The attempts of recycling of composites with saturated graphite reinforced and an OT7-alloy matrix
Dorota Nagolska, Michał Szweycer Politechnika Poznańska, Instytut Technologii Materiałów, ul. Piotrowo 3, 61-138 Poznań
Quarterly No. 2, 2006 pages 55-59
DOI:
keywords: metal-matrix composites, recycling
abstract Recycling of metal composites with saturated reinforcement by separation of the components depends, among others, on surface properties of the reinforcement - liquid matrix - environment system, and the structure of composite reinforcement. The paper presents the results of the analysis of conditions of liquid matrix metal outflow from the reinforcement pores (Fig. 3). It was found that due to complicated structure of the composite reinforcement pores the values of the pressure acting on the matrix metal vary (Fig. 4). This might be conducive to local stoppage of the process of liquid matrix outflow from the composite reinforcement (Fig. 5). Mathematical description of the matrix geometry is very difficult or sometimes even impossible. In consequence, the course of metal matrix outflow from two reinforcement profiles made of the same material of clearly different structures were investigated experimentally. For the investigation purposes a composite of the lead - antimony alloy (OT7) was selected, reinforced with graphite profiles in the form of a sinter and pressed fibers (Table 1 and Fig. 6), of different shapes and pore sizes. The composites have been recycled in two surroundings: air and a mixture of molten salts (Table 2). In case of the graphite sinter reinforced composite recycled in air the yield was insignificant, barely exceeding 5 per cent. On the other hand, in the case of molten salts the yield of 35 per cent was achieved. The metal yield obtained from a graphite fiber reinforced composite was also small, amounting to 9 per cent, reaching 90 per cent for the case of the environment of molten was. The results so obtained confirmed that the process of liquid metal matrix outflow from the reinforcement pores is affected by the surface properties. Results of the calculation and the research indicate that the recycling process is also highly affected by the reinforcement structure. In case of identical surface properties of the system and different reinforcement structures the differences in metal yield values are significant (Fig. 7). The analysis shows that the reinforcement structure is characterized by the angels of flare of the capillaries α, the diameters d1 and d2, and ratios of these values. The quantitative carried out in the present paper is insufficient for purposes of determining the effect of variability of the structure parameters on the metal yield. In order to enable determining influence of these parameters on the metal yield a qualitative analysis must be performed that may be difficult or even unfeasible because of impossibility of mathematical description of the structure. Nevertheless, the experiments related to the OT7 alloy - graphite reinforcement composite enabled answering the question which of the reinforcement types subject to the study has better structure from the recycling point of view. They show that parameters of the reinforcement structure in the form of fibers are more advantageous than for sinter reinforcement.