Untersuchung zum Walzverhalten von gegossenen, partikelverstärkten Metallmatrix-Verbunden
Final Report Abstract
Sheets and strips produced from wrought aluminium matrix composites with hard phasereinforcements are interesting for engineering constructions and advanced packaging material for high technology thermal management. For composite preparation, using particulates as reinforcement and liquid phase processing, e.g. stir-casting, is the most economical process. Proper design of both, casting and rolling procedures is to result in the desirable product properties. Therefore in this work, three commercial wrought Al alloys, Al 6061 and Al 6082 and Al 7108, are investigated as matrix materials. Two different SiC particulate sizes of 15 μm and 8 μm are considered with volume fractions “Vf ” of 0 - 30%. For successful insertion of particles into the melt, better particles / matrix wetting and particles distribution, minimized SiC / Al reaction, optimum casting procedures and materials pre-treatment have been applied. Thermo-mechanical simulation indicates that step rolling at 450°C using a rate of 1 s-1 rate represents suitable forming conditions. An intermediate heat treatment period of 10 s to 1 h between two successive rolling steps is defined as a function of the reduced thickness. Generally, the quality of the rolled product improved with improving casting quality. Successive hot rolling resulted in decreasing void and the agglomeration clusters and hence enhanced mechanical properties are achieved. Additionally, the thermo-mechanical simulator is used to characterize the materials for their compressive flow behaviour in terms of flow stress, E-modulus and the strain hardening coefficient. The dependence of these parameters on the temperature and SiC-size and - volume fraction is defined. Furthermore, two heat treatments are applied on the as rolled PMMCs, namely annealing- and T6-treatments. The mechanical properties at room temperature are determined for the as rolled, annealed and T6-treated materials by tensile test. The results can contribute to the manufacturing of Al-PMMCs rolled sheets and their applications. Forming limit diagram (FLD) is to be constructed for the Al/SiC systems at different SiC contents and particle sizes, particularly for the annealed materials. Simulation of the material flow and the corresponding stress on the particle is an interesting aspect for subsequent research. Further improvement of the cast composite quality is still under consideration. Application of direct strip casting (DSC) of stirred Al-SiC slurry can be considered for developing better cast composite quality and less following rolling steps, thus being more economical. The equipment, which is available at IMET is currently being used for magnesium casting, and could be modified to suit casting of Al-PMMCs.
Publications
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"Sequential Rolling and Heat Treatment of Stir Cast Aluminium Silicon Carbide Composite”, Euro ECAA 2011, 5-7 Oct. 2011, Bremen, Germany
A. El-Sabbagh, M. Soliman, M. Taha, H. Palkowski
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“Experimental Investigation on Rolled Stir Cast Composites of Aluminium 6061 and 6082 Alloys with Silicon Carbide Particulates”, Processing, Performance and Failure Analysis of Engin. Materials, Nov. 14-17, 2011, Luxor, Egypt
Ahmed M. El-Sabbagh, Mohamed A. Taha, Heinz Palkowski
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Hot rolling behaviour of stir-cast Al 6061 and Al 6082 alloys – SiC fine particulates reinforced composites, Journal of Materials Processing Technology, 212 (2012), pp. 497– 508
A. El-Sabbagh, M. Soliman, M. Taha and H. Palkowski
