References of "Lecomte-Beckers, Jacqueline"
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See detailFriction Stir Processing of Magnesium Matrix Composites reinforced with Carbon Fibres: Influence of the Matrix Characteristics and of the Processing Parameters on Microstructural Developments
Mertens, Anne ULg; Simar, Aude; Montrieux, Henri-Michel ULg et al

in W.J.Poole, K.U.Kainer (Ed.) Proceedings of the 9th International Conference On Magnesium Alloys and their Apllications (2012, July 12)

Processing of magnesium matrix composites reinforced with C fibres by ‘liquid state’ methods such as squeeze casting are usually impaired by the poor wettability of C substrates by liquid Mg. As a ... [more ▼]

Processing of magnesium matrix composites reinforced with C fibres by ‘liquid state’ methods such as squeeze casting are usually impaired by the poor wettability of C substrates by liquid Mg. As a consequence, ‘solid state’ processes such as Friction Stir Processing (FSP) appear as very promising alternative processing routes for the production of C-Mg composites. And, more particularly, FSP of a C fabric between two sheets of the fairly ductile Mg alloy AZ31B was shown to be a simple and innovative process for a large-scale production of magnesium matrix composites reinforced with short C fibres. In the present work, FSP of a C fabric between two metal sheets or thin plates has been performed using two different Mg alloys exhibiting quite different mechanical behaviours, i.e. alloy AZ31B and the more brittle alloy AZ91D. And the effect of the matrix characteristics, along with the influence of the FSP experimental parameters such as the rotational and advancing speeds, on the microstructural changes occuring upon processing have been carefully studied. A particular attention has been given to the fragmentation and distribution of the C fibres, as well as to the recrystallisation, solutionising and precipitation processes taking place in the Mg matrix. [less ▲]

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See detailInfluence of the addition of functionalized MWCNT on mechanical properties on epoxy/carbon fiber and epoxy/carbon-aramid fiber composites
Fernandez, Carolina; Flores, Paulo; Montrieux, Henri-Michel ULg et al

in Proceedings of the 1st Brazilian Conference on Composite Materials (2012, July)

We investigated the effect of the inclusion of carbon nanotubes (CNT) on the mechanical properties and wear behavior of epoxy/carbon and epoxy/carbon-aramid composites in this study. Epoxy/carbon and ... [more ▼]

We investigated the effect of the inclusion of carbon nanotubes (CNT) on the mechanical properties and wear behavior of epoxy/carbon and epoxy/carbon-aramid composites in this study. Epoxy/carbon and epoxy/carbon-aramid composites with 0 wt.% CNT and 0.3 wt.% CNT were manufactured by RTM, amino functionalized multi-walled CNT (MWCNT) were used to modify the matrix. Tensile, compression, two rail shear, Charpy impact tests and Pin On Disc (POD) were performed on the four composites. The EP/CAF composites showed better impact resistance than the ones containing carbon woven. The addition of CNTs improves the shear modulus in 5% for EP/CF composites and 6% for EP/CAF. The results also show that the dynamic friction coefficient is independent of the CNT content, and the specific wear rate shows no improvement with the selected test parameters. [less ▲]

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See detailProcessing of Carbon Fibers Reinforced Mg Matrix Composites Via Pre-infiltration with Al
Mertens, Anne ULg; Montrieux, Henri-Michel ULg; Halleux, Jacques et al

in Journal of Materials Engineering and Performance (2012), 21(5), 701-706

Mg-C composites offer a suitable alternative to Al alloys while allowing for a significant weight reduction, but their production can be impaired by the poor wettability of C substrates by Mg. In the ... [more ▼]

Mg-C composites offer a suitable alternative to Al alloys while allowing for a significant weight reduction, but their production can be impaired by the poor wettability of C substrates by Mg. In the present work, a new 'liquid' processing route has been investigated. By making use of the well-known effect of a pre-treatment of the C fibres with an aqueous solution of K2ZrF6 in favouring spontaneous wetting of C with Al, C yarns have been pre-impregnated with Al and the feasibility of further using them as reinforcements in Mg matrix composites has been assessed. More particularly, it has thus been shown that, under the thermal conditions involved in the process, C fibres did not suffer damage due to chemical reaction with Al, and also that special care should be taken in order to control the surface condition of the pre-infiltrated yarns. [less ▲]

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See detailTi alloys processed by selective laser melting and by laser cladding: microstructures and mechanical properties
Mertens, Anne ULg; Contrepois, Quentin ULg; Dormal, Thierry ULg et al

in proceedings of 12th EUROPEAN CONFERENCE ON SPACECRAFT STRUCTURES, MATERIALS & ENVIRONMENTAL TESTING, Noordwijk 20-23 mars 2012 (2012, March)

