References of "Rassili, Ahmed"
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See detailTooling Materials and Solutions for Thixoforming of Steel
Rassili, Ahmed ULg; Falzone, Salvatore ULg; Lecomte-Beckers, Jacqueline ULg

in Solid State Phenomena (2013), 192-193

The aim of this work is to evaluate the thermal and mechanical loadings applied to the tools during steel thixoforming process in order to determine appropriate tool materials and solutions. This ... [more ▼]

The aim of this work is to evaluate the thermal and mechanical loadings applied to the tools during steel thixoforming process in order to determine appropriate tool materials and solutions. This evaluation was realized thanks to experimental trials and to the finite elements simulations. The effect of these loadings on the tool’s failure modes are highlighted and compared to the ones observed in classical forming processes. Beyond this, the failure modes of different tool materials and solutions are presented. The tested materials are hot-working tool steels. Other possibilities and tool coating or surface treatments are discussed as well. [less ▲]

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See detailCharacterization of thixoforming process of 100Cr6 steel
Solek, Krzysztof; Rassili, Ahmed ULg; Pierret, Jean-Christophe ULg et al

in Transactions of nonferrous metals society of China (2010), 20(special 3), 916-920

The main goal of this work is an analysis of the semi-industrial process of steel thixoforming. The process was carried out using industrial equipment. This equipment consists of a heating device ... [more ▼]

The main goal of this work is an analysis of the semi-industrial process of steel thixoforming. The process was carried out using industrial equipment. This equipment consists of a heating device, industrial robots and a hydraulic press. The globular microstructure ensuring thixotropic properties was obtained using the SIMA method. It is one of the simpler and cheaper methods which could be easy applied in case of steel alloys. In this work the hot forged rods, commercially produced from 100Cr6 steel, were used. The first part of the work concerned the determination of the proper temperature range, for thixoforming of 100Cr6 steel. Next, some heating tests were carried out in order to obtain as uniform temperature distribution as possible. Heating process was executed using inductive heating. Microstructure analysis of heated samples reveals globular particles surrounded by liquid phase. Next the thixoforming process was carried out using closed-die forming technique. Completely filled die cavity and good microstructure of the part show that applied process parameters were properly selected. [less ▲]

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See detailStability of steel thixoforging process
Pierret, Jean-Christophe ULg; Rassili, Ahmed ULg; Vaneetveld, Grégory ULg et al

in Transactions of Nonferrous Metals Society of China (2010), 20(Special 3), 937-942

Whereas thixoforming of aluminum and other low melting point alloys is now an industrial reality, thixoforming of high melting point alloys, as steel, is still at the research level. High temperature ... [more ▼]

Whereas thixoforming of aluminum and other low melting point alloys is now an industrial reality, thixoforming of high melting point alloys, as steel, is still at the research level. High temperature issues, die wearing and production rate are problems that must be solved and are more and more investigated. This work focus on the study of a thixoforming line stability in the aim of industrialization of the process. The line is fully automated in order to maximize the repeatability of the experiments. Studied parameters are the heating cycle, the slug temperature, the tool temperature and the forming speed. For each of them we will give an order of magnitude of the expected variations in a steady-state process as well as the effects of these variations on the process itself (forming load and parts quality). Three different tools, and so three slugs and parts geometries, have been used in the experiments and are presented. Some mathematical simulations have been realized on the finite elements code Forge2008© with a semi-solid constitutive law and are also compared to the experiments. So the capacity of the model to represent the process stability is discussed as well. [less ▲]

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See detailX38CrMoV5 hot-work tool steel as tool material for thixoforging of steel, numerical and experimental evaluation
Rassili, Ahmed ULg; Pierret, Jean-Christophe ULg; Vaneetveld, Grégory ULg et al

in Transactions of Nonferrous Metals Society of China (2010), 20(Special 3), 713-718

