PSI - Issue 77

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

203

6

1 cm

1 cm

1 cm

1 cm

(a)

(b)

(c)

(d)

(e)

1 cm

Fig. 4. (a) to (c) macroscopic fracture surface of the laser welded specimens LT1 to LT3, (d) macroscopic fracture surface of the MIG welded specimen MT3 with failure in the additively manufactured part,(e) crack in the additively manufactured part in specimen MT3 before failure

For LT1, strain localization initially appeared in the weld region (Fig. 5 (b)). As loading progressed, the localization gradually shifted into the S460NL base material (Fig. 5 (c) to (e)). Just before fracture, strain was almost completely concentrated in the S460, where final failure occurred. MT2 showed a similar behavior, with strain eventually local izing in the S460NL base material. In the intermediate stages (Fig. 5 (g) to (k)), the HAZ on both sides of the weld became visible. The S460NL HAZ accumulated more strain than the AM HAZ, particularly evident in Fig. 5 (h) and (i). Subsequently, strain localization migrated fully into the S460NL base material until fracture.

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(k)

(l)

(m)

Fig. 5. (a) to (f) true tangential strain in vertical direction of the laser welded specimen LT1, (g) to (m) true tangential strain in vertical direction of the MIG welded specimen MT2

Fig. 6 shows the progression of the distribution of the strains in the di ff erent parts of the MT2 MIG welded spec imen. Polygon gauges were used in the DIC evaluation to capture the AM base material, the weld, both HAZs, and the S460NL base material. In Fig. 6 the nominal stress strain curve of specimen MT2 is shown. Furthermore, the distribution of strains in the specimen is given. The distribution of strains is the measured mean surface true tangential strain in vertical direction at the given location normalized over the total measured mean surface true tangential strain in vertical direction across the whole gauge length and specimen width. This value shows how the overall strain is distributed in the di ff erent parts of the joint. It is visible, that in the first 1 % engineering strain of the tensile test the strain localized in the HAZ of the S460NL and the AM material, followed by the weld. In both base materials nearly no strain is localized. After reaching the overall yielding point of the joint, the S460NL base material takes more strain. From 6.5 % engineering strain to the end of the tensile test the most strain is localized in the S460NL base material. Just before failure, the AM base material takes only 1.0 % of the total strain. The weld and AM HAZ carry 7.2 % and 11.4 %, respectively. In contrast, the S460NL HAZ and base material accounted for 23.1 % and 57.3 %. This confirms that strain accumulation and failure were dominated by the S460NL side, while the AM material carried only minor portions of the total strain.

3.4. Mechanical Behavior of Heat-Treated Specimens

The tensile properties of the heat-treated Printdur ® HSA specimens are summarized in Fig. 7. Fig. 7 (a) shows the ultimate tensile strength (UTS) and yield strength, while Fig. 7 (b) presents the elongation at fracture. Each data point represents the mean of three tests, with error bars indicating the scatter. A clear temperature-dependent trend was observed. With increasing peak heat-treatment temperature, both UTS and yield strength decreased, whereas elongation at fracture increased. This indicates a progressive softening of the