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  • 1
    Online Resource
    Online Resource
    Investigation of High-Depostition-Rate Additive Manufacturing of Ti-6Al-4V via Laser Material Deposition
    University of Liege ; 2021
    In:  ESAFORM 2021
    Details
    In: ESAFORM 2021, University of Liege
    Abstract: Ti-6Al-4V is the most prominent titanium alloy widely used e.g. for aerospace applications. Conventionally, many Ti-6Al-4V aerospace components are produced by a multi-stage hot forging process followed by subsequent machining which often generates a high amount of scrap. Additive manufacturing (AM), such as powder-based laser material deposition (p-LMD), enables parts to be made with geometric freedom and near-net-shape, but so far lacks high deposition rates. The present study proposes high-deposition-rate laser material deposition manufacturing using a large laser beam diameter and increased scanning speed to achieve deposition rates up to 5 kg/h. As Ti-6Al-4V is prone to oxygen pick-up, the process was performed in an inert atmosphere. We determined suitable process windows for tracks without fusion defects and low porosity and investigated microstructure and hardness.
    Type of Medium: Online Resource
    URL: Journal
    URL: Article
    DOI: 10.25518/esaform21
    DOI: 10.25518/esaform21.486
    Language: English
    Publisher: University of Liege
    Publication Date: 2021
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  • 2
    Online Resource
    Online Resource
    Deposition strategies for generating cuboid volumes using extreme high-speed directed energy deposition
    Laser Institute of America ; 2022
    In:  Journal of Laser Applications Vol. 34, No. 4 ( 2022-11-01)
    Details
    In: Journal of Laser Applications, Laser Institute of America, Vol. 34, No. 4 ( 2022-11-01)
    Abstract: Extreme high-speed directed energy deposition (EHLA) is a variant of directed energy deposition (DED-LB) developed at Fraunhofer ILT in cooperation with RWTH Aachen University. Because of a powder gas jet setup that is aimed at melting particles in the laser beam before they enter the melting pool, high process speeds of up to several hundred meters per minute and a layer thickness as thin as 25 μm can be achieved. EHLA is generally applied for rotationally symmetric coating applications. In previous experiments on a prototype machine of ponticon GmbH, EHLA was used for building up dense volumes, thus qualifying its use for additive manufacturing, now termed EHLA 3D. In this work, using iron-base alloy 1.4404 and a process speed of 40 m/min, cubic volumes are produced with EHLA 3D. Different deposition strategies commonly used in DED-LB are tested for their transferability to EHLA 3D. The results of different deposition strategies achieving the best near net shape geometry are shown in comparison to DED-LB. Furthermore, the influence of the deposition strategy and used technology on thermal management and microstructure are investigated. The best near net shape is achieved in this comparison using a contour-hatch strategy with 1.5 contours per layer and a 90° rotation of the hatch, both for EHLA and DED-LB. The microstructure of EHLA 3D built cubes is more similar to a typical laser powder bed fusion microstructure than to a typical DED-LB microstructure with respect to grain size and structure.
