Metal matrix composites (MMC) are a class of materials in which the metal matrix is reinforced with discrete reinforcing phases. In the context of searching for materials with improved tribological, thermal and mechanical properties, particular attention is drawn to the use of quasi-crystalline phases, in particular, the icosahedral Al-Cu-Fe alloy, as reinforcing elements. Gas-atomized Al-Cu-Fe powders, due to their spherical shape and controlled particle size, are ideal for uniform distribution in a metal matrix.
The process of creating MMCs reinforced with gas-atomized Al-Cu-Fe powders includes several stages: powder preparation, mixing of the reinforcing phase with the metal matrix, and consolidation. The choice of the optimal consolidation method (e.g. powder metallurgy, injection molding, spraying) plays a decisive role in ensuring high density and homogeneity of the final material.
To obtain powders with an icosahedral quasicrystalline structure, the Al62Cu26Fe12 alloy was processed by gas atomization. High-purity aluminum was used as a base for creating composite materials, to which Al62Cu26Fe12 powders were added during casting. The application of a nickel layer, approximately 5 μm thick, to Al62Cu26Fe12 particles effectively prevented changes in their original structure during casting.
The obtained composites demonstrated a sufficiently strong bond between the Al62Cu26Fe12 particles and the aluminum matrix, despite the partial dissolution of small satellite particles. Compression and indentation tests revealed a significant increase in the yield strength of the composites, especially at a concentration of reinforcing particles up to 10% by volume. To explain the observed strengthening, possible mechanisms were analyzed to assess the contribution of icosahedral phases and associated crystalline phases to the increase in yield strength.
The mechanical properties of such composites, such as tensile strength, elastic modulus and hardness, show significant improvement compared to the matrix material without reinforcement. The presence of the quasi-crystalline Al-Cu-Fe phase provides effective dislocation inhibition and increased wear resistance. In addition, thermal stability and oxidation resistance also represent significant advantages due to the presence of the icosahedral phase. Further research is aimed at optimizing the composition, particle size and consolidation method to achieve maximum improvement in the performance of MMCs reinforced with gas-atomized Al-Cu-Fe powders.
Author: SM Lee, JH Jung,E Fleury,W. T. Kim,D.H. Kim
Institute: Department of Metallurgy, Center for Non-Crystalline Materials, Yonsei University, 134 Sincheon-dong, Seodaemun-gu, Seoul, 120-749, South Korea