Whereas thixoforming of low melting point alloys as aluminum or magnesium is now an industrial reality, thixoforming of high melting point alloys, as steel, is still at the research level. High working ... [more ▼]

Whereas thixoforming of low melting point alloys as aluminum or magnesium is now an industrial reality, thixoforming of high melting point alloys, as steel, is still at the research level. High working temperature, die wearing and production rate are problems that must be solved and are under investigation. The aim of this work is to evaluate the thermal and mechanical loadings applied to the tools during the steel thixoforging process in order to determine if classical hot-work tool steel could be an appropriate tool material. This evaluation has been realized thanks to experimental trials and to simulations on the finite elements code Forge2008©. The effect of the loadings on the tool’s failure modes are highlighted and compared to the ones observed in classical hot forging. Beyond this, the failure modes of hot-work tool steel, the X38CrMoV5 or H11, is presented. [less ▲]

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See detailConception of tooling adapted to the thixoforging of high solid fraction hot-crack-sensitive aluminium alloys
Vaneetveld, Grégory ULg; Rassili, Ahmed ULg; Pierret, Jean-Christophe ULg et al

in Transactions of Nonferrous Metals Society of China (2010), 20(9), 1712-1718

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<fs<1), which involves the processing of alloys in the semi-solid state. Tooling has to be adapted to this particular ... [more ▼]

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<fs<1), which involves the processing of alloys in the semi-solid state. Tooling has to be adapted to this particular process to benefit of shear thinning and thixotropic behaviour of such semisolid material. Tooling parameters, as the forming speed and tool temperature, have to be accurately controlled because of their influence on thermal exchanges between material flow and tool. These thermal exchanges influence the high-cracking tendency and the rheology of the semisolid material during forming which affect parts properties. This paper shows, thanks to extrusion tests, how thermal exchanges influence surface quality of thixoforged parts made in 7075 aluminium alloys at high solid fraction by modifying process parameters like forming speed, tool temperature and tool thermal protector. A direct application is the evaluation of surface quality of thixoforged thin wall parts made in 7075 aluminium alloys. [less ▲]

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See detailThixoextrusion of A357 aluminium alloy
Forn, Antonio; Rassili, Ahmed ULg; Vaneetveld, Grégory ULg et al

in Transactions of Nonferrous Metals Society of China (2010)

The aim of this work is to attempt the application of A357 Al-Si-Mg cast alloy in the thixoextrusion process, evaluating the different parameters effect. Thixoextrusion offers several advantages compared ... [more ▼]

The aim of this work is to attempt the application of A357 Al-Si-Mg cast alloy in the thixoextrusion process, evaluating the different parameters effect. Thixoextrusion offers several advantages compared to traditional hot-extrusion such as lower pressure, minor friction forces, higher material fluidity, longer tool life, etc. This type of semi-solid process requires high solid fractions (0.5<fs<1). Aluminium alloy A357 is a commercial cast alloy characterized by high strength, ductility and corrosion resistance. It is commonly used for cast production of automotive components and it is also suitable for semi-solid process, due to its ample range of solidification. A357 aluminium alloy has been used as a feedstock for thixoextrusion in order to investigate thixoformability at high solid fraction. Alloys with high solid fraction are less sensitive to temperature drops and allow laminar flow at higher speeds. To know the parameters that improve the mechanical properties of thixoextruded parts, some extrusion tests at constant speeds have been carried out. The results were used as the main criteria for assessing the thixoforming viability of the A357 alloy. [less ▲]

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See detailFriction coefficients evaluation for steel thixoforging
Pierret, Jean-Christophe ULg; Rassili, Ahmed ULg; Vaneetveld, Grégory ULg et al

in Proceedings of The 13th Esaform Conference on Material Forming (2010) - semi-solid processing (2010)

Since the first works on thixoforming, lot of studies have been performed all over the world and the behaviour of the globular semi-solid slurry is now quite well understood. This knowledge had lead to an ... [more ▼]

