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Reaction Mechanisms in Al2O3/CuO Infiltration by Liquid Al

Authors

  • M. Guedes,

    1. Department of Mechanical Engineering, Escola Superior de Tecnologia de Setúbal, Polytechnic Institute of Setúbal, Setúbal, Portugal
    2. ICEMS, Instituto Superior Técnico, Lisboa, Portugal
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    • Member, The American Ceramic Society.
  • J. M. F. Ferreira,

    Corresponding author
    1. Department of Ceramics and Glass Engineering, University of Aveiro, Aveiro, Portugal
    2. CICECO, University of Aveiro, Aveiro, Portugal
    • Department of Mechanical Engineering, Escola Superior de Tecnologia de Setúbal, Polytechnic Institute of Setúbal, Setúbal, Portugal
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  • A. C. Ferro

    1. Department of Mechanical Engineering, Instituto Superior Técnico, Lisboa, Portugal
    2. ICEMS, Instituto Superior Técnico, Lisboa, Portugal
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Author to whom correspondence should be addressed. e-mail: mafalda.guedes@estsetubal.ips.pt

Abstract

This work studies reactive mechanisms involved in liquid Al infiltration of green preforms containing tailored amounts of Al2O3 and CuO. Infiltration reactions involving Al and copper oxides are expected to produce Al2O3, as fine particulate reinforcements, and Cu, as Al-matrix strengthener. Preforms with 75 mol%-CuO were infiltrated with Al at 1000°C and 1100°C in air. Under low PO2, copper oxides are reduced to Cu, blocking the opportunity for reactive infiltration. Also, the Al-Cu/Al2O3 contact angle is insufficiently low to drive spontaneous infiltration. At 1000°C, infiltration is incipient, indicating that CuO reaction with Al is not sufficiently vigorous to destabilize enveloping Al2O3. At 1100°C, CuO reduces to Cu2O and infiltration is triggered, although the process is incomplete due to formation of a compact Al2O3 layer which inhibits metal supply to the reaction front. At or behind the halted infiltration front consumption of starting Al2O3 particles and formation of CuAlO2 occur. The space among these phases is occupied by a Cu-rich matrix, rendering an almost totally densified microstructure. This study shows that liquid Al infiltration of Al2O3/CuO greens is possible at 1100°C, in air, due to destabilization of the Al2O3 enveloping film and reactive infiltration, promoted by the redox reaction between Al and copper oxide.

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