Viewpoint: metallurgical aspects of powder bed metal additive manufacturing

Hebert, Rainer J.

doi:10.1007/s10853-015-9479-x

Cited by 171 publications

(88 citation statements)

References 46 publications

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“…Most of these studies intend to optimize the SLM process by relating the observed process outcomes with input parameters such as laser beam power and velocity, powder layer thickness, hatch spacing or scanning strategy. There are also some -but considerably less -contributions that have studied the influence of the powder feedstock on the process outcome [3,4,26,27,32,71,78]. However, only very few of these works have studied the actual interplay of powder particle properties (mechanical, thermal, optical and chemical properties on particle surfaces), bulk powder properties (morphology, granulometry and resulting flowability) as well as resulting powder layer characteristics (packing density, surface uniformity as well as effective thermal and mechanical properties) during the powder recoating process applied between two subsequent material layers in metal additive manufacturing.…”

Section: Introductionmentioning

confidence: 99%

Modeling and characterization of cohesion in fine metal powders with a focus on additive manufacturing process simulations

et al. 2019

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The cohesive interactions between fine metal powder particles crucially influence their flow behavior, which is in turn important to many powder-based manufacturing processes including emerging methods for powder-based metal additive manufacturing (AM). The present work proposes a novel modeling and characterization approach for micronscale metal powders, with a special focus on characteristics of importance to powder-bed AM. The model is based on the discrete element method (DEM), and the considered particle-to-particle and particle-to-wall interactions involve frictional contact, rolling resistance and cohesive forces. Special emphasis lies on the modeling of cohesion. The proposed adhesion force law is defined by the pull-off force resulting from the surface energy of powder particles in combination with a van-der-Waals force curve regularization. The model is applied to predict the angle of repose (AOR) of exemplary spherical Ti-6Al-4V powders, and the surface energy value underlying the adhesion force law is calibrated by fitting the corresponding angle of repose values from numerical and experimental funnel tests. To the best of the authors' knowledge, this is the first work providing an experimental estimate for the effective surface energy of the considered class of metal powders. By this approach, an effective surface energy of 0.1mJ/m 2 is found for the investigated Ti-6Al-4V powder. This value is considerably lower than typical experimental values for flat metal contact surfaces in the range of 30 − 50mJ/m 2 , indicating the crucial influence of factors such as surface roughness and potential chemical surface contamination / oxidation on fine metal powders. More importantly, the present study demonstrates that a neglect of the related cohesive forces leads to a drastical underestimation of the AOR and, consequently, to an insufficient representation of the bulk powder behavior.

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Section: Introductionmentioning

confidence: 99%

Modeling and characterization of cohesion in fine metal powders with a focus on additive manufacturing process simulations

et al. 2019

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“…The microstructure of materials produced in this way is oriented following their build direction. As a result AM materials have anisotropic properties [3,4].…”

Section: Introductionmentioning

confidence: 99%

High temperature oxidation of IN 718 manufactured by laser beam melting and electron beam melting: Effect of surface topography

2018

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A B S T R A C TThe oxidation behaviour of IN 718 alloys produced by laser beam melting and electron beam melting was compared to that of the wrought alloy at 850°C in laboratory air. Oxide scales of all alloys were similar in nature and morphology with small differences due to powder particles sintered on the surface of additive manufacturing parts. Nevertheless, major differences in surface topography were noticed, these could affect surface area estimations and consequentlymass gain estimations. A quantitative correlation was determined between apparent parabolic rate constant and surface area.

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“…As observed in literature in previous studies [2,3,17,[21][22][23]] the L-PBF process is very complex from a physical point of view, due to the extremely rapid interaction between a concentrated laser source and micrometric metallic powders. This generates an extremely rapid melting and subsequent very fast solidification rate.…”

Section: Microstructure and Mechanical Propertiesmentioning

confidence: 93%

Laser Powder Bed Fusion of Aluminum Alloys

Manfredi¹,

Bidulský²

2017

Acta Metall Slovaca

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The aim of this study is to analyze and to summarize the results of the processing of aluminum alloys, and in particular of the Al-Si-Mg alloys, by means of the Additive Manufacturing (AM) technique defined as Laser Powder Bed Fusion (L-PBF). This process is gaining interest worldwide thanks to the possibility of obtaining a freeform fabrication coupled with high mechanical strength and hardness related to a very fine microstructure. L-PBF is very complex from a physical point of view, due to the extremely rapid interaction between a concentrated laser source and micrometric metallic powders. This generate very fast melting and subsequent solidification on each layer and on the previously consolidated substrate. The effects of the main process variables on the microstructure and mechanical properties of the final parts are analyzed: from the starting powder properties, such as shape and powder size distribution, to the main process parameters, such as laser power, scanning speed and scanning strategy. Furthermore, some examples of applications for the AlSi10Mg alloy are illustrated.

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Viewpoint: metallurgical aspects of powder bed metal additive manufacturing

Cited by 171 publications

References 46 publications

Modeling and characterization of cohesion in fine metal powders with a focus on additive manufacturing process simulations

Modeling and characterization of cohesion in fine metal powders with a focus on additive manufacturing process simulations

High temperature oxidation of IN 718 manufactured by laser beam melting and electron beam melting: Effect of surface topography

Laser Powder Bed Fusion of Aluminum Alloys

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