Author: Liming Zhang, Reinhard Lück

Institute: Max Planck Institute for Metal Science, Seystrasse 92, Stuttgart, D-70174, Germany

Phase equilibria of the icosahedral phase of Al-Cu-Fe represent an important area of ​​research in materials science, especially in the context of aluminum alloying systems. The icosahedral phase (I-phase) is one of the structural modifications characterized by a high level of symmetry and unique properties such as high strength and corrosion resistance.

In the Al-Cu-Fe system, the I-phase plays a key role in the formation of intermetallic compounds and connecting phases, which determines the mechanical and thermal properties of the alloys. Phase diagrams, which display the equilibria between the different phases, are the main tool for understanding the thermodynamics of the system. It is important to note that the I-phase is formed as a result of annealing processes, which precipitate copper and iron atoms in the aluminum matrix.

A thermodynamically stable face-centered icosahedral phase (FCI) with outstanding structural quality in the Al–Cu–Fe ternary system was synthesized by Cai et al. The first report of this phase mentioned the composition Al65Cu20Fe15. However, subsequent studies showed that this composition may not be in the single-phase region at equilibrium. It was also noted that the compositional region of the stable ideal i-phase is very narrow (approximately Al62Cu25.5Fe12.5) and is subject to temperature variations. Attempts to obtain Al–Cu–Fe single crystals using Bridgman or Czochralski methods were less effective than annealing procedures. Knowing the equilibrium phase diagram is necessary for growing single crystals, and therefore we reinvestigated the phase equilibrium of the icosahedral phase of Al–Cu–Fe.

There are many publications on the phase diagram of the aluminum region of the Al–Cu–Fe system; only those related to the icosahedral phase region are considered. The first detailed study of the phase equilibria in the aluminum region was carried out by Bradley and Goldschmidt , who identified several ternary phases including ψ-Al6Cu2Fe1, but the structure of the ψ phase remained uncertain. Calvayrac et al. confirmed that the ψ phase does correspond to the i phase identified by Tsai et al. Most of the room-temperature phase diagram schemes presented in the literature are based on Bradley’s data, but disagreement remains regarding high temperatures such as the stoichiometry and structure of the i phase. The i phase region presents several modifications, and it is difficult to distinguish the phase states of the icosahedral quasicrystal from the variants by DTA or MTA using SEM/EDX methods. Therefore, the i-phase is considered as a single Gibbs phase without discussing its variants.

Modern research methods such as X-ray diffraction and electron microscopy allow detailed study of the structure and properties of this phase. Understanding the phase equilibria in Al-Cu-Fe systems facilitates the development of new materials with improved performance characteristics, which find application in the aviation and automotive industries.

We use cookies in order to give you the best possible experience on our website. By continuing to use this site, you agree to our use of cookies.
Accept