Since the first works on thixoforming, lot of studies have been performed all over the world and the behaviour of the globular semi-solid slurry is now quite well understood. This knowledge had lead to an industrialisation of the technology for low melting point alloys as aluminium or magnesium. For high melting point alloys as steel, this industrialisation is still a wish but seems closer each year. In the aim of this development of the process, it is important to be able to accurately represent the behaviour of the slurry during thixoforming. In this goal, lot of constitutive models has been proposed during the last years. However, until now there isn’t any study about the friction in the case of thixoforming. This knowledge is needed as friction has an important effect on the flow of the slurry during the shaping. The aim of this work is so to propose a quantification of the friction coefficients for the thixoforming technology thanks to experiments on a dedicated tool and comparison with simulations run on the finite elements code Forge2008©. The friction law is a Coulomb limited Tresca one. [less ▲]

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See detailValidation of a one-phase thermomechanical model for thixoforming of steel by comparison between numerical and experimental results on two semi-solid extrusion tests
Koeune, Roxane ULg; Rassili, Ahmed ULg; Pierret, Jean-Christophe ULg et al

in Yonglin, Kang (Ed.) 11th International Conference on Semi-Solid Processing of Alloys and Composites (2010)

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See detailBenefits of thixoforging hot-crack-sensitive aluminium alloys at high solid fraction
Vaneetveld, Grégory ULg; Rassili, Ahmed ULg; Pierret, Jean-Christophe ULg et al

in International Journal of Material Forming (2010), 2

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See detailIdentification of Suitable Steels : Chapter 3
Rassili, Ahmed ULg; Robelet, Marc; Lecomte-Beckers, Jacqueline ULg

in Rassili, Ahmed; Atkinson, Helen (Eds.) Thixoforming steels (2010)

A range of steels is normally industrially available. The question here is to identify those which are most suitable for thixoforming and to adapt the composition to maximise the chances of success. In ... [more ▼]

A range of steels is normally industrially available. The question here is to identify those which are most suitable for thixoforming and to adapt the composition to maximise the chances of success. In this chapter, the influence of alloying elements on the solidus and liquidus temperatures and on the thixoforming window is identified. Some case studies for low and medium carbon steels are given. Thermophysical properties are important for processing and some information is given on the characterisation of these. High carbon chromium steels are another class of steels which are potentially of use. The effect of modifying the Mn and Si content of such steels is described. Thermodynamic prediction is a powerful tool and results from such studies are given. There is then an analysis of the influence of micro-segregation, which results from the original hot rolling, and its interaction with heating speed during the reheating for thixoforming. [less ▲]

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See detailInfluence of the chemical composition on the thixoformability of steels
Pierret, Jean-Christophe ULg; Rassili, Ahmed ULg; Vaneetveld, Grégory ULg et al

in International Journal of Material Forming (2009)

This work deals with the qualification of a variety of steels for their shaping by the thixoforging process. This technology requires setting up a globular microstructure inside the material during ... [more ▼]

This work deals with the qualification of a variety of steels for their shaping by the thixoforging process. This technology requires setting up a globular microstructure inside the material during reheating to a temperature between the solidus and liquidus. As the evolution of the liquid fraction is strongly connected to the steel composition, it is useful to understand how low carbon steel could be alloyed and still thixoformable. The most critical parameter for this is the carbon content. In this study, a theoretical analysis of the phase evolution during the reheating has been performed on the MT Data software to investigate the influence of alloying elements. These first results have been confirmed by Differential Thermal Analysis and by inductive heating experiments on steel slugs. Finally, some parts have been shaped using a thixoforming tool mounted on a hydraulic press. Micrographs of reheated slugs as well as of actual parts are also presented in this paper. [less ▲]

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See detailBenefits of thixoforging hot-crack-sensitive aluminium alloys at high solid fraction
Vaneetveld, Grégory ULg; Rassili, Ahmed ULg; Pierret, Jean-Christophe ULg et al

in Proceedings of The 13th Esaform Conference on Material Forming (2010) - semi-solid processing (2009)

