA condition. For both cases elongation at fracture present a decrease with increasing artificial ageing. The elongation reduction reaches around 90 % for AA4047 and 80 % for AA2319. The nominal thickness of 5.0 mm samples presents higher yield stress than the samples of 3.2 mm for the case of AA4047 filler material. Regarding elongation at fracture, specimens with 5.0 mm thickness exhibit a significant reduction (~ 85 %) with increasing ageing up to over ageing condition. Similar for the case of 3.2 mm thickness, the decrease is slightly lower, by about 75 %. The highest quality index is presented in the PA condition for all investigated cases. These diagrams can be employed to identify optimal conditions for AA2198 welded joints, facilitating an acceptable “balance” between yield stress and tensile ductility. The design engineer must determine the appropriate artificial ageing conditions based on specific thresholds for yield stress and ductility to achieve the highest possible quality for mechanical performance. Acknowledgements . The work has been financed by the Hellenic Foundation for Research and Innovation H.F.R.I.- Project ID 03385 Acronym CorLi-Corrosion susceptibility, degradation and protection of advanced Al-Li aluminium alloys. The authors would also like to thank Dr. N. Kashaev and professor B. Klusemann from Helmholtz Zentrum Hereon and Leuphana University of Lüneburg for fruitful discussions on the manuscript.