    Type of Medium: Online Resource
    ISSN: 1042-346X , 1938-1387
    URL: Article
    DOI: 10.2351/7.0000770
    Language: English
    Publisher: Laser Institute of America
    Publication Date: 2022
    detail.hit.zdb_id: 2084611-3
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  • 3
    Online Resource
    Online Resource
    Setup for electrical resistance measurement for laser material deposition with coaxial wire feed and use for process control
    Laser Institute of America ; 2023
    In:  Journal of Laser Applications Vol. 35, No. 1 ( 2023-02-01)
    Details
    In: Journal of Laser Applications, Laser Institute of America, Vol. 35, No. 1 ( 2023-02-01)
    Abstract: Within laser additive manufacturing (directed energy deposition with laser beam), processes are further distinguished by the form of the filler material. In terms of availability, storage, safety, and cost, wire is commonly the preferred filler material in comparison to powder. Despite these advantages, due to the different material transfer modes, a greater process control is required. Within this work, an experimental setup for electrical-resistance-measurement within the laser material deposition process with a coaxial wire feed and its possible use for an automated process control is investigated. The measurement is performed between a wire, a substrate, and over the melt pool. One main influencing factor on process stability is derived from the timing of the trigger sequence of the laser power, process feed, and wire feed at the start and end points of every track. Consequently, inaccurate settings of the trigger sequence can, e.g., lead to deviations in track length and part geometry. Additionally, a smooth transfer of the wire into the melt pool is imperative during part build-up to ensure a stable deposition process. Variation in laser power, wire feed, process feed, or wire transfer mode can lead to process instabilities. This can result in imperfections, bonding defects, or pores in the tracks and layers that will add up in built components and must be avoided for defectfree three-dimensional geometries. Within the experiments, it is investigated whether the resistance-measurement provides consistent results under varying conditions and potentially can be utilized to automate the trigger sequence of deposition. Furthermore, it is investigated whether different wire transfer modes can be linked to the measured resistance values during welding of single tracks.
    Type of Medium: Online Resource
    ISSN: 1042-346X , 1938-1387
    URL: Article
    DOI: 10.2351/7.0000766
    Language: English
    Publisher: Laser Institute of America
    Publication Date: 2023
    detail.hit.zdb_id: 2084611-3
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  • 4
    Online Resource
    Online Resource
    Development of a high-speed laser material deposition process for additive manufacturing
    Laser Institute of America ; 2021
    In:  Journal of Laser Applications Vol. 33, No. 1 ( 2021-02-01)
    Details
    In: Journal of Laser Applications, Laser Institute of America, Vol. 33, No. 1 ( 2021-02-01)
    Abstract: Extreme high-speed laser material deposition (EHLA) is a variant of laser material deposition (LMD) with a modified powder gas jet focus. EHLA allows deposition at high process speeds in the range of several hundred meters per minute and the deposition of layers as thin as 25 μm. Feed rates can be in the range of 50 g/min or above. The processing of material combinations with poor weldability or different melting points is possible, with simultaneously smaller heat-affected zone and dilution zone compared to conventional LMD. Until now, EHLA has mainly been used for applying wear-resistant and corrosion-resistant coatings to rotationally symmetric parts, where high process speeds are achieved by rotation of the substrate. Developing EHLA for additive manufacturing (AM) aims at manufacturing highly individualized parts with high volume buildup rates and finer structural resolution compared to conventional LMD. The main steps toward harnessing EHLA for AM, termed EHLA 3D, are (a) process parameter development for volume buildup through deposition of multiple layers on top of each other and (b) the development of system technology that allows relative spatial movement between the powder nozzle and the substrate at high speeds and high accuracy in three dimensions. With a fast back-and-forth motion, high acceleration rates are necessary to ensure high volume buildup rates and high powder deposition efficiency. In this work, a specially designed tripod machine concept that has been developed in cooperation at Fraunhofer ILT is introduced. Theoretical considerations concerning achievable powder deposition efficiency as a function of process speed and acceleration of the handling system are presented. Furthermore, the results of process parameter development for up to 40 m/min with the iron-base alloy 1.4404 are shown. Virtually pore-free deposition of cuboid volumes is demonstrated. The mechanical values of the additively manufactured volumes are compared to the values for solution-annealed material, conventional LMD-manufactured samples, and samples produced by laser powder bed fusion (LPBF). Finally, an outlook on future research activities required for further development of EHLA 3D is given, covering system technology, buildup strategies, software integration, and possible applications of the new technology in repair, coating, and (hybrid-)additive contexts.