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<fs<1), which involves the processing of alloys in the semi-solid state. The use of semi-solid material with globular ... [more ▼]

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<fs<1), which involves the processing of alloys in the semi-solid state. The use of semi-solid material with globular microstructure helps to decrease forming load. But the introduction of a liquid phase in the material is a source of defects that limit mechanical properties of thixoforged parts. One of these defects is the hot cracking for some hot crack-sensitive wrought aluminium alloys. Hot cracking occurs because of strain and deformation during last step of solidification. This paper shows how thixoforging process helps to lower hot cracking tendency without modification of the alloy composition by decreasing strain and deformation due to shrinkage. Different experimental tests by extrusion of 7075 aluminium alloys are used. [less ▲]

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See detailElectron backscattered diffraction of aluminium alloy 7075 samples after heat treatment
Vaneetveld, Grégory ULg; Rassili, Ahmed ULg; Lecomte-Beckers, Jacqueline ULg et al

in International Journal of Material Forming (2009)

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<fs<1), which involves the processing of alloys in the semi-solid state. The use of semi-solid material with globular ... [more ▼]

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<fs<1), which involves the processing of alloys in the semi-solid state. The use of semi-solid material with globular microstructure helps to decrease forming load. But the introduction of a liquid phase in the material is a source of defects that limit mechanical properties of thixoforged parts. One of these defects is the hot cracking for some hot crack-sensitive wrought aluminium alloys. Hot cracking occurs because of strain and deformation during last step of solidification. This paper shows how thixoforging process should help to lower hot cracking tendency without modification of the alloy composition by decreasing strain and deformation due to shrinkage. Different experimental tests by extrusion of 7075 aluminium alloys are used. [less ▲]

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See detailImprovement in Thixoforging of 7075 Aluminium Alloys at High Solid Fraction
Vaneetveld, Grégory ULg; Rassili, Ahmed ULg; Pierret, Jean-Christophe ULg et al

in Solid State Phenomena (2008), 141-143

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.5<1). 7075 aluminium alloys have been used as a feedstock for thixoforging in order to investigate thixoformability of a ... [more ▼]

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.5<1). 7075 aluminium alloys have been used as a feedstock for thixoforging in order to investigate thixoformability of a high performance aluminium alloy at high solid fraction. Higher solid fraction of 7075 alloy is less sensitive to temperature, avoids metal splash at high speed and allows laminar flow at high speed. Hot tool combined with lubricant tool coating are used to slow down the solidification rate of the high solid fraction metal by decreasing thermal exchanges with the tool. Improved thermal and forming parameters [1-2] will be applied to produce an automotive component by thixoforging and mechanical properties have been measured from tensile samples. High mechanical properties are obtained after T6 thermal treatment. [less ▲]

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See detailInfluence of parameters during induction heating cycle of 7075 aluminium alloys with RAP process
Vaneetveld, Grégory ULg; Rassili, Ahmed ULg; Atkinson, Helen

in Solid State Phenomena (2008), 141-143

Thixoforging involves shaping alloys with a globular microstructure in the semi-solid state. To reach this kind of material, the Recrystallisation and Partial Melting (RAP) process can be used to obtain a ... [more ▼]

Thixoforging involves shaping alloys with a globular microstructure in the semi-solid state. To reach this kind of material, the Recrystallisation and Partial Melting (RAP) process can be used to obtain a globular microstructure from extruded material with liquid penetrating the recrystallised boundaries. Induction heating is used to apply the RAP process to slugs. One of the benefits of using this method of heating is the fast heating rate (20°C/s). This paper will help to improve heating parameters by showing their influence on 7075 aluminium alloy recrystallisation. These parameters are the heating rate; heating frequencies-power; presence or not of protective gas; position of the slug in the inductor; energy stored inside the slug; oxide layer on the slug side; chamfer of the slug upper corner. [less ▲]

