The study is devoted to the investigation of phase transformations in quenched Al61Cu26Fe13 alloys, with an emphasis on the relationship between the icosahedral phase and the β-solid solution. Analysis of diffraction patterns revealed the presence of ordered ω-like displacements, which play a key role in the mechanism of these transformations.
In rapidly cooled Al61Cu26Fe13 alloys, specific orientational relationships were recorded between the crystal lattice of the icosahedral phase (ι-phase) and the lattice of the β(CsCl)-solid solution (where the β-solid solution contains regions with ω-like displacements): [111]β || A2, [110]β || A5. It was established that a state with a modulated structure of the ι-phase is formed at the interface between the ι-phase (dendrite)/β-solid solution (interdendrite regions). It is assumed that the regions of ordered ω-like displacements play a role in the successive transformations (both direct and inverse) ι-phase → modulated ι-structure → heterogeneous β-solid solution, occurring at grain boundaries due to stresses arising during quenching of alloys.
In rapidly quenched Al61Cu26Fe13 alloys [ι-phase + β(CsCl)-solid solution], an inhomogeneous state of the β-solid solution was discovered, characterized by an incommensurate ω-phase in the bcc-solid solution. It was previously established that this state of the β-solid solution exhibits “dielectric” behavior of the electronic properties, similar to the behavior of quasi-crystalline alloys. This stimulates further research into the structural relationships in this class of systems, as well as interest in elucidating the role of ordered ω-like displacements in the structural transformations β-solid solution → ι-phase, ι → β-solid solution. The mechanism of these transformations is the subject of active research.
Experimental data indicate that under certain heat treatment conditions the icosahedral phase can transform into a β-solid solution, and vice versa. This process is accompanied by a reorganization of the atomic structure and a change in the degree of order.
It is assumed that ordered ω-like displacements serve as a kind of “bridge” between the two phases, facilitating the transition from one crystal structure to another. Further research is aimed at a detailed study of the kinetics of these transformations and determining the optimal conditions for obtaining a given phase structure of the alloy. The results obtained can be used to develop new materials with improved properties.
Author: E. V. Shalaeva
Institute: Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, Pervomayskaya Street, 91, 620219 Yekaterinburg, Russia