References of "Lecomte-Beckers, Jacqueline"
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See detailFusion-based Additive Manufacturing for Processing Aluminum Alloys: State-of-the-Art and Challenges
Mertens, Anne ULg; Delahaye, Jocelyn ULg; Lecomte-Beckers, Jacqueline ULg

in Advanced Engineering Materials (in press)

Starting early 2015, the fusion-based additive manufacturing of Al alloys has been developing at an ever faster pace after undergoing a comparatively slow start with respect to other metallic materials ... [more ▼]

Starting early 2015, the fusion-based additive manufacturing of Al alloys has been developing at an ever faster pace after undergoing a comparatively slow start with respect to other metallic materials. This paper reviews the recent developments with the aim of identifying major challenges and opportunities for future work. Laser Beam Melting proves the most useful technique for the additive fabrication of Al components with strongly out-of-equilibrium microstructures and potentially enhanced mechanical behavior. Laser Cladding is also promising for specific applications such as repairs and coatings. However, a deeper understanding of the thermal history during fabrication is still needed to further optimize the microstructures and usage properties. The design of new high strength alloys and of Al-matrix composites, and the development of better adapted post-processing procedures to take greater advantage of the specificities of fusion-based additive techniques are two other important issues in view of reaching the full potential of additive Al components. [less ▲]

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See detailMicro-mechanical testing of magnesium based composites reinforced by carbon fibers manufactured by friction stir processing
Simar, Aude; Ryelandt, Sophie; Delannay, Francis et al

Conference (2017, February 28)

Short C fibres–Mg matrix (AZ91D) composites have been produced by friction stir processing sandwiches made of a layer of C fabric stacked between two sheets of Mg alloy. The process parameters have been ... [more ▼]

Short C fibres–Mg matrix (AZ91D) composites have been produced by friction stir processing sandwiches made of a layer of C fabric stacked between two sheets of Mg alloy. The process parameters have been optimized to ensure a good fiber distribution. 3D X-ray tomography reveals that the fibers orient like onion rings. Thermal treatments have allowed to modify the flow stress level of the matrix material. Tensile testing inside the scanning electron microscope have revealed the decohesion at the fiber/matrix interface if the fibers are preferentially oriented perpendicularly to the loading direction. Modelling allows to estimate the stress needed to initiate this decohesion is about 250 MPa, i.e. appearing early in heat treated samples. To compare with different loading conditions, micro-compression and instrumented micro-indentation testing have also been performed. The consequence of the loading path on the decohesion is discussed. [less ▲]

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See detailThermal history modelling to understand microstructures observed in repair technology of Ti-6Al-4V
Tran, Hoang Son ULg; Tchuindjang, Jérôme Tchoufack ULg; Hakan, Paydas et al

in Extended Abstract book of 14th Conf. on Computer Methods in Materials Technology KomPlasTech 2017 (2017, January)

Laser cladding is a metal deposition technique used to fabricate or repair components. In the present work Ti-6Al-4V deposits with a variable thickness are studied to assess the use of laser cladding as a ... [more ▼]

Laser cladding is a metal deposition technique used to fabricate or repair components. In the present work Ti-6Al-4V deposits with a variable thickness are studied to assess the use of laser cladding as a repair technology [1]. Solidification following melting and partial remelting of pre-existing layers is coupled with heat treatment of the solidified material due to the repeated heating and cooling cycles during building. The effect of the building strategy on the metallurgical characteristics of the material for a decreasing track length (DTL) or a constant track length (CTL) strategy is analyzed. Depending on the possible heat accumulation, the nature of the phases are determined by metallography and hardness maps of the deposits. Optical Microscopy (OM), Stereo Microscopy (SM), and Scanning Electron Microscopy (SEM) were used in order to study the microstructure. The generation of the microstructure results from the material thermal history. This one is computed by Finite Element Method and a careful analysis establishes the link between the phase state and the detailed thermal history. [less ▲]

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See detailAssessment of corrosion resistance, material properties, and weldability of alloyed steel for ballast tanks
De Baere, Kris; Verstraelen, Helen; Willemen, Remke et al

in Journal of Marine Science & Technology (2017), 22(1), 176-199

Ballast tanks are of great importance in the lifetime of modern merchant ships. Making a ballast tank less susceptible to corrosion can, therefore, prolong the useful life of a ship and, thereby, lower ... [more ▼]

