Wettability in pressure infiltration of SiC and oxidized SiC particle compacts by molten Al and Al-12wt%Si alloy
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J. Tian Institute of Material Science and Engineering, Ocean University of China, Qingdao 266100, People’s Republic of China
C. Garcia-Cordovilla Centro de Investigación y Desarrollo, Flat Rolling Products, Alcoa Europe, E-03080, Alicante, Spain
E. Louis Departamento de Física Aplicada, Universidad de Alicante, E-03080, Alicante, Spain; Instituto de Materiales, Universidad de Alicante, E-03080, Alicante, Spain; and Unidad Asociada of the Consejo Superior de Investigaciones Científicas, Universidad de Alicante, E-03080, Alicante, Spain
J. Narciso Instituto de Materiales, Universidad de Alicante, E-03080, Alicante, Spain; and Departamento de Química Inorgánica, Universidad de Alicante, E-03080, Alicante, Spain (Received 9 February 2007; accepted 24 April 2007)
The infiltration behavior of compacts of SiC particles in two surface conditions, as-received and thermally oxidized, was investigated by using pure Al and Al-12wt%Si as infiltrating metals. Analysis of the threshold pressure for infiltration revealed that the process is governed by the same contact angle for all different systems, no matter the metal or particle condition. This leads to the conclusion that oxidation does not modify the wetting characteristics of the particles, most probably because they are already covered by a thin native oxide layer that remains unaltered in processing routes involving short contact times and low temperatures, such as actual conditions of pressure infiltration at 700 °C.
I. INTRODUCTION
As interest has increased in developing potential applications of metal matrix composites, it is well known that the final properties of a composite material are strongly dependent on the interface between the matrix and reinforcement.1–3 In the processing of these materials, interfacial phenomena are critical as well, especially when there exists some affinity between the matrix and reinforcement and they react to form undesirable phases. Practical examples, which include the systems Al/C,4 Al/SiC,5 Al/BC,6 and Al-Mg/Al2O3,7,8 have forced the researchers to adopt solutions to reduce or control the reactivity of the matrix and reinforcement. The first approach consists of minimizing exposure to high temperatures during processing.6,9 Alloying additions to the matrix have also been shown to be effective to prevent reaction in some systems; for example, addition of 6–
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2007.0282 J. Mater. Res., Vol. 22, No. 8, Aug 2007
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7 wt% of Si to Al seems adequate to prevent any reaction with SiC.10 Another approach, which is more sophisticated and expensive, is to chemically modify the surface of the reinforcement with a coating.11,12 The second interfacial phenomenon that becomes very important in the processing of metal matrix composites is the wettability of the reinforcement by the metal that is used as the matrix. Because wetting of reinforcements by metals is generally poor, there have been many attempts to
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