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1 Journal of Achievements in Materials and Manufacturing Engineering

1 2012

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Processing and properties of AA7075/ porous SiO2-MgO-Al2-O3- composite

Robert M. H., Jorge A. F.

Journal of Achievements in Materials and Manufacturing Engineering

2012

Vol. 54, nr 1

7--15

Purpose: the work presents a new composite based in Al matrix reinforced with porous, lightweight and low cost SiO2-/MgO/Al2-O3- ceramic particles. The new material can present a unique combination of properties: those related to metal/ceramic composites and still associating some characteristics of cellular materials, as the low density and high plastic deformation under compression stresses. Design/methodology/approach: processing technique involves the infiltration of AA7075 alloy in the semisolid thixotropic state into a layer of porous ceramic particles. Products were analyzed by X-ray tomography, optical and electronic microscopy to observe microstructure and metal/ceramic interfaces. Density was measured by He picnometry; semi-static compression tests were performed to evaluate the deformation ability of the material. Thermal properties were theoretically evaluated. Findings: concerning the production method, thixoinfiltration is a feasible processing route, with no difficult control of parameters and does not rely on specific and onerous equipment. Moreover, it is flexible to different alloys. Concerning the product, low density composites can be produced with good dispersion of reinforcement and reliable internal quality; this material presents a plateau of plastic deformation at low stresses under compression, signalizing a potential application as energy absorbers. Theoretical simulations show also good thermal insulation ability. Research limitations/implications: as a new product, the full characterization of properties of the new composite is still to be achieved. Therefore, the full potential of commercial application is to be determined. The product can present limitations for application involving tensile stresses due to poor metal/ceramic interfaces. Practical implications: the thixoinfiltration can represent an alternative, low cost processing route for low density composites. The new composites presented are low weight and low cost material, presenting a unique combination of properties which can bring a whole new application field, as low cost, low density components for energy absorption and thermal insulation. Originality/value: both the processing route and the material produced - a low density metal/ceramic composite, using porous ceramic particulates as reinforcement, are new concepts under development by the proposing group at FEM/UNICAMP.