Laser-based powder bed fusion of metals (PBF-LB/M) is a manufacturing process particularly suited for producing application-oriented components. By adjusting the process parameters across the component, it is possible to create a defined, sharp gradient in the microstructure and crystallographic texture within a component. This results in an interface that significantly influences the crack propagation behavior [1]. When evaluating this behavior across such an interface in the as-build condition but also under applied external load, not only the microstructure but also the residual stress distribution around cracks and the interface must be considered. To address this, the local residual stress distributions around cracks in microstructurally graded 316L compact tension (CT) specimens are investigated by mapping experiments. The investigated CT-specimens feature a finer-grained-, less textured (“400 W”) region adjacent to a coarse-grained, strongly textured (“1 kW”) region [2]. High-energy synchrotron X-ray diffraction is used to analyze the local stress distribution around cracks before and after propagating across the interface. To ensure that the diffraction data only includes information from the bulk of the samples, a conical slit system is used at beamline P07@Perta III at DESY. This conical slit system restricts the gauge volume to the bulk of the CT-specimen, excluding the near surface regions, while still enabling the analysis of full Debye-Scherrer rings from multiple {hkl} planes. The measurement strategy is adapted to enable the assessment of the strongly textured and coarse-grained region. The proposed contribution presents findings on this ongoing research topic. As an example of the results, Figure 1 is showing the local lattice strain distribution (depicted for the {311}-planes) analyzed under an applied tensile load of 860 N in a CT-specimen with a crack with a length of ≈7 mm. The crack propagated from the finer-grained “400 W”-region across the interface into the more coarse-grained “1 kW”-region. The overarching goal is to deepen the understanding of how microstructure, texture, and residual stresses interact and influence the crack propagation across microstructural interfaces within components.

References

[1] F., Brenne; T. Niendorf; Materials Science & Engineering A, 2019, A764

[2] N. Möller; et al.; Advanced Engineering Materials, 2025

Florian Loebich (M.Sc.)