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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 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 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 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 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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