Chapter 42 Analysis of Interfaces in AA7075/ Recycled WC Particles Composites Produced via Liquid Route Marina Ferraz Viana and Maria Helena Robert Abstract Casting of composites is a simple and low cost route to produce composites, which allows numerous possibilities in terms of reinforcement location in the cast part and high geometry flexibility of the products. However, interfaces between reinforcement and metal depend on the behaviour of the particles in liquid metal during processing. The work investigates the effects of parameters such as temperature and time of contact between WC particles and liquid aluminium, and reinforcement content, in the production of cast AA7075/WC composites. WC particles coming from recycled cutting tools are used as reinforcement for aluminium alloys AA 7075, widely used in aeronautical domain. Reinforcement contents of 15 and 30 wt %, temperatures of 700, 740 and 780C, and contact time of 1, 2, 3 and 4 h were the values of the investigated variables. Microstructure of cast composites produced under these conditions were analysed by OM, SEM and EDS microanalysis. A reaction layer was found in the interface between metal and WC, with composition and micro constituents depending on the studied parameters. A mechanism of formation of the reaction layer is proposed. Keywords Composites · Aluminium · WC particles · Casting · Interface 42.1 Introduction Casting of composites is one simple and low cost way of producing metal-matrix composites reinforced with ceramic particles. Such processes are not only flexible in terms of part geometry, reinforcement type and location in the product, but also favour adhesion between matrix and reinforcement, when compared to solid state processes. Generally, it is possible to incorporate up to 30% of particles by those methods. Depending on the nature of matrix and reinforcement materials, chemical reactions may occur while the reinforcement is in contact with the liquid metal – this is favoured by high temperatures and long contact times, and may be desirable when it leads to the formation of in situ reinforcement phases or chemical bonding between the matrix and the reinforcement [1–6]. The interface between matrix and reinforcement is a function of the nature of both materials and the behaviour of particles during processing [1, 2, 7]. In the specific case of particle reinforced composites produced by casting techniques, the ability of the liquid metal to wet the surface of the reinforcement and the chemical affinity between both materials are key in their integration [1, 7, 8]. Generally, ceramic phases whose chemical bonds have a strong metallic character, as WC and the TiC are more easily wet by the liquid metal [7, 8]. Poor adhesion between reinforcing particles and matrix hinders interface quality and is a common issue in the production of such composites. Low wettability and lack of chemical affinity are generally blamed as the root causes of such problems [1, 4, 8–10]. On the other hand, it has been observed that cemented carbides, such as the ones used for producing cutting tools, are not only exceptionally hard and wear resistant [11, 12] but also have great chemical affinity with aluminium [8, 13, 14]. Thus, those are an interesting reinforcement material for wear resistant aluminium composites. Therefore, the aim of this work is to investigate the effects of parameters such as temperature, time of contact between liquid matrix and reinforcement and amount of reinforcement in the casting of aluminium matrix WC composites. M. F. Viana University of Campinas, School of Mechanical Engineering, Department of Materials and Manufacturig Engineering, Cidade Universitária, Barão Geraldo, Campinas, SP, Brazil M. H. Robert ( ) University of Campinas, Mechanical Engineering Faculty, Campinas, Brazil e-mail: helena@fem.unicamp.br © The Society for Experimental Mechanics, Inc. 2019 P. R. Thakre et al. (eds.), Mechanics of Composite, Hybrid and Multifunctional Materials, Volume 5, Conference Proceedings of the Society for Experimental Mechanics Series, https://doi.org/10.1007/978-3-319-95510-0_42 311
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