Ballast tanks are of great importance in the lifetime of modern merchant ships. Making a ballast tank less susceptible to corrosion can, therefore, prolong the useful life of a ship and, thereby, lower its operational cost. An option to reinforce a ballast tank is to construct it out of a corrosion-resistant steel type. Such steel was recently produced by POSCO Ltd., South Korea. After 6 months of permanent immersion, the average corrosion rate of A and AH steel (31 samples) was 535 g m−2 year−1, while the Korean CRS was corroding with 378 g m−2 year−1. This entails a gain of 29 %. Follow-up measurements after 10, 20, and 24 months confirmed this. The results after 6 months exposure to alternating wet/dry conditions are even more explicit. Furthermore, the physical and metallurgical properties of this steel show a density of 7.646 t/m3, the elasticity modulus 209.3 GPa, the tensile strength 572 MPa, and the hardness 169HV10. Microscopically, the metal consists of equiaxed and recrystallized grains (ferrite and pearlite), with an average size of between 20 and 30 µm (ASTM E 112—12 grain size number between 7 and 8) with a few elongated pearlitic grains. The structure is banded ferrite/pearlite. On the basis of a series of energy dispersive X-ray spectrometer measurements the lower corrosion rate of the steel can be attributed to the interplay of Al, Cr, their oxides, and the corroding steel. In addition, the role of each element in the formation of oxide layers and the mechanisms contributing to the corrosion resistance are discussed. [less ▲]

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See detailOxidative wear behaviour of laser clad high speed steel thick deposits: influence of sliding speed, carbide type and morphology
Hashemi, Seyedeh Neda ULg; Mertens, Anne ULg; Montrieux, Henri-Michel ULg et al

in Surface & Coatings Technology (2017), 315

The oxidative wear behaviour of four different High Speed Steel (HSS) thick coatings (one cast material and three laser clad deposits with varying Mo, V and W contents) was investigated using a pin-on ... [more ▼]

The oxidative wear behaviour of four different High Speed Steel (HSS) thick coatings (one cast material and three laser clad deposits with varying Mo, V and W contents) was investigated using a pin-on-disc tribometer at two different sliding speeds of 10cm/s and 50cm/s. Microstructural characterisation (before and after the wear tests) was carried out by SEM and wear debris was analysed by XRD. For all four materials, the oxide layer was formed of hard and brittle haematite-type α-Fe2O3, prone to break and release debris that acted as a third body, thus increasing sample wear. The laser clad HSS materials exhibited a higher wear resistance than their conventional cast counterpart, thanks to their finer microstructures. In particular, the coarser MC and M2C carbides present in the cast material were sensitive to cracking during the wear tests, releasing debris that contributed to increased third body abrasion together with oxide fragments. A detailed comparison of the wear behaviour of the three laser clad deposits, in correlation with their different microstructures, further demonstrated that harder V-rich MC carbides offered better wear resistance compared to the softer W-rich M2C carbides. The morphology of the carbides also played a role in determining the wear resistance at the higher sliding speed of 50 cm/s. Clover-shaped primary MC carbides resisted wear better than angular ones due to their better geometric anchoring. Similarly, the geometric anchoring of eutectic M2C carbides, forming a quasi-continuous network at the grain boundaries of the matrix, proved beneficial at higher sliding speed. [less ▲]

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See detailOn the Elaboration of Metal-Ceramic Composite Coatings by Laser Cladding
Mertens, Anne ULg; L'Hoest, Thibaut; Magnien, Julien et al

in Materials Science Forum (2017), 879

This paper reports on a preliminary investigation into the elaboration, by the additive process known as laser cladding, of composite coatings with a matrix of stainless steel 316L reinforced with varying ... [more ▼]

This paper reports on a preliminary investigation into the elaboration, by the additive process known as laser cladding, of composite coatings with a matrix of stainless steel 316L reinforced with varying contents of tungsten (WC) or silicon carbides (SiC) particles. Laser cladding is characterised by ultra-fast solidification and cooling rates, thus giving rise to ultra-fine out-of-equilibrium microstructures and potentially enhanced mechanical properties. Both types of composite coatings – i.e. with SiC or WC ‒ are compared in terms of their microstructures and hardness. Special attention is given to the dissolution of the carbides particles and to interfacial reactions taking place between the particles and the metallic matrix. [less ▲]

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See detailLaser Cladding Finite Element Modelling Application to Ti6Al4V,
Tran, Hoang Son ULg; Brusten, Romain; Jardin, Ruben et al

Conference (2016, November 03)

Corrélation entre les champs thermiques prédits et la microstructure observée.

