References of "Lecomte-Beckers, Jacqueline"
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See detailFractography survey on high cycle fatigue failure: Crack origin characterisation and correlations between mechanical tests and microstructure in Fe-C-Cr-Mo-X alloys
Tchuindjang, Jérôme Tchoufack ULg; Lecomte-Beckers, Jacqueline ULg

in International Journal of Fatigue (2007), 29(4), 713-728

Raw materials were cast from different specific processes in order to produce cleaner steels with a reduced amount of inclusions. Studied materials that are HSS hardened alloys belonging to the Fe-Cr-C-X ... [more ▼]

Raw materials were cast from different specific processes in order to produce cleaner steels with a reduced amount of inclusions. Studied materials that are HSS hardened alloys belonging to the Fe-Cr-C-X system were shared out in four groups depending on the tempering temperature and the presence of secondary and primary carbides. Both inclusions and carbides were roughly assessed by means of Image Analysis. Forging was done on all studied materials with different reduction ratios in order to highlight the texture influence oil mechanical properties. High cycle fatigue tests were made using the boundary method to allow a quick evaluation of results. Fractographic analyses carried out on broken samples led to the definition of four failure modes depending on the nature and the location of the point from which the crack was initiated in one hand, and the roughness of striations in the propagating area over and around the initiation point. Internal and surface crack initiation points were found, the latter being more harmful than the first ones. Though oxides appeared to be more detrimental than other inclusions, primary carbides were also found to be both crack initiation candidates and crack propagation enhancers. Various parameters likely to influence high cycle fatigue failures were finally defined, the most significant one dealing with the nature and location of embedded precipitates and the forging reduction ratio. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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See detailImprovement in HSS grade for early stands of hot strip mills - Metallurgical features and mechanical properties assessment
Ernst, Roger; Breyer, Jean-Pierre; Tchuindjang, Jérôme Tchoufack ULg et al

in Proceedings of the 43rd Seminar of Rollings (2007)

Aurora and Kosmos grades are HSS alloys belonging to the complex Fe-Cr-C-X system, where X is a strong carbide former element of the V, Mo or W type. Both alloys were metallurgically characterised prior ... [more ▼]

Aurora and Kosmos grades are HSS alloys belonging to the complex Fe-Cr-C-X system, where X is a strong carbide former element of the V, Mo or W type. Both alloys were metallurgically characterised prior to their comparison. Metallurgical analyses involved phases identification and carbides quantification by using Scanning Electron Microscopy and Energy Dispersive X rays. Differential Thermal Analysis was performed to allow a better understanding of the solidification sequence of studied alloys while mechanical tests performed were compressive at room temperature and bulk hardness at usual service temperatures. An attempt was made in order to connect experimental results to the good behaviour in operation of Aurora grade. In fact Aurora grade appeared to exhibit strong metallurgical differences when compared to Kosmos grade, especially as concern in nature and amount of carbides. [less ▲]

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See detailStudy of transformations and microstructural modification in Ti-LCB and T-555 alloys using Differential Scanning Calorimetry
Carton, Marc ULg; Pascal, Jacques; Clement, Nicolas et al

in Proceedings of Ti-2007 Science and technology - 11th World Conference on Titanium (JIMIC 5) (2007)

The aerospace industry is the single largest market for titanium products primarily due to the exceptional strength to weight ratio, elevated temperature performance and corrosion resistance. Titanium ... [more ▼]

The aerospace industry is the single largest market for titanium products primarily due to the exceptional strength to weight ratio, elevated temperature performance and corrosion resistance. Titanium applications are most significant in jet engine and airframe components that are subject to high temperatures. The studied Ti-LCB and Ti-555 titanium alloys must present good properties to fatigue damage as they are located in a low-pressure compressor. In order to avoid this damage, an optimized alloy microstructure is required. In our case, the optimal microstructure would be a beta matrix in which small alpha particles are uniformly distributed, obtained after a combination of thermomechanical and thermal treatments. The understanding of the mechanisms ruling the microstructure evolution is achieved through the study of phase transformations versus temperature. During heating, the ωath phase is transformed into the ωiso phase, allowing itself the appearance of the α phase. Then this α phase is transformed progressively into the β phase, and the structure becomes totally β when the transus temperature is reached. Therefore, a thermal analysis tool such as DSC (Differential Scanning Calorimetry) was used in order to characterise the phase transformations of the material during imposed controlled temperature programs. [less ▲]

