High-entropy alloys (HES) attract considerable attention due to their unique properties due to the high concentration of various elements and their interaction at the atomic level. Quasicrystalline wind turbines, in particular, exhibit a combination of high hardness, corrosion resistance, and low thermal conductivity, which makes them promising for various applications.
In this paper, we study the phase transition in a high-entropy Al20Si20Mn20Fe20Ga20 quasicrystalline alloy between a decagonal quasicrystalline phase and its approximant (1/0, 2/1). Using differential scanning calorimetry (DSC) and X-ray diffraction, it has been established that the alloy heats up to a reversible phase transition at a temperature of about 700°C.
Analysis of diffraction patterns showed that the alloy is in a decagonal quasicrystalline state at room temperature. When heated to 700°C, the appearance of reflexes corresponding to the approximant (1/0, 2/1) is observed, which indicates a phase transition. When the alloy is cooled to room temperature, the reverse transition to the decagonal phase occurs.
Unlike classical high-entropy alloys with their simplified crystal lattice, high-entropy quasicrystals are characterized by the presence of several key alloying components and a more complex structure. However, the microstructural features of these quasicrystalline phases remain poorly understood. This paper presents a study of complex domain structures of approximants of a high-entropy decagonal quasicrystal (HE-DQC) in an AlSi20Mn20Fe20Ga20 alloy, performed using scanning transmission electron microscopy with spherical aberration correction and atomic resolution.
It is of fundamental importance to detect the phase transformation from HE-DQC to an orthorhombic approximating phase of type (1/0, 2/1) with lattice parameters a = 0.73 nm, b = 1.23 nm, and c = 2.24 nm. The study found that this phase transition is initiated by the multicenter nucleation and growth of oriented hexagonal structural elements, as well as phase rearrangements of the main building blocks. The results obtained contribute to a deeper understanding of the mechanisms of the formation of periodic structures in high-entropy decagonal quasicrystals.
The DSC results confirm the presence of a reversible phase transition, which manifests itself as an endothermic peak during heating and an exothermic peak during cooling. The activation energy of the phase transition was estimated based on the analysis of DSC data.
The study of phase transitions in quasicrystalline wind turbines opens up new possibilities for controlling their structure and properties, which can lead to the creation of materials with specified characteristics for various applications.
Author: Tiantian Zhang, Liangqun Zhao, Haikun Ma, Shuzhao Huang, Li You, Yong Zhang, Zhanbing He
The Institute: State Key Laboratory of Advanced Metals and Materials, Beijing University of Science and Technology, Beijing, 100083, China