Selection of recycling medium for saturated metal-matrix cast composites
Dorota Nagolska, Michał Szweycer Politechnika Poznańska, Instytut Technologii Materiałów, ul. Piotrowo 3, 61-138 Poznań
Annals 3 No. 6, 2003 pages 101-105
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abstract One of the ways of recycling of saturated metal-matrix cast composites, as opposed to the other types of casted metal composites, consists in separation of its components. The paper presents the difference between the systems used for recycling and saturating of these composites (Fig. 1). Theoretical analysis enabled formulating of a condition (2) (Fig. 2) to be met by the medium in order to allow spontaneous course of the process of metallic matrix outflow from reinforcement pores in the threephase system including metal matrix-reinforcement-single-phase medium. This means that separation of the components in the air atmosphere is unfeasible for most of the composites. However, this becomes possible in another medium. Therefore, the requirements to be met by the medium were defined, as to ensure good quality of recovered matrix metal and low cost of the process. The requirements are as follows: – reinforcement wetting angle by the matrix metal in the medium - near 180º; – melting temperature of the medium possibly approximating the melting temperature of the composite matrix metal; – density of the medium lower than that of the liquid metal; – low reactivity of the medium with the matrix metal and composite reinforcement, as well as with refractory materials used for purposes of the recycling process; – no tendency for decomposition and evaporation of the medium under the recycling conditions; – easy separation of the medium from the matrix metal and reinforcing material; – low price as compared to that of the matrix metal. The above specified principles of the medium selection were experimentally verified on the example of a selected composite (AlSi11-SIBRAL) and the medium composed of the mixture of melted salts: 50% NaCl and 50% KCl. Moreover, the results obtained allow to state that the recycling process meets the conditions enabling its application in the industry. Key words: saturated metal-matrix cast composites, recycling