    Type of Medium: Online Resource
    ISSN: 1042-346X , 1938-1387
    URL: Article
    DOI: 10.2351/7.0000320
    Language: English
    Publisher: Laser Institute of America
    Publication Date: 2021
    detail.hit.zdb_id: 2084611-3
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  • 5
    Online Resource
    Online Resource
    High average power ultrafast laser technologies for driving future advanced accelerators
    IOP Publishing ; 2023
    In:  Journal of Instrumentation Vol. 18, No. 08 ( 2023-08-01), p. T08006-
    Details
    In: Journal of Instrumentation, IOP Publishing, Vol. 18, No. 08 ( 2023-08-01), p. T08006-
    Abstract: Large scale laser facilities are needed to advance the energy frontier in high energy physics and accelerator physics. Laser plasma accelerators are core to advanced accelerator concepts aimed at reaching TeV electron electron colliders. In these facilities, intense laser pulses drive plasmas and are used to accelerate electrons to high energies in remarkably short distances. A laser plasma accelerator could in principle reach high energies with an accelerating length that is 1000 times shorter than in conventional RF based accelerators. Notionally, laser driven particle beam energies could scale beyond state of the art conventional accelerators. LPAs have produced multi GeV electron beams in about 20 cm with relative energy spread of about 2 percent, supported by highly developed laser technology. This validates key elements of the US DOE strategy for such accelerators to enable future colliders but extending best results to date to a TeV collider will require lasers with higher average power. While the per pulse energies envisioned for laser driven colliders are achievable with current lasers, low laser repetition rates limit potential collider luminosity. Applications will require rates of kHz to tens of kHz at Joules of energy and high ef ficiency, and a collider would require about 100 such stages, a leap from current Hz class LPAs. This represents a challenging 1000 fold increase in laser repetition rates beyond current state of the art. This whitepaper describes current research and outlook for candidate laser systems as well as the accompanying broadband and high damage threshold optics needed for driving future advanced accelerators.
    Type of Medium: Online Resource
    ISSN: 1748-0221
    URL: Article
    DOI: 10.1088/1748-0221/18/08/T08006
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 2235672-1
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  • 6
    Online Resource
    Online Resource
    Laser Directed Energy Deposition of an AlMgScZr-Alloy in High-Speed Process Regimes
    MDPI AG ; 2022
    In:  Materials Vol. 15, No. 24 ( 2022-12-14), p. 8951-
    Details
    In: Materials, MDPI AG, Vol. 15, No. 24 ( 2022-12-14), p. 8951-
    Abstract: Aluminum-magnesium-scandium-zirconium (AlMgScZr) alloys need to be rapidly cooled from the liquid state to obtain a high degree of solute supersaturation that helps to exploit the precipitation hardening potential of the material. While AlMgScZr alloys have been successfully used in laser powder bed fusion (LPBF) processes, there has been little research in the field of laser directed energy deposition (DED) of the material. The limited previous studies have shown that the performance of AlMgScZr parts fabricated with DED only reached about 60% of that of the parts fabricated with LPBF. In view of breaking through the limitation associated with the process conditions of conventional DED, this work demonstrates the DED of AlMgScZr alloys in high-speed process regimes and elucidates the mechanism of enhancing the hardness and tensile strength of AlMgScZr alloys by increasing the cooling rate by one to two orders of magnitudes, as well as reducing the track overlapping and the porosity of the specimens during the process. A maximum average hardness of nearly 150 HV0.1 and a max. tensile strength of 407 MPa are obtained by using an energy per unit length of 5400 J/m and a powder feed rate per unit length of 0.25 g/m.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma15248951
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2487261-1
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  • 7
    Online Resource
    Online Resource
    Dynamic correction of optical aberrations for height-independent selective laser induced etching processing strategies
    Optica Publishing Group ; 2023
    In:  Optics Express Vol. 31, No. 16 ( 2023-07-31), p. 26104-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 31, No. 16 ( 2023-07-31), p. 26104-
