A laser powder bed fusion system for <i>in situ</i> x-ray diffraction with high-energy synchrotron radiation

Uhlmann, Eckart; Krohmer, Erwin; Schmeiser, Felix; Schell, Norbert; Reimers, W.

doi:10.1063/1.5143766

Cited by 21 publications

(13 citation statements)

References 33 publications

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“…In previous work, a custom LPBF process chamber was developed and integrated into the modular LPBF machine AconityMINI from Aconity3D GmbH, Herzogenrath, Germany, to realize in situ X-ray diffraction experiments with synchrotron radiation [23]. The custom LPBF machine is equipped with a 400 W Ytterbium fiber laser YLR-400-AC from IPG Laser GmbH, Burbach, Germany.…”

Section: Custom Lpbf Machinementioning

confidence: 99%

In situ microstructure analysis of Inconel 625 during laser powder bed fusion

et al. 2021

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Laser powder bed fusion is an additive manufacturing process that employs highly focused laser radiation for selective melting of a metal powder bed. This process entails a complex heat flow and thermal management that results in characteristic, often highly textured microstructures, which lead to mechanical anisotropy. In this study, high-energy X-ray diffraction experiments were carried out to illuminate the formation and evolution of microstructural features during LPBF. The nickel-base alloy Inconel 625 was used for in situ experiments using a custom LPBF system designed for these investigations. The diffraction patterns yielded results regarding texture, lattice defects, recrystallization, and chemical segregation. A combination of high laser power and scanning speed results in a strong preferred crystallographic orientation, while low laser power and scanning speed showed no clear texture. The observation of a constant gauge volume revealed solid-state texture changes without remelting. They were related to in situ recrystallization processes caused by the repeated laser scanning. After recrystallization, the formation and growth of segregations were deduced from an increasing diffraction peak asymmetry and confirmed by ex situ scanning transmission electron microscopy. Graphical Abstract

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Section: Custom Lpbf Machinementioning

confidence: 99%

In situ microstructure analysis of Inconel 625 during laser powder bed fusion

et al. 2021

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“…For the experiments’ conduction at the P07 beamline [ 33 ] at Deutsches Elektronen‐Synchrotron (DESY), Hamburg, Germany, a custom‐made LPBF system was used. This system was designed by Uhlmann et al [ 34 ] to enable the examination of LPBF parts, as they are being built layer by layer using high‐energy synchrotron radiation. Thin cuboid parts were produced from 120 equally processed cp‐Ti powder layers, resulting in the final part dimensions of about 21 mm in length, 2.5 mm in width, and 6 mm in height.…”

Section: Resultsmentioning

confidence: 99%

“…The experimental LPBF system used in this study was described in the previous work. [ 34 ] It was equipped with a 400 W ytterbium fiber laser YLR‐400‐AC from IPG Laser GmbH, Burbach, Germany. The collimated laser beam with a wavelength of 1070 nm was directed and focused onto the powder bed via a three‐axis deflection unit Axialscan‐30 from Raylase GmbH, Wessling, Germany, with a laser focus diameter of ≈60 μm (1/e 2 ).…”

Section: Methodsmentioning

confidence: 99%

“…Measurements were conducted in measurement mode 1 (MM1). [ 34 ] In MM1, the GV was in a defined distance z GV to the topmost layer, the working plane. After processing of a layer, the sample was moved in negative BD by the amount of the layer thickness Δ z , whereas the glassy carbon plates and the working plane stayed on a constant BD level.…”

Section: Methodsmentioning

confidence: 99%

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Internal Stress Evolution and Subsurface Phase Transformation in Titanium Parts Manufactured by Laser Powder Bed Fusion—An In Situ X‐Ray Diffraction Study

et al. 2021

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Laser powder bed fusion (LPBF) is a metal additive manufacturing technology, which enables the manufacturing of complex geometries for various metals and alloys. Herein, parts made from commercially pure titanium are studied using in situ synchrotron radiation diffraction experiments. Both the phase transformation and the internal stress buildup are evaluated depending on the processing parameters. For this purpose, evaluation approaches for both temperature and internal stresses from in situ diffraction patterns are presented. Four different parameter sets with varying energy inputs and laser scanning strategies are investigated. A combination of a low laser power and scanning speed leads to a more homogeneous stress distribution in the observed gauge volumes. The results show that the phase transformation is triggered during the primary melting and solidification of the powder and subsurface layers. Furthermore, the stress buildup as a function of the part height during the manufacturing process is clarified. A stress maximum is formed below the part surface, extending into deeper layers with increasing laser power. A temperature evaluation approach for absolute internal stresses shows that directional stresses decrease sharply during laser impact and reach their previous magnitude again during cooling.

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“…The SLM machine used in the study is a modified version of the commercially available AconityMINI from Aconity3D GmbH. A detailed description of the machine was given by Uhlmann et al [ 23 ] The custom process chamber was developed and built at Technische Universität Berlin. A single‐mode continuous‐wave ytterbium fiber laser, which emits a maximum power of 400 W at a wavelength of 1070 nm, served as the power source.…”

Section: Methodsmentioning

confidence: 99%

In Situ Observation of γ′ Phase Transformation Dynamics During Selective Laser Melting of CMSX‐4

et al. 2021

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Additive manufacturing (AM) of superalloys has been attracting increasing interest. While most studies focus on the processability and mechanical properties of the finished product, it is also necessary to understand the phase transformations during the consecutive melting processes. Herein, the precipitation and dissolution of the γ′ phase in the Ni‐base superalloy CMSX‐4 in a selective laser melting process is reported. These phase transformations are studied in situ by small‐angle X‐ray scattering (SAXS) during AM. Concurrent wide‐angle X‐ray scattering (WAXS) provides information on the evolution of lattice parameters and temperature during the process. Additional thermal and thermodynamic simulations are carried out to support the experiments. The investigations are focused on the influence of different beam scanning strategies as well as the effect of laser power and scanning speed on the phase transformation dynamics. Due to the high cooling and heating rates inherent to AM, phase transformations occur far off equilibrium. Both precipitation and dissolution of γ′ phase are observed. The scan strategies are shown to have a considerable effect on the phase transformation dynamics, which exceed the impact of the beam parameters. The capability of combined SAXS and WAXS for the in situ study of phase transformations in AM processes is demonstrated.

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A laser powder bed fusion system for in situ x-ray diffraction with high-energy synchrotron radiation

Abstract: This paper was selected as Featured ARTICLES YOU MAY BE INTERESTED INEnhanced sensitivity of nanoscale subsurface imaging by photothermal excitation in atomic force microscopy Review of Scientific Instruments 91, 063703 (2020);

Cited by 21 publications

References 33 publications

In situ microstructure analysis of Inconel 625 during laser powder bed fusion

In situ microstructure analysis of Inconel 625 during laser powder bed fusion

Internal Stress Evolution and Subsurface Phase Transformation in Titanium Parts Manufactured by Laser Powder Bed Fusion—An In Situ X‐Ray Diffraction Study

In Situ Observation of γ′ Phase Transformation Dynamics During Selective Laser Melting of CMSX‐4

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