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See detailCorrosion studies of different ferrous alloys for rolling cylinders
Martinez, L.; Gomez, C.; Lecomte-Beckers, Jacqueline ULg et al

in Materials & Design (2007), 28(1), 196-202

The aim of this work is to study the corrosion behaviour in chloride media of a high chromium iron alloy. The influence of the surface finishing as well as the heat treatment was analysed. The technique ... [more ▼]

The aim of this work is to study the corrosion behaviour in chloride media of a high chromium iron alloy. The influence of the surface finishing as well as the heat treatment was analysed. The technique employed for measuring the corrosion behaviour was the Electrochemical Impedance Spectroscopy, an electrochemical technique that allows the observation not only of the corrosion rates but also the changes on the corrosion mechanism of the alloy. The results showed that it is worth performing a double tempering and a having smoother surface finishing only for long exposure periods. A comparison between different oxidising conditions was also performed simulating the life in service of the hot rolling cylinders and revealed an increase in the protective properties as the oxidising time increased due to the chromium present on the alloy (18%). (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailStudy of a 2024 aluminium rod produced by Rotary Forging
Habraken, Anne ULg; Bouffioux, Chantal ULg; Carton, Marc ULg et al

in Journal of Materials Processing Technology (2007), 184

An investigation of the rotary forging process of a 2024 aluminium rod is summarised. Some dispersion in mechanical properties and chemical composition of the base material is permitted. Samples of two ... [more ▼]

An investigation of the rotary forging process of a 2024 aluminium rod is summarised. Some dispersion in mechanical properties and chemical composition of the base material is permitted. Samples of two material batches were selected: one just stays near the upper limit of tolerance and the other has mean properties. Tensile and compression tests confirm the different mechanical behaviours and allow the identification of constitutive laws parameters. Optical metallography after T3 and T10 thermal treatments and differential thermal analysis provide the grain size and precipitation characteristics of each material batch, which explain their different mechanical behaviours. The industrial rod studied is usually forged in two operations: a first forging process, then a T10 thermal treatment followed by a second forging step. Industrial practise shows that manufacturing the rod with one forging step fails. FEM simulations of the process coupled with a fracture criterion confirm the advantage of a two-step process compared to a single forging step. [less ▲]

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See detailMetallurgical assessment of two HSS rolls grades for Hot Strip Mill
Lecomte-Beckers, Jacqueline ULg; Delaunois, Fabienne; Breyer, Jean-Pierre et al

in AISTech-Proceedings of the Iron and Steel Technology Conference (2007)

Aurora and Kosmos grades are HSS alloys used for the manufacturing of rolling mill work rolls for early finishing stands of Hot Strip Mills. Both alloys were metallurgically assessed using Electron ... [more ▼]

Aurora and Kosmos grades are HSS alloys used for the manufacturing of rolling mill work rolls for early finishing stands of Hot Strip Mills. Both alloys were metallurgically assessed using Electron Microscopy, X Rays analysis on carbides and Differential Thermal Analysis. These methods allow a better understanding of the behaviour of the studied alloys during solidification and cooling. Some mechanical tests were also performed. A connection between the laboratory results and the performance in operation of both grades is performed. The strong metallurgical differences especially as concern the nature and amount of carbides allow to explain the good behaviour in service of Aurora. [less ▲]

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See detailTailoring microstructures to improve thermomechanical behaviour of metallic alloys : Ti alloys for Aerospace applications
Lecomte-Beckers, Jacqueline ULg; Carton, Marc ULg

in Proceedings of international workshop : Advancements in design optimization of materials, structures and mechanical systems (2007)

A more rational use of metallic materials for advanced applications (such as for example in aeronautics or fine mechanics) requires to generate the optimal microstructures through the control of the ... [more ▼]

