Understanding thermal behavior in the LENS process

Griffith, Michelle L.; Schlienger, M.E.; Harwell, L.D.; Oliver, Michael S.; Baldwin, Michael; Ensz, Mark T.; Essien, Marcelino; Brooks, J. A.; Robino, C. V.; Smugeresky, John E.; Hofmeister, William; Wert, M. J.; Nelson, D. V.

doi:10.1016/s0261-3069(99)00016-3

Cited by 304 publications

(151 citation statements)

References 5 publications

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“…Thus, the assessment of the microstructure evolution necessitates an understanding of the response of the alloy to these cycles. As shown in previous numerical and experimental studies, [25,32,33] the thermal behavior associated with the LENS process involves a series of wave-shaped thermal cycles. Each peak represents a laser heating event as the laser beam passes over a layer and effectively reheats layers that were deposited previously.…”

Section: Discussionmentioning

confidence: 63%

“…An additional factor that contributes to the observed difference in microstructure between the shell and cubic samples is the fact that the time interval between two sequential layers is shorter for the shell sample than for the cubic sample. According to the experimental and numerical simulation results, [24,25,33] the temperature at the end of each deposition cycle increases with a decreasing interval time, which corresponds to a decrease in the cooling rate during deposition. In addition, the accumulation of thermal energy that is likely to develop during the deposition of multiple layers is also likely to promote crystallization of the microstructure.…”

Section: Microstructure Of Lens-deposited Samplesmentioning

confidence: 99%

“…The LENS process can produce relatively high, localized cooling rates at each deposition point due to the very small size of the melt pool and the conduction of thermal energy into the substrate. [24,25] Therefore, it should be possible to manufacture netshaped MG components using LENS, because the material is deposited as sequential and cumulative layers. In addition, it should be possible to optimize the cooling conditions for MG processing by controlling the processing parameters such as the laser power and travel speed.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Processing and Behavior of Fe-Based Metallic Glass Components via Laser-Engineered Net Shaping

Zheng

Zhou

Smugeresky

et al. 2009

Metall Mater Trans A

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In this article, the laser-engineered net shaping (LENS) process is implemented to fabricate netshaped Fe-based Fe-B-Cr-C-Mn-Mo-W-Zr metallic glass (MG) components. The glass-forming ability (GFA), glass transition, crystallization behavior, and mechanical properties of the glassy alloy are analyzed to provide fundamental insights into the underlying physical mechanisms. The microstructures of various LENS-processed component geometries are characterized via scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The results reveal that the as-processed microstructure consists of nanocrystalline a-Fe particles embedded in an amorphous matrix. An amorphous microstructure is observed in deposited layers that are located near the substrate. From a microstructure standpoint, the fraction of crystalline phases increases with the increasing number of deposited layers, effectively resulting in the formation of a functionally graded microstructure with in-situ-precipitated particles in an MG matrix. The microhardness of LENS-processed Fe-based MG components has a high value of 9.52 GPa.

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Section: Discussionmentioning

confidence: 63%

Section: Microstructure Of Lens-deposited Samplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Processing and Behavior of Fe-Based Metallic Glass Components via Laser-Engineered Net Shaping

Zheng

Zhou

Smugeresky

et al. 2009

Metall Mater Trans A

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“…The enabling technologies such as Laser Engineered Net Shaping (LENS) [1] and Direct Metal Laser Re-Melting (DMLR) [2] use a laser to melt and fuse high strength, high temperature metallic powder particles into a net or neat-net shape solid form on a layer-by-layer basis. The problems associated with such fabrication processes include the high thermally induced stresses generated in the component and also the requirement of high purity inert environments to prevent oxidation during processing [3].…”

Section: Current Technology and Limitationsmentioning

confidence: 99%

Cold Gas Dynamic Manufacturing – A new approach to Near-Net Shape Metal Component Fabrication

et al. 2002

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Cold Gas Dynamic Manufacturing (CGDM) is a high-rate, direct deposition process capable of combining many dissimilar materials in the production of a single component. The process is based on Cold Gas Dynamic Spraying (CGDS) -a surface coating technology in which small, un-heated particles are accelerated to high velocities (typically above 500 m/s) in a supersonic gas jet and directed towards a substrate material. The process does not use a heat source (as with similar plasma and HVOF spray technologies), but rather employs the high kinetic energy of the particles to effect bonding through plastic deformation upon impact with the substrate or previously deposited layer. As a consequence it lends itself to the processing of temperature sensitive material systems such as oxidising, phase-sensitive or nano-structured materials. To achieve metallic bonding incident particles require velocities greater than a certain materialspecific threshold value, such that thin surface films are ruptured, generating a direct interface. This bonding mechanism has been compared to explosive welding. This paper discusses the further development of the CGDS technique from surface coating technology into the basis for a novel Additive Fabrication process. The description of the apparatus is presented in addition to the basic processing conditions for the deposition of aluminium material. Particular attention is paid to the morphology of the deposited material, the microstructure and the interfacial boundary between splats.

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“…Powder material is then injected into the melt pool through nozzles. The incoming powder is metallurgically bonded to the substrate upon solidification [1][2][3][4][5][6][7]. Conventionally, DLD (direct laser deposition) manufactured parts by adding materials layer by layer using pre-alloyed powder.…”

Section: Introductionmentioning

confidence: 99%

Effect of Powder Particle Size on the Fabrication of Ti-6Al-4V Using Direct Laser Metal Deposition from Elemental Powder Mixture

Chen¹,

Yan²,

Li³

et al. 2016

JMEA

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Direct LMD (laser metal deposition) was used to fabricate thin-wall Ti-6Al-4V using the powder mixture of Ti-6 wt.%Al-4 wt.%V. SEM (scanning electron microscopy), OM (optical microscopy) and EDS (energy dispersive spectroscopy) were employed to examine the chemical composition and microstructure of the as-deposited sections. Vickers hardness tests were then applied to characterize the mechanical properties of the deposit samples which were fabricated using pre-mixed elemental powders. The EDS line scans indicated that the chemical composition of the samples was homogenous across the deposit. After significant analysis, some differences were observed among two sets of deposit samples which varied in the particle size of the mixing Ti-6wt.%Al-4wt.%V powder. It could be found that the set with similar particle number for Ti, Al and V powder made composition much more stable and could easily get industry qualified Ti-6Al-4V components.

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Understanding thermal behavior in the LENS process

Cited by 304 publications

References 5 publications

Processing and Behavior of Fe-Based Metallic Glass Components via Laser-Engineered Net Shaping

Processing and Behavior of Fe-Based Metallic Glass Components via Laser-Engineered Net Shaping

Cold Gas Dynamic Manufacturing – A new approach to Near-Net Shape Metal Component Fabrication

Effect of Powder Particle Size on the Fabrication of Ti-6Al-4V Using Direct Laser Metal Deposition from Elemental Powder Mixture

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