References of "Delannay, Francis"
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See detailInfluence of Fiber Distribution and Grain Size on the Mechanical Behavior of Friction Stir Processed Mg-C Composites
Mertens, Anne ULg; Montrieux, Henri-Michel ULg; Lecomte-Beckers, Jacqueline ULg et al

Conference (2012, November 12)

Short C fibers-Mg matrix composites have been produced by friction stir processing sandwiches made of a layer of C fabric stacked between two sheets of either the ductile Mg alloy AZ31B, or of the less ... [more ▼]

Short C fibers-Mg matrix composites have been produced by friction stir processing sandwiches made of a layer of C fabric stacked between two sheets of either the ductile Mg alloy AZ31B, or of the less ductile alloy AZ91D, that is capable of age hardening. It has been shown that the choice of the optimal experimental parameters for the production of sound composites was strongly dependent on the nature of the matrix. 3D X-ray tomography reveals that the fibers orient along the onion rings and that they are more or less fragmented depending on the local shear stress during the process. The fiber volume fraction is increased when the nugget volume decreases in particular for the AZ91D base material and for a high advancing speed for the AZ31B base material. The fiber volume fraction influences directly the grain size, the hardness and the tensile properties of the composites. [less ▲]

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See detailComposite Manufacturing by Friction Stir Processing
Simar, Aude; de Meester, Bruno; Delannay, Francis et al

Conference (2012, October 29)

A new solid-state process developed recently on the same principles as Friction Stir Welding (FSW), Friction Stir Processing appear as a very promising technique for the production of metal matrix ... [more ▼]

A new solid-state process developed recently on the same principles as Friction Stir Welding (FSW), Friction Stir Processing appear as a very promising technique for the production of metal matrix composites and for tailoring materials properties. In the present work, this process has been applied to two different composite systems: (i) magnesium-matrix composites reinforced with carbon fibers, and (ii) copper-matrix composites reinforced with Y2O3 powder. Process optimization and mechanical properties of the composites are discussed in both systems. [less ▲]

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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 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 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 detailC Fibres - Mg Matrix Composites Produced by Squeeze Casting and Friction Stir Processing: Microstructure & Mechanical Behaviour
Mertens, Anne ULg; Simar, Aude; Delannay, Francis

in Materials Science Forum (2012), 706-709

Mg-Al-Zn alloys have been reinforced with carbon fibres using either the liquid state process of squeeze casting (SC), or friction stir processing (FSP), a solid state process developed more recently and ... [more ▼]

Mg-Al-Zn alloys have been reinforced with carbon fibres using either the liquid state process of squeeze casting (SC), or friction stir processing (FSP), a solid state process developed more recently and that appears as a promising alternative for the large-scale production of C-Mg composites. Both processes have shown their ability to produce sound composites with enhanced strength compared to the non-reinforced alloys. in SC composites, the unsized woven C fabric remains intact while in the FSP composites the sized C fabric is fragmented in short fibres, with an aspect ratio typically equal to 4, homogeneously distributed in the Mg alloy matrix. [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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See detailC FIBERS - MG MATRIX COMPOSITES PRODUCED BY SQUEEZE CASTING AND FRICTION STIR PROCESSING: Microstructure & Mechanical Behaviour
Mertens, Anne ULg; Simar, Aude; Delannay, Francis

Poster (2011, August)

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

Mg matrix composites appear as suitable competitors to Al alloys, as they allow for a significant weight reduction while exhibiting potentially comparable mechanical properties. A large variety of processing routes have already been considered for their production, including 'liquid state' processes such as squeeze casting. However these techniques necessitate a very careful control, simultaneously, of the solidification process, the wetting behaviour and the possible interfacial reactions between the reinforcements and the molten metal. 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. As a consequence, 'solid state' processing routes such as friction stir processing, that has been developed more recently, provide promising alternatives for the production of C-Mg composites. In the present work, Mg-Al-Zn alloys have been reinforced with carbon fibers using squeeze casting and friction stir processing. The microstructures and mechanical behaviour of composites produced by both processes have then been characterised and compared to those of non-reinforced samples, with a particular attention to the damage mechanisms prevailing in the composite materials. As a result, both processes have been compared in terms of the properties of their final products and hence their ability to produce sound composites. [less ▲]

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See detailRelative Influence of Aluminium and Silicon on the Kinetics of Bainite Formation from Intercritical Austenite
Mertens, Anne ULg; Jacques, Pascal J.; Sietsma, Jilt et al

in Steel Research International (2008), 79(12), 954-959

Bainite formation from intercritical austenite is of great practical importance for the production of TRIP-assisted steels. Silicon and aluminium play important roles during this transformation by ... [more ▼]

