Oxy-Acetylene Flame Thermal Spray of Al/SiC p Composites with High Fraction of Reinforcements
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JTTEE5 18:642–651 DOI: 10.1007/s11666-009-9393-3 1059-9630/$19.00 Ó ASM International
Oxy-Acetylene Flame Thermal Spray of Al/SiCp Composites with High Fraction of Reinforcements B. Torres, P. Rodrigo, M. Campo, A. Uren˜a, and J. Rams (Submitted June 15, 2009; in revised form July 15, 2009) Aluminum matrix composites reinforced with more that 50 vol.% of SiC particles were fabricated using oxyacetylene thermal spraying. The sprayed material consisted of mixtures of aluminum powder with 60-85 vol.% of SiC particles. To favor the processing of the composite, in some cases, the SiC particles were coated with silica following a sol-gel route. This allowed obtaining as-sprayed samples with thickness above 2 mm and with porosity values below 2%. Post-processing of the samples by hot pressing allowed to reduce further the porosity of the composites and to enhance their microstructural homogeneity. The whole process of spraying and hot pressing has been optimized and the role played by the different spraying parameters and by time length and temperature of hot pressing has been also studied.
Keywords
aluminum metal matrix composites, bulk materials, SiC reinforcement, thermal spray
1. Introduction The electronics industry requires increasing the packaging density and the power of electronic and microwave devices, resulting in the need of implementing carrier and wave confining materials that allow handling higher powers while fitting well into current technology (Ref 1, 2). These materials must have coefficients of thermal expansion (CTE) compatible with those of ceramic substrates used nowadays (alumina, beryllium oxide, or aluminum nitride), or with Si or GaAs semiconductors. In addition, high thermal conductivity is required to prevent the component heating. Kovar is the most used material because of its low CTE in spite of its reduced thermal conductivity and high density. Molybdenum and tungsten, or metal-metal composites such as W-Cu and Mo-Cu, have compatible CTEs and higher thermal conductivities, although they are heavier. Currently, the application of metal matrix composites (MMCs) with high ceramic particle content is getting interest. In particular, AlSiC, i.e. aluminum matrix composites reinforced with more than 50 vol.% of silicon carbide particles (SiCp), combine adequate CTE values (6.5-9 ppm/K at 25-150 °C, tailored by the type and content of particle reinforcement), with high thermal conductivity (from 170 to 200 W/m K), reduced density B. Torres, P. Rodrigo, M. Campo, A. Uren˜a, and J. Rams, Departamento de Ciencia e Ingenierı´a de Materiales, ESCET, Universidad Rey Juan Carlos, C/Tulipa´n s/n, Mo´stoles 28933, Madrid, Spain. Contact e-mail: [email protected].
642—Volume 18(4) December 2009
(below 3 g/cm3) and outstanding values of specific strength and stiffness (Ref 3-5). AlSiC raw materials are affordable, but processing of highly reinforced composites is expensive because high infiltration pressures are usually required, and the machining or welding of these materials is also extremely costl
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