PSI - Issue 77

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

201

4

of di ff erent sub-zones of the HAZ in the additively manufactured material. Heat treatment at 1200 °C reproduces the coarse-grained HAZ, treatment at 1000 °C the fine-grained HAZ, and treatment at 800 °C the inter-critical HAZ. All tensile tests were conducted on an Instron 8032 hydraulic machine with an Instron 8800 digital controller and a ± 100 kN load cell (accuracy class 0.5). For the welded specimens, strain fields were measured using a Dantec Dynamics Q 400 3D digital image correlation (DIC) system. For the heat-treated specimens, strain was recorded using an Epsilon Tech3542 axial extensometer.

(b)

(a)

M7

200.0

10.0

6.0

200.0 66.0

29.5

40.0

40.0

27.0

27.0

5.0

10.0

89.0

9.0

29.5

18.0

36.0

R50.0

10.0

Fig. 2. (a) specimen geometry for tensile testing of welded specimens, (b) specimen geometry for tensile tests of heat-treated specimens

3. Results

3.1. Mechanical Behavior of Laser-Welded Specimens

The mechanical properties obtained from the tensile tests of the laser-welded joints are summarized in Table 3, and the corresponding nominal stress-strain curves are presented in Fig. 3 (a). Stresses and strains were evaluated based on the reference cross-section of the base material (18 mm in width and 6 mm in thickness), while a gauge length of 66 mm was applied for strain measurement. Only the LT1 specimen reached an ultimate tensile strength (UTS) of comparable to the S460NL base material. The other two failed prematurely at di ff erent strengths and elongations at fracture. LT1 reached 695.91 MPa and exhibited a elongation at fracture of 17.87 %, representing the best performance among the laser-welded joints. LT2 failed at 695.96 MPa with a elongation at fracture of 8.76 %, within the weld. LT3 fractured also in the weld at 340.46 MPa with a elongation at fracture of 1.45 %. The mechanical behavior of the dissimilar welded joint shows a yielding behavior, which shows upper and lower yield strengths between 571.87 MPa and 577.55 MPa. The macroscopic fracture surfaces of the laser welded specimens are shown in Fig. 4 (a)–(c). LT1 displayed a rough surface with pronounced necking, consistent with ductile fracture and higher elongation. LT2 showed a mixed fracture mode with locally ductile features but overall brittle failure. LT3 exhibited a flat macroscopic fracture surface without plastic deformation, characteristic of brittle failure. Additionally, a significant number of pores are evident on the macroscopic fracture surfaces of LT2 and LT3. The MIG-welded specimens exhibited more consistent performance (Table 3, Fig. 3 (b)). Two of the three speci mens reached UTS values above 699 MPa with elongations at fracture above 16 % and fractured in the S460NL base material. Only one specimen failed prematurely. Overall, MIG welding produced joints with mechanical properties closely matching those of the S460NL base steel. MT1 represents the best performing among the MIG-welded joints and reached a UTS of 702.24 MPa and an elongation at fracture of of 15.76 %. MT2 reached a UTS of 699.04 MPa with a elongation at fracture of 16.29 %. MT3 fractured in a pre-exsisting crack from manufacturing at 419.30 MPa with a elongation at fracture of 1.01 %. The mechanical behavior of the dissimilar welded joints of MT1 and MT2 3.2. Mechanical Behavior of MIG-Welded Specimens