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See detailOn the effect of microstructural anisotropy on the mechanical and thermophysical properties of Ti6Al4V processed by Laser Beam Melting
Mertens, Anne ULg; Paydas, Hakan ULg; Rigo, Olivier et al

Conference (2016, August 05)

Laser beam melting (LBM) is a strongly directional process in which a metallic powder is deposited layer by layer in a powder bed and molten locally according to the desired shape. When processing Ti6Al4V ... [more ▼]

Laser beam melting (LBM) is a strongly directional process in which a metallic powder is deposited layer by layer in a powder bed and molten locally according to the desired shape. When processing Ti6Al4V, it is well known that the latest layer tends to solidify epitaxially on the previous layers, thus giving rise to elongated columnar primary β(BCC) crystals extending over several successive layers. These primary β grains then transforms into the α(HCP) structure upon cooling. The present work aimed at studying the microstructural anisotropy of LBM Ti6Al4V, as well as its consequences on the mechanical and thermophysical properties (i.e. thermal expansion and thermal conductivity). In order to gain a deeper undestanding of thermal phenomena in the LBM of Ti6Al4V, great care was also taken to characterize the thermophysical properties over a wide temperature range from room temperature. [less ▲]

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See detailAlumina and zircon refractory ceramic molds fabrication by additive methods for metal alloys casting
Bister, Geoffroy; Hautcoeur, Dominique; Deschuyteneer, Dorian et al

Conference (2016, July 19)

Traditional processes for the foundry molds fabrication need numerous and rather time consuming steps. These processes are not really adapted to small series or prototypes. The research project exposed in ... [more ▼]

Traditional processes for the foundry molds fabrication need numerous and rather time consuming steps. These processes are not really adapted to small series or prototypes. The research project exposed in this contribution proposes an alternative method combining the advantages of molding (free formulation of metal alloys, economy on material and on time of machining) with those of the additive processes (short steps between 3D-model and final product, very complex geometries available). For short series the selective laser melting process (SLM) allows the building of molds in a very short time compared to the traditional investment casting method. This technique also permits the unique advantage to control the design of the shell thickness and structure in order to have a better control of the thermal fluxes during metal cooling. This would potentially ensure a better control of the casting defaults. In this presentation, molds built with alumina and zircon as raw materials will be presented. Two metallic alloys have been tested in order to validate alumina and zircon as mold materials; the first, AlCu4MgSi chosen as low melting point alloy reference and the second, stainless steel 316L, as high melting point alloy reference [less ▲]

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See detailOn the role of interfacial reactions, dissolution and secondary precipitation during the laser additive manufacturing of metal matrix composites - A Review
Mertens, Anne ULg; Lecomte-Beckers, Jacqueline ULg

in Shishkovsky, I.V. (Ed.) New Trends in 3D Printing (2016)

Since current trends in the transportation, energy or mechanical industries impose increasingly demanding service conditions for metallic parts, metal matrix composites (MMC) are the object of a growing ... [more ▼]

Since current trends in the transportation, energy or mechanical industries impose increasingly demanding service conditions for metallic parts, metal matrix composites (MMC) are the object of a growing interest. Powder-based laser additive manufacturing, that allows to make parts with complex shapes, appears particularly adapted for the production of MMCs. This paper reviews the current state-of-the-art in the production of MMCs by additive processes, with the aim of assessing the potentials and difficulties offered by these techniques. Two main processing routes are envisaged i.e. (1) the processing of ex-situ composites in which the reinforcing phase as a powder – often of ceramic particles − is directly mixed with the powder of the matrix alloy, and both powders are simultaneously processed by the laser. (2) Alternatively, the reinforcing phase can be produced in-situ by a chemical reaction during the fabrication of the composite. For both processing routes, a careful control is needed to overcome challenges brought e.g. by the behaviour of the reinforcement particles in the laser beam, by changes in laser absorptivity or by the dissolution of the reinforcing particles in the molten metal, in order to produce metal matrix composites with enhanced usage properties. [less ▲]

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See detail2D and 3D FE models of laser cladding process
Jardin, Ruben; Hoang, Son Tran; Hashemi, Seyedeh Neda ULg et al

in Booklet of the conference with extended abstract and short paper of less than 6 pages (2016, July)

Lien entre le champ thermique 2D et 3D calculé pour un cas de laser cladding d acier au chrome

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See detailMicrostructural evolution during the heat treatment of Laser Beam Melted AlSi10Mg
Mertens, Anne ULg; Dedry, Olivier ULg; Reuter, David et al

Conference (2016, June 01)

Al alloy AlSi10Mg processed by Laser Beam Melting (LBM) exhibits a much finer microstructure than its cast counterpart due to the ultra-fast cooling rates imposed in the LBM process. One important ... [more ▼]

