PSI - Issue 77

Jakob Blankenhagen et al. / Procedia Structural Integrity 77 (2026) 198–206 Author name / Structural Integrity Procedia 00 (2026) 000–000

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In contrast, MIG welding produced more reliable joints. Two specimens achieved UTS values comparable to S460NL and fractured in the base material, demonstrating that the weld zone itself did not limit performance. The only deviation was specimen MT3, which failed in the AM part due to a pre-existing manufacturing defect, which acted as a stress concentrator and led to premature failure. Overall, these results indicate that MIG welding provides superior joint quality for hybrid connections, whereas laser welding su ff ers from weld porosity and limited reproducibility. The dilatometer experiments reproduced the mechanical response of di ff erent HAZ sub-zones in Printdur ® HSA. A clear temperature-dependent trend was observed: with increasing peak temperature, both UTS and yield strength decreased, while elongation at fracture increased. This softening e ff ect is attributed to grain coarsening and microstruc tural recovery at elevated treatment temperatures which is common in additively manufactured austenitic steels like 316L (Schreiber et al. (2024); Zhou et al. (2025)). Furthermore, it was shown that for PBF-LB / M / 316L heat-treatment at 800 °C for elevated times leads to elimination of cell structures, which leads to an increase in cell size and a decrease in dislocation density (Sua´rez Ocan˜o et al. (2025)). Fundamentally, this softening of the material can be described with the Hall-Petch relationship, which states that the strength of the material is depended on the grain size (Hall (1951); Petch (1953)). The intercritical (800 °C) and fine-grained (1000 °C) zones therefore retained higher strength, whereas the coarse-grained zone (1200 °C) showed the lowest strength but highest ductility. The influence of cooling rate (t 8 / 5 time) was less pronounced. No systematic e ff ect was observed at high tem peratures (1000–1200 °C). At 800 °C, however, slower cooling (longer t 8 / 5 ) slightly reduced strength and increased ductility, suggesting a greater sensitivity of the intercritical HAZ to cooling conditions. Overall, the mechanical re sponse of the heat-treated specimens confirms that temperature is the dominant factor in determining HAZ behavior, while cooling rate plays only a secondary role. The comparison of welded specimens with dilatometer simulations highlights the role of HAZ properties in joint performance. The reduced strength and increased ductility observed in heat-treated specimens at high temperatures (1000–1200 °C) align with the softening behavior expected in the coarse-grained HAZ of the AM material. The superior performance of MIG-welded joints can be related to a more favorable stress redistribution. DIC analyses confirmed that strain preferentially accumulated in the S460NL HAZ and base material, while the AM side contributed only marginally. This behavior reflects the higher ductility of the AM material after thermal exposure, as revealed by the dilatometer tests. Consequently, the welds themselves did not limit the joint strength. Taken together, these findings demonstrate that the mechanical performance of dissimilar welded joints between AM and construction steel is governed by the interaction between weld quality and HAZ properties. MIG welding provides robust joint behavior by shifting strain localization toward the ductile S460NL side, whereas laser welding is more sensitive to weld defects. From this study, the following conclusions can be drawn about the mechanical behavior of dissimilar weld joints between PBFLB / M / Printdur ® HSA manufactured and structural steel S460NL: • This study demonstrated the feasibility of welding additively manufactured Printdur ® HSA to conventional structural steel (S460), showing that robust dissimilar joints can be achieved when welding parameters and material conditions are properly controlled. • MIG welding produced joints with mechanical properties comparable to the S460NL base material. Failures predominantly occurred in the S460NL base metal, indicating that the weld did not limit performance. • Laser welding resulted in less reproducible joints. Failures were frequently located in the weld, caused by porosity and associated with premature fracture. • One MIG-welded specimen failed within the AM part due to a pre-existing manufacturing defect, highlighting the influence of residual stresses and heat contraction during the AM process. • Dilatometer experiments reproduced the mechanical response of di ff erent HAZ sub-zones of Printdur ® HSA. Increasing heat-treatment temperature reduced strength but enhanced ductility, confirming a softening of the AM material at elevated thermal exposure. 5. Conclusions and Outlook