    Abstract: Optical aberrations are a critical issue for tight focusing and high precision manufacturing with ultrashort pulsed laser radiation in transparent media. Controlling the wave front of ultrashort laser pulses enable the correction of low order phase front distortion and significantly enhances the simplification of laser-based manufacturing of 3D-parts in glass. The influence of system-inherent, dominating aberrations such as spherical and astigmatic aberrations affect the focal area, the beam caustic and therefore the focus intensity distribution. We correct these aberrations by means of a spatial light modulator (SLM) for various processing depths in glass thickness of up to 12 mm. This flexible aberration correction significantly simplifies the process control and scanning strategies for the selective laser induced etching process. The influence on the selectivity is investigated by comparing the three different focus conditions of the intrinsic microscope objective aberration corrected, the aberrated and the SLM aberration corrected beam profile. The previously necessary pulse energy adjustment for different z positions in the glass volume is compensated via SLM aberration correction in the end. Furthermore, the spatial extend of the modified and etched area is investigated. In consequence, a simplified scan strategy and depth-independent processing parameters can be achieved for the selective laser induced etching process.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.493088
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2023
    detail.hit.zdb_id: 1491859-6
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  • 8
    Online Resource
    Online Resource
    Nd:Glass Laser Design for Laser ICF Fission Energy (LIFE)
    Informa UK Limited ; 2009
    In:  Fusion Science and Technology Vol. 56, No. 2 ( 2009-08), p. 607-617
    Details
    In: Fusion Science and Technology, Informa UK Limited, Vol. 56, No. 2 ( 2009-08), p. 607-617
    Type of Medium: Online Resource
    ISSN: 1536-1055 , 1943-7641
    URL: Article
    DOI: 10.13182/FST18-P8031
    Language: English
    Publisher: Informa UK Limited
    Publication Date: 2009
    detail.hit.zdb_id: 2132501-7
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  • 9
    Online Resource
    Online Resource
    Geometry Effect on Microstructure and Mechanical Properties in Laser Powder Bed Fusion of Ti-6Al-4V
    MDPI AG ; 2022
    In:  Metals Vol. 12, No. 3 ( 2022-03-12), p. 482-
    Details
    In: Metals, MDPI AG, Vol. 12, No. 3 ( 2022-03-12), p. 482-
    Abstract: Laser Powder Bed Fusion (LPBF) of Ti-6Al-4V enables the manufacturing of complex parts for lightweight applications. The emerging microstructure in the LPBF process and thus the mechanical properties are defined by the thermal cycles, which are locally variable for complex geometries. Predictions of local mechanical properties by simulation would reduce the development time of new applications drastically but are today not possible on part scale, so new part applications must be qualified experimentally at great effort. In this study, representative geometry sections were transferred into a simplified sample shape to mechanically characterize different geometry-dependent microstructures. In areas exposed to comparatively increased heat input over time, a lamellar α + β microstructure with β fraction up to 20% was measured in contrast to the common martensitic α′ microstructure of LPBF-manufactured Ti-6Al-4V, resulting in reduced tensile strength and fatigue life. For the first time, a correlation was successfully established between ultimate tensile strength of multiple geometries and the corresponding temperature–time cycles. With reduced computational effort by use of simplifying assumptions in the simulation, this correlation model can theoretically be applied to the part level. This work has laid the foundation for the simulation-based prediction of mechanical properties for entire parts manufactured with LPBF.
    Type of Medium: Online Resource
    ISSN: 2075-4701
    URL: Article
    DOI: 10.3390/met12030482
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2662252-X
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  • 10
    Online Resource
    Online Resource
    Are you looking for the next useful mission? : Improving sustainability thanks to Digital Photonic Production
    Wiley ; 2022
    In:  PhotonicsViews Vol. 19, No. 2 ( 2022-04), p. 1-1
    Details
    In: PhotonicsViews, Wiley, Vol. 19, No. 2 ( 2022-04), p. 1-1
    Type of Medium: Online Resource
    ISSN: 2626-1294 , 2626-1308
    URL: Issue
    URL: Article
    DOI: 10.1002/phvs.v19.2
    DOI: 10.1002/phvs.202270201
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2941737-5
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