Aluminum-based metal matrix composites (MMCs) reinforced with quasicrystalline Al–Cu–Fe particles represent a promising class of materials due to their combination of high strength, lightness, and improved thermal properties. The key factor determining the mechanical properties of such composites is the interaction between the matrix and the reinforcing particles.
In particular, the formation of intermetallic phases in the Al/Al–Cu–Fe quasicrystal interphase zone plays an important role in strengthening the material. These phases can arise as a result of diffusion processes at elevated temperatures, contributing to improved adhesion between the matrix and reinforcing particles. The formation of intermetallic compounds such as AlxFey leads to the creation of barriers to dislocation movement, which increases the yield strength and strength of the composite.
The mechanism of strengthening due to interphase reaction in Al/Al–Cu–Fe CMM includes several stages. First, copper and iron atoms diffuse from the quasicrystalline particle into the aluminum matrix. Then, these atoms react with aluminum, forming intermetallic phases. The size, morphology, and distribution of these phases significantly affect the degree of strengthening.
Composite materials are complex systems where the components are often not in thermodynamic equilibrium during manufacture or use. However, diffusion processes and phase transformations can occur at the interfaces between the components. These temperature-dependent reactions have a significant impact on the properties of metal matrix composites. Thermodynamic and kinetic principles make it possible to predict and control changes in the structure of interfaces.
Powder metallurgy, using lower temperatures, provides better control over the kinetics of interfacial reactions. These reactions are influenced by (1) the surface energy at the interfaces, including nucleation, and (2) stresses arising from diffusion. Reactions between the matrix and reinforcement can degrade the properties of composites. For example, in Mg/Al2O3 composites, such a reaction leads to the formation of a brittle interface, which reduces strength.
However, interphase reactions are not always undesirable. In Al/Al–Cu–Fe composites, the reaction between the aluminum matrix and the quasicrystalline reinforcement contributes to increased strength by forming the ω-phase Al7Cu2Fe. This phase has a tetragonal structure and is classified as a complex metallic alloy. Al/ω composites exhibit higher strength and yield strength than Al/QC at temperatures up to 570 K.
According to the Al–Cu–Fe phase diagram, the ω-phase exists between the icosahedral phase and aluminum. When processed at temperatures above 723 K, atomic diffusion occurs, leading to a transition from the quasicrystalline to the ω-phase. In this paper, the reaction between the aluminum matrix and the Al62.5Cu25Fe12.5 reinforcement to form the ω-phase Al7Cu2Fe and its effect on the mechanical properties of composites are investigated.
Author: F. Aliab, S. Scudino, M. S. Anwar, R. N. Shahid, V. C. Srivastava, V. Uhlenwinkel, M. Stoica, G. Vaughan, J. Eckert
Institute: IFW Dresden, Institute for Complex Materials, PO Box 27 01 16, D-01171 Dresden, Germany, Materials Processing Group, DMME, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad, Pakistan, Metal Extraction and Forming Department, National Metallurgical Laboratory, Jamshedpur 831007, India, Institute of Materials Technology, University of Bremen, D-28359 Bremen, Germany, European Synchrotron Radiation Facility ESRF, BP 220, 38043 Grenoble, France, Dresden University of Technology, Institute of Materials Science, D-01062 Dresden, Germany