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See detailExtrusion tests of 7075 aluminium alloy at high solid fraction
Vaneetveld, Grégory ULg; Rassili, Ahmed ULg; Pierret, Jean-Christophe ULg et al

in International Journal of Material Forming (2008), 1(1), 1019-1022

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.5<fs<1). 7075 aluminium alloy has been used as a feedstock for thixoforging in order to investigate thixoformability of a ... [more ▼]

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.5<fs<1). 7075 aluminium alloy has been used as a feedstock for thixoforging in order to investigate thixoformability of a high performance aluminium alloy at high solid fraction. Higher solid fraction of 7075 alloy is less sensitive to a drop in temperature, avoids metal splash at high speed, allows laminar flow at high speed. Hot tool is used to slow down the solidification rate of the high solid fraction metal by decreasing thermal exchanges. To determine the best parameters to achieve maximum mechanical properties in thixoforging of 7075 aluminum alloy, we need to consider the impact of some parameters such as tool temperature, shear rate. For this, we use extrusion tests with constant speed [1] where these parameters are known. The result of this study is that each parameter has its level of impact on the thixoforging: the temperature of the tool and the deformation rate shouldn't be high to avoid cracks. Thermal exchanges between the material flow and the tool have to be reduced to avoid high solidification rate [2]. [less ▲]

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See detailSteel thixoforming, influence of forming parameters on the microstructure
Pierret, Jean-Christophe ULg; Rassili, Ahmed ULg; Vaneetveld, Grégory ULg et al

in International Journal of Material Forming (2008), 1(1), 1011-1014

Forming of parts in the semi-solid state is quite a complex process, especially for high melting point alloys such as steel. A reason for this complexity is the amount of parameters involved in the ... [more ▼]

Forming of parts in the semi-solid state is quite a complex process, especially for high melting point alloys such as steel. A reason for this complexity is the amount of parameters involved in the process. Among these we could quote liquid fraction, shear rate, shape factor, contiguity, tool temperature, agglomeration level, heating rate, protecting gas, temperature distribution, lubricant. Of course all of these parameters don’t have the same order of importance. In this paper we show the influence of a set of chosen parameters and we highlight their effects on the microstructure and so, on the deformation behavior. The studied parameters are the heating conditions, the tool temperature, the part temperature, the thermal exchanges between the part and the dies and the forming rate. [less ▲]

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See detailRobustness of a thixoforming production line
Pierret, Jean-Christophe ULg; Rassili, Ahmed ULg; Vaneetveld, Grégory ULg et al

in Solid State Phenomena (2008), 141-143

The development of the thixoforming process made great progress since its beginning. But whereas thixoforming of aluminium and other low melting point alloys is now an industrial reality, thixoforming of ... [more ▼]

The development of the thixoforming process made great progress since its beginning. But whereas thixoforming of aluminium and other low melting point alloys is now an industrial reality, thixoforming of high melting point alloys, as steel, is still at the research level. High temperature issues, die wearing and production rate are problems that must be solved and are more and more investigated. This work is a study of the robustness of a complete thixoforming unit dealing with steel. This flexible unit allows parts of various shapes be formed in conditions close to industrial ones. The study focus on the heating strategy, heat exchanges between the slug and the tool, the feeding and the cycle time. In this work, modelling has been used to simulate heating and feeding. In parallel, experiments have been made to obtain the needed parameters, to validate the modelling and to evaluate the capacities of such a line. [less ▲]

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See detailTHIXOFORMAGE DES METAUX: Mise en forme rapide de pièces fonctionelles “near-net-shape” à design complexe dignes du forgeage!
Rassili, Ahmed ULg; Vaneetveld, Grégory ULg; Pierret, Jean-Christophe ULg et al

Poster (2007, June 14)

Présentation du laboratoire de thixofomage de métaux.

Detailed reference viewed: 86 (3 ULg)