Selective laser melting (SLM) and laser cladding were developed in the late 1990s as economic layer-by-layer near-net-shape processes allowing for the production – and also, in the case of laser cladding ... [more ▼]

Selective laser melting (SLM) and laser cladding were developed in the late 1990s as economic layer-by-layer near-net-shape processes allowing for the production – and also, in the case of laser cladding, the restoration - of complex parts. Both techniques involve the melting of a metallic powder with a laser. In the case of SLM, the metallic powder is deposited layer by layer and then molten locally according to the desired shape, whereas in laser cladding the metallic powder is projected onto a substrate through a tube coaxial with the laser. In both processes, the metallic melt pools then cool down and solidify very rapidly, thus producing strongly out of equilibrium microstructures that might exhibit high internal stresses. In the present work, efforts have been made to enhance the flexibility of the laser cladding process: a second laser with a maximum power of 300W was installed beside the original laser (with a higher maximum power of 2000W), thus allowing for the processing of parts with thinner walls and/or coatings. Moreover, flexibility was also improved in relation with the geometry of the parts by use of a 5-axes displacement control. Samples of alloy Ti-6Al-4V, that is widely used in the aeronautic industry due to its high specific strength, have been processed both by SLM and by laser cladding. The resulting microstructures have been characterised in details by optical microscopy, SEM and EBSD so as to allow for a better understanding of the solidification process and of the subsequent phase transformations taking place upon cooling for both techniques. The influence of processing parameters such as the orientation of the deposition of the successive powder layers on the mechanical properties was also investigated by means of uniaxial tensile testing performed on samples with different deposition orientations in regard to the direction of mechanical solicitation. Moreover, some of the samples for mechanical testing had undergone an annealing treatment at 640°C for 4 hours to relieve internal stresses, in order to assess more precisely the effect of those stresses on the tensile properties. [less ▲]

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See detailCurrent Developments of Alloyed Steels for Hot Strip Roughing Mills : Characterization of High-Chromium Steel and Semi-High Speed Steel
Lecomte-Beckers, Jacqueline ULg; Sinnaeve, Mario; Tchuindjang, Jérôme Tchoufack ULg

in Iron and Steel Technology (2012)

Two alloys grades for work rolls used in the roughing stand of Hot Strip Mill - high chromium steel (HCS) and semi-high-speed steel (semi-HSS), In this paper, the new semi-high-speed steel grade is studied

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See detailMicrostructure and mechanical properties of stir processed magnesium matrix composites reinforced with carbon fibres
Simar, Aude; Mertens, Anne ULg; Montrieux, Henri-Michel ULg et al

Conference (2012, January 26)

Mg-Al-Zn alloys have been reinforced with carbon fibres using friction stir processing (FSP) which appears as a promising alternative for the large-scale production of C-Mg composites. The process has ... [more ▼]

Mg-Al-Zn alloys have been reinforced with carbon fibres using friction stir processing (FSP) which appears as a promising alternative for the large-scale production of C-Mg composites. The process has shown its ability to produce sound composites with enhanced strength compared to the non-reinforced alloys. The C fabric is fragmented in short fibres leading to a reduction in grain size and an improved hardness. [less ▲]

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See detailDensity and porosity control of sintered 316L stainless steel parts produced by additive manufacturing
Verlee, Bruno; Dormal, Thierry ULg; Lecomte-Beckers, Jacqueline ULg

in Powder Metallurgy (2012), 55(4), 260-267

Additive manufacturing (AM) techniques offer the possibility to build complex geometries with integrated functionalities. Three-dimensional (3D) printing of metallic powder is probably the only AM ... [more ▼]

Additive manufacturing (AM) techniques offer the possibility to build complex geometries with integrated functionalities. Three-dimensional (3D) printing of metallic powder is probably the only AM technique that can build controlled porosity sintered parts, such as filter elements and fluid permeable components. Many building and sintering parameters can be set to adjust porous properties of the final part. The effects of particle size, paricul shape, sintering temperature and sintering time on the final properties of the sinteres parts have been analysed. Correlations have been established between these properties and process parameters [less ▲]

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See detailComparison between High Chromium Steel and Semi HSS used in Hot Strip Mill Roughing Stands
Lecomte-Beckers, Jacqueline ULg; Sinnaeve, Mario; Tchuindjang, Jérôme Tchoufack ULg

in Proceedings of the 13th Southern African Roll Users Conference (SARUC 2011) (2011, October)

Two alloys grades for work rolls used in the roughing stand of Hot Strip Mill (HSM) are compared. The first grade known as High Chromium Steel (HCS) is presently the most widely used alloy for such an ... [more ▼]

