In-plane anisotropy of selective laser-melted stainless steel: The importance of the rotation angle increment and the limitation window

Hitzler, Leonhard; Hirsch, Johann; Tomas, Josef; Merkel, Markus; Hall, Wayne; Öchsner, Andreas

doi:10.1177/1464420718757068

Cited by 15 publications

(14 citation statements)

References 42 publications

(116 reference statements)

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“…The basic properties and the thermal properties of 316L stainless steel powder and solid 316L at different temperatures are shown in Table 1. Meanwhile, the mechanical properties of printed 316L are anisotropic in practice [38,39]. However, it is very difficult to obtain the whole basic parameter data of the anisotropic materials of 316L and was conducted on simplification processing as isotropic for the thermodynamic simulation in this model.…”

Section: Materials Properties Of 316lmentioning

confidence: 99%

Finite Element Analysis of Thermal Stress and Thermal Deformation in Typical Part during SLM

Bian

Shao

2019

Applied Sciences

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Selective laser melting (SLM) constitutes an additive manufacturing (AM) method. Many issues such as thermal strain and macro-thermal deformation, which are caused by the thermal stress of different process parameters, are not clear. In this paper, an efficient and fast manufacturing simulation method was researched based on a moving heat source model and an elastoplastic theory of welding simulation, which was studied based on the thermodynamic coupling algorithm with a software-developed application for the SLM process. Subsequently, typical case results of thin and hollow plate part formation and the corresponding performances were simulated in detail. The results demonstrated that the effective thermal stress increased as the layer height increased from the surface layer to the substrate, while the thermal strain followed an approximate change rule. In addition, the stress was released from the underlying substrate when the support was removed. Moreover, the largest single axis plane stress was changed from tension to compression from the edge to the center, finally reaching equilibrium. In particular, maximum macro thermal deformation occurred at the printed support structure to the samples, displaying similar results in other locations such as the corners. Finally, the effectiveness of the simulation could be verified from the realistic printed part, which could provide proof for the quality prediction of the part that is actually forming.

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Section: Materials Properties Of 316lmentioning

confidence: 99%

Finite Element Analysis of Thermal Stress and Thermal Deformation in Typical Part during SLM

Bian

Shao

2019

Applied Sciences

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“…In multi-axis additive manufacturing, the adaptation of the building direction is a key step as well in building parts without support structures [42]. For the in-plane anisotropy under a certain setting of process parameters it was found by Hitzler L. [43], that only the linear elastic properties and the breaking elongation were affected, whereas the other material properties such as relative density, surface hardness and tensile strength remained stable. On the other hand, if considering the anisotropy of the manufacturability of inclined surfaces, we will have more freedom in the design of 3D parts that can be built without supports relative to selecting a constant polar angle threshold.…”

Section: Case Studymentioning

confidence: 99%

A feasible method of support slimming based on the different thresholds of polar angles in selective laser melting

Zhang¹,

Mao²,

Fu³

et al. 2018

Materials & Design

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The large thermal deformation induced by the high temperature gradient severely restricts the threshold level of polar angle in selective laser melting (SLM). As such, different types of support structures are usually added to improve the manufacturing capacity and broaden the application of SLM technology. However, enormous support structures will result in large time consumption, material waste, high labor intensity and inferior surface quality of part. In this research, a feasible method of slimming support structures was presented. Firstly, a series of experiments for exploring the thresholds of polar angles at different azimuth angles relative to the recoating direction of powders were conducted and the effect of powder recoating by scraper on the building of inclined surfaces was analyzed. Then, a generation algorithm of slimmed support structures was proposed based on the varying thresholds of polar angles. In addition, several typical cases demonstrated the usefulness of this method by eliminating the quantities of their support structures by 35 percent% in average.

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“…Al-Si-Mg alloys exhibit a unique microstructure in their as-fabricated state, whereby the macroscopic anisotropy characteristics are predominantly governed by the localized formation of silicon segregations; see Figure 1 [3,4]. This is in strong contrast to other alloys, like austenitic stainless steels or Inconel, with their dominating characteristic being their grain morphology [5,6]. The cause for the major impact of the Si-segregations is thought to be their location, as they occur most prevalently in remolten areas, i.e., in the bonding areas between single scan tracks and subsequent layers [7].…”

Section: Introductionmentioning

confidence: 99%

Heat Treatments and Critical Quenching Rates in Additively Manufactured Al–Si–Mg Alloys

Hitzler¹,

Hafenstein²,

Martín

et al. 2020

Materials

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Laser powder-bed fusion (LPBF) has significantly gained in importance and has become one of the major fabrication techniques within metal additive manufacturing. The fast cooling rates achieved in LPBF due to a relatively small melt pool on a much larger component or substrate, acting as heat sink, result in fine-grained microstructures and high oversaturation of alloying elements in the α-aluminum. Al–Si–Mg alloys thus can be effectively precipitation hardened. Moreover, the solidified material undergoes an intrinsic heat treatment, whilst the layers above are irradiated and the elevated temperature in the built chamber starts the clustering process of alloying elements directly after a scan track is fabricated. These silicon–magnesium clusters were observed with atom probe tomography in as-built samples. Similar beneficial clustering behavior at higher temperatures is known from the direct-aging approach in cast samples, whereby the artificial aging is performed immediately after solution annealing and quenching. Transferring this approach to LPBF samples as a possible post-heat treatment revealed that even after direct aging, the outstanding hardness of the as-built condition could, at best, be met, but for most instances it was significantly lower. Our investigations showed that LPBF Al–Si–Mg exhibited a high dependency on the quenching rate, which is significantly more pronounced than in cast reference samples, requiring two to three times higher quenching rate after solution annealing to yield similar hardness results. This suggests that due to the finer microstructure and the shorter diffusion path in Al–Si–Mg fabricated by LPBF, it is more challenging to achieve a metastable oversaturation necessary for precipitation hardening. This may be especially problematic in larger components.

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In-plane anisotropy of selective laser-melted stainless steel: The importance of the rotation angle increment and the limitation window

Cited by 15 publications

References 42 publications

Finite Element Analysis of Thermal Stress and Thermal Deformation in Typical Part during SLM

Finite Element Analysis of Thermal Stress and Thermal Deformation in Typical Part during SLM

A feasible method of support slimming based on the different thresholds of polar angles in selective laser melting

Heat Treatments and Critical Quenching Rates in Additively Manufactured Al–Si–Mg Alloys

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