Bainite formation from intercritical austenite is of great practical importance for the production of TRIP-assisted steels. Silicon and aluminium play important roles during this transformation by delaying carbide precipitation, thus favouring the carbon enrichment of untransformed austenite, which makes its stabilisation down to room temperature possible. Previous studies have shown a strong dependence of bainite formation kinetics on both chemical composition and transformation temperature. In the present work, the effect of silicon and aluminium contents on bainite formation kinetics is investigated experimentally using dilatometry combined with microscopical observations. The experimental results are analysed by comparison with thermodynamic parameters, such as the activation energy G* for nucleation of bainite and the carbon content CT0 corresponding to the T0-curve. It is shown that the faster transformation kinetics induced by the substitution of silicon by aluminium can be ascribed (i) to a higher driving force for nucleation, (ii) to a higher carbon content CT0 at the T0-curve and (iii) to the precipitation of carbide in austenite in steels with a low Al content. [less ▲]

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See detailOn the influence of aluminium and silicon contents on the kinetics of bainite transformation of intercritical austenite
Mertens, Anne ULg; Jacques, Pascal J.; Zhao, Lie et al

in Journal de Physique IV (2003), 112

TRIP-assisted steels show enhanced mechanical properties thanks to the strain-induced transformation of retained austenite to martensite (TRIP effect). Stabilisation of austenite is made possible by the ... [more ▼]

TRIP-assisted steels show enhanced mechanical properties thanks to the strain-induced transformation of retained austenite to martensite (TRIP effect). Stabilisation of austenite is made possible by the combination of appropriate chemical composition (containing classically high levels of silicon, or, as developed more recently, aluminium) and of a two-steps heat treatment comprising an intercritical annealing followed by an isothermal holding in the bainite formation range. A detailed understanding of the effects of both elements on the bainite transformation kinetics is thus of primary importance for the optimisation of austenite retention. The present study aims at a better knowledge of the influence of aluminium levels on the kinetics of the bainite transformation of intercritical austenite, as compared to the effect of silicon. The bainite transformation kinetics was followed by dilatometry in a set of 6 steel grades with varying aluminium and silicon contents. These dilatometry experiments were coupled with a characterisation of the microstructures by X-ray diffraction, SEM and image analysis. It was shown that aluminium has a less pronounced effect than silicon in retarding the bainite transformation [less ▲]

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See detailOn the influence of aluminium and silicon contents on the kinetics of bainite transformation of intercritical austenite
Mertens, Anne ULg; Jacques, Pascal J.; Zhao, Lie et al

Conference (2002, June)

TRIP-assisted steels show enhanced mechanical properties thanks to the strain-induced transformation of retained austenite to martensite (TRIP effect). Stabilization of austenite is made possible by the ... [more ▼]

TRIP-assisted steels show enhanced mechanical properties thanks to the strain-induced transformation of retained austenite to martensite (TRIP effect). Stabilization of austenite is made possible by the combination of appropriate chemical composition (containing classically high levels of silicon, or, as developed more recently, aluminium) and of a two-steps heat treatment comprising an intercritical annealing followed by an isothermal holding in the bainite formation range. A detailed understanding of the effects of both elements on the bainite transformation kinetics is thus of primary importance for the optimization of austenite retention. The present study aims at a better knowledge of the influence of aluminium levels on the kinetics of the bainite transformation of intercritical austenite, as compared to the effect of silicon. The bainite transformation kinetics was followed by dilatometry in a set of 6 steel grades with varying aluminium and silicon contents. These dilatometry experiments were coupled with a characterization of the microstructures by X-ray diffraction, SEM and image analysis in order to assess the occurrence of an incomplete reaction phenomenon. It was shown that aluminium has a less pronounced effect than silicon in retarding the bainite transformation. A model was proposed to account for this retarding effect as a function of aluminium or silicon contents. [less ▲]

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See detailOn the optimisation of the mechanical properties of two aluminium-alloyed multiphase TRIP-assisted steels
Mertens, Anne ULg; Jacques, Pascal J.; Harlet, Philippe et al

in De Cooman, Bruno C. (Ed.) Proccedings of the International Conference on TRIP-Aided High Strength Ferrous Alloys (2002, June)