Two alloys grades for work rolls used in the roughing stand of Hot Strip Mill (HSM) are compared. The first grade known as High Chromium Steel (HCS) is presently the most widely used alloy for such an application, while the second one known as semi-High Speed Steel (semi-HSS) is the new grade developed to improve the overall performance of the work roll in the roughing stands of the HSM. In the present paper, the new semi-HSS grade is studied starting from three chemical compositions closed one to another, the variation in the alloying elements is intended to assess, on one hand the effect of a small increase of the carbon content, and on the other hand the influence of the addition of a strong MC carbide forming element. The comparison of HCS and semi-HSS grades involves many fields. Regarding the metallurgical aspect, such a comparison led to the enhancement of the solidification range, the crystallization behavior and the microstructure in the as-cast condition for both grades. Furthermore, corrosion behavior and performances of the work rolls in service are compared. Various techniques are used in order to characterize both grades, such as Differential Thermal Analysis (to determine phase transformations temperatures, the crystallization behavior and the interval of solidification), hardness measurements, optical microscopy, scanning electron microscopy associated with energy dispersive X ray spectroscopy (to determine the nature and the composition of phases, especially matrix and carbides). Finally micro-macro relations between the nature of the microstructure and the properties of HCS and semi-HSS rolls grades in service conditions could be established. [less ▲]

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See detailRapidly solidified microstructure of 3D parts fabricated by selective laser melting (SLM) - Examples of stainless steel 316L and titanium Ti-6Al-4V
Contrepois, Quentin ULg; Lecomte-Beckers, Jacqueline ULg

Poster (2011, September 12)

Laser additive manufacturing process capable of producing fully dense metallic parts direct from 3D CAD know a fast development. Major concerns are made to achieve the best accuracy of the final geometry ... [more ▼]

Laser additive manufacturing process capable of producing fully dense metallic parts direct from 3D CAD know a fast development. Major concerns are made to achieve the best accuracy of the final geometry and the reduction of the residual stresses but metallurgical aspects are also essential. The process can be described as a succession of very small welds. A key in the optimization of the mechanical properties is the understanding of the specific solidification mechanisms. Microstructures of two alloys were studied by metallographic examination and EBSD analysis. [less ▲]

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See detailCharacterization of the β Phase Decomposition in Ti-5Al-5Mo-5V-3Cr at Slow Heating Rates
Contrepois, Quentin ULg; Carton Marc; Lecomte-Beckers, Jacqueline ULg

in Open Journal of Metal (2011), 1

The influence of slow heating rates: 2, 5, 10 and 30°C/min (0.033, 0.083, 0.166 and 0.50°C/s) on the β phase decomposition of Ti-5Al-5Mo-5V-3Cr (Ti-5553) during continuous heating were characterized by ... [more ▼]

The influence of slow heating rates: 2, 5, 10 and 30°C/min (0.033, 0.083, 0.166 and 0.50°C/s) on the β phase decomposition of Ti-5Al-5Mo-5V-3Cr (Ti-5553) during continuous heating were characterized by differen-tial scanning calorimetry (DSC) analysis, light microscopy, scanning electron microscopy, X-ray diffraction and hardness testing. Starting microstructure was the β phase obtained by heating the Ti-5553 above the Tβ temperature and a water quench. Results show that heating rate has a significant impact on the precipitation mechanisms and on the β→α transformation in this range of heating rates. The main formation of α precipi-tates occurs between 500 and 600°Cat all heating rates tested. A heating at 2°C/min produces very fine and homogeneously distributed α plate precipitates which have nucleated on the nanometer size ωiso precipitates. The ωiso precipitates between 350 and 400°C. At higher heating rates 10, 15 or 30°C/min, the amount of pre-cipitation of ωiso is lower so an additional formation of nanometer size precipitates occurs between 450 and 500°C. It is supposed that both precipitates act as nucleation sites for α phase precipitation. The resultant mi-crostructure consists in a fine intragranular distribution of α precipitates and a coarser precipitation of α at the grain boundaries. It is shown that the precipitation of ωiso phase retards or prevents the precipitation of nanometer size precipitates occurring between 450 and 500°C. This cannot be generalized to all the β-metastable titanium alloys since Ti-LCB does not exhibit the same heating rate dependence on DSC curves. [less ▲]

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See detailEnhancement of in-situ Transformation of M2C Eutectics Carbides during High Temperature Heat Treatment on a HSS and a Semi-HSS Grades
Tchuindjang, Jérôme Tchoufack ULg; Sinnaeve, Mario; Lecomte-Beckers, Jacqueline ULg

Poster (2011, September)

Alloys of the complex system Fe-Si-C-Cr-C-X, where X is a strong carbide forming-element are well known to exhibit interesting mechanical properties, including wear and abrasion resistances. Such a ... [more ▼]