A more rational use of metallic materials for advanced applications (such as for example in aeronautics or fine mechanics) requires to generate the optimal microstructures through the control of the elaboration and fabrication processes. In this context, the description of the critical parameters of the microstructure of the metallic materials, which influence the mechanical properties, is necessary. This step requires the knowledge of the thermically and thermomecanically activated phenomenons (phase transformation, recrystallisation,...). The interpretation and the synthesis of these observations are integrated within physical models which provide the elements necessary to the development of the physical or mathematical macroscopic model. This paper will develop one example of the laboratory MMS researches (Special Metallic Materials) concerning the study of the physicochemical mechanisms controlling the microstructural genesis and the optimization of the mechanical properties. In the case of nanostructured alpha/beta titanium alloys, bonds between mechanical properties and active microstructural elements will be presented. [less ▲]

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See detailDetermination of the Influence of Alloying Elements on Solidification Parameters for the Study of the Thixoformability of a Chromium Steel
Fraipont, Céline; Lecomte-Beckers, Jacqueline ULg

in Proceedings of The 10th Esaform Conference on Material Forming (2007)

This paper deals with the examination of the influence of alloying elements on the thixoformability of a chromium steel. It focuses on the liquid fraction curves of different chromium steel with and ... [more ▼]

This paper deals with the examination of the influence of alloying elements on the thixoformability of a chromium steel. It focuses on the liquid fraction curves of different chromium steel with and without modification of composition. The liquid fraction versus temperature has been obtained experimentally by differential thermal analysis (DTA), limited to low heating rates. The correlation between liquid fraction and temperature has been studied. The effect of modifications of composition was observed. [less ▲]

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See detailCorrosion behaviour of different hot rolled steels
Perez, F. J.; Martinez, L.; Hierro, M. P. et al

in Corrosion Science (2006), 48(2), 472-480

The oxidation-corrosion behaviour of hot rolled alloys was examined by electrochemical impedance spectroscopy. The corrosion behaviour of the non-oxidised alloys was first determined in order to have a ... [more ▼]

The oxidation-corrosion behaviour of hot rolled alloys was examined by electrochemical impedance spectroscopy. The corrosion behaviour of the non-oxidised alloys was first determined in order to have a reference behaviour. Then, each alloy was oxidised for 1 and 3 days at 650 degrees C in air and its corrosion behaviour was also determined. For all the alloys, Fe2O3 was formed at the scale-gas interface. However, the Fe2O3 crystallographic structures varied as a function of the alloy composition. Differences in the corrosion behaviour are due to the thickness, the microstructure and the porosity of the scale. The new graphite chromium iron alloy (Hi-Cr + C) have an oxidation-corrosion behaviour close to the indefinite chill double paired (ICDP) one and is therefore thought to be a good candidate to replace the ICPD alloy. In the case of the high speed steel (HSS) alloy, the oxidation-corrosion kinetics are too slow to prevent sticking problems. The Co addition decreases the corrosion-oxidation rates for the non-oxidised and oxidised samples but this effect is limited in time. (C) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailThixoforging of 7075 aluminium alloys at high solid fraction
Vaneetveld, Grégory ULg; Rassili, Ahmed ULg; Lecomte-Beckers, Jacqueline ULg et al

in Solid State Phenomena (2006), 116-117

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.5 < f(s) < 1), which involves the processing of alloys in the semi-solid state. 7075 alloy has been used as a feedstock for ... [more ▼]

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.5 < f(s) < 1), which involves the processing of alloys in the semi-solid state. 7075 alloy has been used as a feedstock for thixoforming in order to investigate thixoformability of a high performance aluminium alloy at high solid fraction. The microstructure in semi-solid state consists of fine spheroidal solid grains surrounded by liquid. Thixo behaviour allows laminar flow that avoids macro-porosity and other casting defects and gives better mechanical properties; so we can reduce the weight of functional parts. Higher solid fraction of 7075 alloy is less sensitive to temperature, avoids metal splash at high speed, allows laminar flow at high speed and gives a good smooth surface without stick-slip phenomenon. The process is quicker with less energy and so the production rate increases and the tool has longer life. However, high solid fraction promotes freezing flow because of faster solidification and the lack of liquid phase. This freezing flow creates solid/liquid segregation and increases the forming force. [less ▲]