Al alloy AlSi10Mg processed by Laser Beam Melting (LBM) exhibits a much finer microstructure than its cast counterpart due to the ultra-fast cooling rates imposed in the LBM process. One important consequence of this microstructural refinement is that a classical T6 age hardening heat treatment will not have the same effect on LBM AlSi10Mg when compared with cast AlSi10Mg. Indeed, a previous study by the present authors has shown that heat treating LBM AlSi10Mg at 510°C for 6 hours followed by a second isothermal hold at 170°C for 6 hours brought a marked improvement of the yield stress by 30% and of the elongation at break by 220%. However, this was achieved at the expense of a decrease in both hardness and ultimate tensile strength. A better understanding of the underlying phenomena is needed in order to optimize the heat treatment of LBM AlSi10Mg. The present work hence aims at investigating in more depth the microstructural evolution induced upon heat treating LBM AlSi10Mg. Changes in texture as well as in the distribution of Si-rich precipitates (size, morphology...) have been studied, with a particular attention to those changes taking place during the first step of the heat treatment at the higher temperature of 510°C. [less ▲]

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See detailOn the laser additive manufacturing of metal matrix composites
Mertens, Anne ULg; L'Hoest, Thibaut; Lecomte-Beckers, Jacqueline ULg et al

Conference (2016, May 27)

This paper reviews the challenges and opportunities related to the production of of metal matrix composites (MMCs) and functionally graded materials (FGMs) by additive manufacturing laser-based ... [more ▼]

This paper reviews the challenges and opportunities related to the production of of metal matrix composites (MMCs) and functionally graded materials (FGMs) by additive manufacturing laser-based technologies. Special attention is given to issues such as the stability of the reinforcement particles under the laser beam, particles’ dissolution in the metallic melt pool and interfacial reactions between the particles and the metallic matrix. Illustrations are taken from a preliminary investigation, by the MMS Unit, into the laser cladding of stainless steel + carbides composite coatings, as well as from the open scientific literature. [less ▲]

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See detailUnderstanding the effect of thermal treatments on the ductility of LBM AlSi10Mg
Mertens, Anne ULg; Dedry, Olivier ULg; Lecomte-Beckers, Jacqueline ULg et al

Conference (2016, May 26)

This communication reviews the additive manufacturing activities of the MMS Unit, University of Liège, with a particular focus on the study of post-processing treatments of Al alloy AlSi10Mg. Al alloy ... [more ▼]

This communication reviews the additive manufacturing activities of the MMS Unit, University of Liège, with a particular focus on the study of post-processing treatments of Al alloy AlSi10Mg. Al alloy AlSi10Mg processed by Laser Beam Melting (LBM) exhibits a much finer microstructure than its cast counterpart due to the ultra-fast cooling rates imposed in the LBM process. One important consequence of this microstructural refinement is that a classical T6 age hardening heat treatment will not have the same effect on LBM AlSi10Mg when compared with cast AlSi10Mg. Indeed, a previous study by the present authors has shown that heat treating LBM AlSi10Mg at 510°C for 6 hours followed by a second isothermal hold at 170°C for 6 hours brought a marked improvement of the yield stress by 30% and of the elongation at break by 220%. However, this was achieved at the expense of a decrease in both hardness and ultimate tensile strength. A better understanding of the underlying phenomena is needed in order to optimize the heat treatment of LBM AlSi10Mg. The present work hence aims at investigating in more depth the mechanical and microstructural evolution induced upon heat treating LBM AlSi10Mg. [less ▲]

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See detailOn the Laser Cladding of Ti Alloy Ti-6Al-4V with Low Laser Power
Mertens, Anne ULg; Paydas, Hakan ULg; Tchuindjang, Jérôme Tchoufack ULg et al

in Ventakesh, V.; Pilchak, A.L.; Allison, J.E. (Eds.) et al Proc. of the 13th World Conference on Titanium (2016, May 06)

Laser cladding is an economic layer-by-layer near-net-shape process for the production and the repair of metallic parts. In this process, a metallic powder is projected onto a substrate while being molten ... [more ▼]

