Développement d’une ailette d’obus en composite magnésium renforcé de fibres de carbone

Report (2012)

This report describes the accomplished breakthrough for the manufacturing of long carbon fibres reinforced magnesium alloy (AZ91). Infiltration can be performed with non-equilibrium conditions such as ... [more ▼]

This report describes the accomplished breakthrough for the manufacturing of long carbon fibres reinforced magnesium alloy (AZ91). Infiltration can be performed with non-equilibrium conditions such as fibres preheating, high liquid compacting pressure and low contact times. Thanks to specific TEOS sol/gel treatment, the reached fibre rate is 60 vol.% and the measured Young's modulus of the composite is ca. 110 GPa. The presence of defects including fibre yarns misorientation, unreinforced areas seems very detrimental to the bending properties. Other advanced infiltration techniques with Al pretreatment (K2ZrF6) of fibres is also considered. [less ▲]

Composite Manufacturing by Friction Stir Processing

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 ▲]

Friction Stir Processing of Magnesium Matrix Composites reinforced with Carbon Fibres: Influence of the Matrix Characteristics and of the Processing Parameters on Microstructural Developments

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 ▲]

Processing of Carbon Fibers Reinforced Mg Matrix Composites Via Pre-infiltration with 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 ▲]

Ti alloys processed by selective laser melting and by laser cladding: microstructures and mechanical properties

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 ▲]

Utilisation et technique de production du fer et du bois dans les charpentes de comble mosanes : premiers jalons d’une évolution du XIIe au XVIIIe siècle

in ArchéoSciences (2012), 36

The development of a comparative approach between the evaluation of the quantity of timber used in a roof frame and the volume of wood present in this same attic allows the acquisition of information ... [more ▼]

The development of a comparative approach between the evaluation of the quantity of timber used in a roof frame and the volume of wood present in this same attic allows the acquisition of information about the economical, technical and social contexts in which a timber frame was drawn up. By carrying out this kind of comparison in a systematic way in twenty-tree religious mosan buildings (Belgium and Netherlands), it’s possible to trace, step by step, thanks to dendrochronologic dating of the attics since 12th until 18thcentury, the causes and consequences which influence the methods of constructions of the carpenters. In parallel, the confrontation of this result with the volumes of iron used in the attics reveals the growing importance of this material in function of the time and of the architectural principles. This part of the study was enriched by archeometallurgic analyses intended to identify the process of reduction employed to produce this metal with the aim to measure the possible influence of iron process innovations on the use of iron in the medieval and modern frames, knowing that Wallonia knew from the end of the Middle Ages the early development of the indirect iron process instead of the direct iron process. [less ▲]

Processing of carbon fibers reinforced Mg matrix composites via pre-infiltration with 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 ▲]

C FIBERS - MG MATRIX COMPOSITES PRODUCED BY SQUEEZE CASTING AND FRICTION STIR PROCESSING: Microstructure & Mechanical Behaviour

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 ▲]

Iron production in the region of Liège in the Middle Age: Contribution of slag inclusions analyses

Conference (2009, February)

Relative Influence of Aluminium and Silicon on the Kinetics of Bainite Formation from Intercritical Austenite

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 ▲]