Alloys of the complex system Fe-Si-C-Cr-C-X, where X is a strong carbide forming-element are well known to exhibit interesting mechanical properties, including wear and abrasion resistances. Such a tribological behavior is mainly due to the presence of carbides especially those obtained during the solidification route and that are known as primary or eutectic carbides. It may therefore be interesting to determine the relative stability of primary carbides when considering thermal and thermomechanical treatments performed at a temperature high enough to allow either the homogenization of the matrix or the occurrence of a desired grain size. This thermal stage is often required to produce tailored microstructures that can lead to improved mechanical properties. In this work a series of thermal treatments performed on samples originated form casting foundry parts were done. Raw materials are both HSS and semi-HSS grades used in application where wear resistance is needed. Thermo- Calc® (TC) simulations and Differential Thermal Analysis (DTA) were performed to determine the crystallization behavior and the subsequent solid state transformations of the studied alloys respectively in equilibrium and in non equilibrium conditions. Light and Scanning Electron Microscopies were done together with hardness measurements in order to enhance metallurgical features of the heat treated samples. Image analysis yielded the determination of carbides volume fractions. It appears from microstructural analyses and carbides quantification that Mo-rich eutectic carbides undergo in situ phase transformations during heat treatments. In fact Mo-rich M2C carbides transform themselves into MC, M6C and M3C, through a so-called budding phenomenon. Such a phenomenon is the evidence of a preferential migration of some atoms that escape from the parent M2C carbide to diffuse further away from their initial site with increasing time and temperature. The stable or metastable nature of eutectic carbides is also discussed from DTA and TC results, as M2C carbides found in both as-conditions and DTA samples were not predicted by equilibrium conditions. [less ▲]

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See detailProcessing of carbon fibers reinforced Mg matrix composites via pre-infiltration with Al
Mertens, Anne ULg; Lecomte-Beckers, Jacqueline ULg; Montrieux, Henri-Michel ULg et al

Conference (2011, September)

Mg matrix composites appear as suitable competitors to Al alloys for a wide number of applications, as they allow for a significant weight reduction while exhibiting potentially comparable mechanical ... [more ▼]

Mg matrix composites appear as suitable competitors to Al alloys for a wide number of applications, as they allow for a significant weight reduction while exhibiting potentially comparable mechanical properties. And a large variety of processing routes have already been considered for their production, including 'liquid state' processes such as squeeze casting. These techniques necessitate a very careful control of the wetting behaviour and of the possible interfacial reactions between the reinforcements and the molten metal, along with the solidification process. And this is more particularly true in the case of Mg matrix composites with carbon fibers reinforcements, as Mg alloys are known to exhibit a poor wetting behaviour on carbon substrates. [less ▲]

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See detailInterfacial phenomena in carbon fibre reinforced magnesium alloys processed by squeeze casting and thixomolding
Montrieux, Henri-Michel ULg; Mertens, Anne ULg; Halleux, Jacques et al

Conference (2011, September)

Composite materials are known to combine interesting properties of different materials. This research concerns magnesium alloys reinforced by carbon fibre weaves. Such a material can theoretically exhibit ... [more ▼]

Composite materials are known to combine interesting properties of different materials. This research concerns magnesium alloys reinforced by carbon fibre weaves. Such a material can theoretically exhibit a high yield strength/density ratio. This composite is thought to be especially promising for aeronautics. A pre-treatment of carbon weaves ensure two fundamental functions. The first is to provide stiffness and cohesion. It helps keeping fibres aligned and well placed in the mould during casting to ensure optimal properties of the final part in the main load directions. This is imperative when the composite is formed with thixomolding for which semi liquid metal is injected with a very high speed. Nevertheless the problem of geometrical carbon weaves stability is also encountered with squeeze casting. The second objective of the pre-treatment is to provide a porous network in the weaves to enhance infiltration by the capillary action. The two functions can be assumed by coating fibres with Al(H2PO4)3, SiO2 combined with starch, or some other oxide containing mixtures. The general process is to assemble carbon weaves, infiltrate them in an aqueous solution or dispersion of oxides and lastly heat them at high temperature to promote covalent bonds with fibres and vaporize or crack carbonaceous agents to let a porous medium. Further the chemical interaction between the coated fibres and the liquid metal during infiltration can influence the species which are present at the interfaces. As magnesium oxide is stable magnesium can react with oxides. This could lead to better wettability of treated weave. However such chemical reactions seem to be thermally activated and take many seconds to initiate, whereas solidification of magnesium is achieved faster. Furthermore the addition of some carbide former elements (Si, Ti, Zr) to a magnesium based alloy can also influence chemical affinity. In conclusion CMg-MMC research concerns composites with low density, high potential mechanical properties and possibility of processing through thixomolding. Firstly the reach of the theoretical performance of the composite includes the ability of dealing with the interaction between fibres and liquid metal. Secondly primary treatment could help to form bonds between matrix and fibres, make rigid weaves and promote a further infiltration. Thirdly chemical affinity between the fibres, magnesium alloy and coating can influence the infiltration. [less ▲]

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