Changes in properties of aluminium matrix composite reinforced with SiC particles after multiple remelting

Following the EU environmental regulations (e.g. Directive 2000/53/EC of the European Parliament and of the Council of 18 September 2000 on end-of-life vehicles), there is a need for information regarding the behaviour of materials during different recycling treatments before the introduction of new products in industry. This research is devoted to the scientific and practical aspects of recycling of cast metal matrix composites (MMCs) that among other applications, are used in car vehicles in steadily increasing numbers. The analysis of conditions for MMC remelting and the effects of number of remelting cycles on selected physical and mechanical properties has been performed on aluminium matrix composite (A359 aluminium alloy reinforced with 10 vol.%SiC particulates). After each remelting operation, structural characterisation as well as the measurements of electrical conductivity, density, hardness (HBW), ultimate strength (R(m)), Young's modulus (E), elongation (A), yield limit (R(0.2)), elastic limit (R(0.05)) and wear resistance were carried out and compared with investigations of as-received composite material. For multiple remelting (up to nine remelts), structural observations by optical microscopy did not demonstrate any remarkable changes, compared to as-received composite. Moreover, there was no significant degradation of SiC particles. At the same time, a continuous decrease in utility properties of composite material with increasing number of remelting cycles was recorded, showing their tolerable reduction after the ninth remelting.