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See detailInfluence of excessive carbides upon strength of hot rolled rolls of steel similar to high speed grade
Lecomte-Beckers, Jacqueline ULg; Herman, M.; Breyer, J. P.

in Stal' (2006), 9

This paper will illustrate the choice of the alloying elements and their content in the current grade. By using sophisticated laboratory examination techniques such as differential thermal analysis ... [more ▼]

This paper will illustrate the choice of the alloying elements and their content in the current grade. By using sophisticated laboratory examination techniques such as differential thermal analysis, scanning electron microscopy and image analysis, the metallurgical parameters of Aurora grade will be described and compared to those of the Kosmos grade. An attempt will also be made to connect all our laboratory results to the good behaviour of the alloy in operation in the early stands of Hot Strip Mills. [less ▲]

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See detailDetermination of solidification parameters used for the prediction of the thixoformability of several steel alloys
Lecomte-Beckers, Jacqueline ULg; Rassili, Ahmed ULg; Robelet, Marc et al

in Solid State Phenomena (2006), 116-117

This paper focuses on the liquid fraction curves of several steels and the correlation between liquid fraction, temperature and heating rate. The work has been performed along two main axes. First, the ... [more ▼]

This paper focuses on the liquid fraction curves of several steels and the correlation between liquid fraction, temperature and heating rate. The work has been performed along two main axes. First, the solid fraction versus temperature has been obtained experimentally by differential scanning calorimetry (DSC), limited to low heating rates. Then, a shift of the liquid fraction curves has been noticed at high industrial heating rates. The quantification of this effect could not be carried out by DSC and required the elaboration of another experimental device. [less ▲]

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See detailInfluence of experimental parameters on properties and microstructure of the steel X210CrW12 in the semi-solid state
Fraipont, Céline; Puettgen, Wolfgang; Bleck, Wolfgang et al

in Solid State Phenomena (2006), 116-117

This paper deals with the examination of the steel grade X210CrW12 and its suitability for Thixoforming. In the semi-solid state, the microstructure of this steel consists of a homogeneous distribution of ... [more ▼]

This paper deals with the examination of the steel grade X210CrW12 and its suitability for Thixoforming. In the semi-solid state, the microstructure of this steel consists of a homogeneous distribution of globular particles surrounded by liquid. Additionally, carbides are stabile up to fraction liquid contents of approximately 40%. After quenching, this steel reveals a globular austenitic microstructure with eutectic (former liquid phase) at the grain boundaries. Compression tests permit to determine the influence of different process parameters on the properties and the material behaviour in the semi-solid state. Their influence on the microstructure was investigated but not yet highlighted. Further investigations on this steel allow a fine-tuning to establish optimal process windows of the different thixoforming- and rheoforming-routes. [less ▲]

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See detailCharacterization of Duplex steel Uranus 76N during deformation and heat treatment
Lecomte-Beckers, Jacqueline ULg; Moureaux, P.; Carton, Marc ULg et al

in Physica Status Solidi A. Applications and Materials Science (2006), 203(15), 3651-3664

Duplex Uranus 76N is characterized by metallography, thermal and mechanical analysis. The investigation shows that the microstructure of such a Duplex strongly depends on the cooling conditions ... [more ▼]

Duplex Uranus 76N is characterized by metallography, thermal and mechanical analysis. The investigation shows that the microstructure of such a Duplex strongly depends on the cooling conditions determining the quantity of austenite formed in the ferrite matrix. Numerical simulations of 76N behavior during the rolling process and service life require the knowledge of the recrystallization state during rolling steps at high temperature, thermal parameters such as dilatation, density, specific heat, thermal diffusivity, thermal conductivity and mechanical constitutive laws. These material parameters are determined and presented in this study. [less ▲]

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