Aluminium-alloyed multiphase TRIP-assisted steels have been recently developed, so as to get rid of the disdavantages related to the high silicon contents classically used so far in TRIP-assisted steels ... [more ▼]

Aluminium-alloyed multiphase TRIP-assisted steels have been recently developed, so as to get rid of the disdavantages related to the high silicon contents classically used so far in TRIP-assisted steels. It has been shown that aluminium has a stronger ferritising effect than silicon and that it is slightly less efficient as far as austenite retention is concerned. A careful selection of the aluminium content and of the processing conditions is thus of primary importance in order to optimise the mechanical properties. The present study aims at determining the optimal heat treatment conditions leading to enhanced mechanical properties for two low aluminium-alloyed grades containing with mass contents of 0.12% C, 1.5% Mn and 0.5% Al or 1.0% Al, respectively. The microstructures generated during the heat treatment were assessed using SEM, X-ray diffraction and Mössbauer spectrometry. The mechanical properties were evaluated by uniaxial tensilte testing and the strain-hardening behaviour was characterised by means of an incremental strain-hardening exponent. The relations between the observed microstructures and the mechanical properties were discussed and, as a consequence, the importance of a careful control of the isothermal bainitic holding was highlighted. [less ▲]

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See detailOn the sources of work hardening in multiphase steels assisted by transformation-induced plasticity
Jacques, Pascal J.; Furnémont, Quentin; Mertens, Anne ULg et al

in Philosophical Magazine A (2001), 81(7), 1789-1812

The mechanisms effectively responsible for the enhancement of the work-hardening capabilities of multiphase steels assisted by transformation-induced plasticity are highlighted. Different microstructures ... [more ▼]

The mechanisms effectively responsible for the enhancement of the work-hardening capabilities of multiphase steels assisted by transformation-induced plasticity are highlighted. Different microstructures, some containing a proportion of retained austenite with various mechanical stabilities, are studied. The dislocation density generated within ferrite by the mechanically induced martensitic transformation of retained austenite is shown to scale with the incremental work-hardening exponent. The acoustic emission generated during tensile straining was also measured. The acoustic emission was revealed to result mainly from dislocation motion, especially from the motion of the additional dislocation density generated in intercritical ferrite by the strain-induced martensitic transformation. [less ▲]

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See detailThe Developments of Cold-rolled TRIP-assisted Multiphase Steels. Al-alloyed TRIP-assisted Multiphase Steels
Jacques, Pascal J.; Girault, Etienne; Mertens, Anne ULg et al

in ISIJ International (2001), 41(9), 1068-1074

The influence of heat-treating conditions on the retention of carbon-enriched austenite of TRIP-assisted multiphase steel grades containing different amounts of silicon and/or aluminium is investigated ... [more ▼]

The influence of heat-treating conditions on the retention of carbon-enriched austenite of TRIP-assisted multiphase steel grades containing different amounts of silicon and/or aluminium is investigated. The ensuing mechanical properties resulting from the TRIP effect are also scrutinised. The bainite transformation kinetics was followed by dilatometry whereas a detailed characterisation of the microstructures led to the construction off transformation maps giving the volume fractions of the different phases and the carbon content of the austenite. The role of silicon and aluminium additions (i)on the retention of austenite by partial bainite transformation and (ii) on the mechanical properties is enlightened. A strong influence of the solid-solution strengthening effect of silicon is highlighted. Aluminium seems to be an effective alloying element for the retention of austenite in TRIP-aided steels even if lower strength levels can be attained. A mixed Al-Si TRIP-aided steel seems to be a very good compromise between the processing needs, the required mechanical properties and the industrial constraints. [less ▲]

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See detailOn the influence of aluminium content on the stability of retained austenite in multiphase TRIP-assisted steels
Mertens, Anne ULg; Jacques, Pascal J.; Lazarova, Roumiana et al

in Journal de Physique IV (2001), 11

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See detailOn the influence of aluminium content on the stability of retained austenite in multiphase TRIP-assisted steels
Mertens, Anne ULg; Jacques, Pascal J.; Lazarova, Roumiana et al

Poster (2000, September)

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See detailInfluence of Silicon and Aluminium Contents on the Phase Transformations During the Heat-Treatment of TRIP-assisted Multiphase Steels
Jacques, Pascal; Girault, Etienne; Mertens, Anne ULg et al

in Mideat, S. J.; Pfaffmann, G. D. (Eds.) Proceedings of the International Symposium in honor of Prof. G. Krauss, 19th Heat Treating Society Conference (1999, November)

Detailed reference viewed: 46 (0 ULg)