Additive manufacturing (AM) opens up new ways to produce parts with high geometric complexity, e.g. involving internal structures, which led to an increased interest of science and industry in the recent years [1]. The mechanical behavior and load-bearing capacity of additively manufactured components, however, are still not completely understood and are the subject of intense research efforts [2]. In particular, residual stresses (RS) play an important role for the strength and fatigue properties. Therefore, RS distributions were investigated in various parts, fabricated from aluminium alloy powder (AlSi10Mg) using the Laser Powder Bed Fusion (LPBF) technique.

Residual stress fields were determined using high-energy X-ray diffraction at the Hereon beamlines of Petra III at Deutsches Elektronen Synchrotron (DESY). High photon energies were used to allow penetration of thicker structures. Angle-dispersive diffraction was used in transmission geometry and energy-dispersive techniques were used to obtain three-dimensional spatial resolution.

Different structures with increasing complexity were produced to study the influence of geometry on the RS distribution. Thin walls are the simplest structures, showing an influence of edge geometry. The RS fields get more complex with increasing geometrical complexity, e.g. for tubes or honeycomb structures. The principal stress directions were observed to rotate in a honeycomb structure. Typical stress distributions will be shown and discussed in the context of the specific microstructure of the AM parts.

References

[1] Yang, L., et al., Additive manufacturing of metals: the technology, materials, design and production. 2017: Springer.

[2] Campbell, I., et al., Wohlers report 2018: 3D printing and additive manufacturing state of the industry: annual worldwide progress report. 2018: Wohlers Associates.