Influence of multiple remelting of particulate reinforced cast aluminum composites on their properties and structure

The work presents the basic aspects of recycling of metal composites, cast on the example of aluminum composites, as well as the problems and limitations which they involve. We examined the usefulness of the method of direct remelting for the recycling of commercial composites, with the aluminum matrix, reinforced with silicon carbide particles. The tests included a group of DURALCAN composites with a variable content of reinforcement (F3S.10S, F3S.20S and F3S.30S) and – as the reference material – the A359 matrix alloy. The specific simulation of recycling was performed by way of a nine-fold remelting of the examined material and by drawing samples from each melt. We directed the tests of a range of physical, thermophysical, strength and tribological properties, also determining the metallographic characteristics. A multiple and excessive remelting of composites, by lowering the level of properties, limits their application abilities in „responsible” products, and yet the optimal number of remeltings makes it possible to apply them in full-value elements of machines and devices. A significant role in this process is played by the fulfillment of the technological regimes of multiple remelting. A detailed analysis of the mutual quantitative dependences in the relation microstructure-utilitarian properties of the composites, revealing those microstructure parameters which determine the final level of their properties was presented. On the example of a composite brake disk, cast after the fourth remelting of the F3S.20S, it was stated that the applied method of direct remelting can be recommended for the application in product recycling.