Papers by Keyword: Rheo-Casting

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Authors: J. Wannasin, R. Andy Martinez, Merton C. Flemings
Abstract: Various processing methods exist for applying agitation to a molten metal during solidification to obtain metal slurries suitable for semi-solid metal processing. . In this paper, a new technique to achieve semi-solid metal structure using agitation during solidification is reported. The technique applies a new medium and means to efficiently create semi-solid metal structures. The results of a systematic study showing the feasibility and the necessary conditions to achieve the structure are discussed.
Authors: E. Evangelista, Marcello Cabibbo, S. Spigarelli, C. Scalabroni, Luigi Balloni, R. Villa, G.L. Chiarmetta
Abstract: The tensile properties and the microstructure of an Al-7%Si-0.6%Mg-0.5%Cu rheo-cast component were investigated. The material underwent a T5 treatment, consisting in ageing at 160, 175 and 190°C for durations ranging from 0.5 to 48h. Tensile testing indicated that the T5 treatment resulted in a relatively good level of strength and in a comparatively low ductility. In order to improve ductility, maintaining as low as possible the cost of the final component, a single solution treatment at 500°C for 4h was subsequently applied. The tensile strength and ductility of the solution treated and aged material were higher than in the T5 condition. These differences were attributed to the microstructural evolution occurring during exposure at 500°C, in particular to the spheroidization of eutectic-Si and to a more homogeneous distribution of the precipitates.
Authors: Gonasagren Govender, L. Ivanchev, N. Jahajeeah, R Bëan
Abstract: The Council for Science and Industrial Research has developed and patented a rheocasting process. The process involves the preparation of semi-solid slurries from liquid metal, by controlled cooling and MHD stirring using induction coils. An industrial prototype was designed and built to test the system in an industrial environment. A semi-solid high pressure die casting cell was set up with an industrial partner and the system was tested under normal production conditions. The production cell consisted of the CSIR rheocasting system, a six axis robot, dosing furnace and 400 ton H-400SC shot controlled Bühler HPDC machine. An engine mounting bracket originally designed for liquid HPDC was redesigned for SSM forming (casting) taking into consideration the flow and thermal behaviour of semi-solid casting process, the function of the component and the required mechanical properties. Although a full production run was not completed due to an ancillary equipment failure, sufficient castings were produced to perform preliminary evaluation of the components. The processing parameters used were, die temperature of 250°C, SSM casting temperature of 580°C ±1Cº and a piston injection velocity of 0.13 m/s. Initial evaluation showed evidence of casting defects due to a combination of factors: die design/manufacture, casting parameters and poor foundry practice. From the mechanical tests it was evident that if the die design, casting parameters and foundry practice are optimized components with adequate mechanical properties can be reliably produced.
Authors: Ryoji Nakamura, T. Asai, Hisaki Watari, Shinji Kumai
Abstract: Rheo-casting of 4045 aluminum alloy bar was operated using an unequal diameter twin roll caster and a cooling slope. The semisolid slurry was made by the cooling slope. The thickness of the bar was 12 mm and width was 100mm. The casting speed was 1m/min. Quantity of the melt poured on the cooling slope was important to make sound bar. The primary crystal became spherical, and its size was about 40μm.
Authors: Roger Sauermann, Bernd Friedrich, T. Grimmig, M. Buenck, Andreas Bührig-Polaczek
Abstract: This investigation describes the development and evaluation of thixoformable alloys on Al-Li-Mg basis in the scope of the collaborative research center SFB 289 at RWTH Aachen University. Scandium and zirconium was added to Al-Li2.1-Mg5.5 (A1420) with the aid of DoE (Design of Experiments) and precursor billets were manufactured by pressure induction melting (PIM). To evaluate the thixoformability of the synthesized alloys high-quality semi solid processed demonstrators were manufactured by the Rheo-Container-Process. Subsequent heat treatment raised the mechanical properties to maximum values of tensile strength of 432MPa, yield strength of 220MPa and an elongation of 13%. The RCP-Process was designed for the special requirements of this high reactive alloy. The paper will present extraordinary benefits in terms of properties and process simpleness for the semi-solid processing of Al-Li alloys.
Authors: Chun Pyo Hong, J.M. Kim
Abstract: Among semisolid forming processes, increasing attention has now been focused on the commercialization of casting processes based on rheocasting in aluminum automotive casting fields because of its advantages compared to thixoforming, in regards to the efficiency in cost and productivity, and mechanical properties. In this paper, an advanced rheocasting process is introduced, which has been developed recently at Yonsei University and is now on the way to practical uses in Korea and Japan. In this method, the semisolid slurry production is based on the nucleation method, in which the nuclei of primary  phase formed in the melt are prevented to grow into dendrites, instead they grow into fine globular particles to become semisolid slurry having rheological behavior. By increasing the number of nuclei, very fine and uniform globular microstructures can be obtained, resulting in an increase of mechanical properties. Recently, commercial rheo-diecasting machines based on the present method have been developed, and now are being used in manufacturing aluminum automotive casting parts. Furthermore, the present method is now being tested to investigate its possibility of application to various alloy systems.
Authors: Shae K. Kim, Young Chul Lee
Abstract: Novel In-mold rheocasting, which can satisfy all the development direction of rheocasting, has been successfully developed. In-mold rheocasting requires no additional processing equipment except diecasting machine, no grain refinement procedure and no additional cycling time to produce slurry-on-demand. Process concept of In-mold rheocasting is simply based on the paradigm shift from HOW to WHERE for producing slurry-on-demand and the shift from obtaining PERFECT solid globules to casting OPTIMUM products. Optimum external field can be generated in mold, that is, in die cavity exactly around biscuit. This paper will demonstrate the possibility to achieve slurry-on-demand by In-mold rheocasting and some commercial products.
Authors: J. Wannasin, S. Junudom, T. Rattanochaikul, Merton C. Flemings
Abstract: A simple and efficient rheocasting process that has recently been invented is being developed for aluminum die casting applications. The process called Gas Induced Semi-Solid (GISS) utilizes the combination of local rapid heat extraction and agitation achieved by the injection of fine gas bubbles through a graphite diffuser to create semi-solid slurry. In the GISS process, the die casting machine and the process cycle remain little changed from those of conventional die casting. The GISS unit creates a low solid fraction of semi-solid slurry in the ladle during the ladle transfer to the shot sleeve. The semi-solid slurry is then poured directly into the shot sleeve. This paper presents the detailed description of the process. The results of the semi-solid die casting experiments with ADC10 alloy using the GISS process are also reported and discussed.
Authors: Antonio Forn, Maite T. Baile, Enric Martín, Elisa Rupérez
Abstract: This paper describes the heat treatment effect on the eutectic silicon evolution in the A357 alloy, obtained by semisolid forming process (SSM). The coarsening rate of the silicon was determined by Image Analysis Technique in specimens from rheocasting ingots and thixocasting components. The study was realized in the temperature range from 450 to 550°C by applying heating times between 1 and 24 hours. The results show that during the heat treatment the coarsening and sphereodization of the silicon particles is produced and the fragmentation stages, which are observed in conventional alloys, do not appear. Kinetic silicon growth has been adjusted to the Oswald’s ripening equation.
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