Laser cladding is an economic layer-by-layer near-net-shape process for the production and the repair of metallic parts. In this process, a metallic powder is projected onto a substrate while being molten by a laser beam. Laser sources with fairly high power – i.e. typically 2kW − are often used to ensure short building times and high productivity. However, this approach has limitations. Indeed, it is very difficult to produce thin walls at high laser power. Moreover, an increase of the incident energy may give rise to a relatively coarser microstructure, and this will in turn affect the mechanical properties of the component. In order to address these issues, this paper aims at assessing the potential of a laser source with a lower maximum power of 300W to enhance the flexibility of the process. Two types of samples – i.e. thin walls or bulk deposits − were produced at low laser power from alloy Ti-6Al-4V. Their geometry, microstructures and local hardness are characterised and correlated with the thermal history experienced during fabrication. [less ▲]

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See detailRAPPORT FINAL - Portefeuille de projets TipTopLam
Gravet, Denis; Carton, Marc; Contrepois, Quentin et al

Report (2016)

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See detailRefractory ceramic molds fabrication by additive methods for low and high melting point metal alloys casting
Bister, Geoffroy; Deschuyteneer, Dorian; Hautcoeur, Dominique et al

Conference (2016, March 23)

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See detailLocal thermal history during the laser additive manufacturing of steel
Mertens, Anne ULg; Hashemi, Seyedeh Neda ULg; Tchuindjang, Jérôme Tchoufack ULg et al

Conference (2016, February 09)

Laser additive manufacturing techniques – such as laser cladding − were developed in the late 1990s as economic layer-by-layer near-net-shape processes allowing for the production or restoration of ... [more ▼]

Laser additive manufacturing techniques – such as laser cladding − were developed in the late 1990s as economic layer-by-layer near-net-shape processes allowing for the production or restoration of complex metallic parts. These techniques are characterised by ultra-fast solidification and cooling rates, thus giving rise to ultra-fine out-of-equilibrium microstructures with potentially enhanced mechanical properties. However, the general quality of a component, as well as its dimensional accuracy, microstructure and final usage properties are strongly influenced by the local thermal history experienced during fabrication. As a consequence, a deeper understanding of the influence of the various processing parameters on the local thermal history during fabrication is of paramount importance, and it can only be reached by combining detailed experimental studies and modeling. Keeping this in mind, the present paper reviews on-going investigations carried out in the Metallic Materials Science Unit of the University of Liege in the laser additive manufacturing of HSS and of stainless steel 316L. [less ▲]

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See detailFLYCOAT - Programme d'excellence : Rapport scientifique et technique 1°phase 1er Mars 2015 au 29 Février 2016
Dedry, Olivier ULg; Mertens, Anne ULg; Lecomte-Beckers, Jacqueline ULg

Report (2016)

Le projet FLYCOAT innovera dans les domaines suivants : - Résistance à l’usure : améliorer les revêtements existants par des procédés de fabrication innovants, pour répondre à des propriétés spécifiques ... [more ▼]

Le projet FLYCOAT innovera dans les domaines suivants : - Résistance à l’usure : améliorer les revêtements existants par des procédés de fabrication innovants, pour répondre à des propriétés spécifiques, comme la tenue à l’érosion et à l’impact (grêle, gravillonnage) - Protection anti-corrosion : obtenir des performances équivalentes aux systèmes actuels en l’absence de chromates - Propriétés électriques : conférer des propriétés antistatiques - Propriétés thermiques : améliorer la résistance à la thermo-oxidation et au cyclage thermique. - Résistance aux liquides aéronautiques. [less ▲]

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See detailStudy of the effect of amino-functionalized multiwall carbon nanotubes on dry sliding wear resistance properties of carbon fiber reinforced thermoset polymers
Pincheira, G.; Montalba, C.; Gacitua, W. et al

in Polymer Bulletin (2016)

This work investigates the effect of multiwall carbon nanotubes (MWCNTs) on the mechanical and tribological behavior of a fiber reinforced composite (FRC). Fiber reinforced composites and nano-engineered ... [more ▼]

This work investigates the effect of multiwall carbon nanotubes (MWCNTs) on the mechanical and tribological behavior of a fiber reinforced composite (FRC). Fiber reinforced composites and nano-engineered FRCs are manufactured by resin transfer molding. In-plane tensile tests, in-plane shear tests and through-thickness compression tests are used to assess the influence of MWCNTs on the material mechanical behavior. Pin on disk dry sliding tests are used to quantify the effect of MWCNTs on the friction coefficient and the specific wear rate. It was determined that (1) MWCNTs have an influence on the improvement on both the through-thickness compression strength and the specific wear rate, and (2) they do not influence the material stiffness, in-plane tensile and shear strengths and the friction coefficient. It is assumed that the observed improvements are due to the demonstrated positive influence of the MWCNTs effect on the matrix/reinforcement interfacial strength and on the matrix fracture toughness. [less ▲]

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