PSI - Issue 33

A. Kansy et al. / Procedia Structural Integrity 33 (2021) 1173–1180 A. Kansy, M. Kaynak, C. Bleicher, H. Kaufmann/ Structural Integrity Procedia 00 (2019) 000–000

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3. Test results and discussion 3.1. Metallographic investigations

Metallographic sections were removed from tested fatigue specimens and examined by light microscopy. Representative images of the microstructures are shown in Figure 2. The left side shows the microstructure of the cast sample, the right side shows the microstructure of the component. Both graphite arrangements are classified as A graphite, which mainly occurs at low undercooling of near-eutectic compositions. A-Graphite is characterized by regularly distributed lamellae and a low degree of branching. When comparing the graphite morphology of both samples, it can be observed that for the component the graphite content is lower and the shape of the lamellae is finer.

Figure 2. Light microscopic microstructural analysis of EN-GJL-300; left: cast sample, right: component

3.2. Fatigue tests Figure 3 shows the S-N curves for the unnotched specimens with 12 mm diameter (HSV 90% of 3240 mm³) removed from the component (red) and cast samples (blue).

Figure 3. S-N curves of unnotched specimens with 12 mm diameter, HSV 90% of 3240 mm³; red curve: component; blue curve: cast samples