Mechanical alloying (MA) is a powerful tool for creating new materials with unique properties that differ from those that can be obtained by traditional methods. In particular, MA allows synthesizing metastable phases and expanding the solubility limits in alloys. The Al70Cu20Fe10 alloy, chosen as the object of study, is of interest due to its ability to form a quasi-crystalline phase with unusual physical properties.
In this paper, we investigate the phase transformations occurring in the Al70Cu20Fe10 alloy subjected to mechanical alloying and subsequent annealing. ML was carried out in a ball mill in an argon atmosphere to prevent oxidation. The resulting powder was then annealed at different temperatures to stimulate crystallization and the formation of equilibrium phases.
X-ray diffraction and differential scanning calorimetry (DSC) were used to analyze the phase composition and thermal characteristics of the samples. The results showed that the MA process forms a nanocrystalline structure with a high defect density. Subsequent annealing results in recrystallization, grain growth, and the formation of various phases, including θ-Al2Cu, α-AlFeCu, and, under certain conditions, quasicrystalline i-AlCuFe.
Annealing temperature plays a key role in the formation of the phase composition. At low temperatures, recrystallization and grain growth processes predominate, while at higher temperatures, intermetallic phases form and grow. Optimization of annealing parameters allows controlling the phase composition and, consequently, the properties of the resulting material.
In this study, the phase change processes occurring during mechanical alloying (MA) and subsequent annealing of the Al70Cu20Fe10 alloy were investigated using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). No formation of the icosahedral quasicrystalline phase (i-phase) was detected in the Al70Cu20Fe10 alloy during the milling process. A new completely disordered β-Al(Cu,Fe)-phase was first formed in the milled powders after 40 hours of MA, transforming into a stable β-phase with the B2 structure when the milling time was increased to 70 hours.
In annealed samples, the i-phase appears, and its amount increases with increasing mechanical processing time. In addition, the ω-Al7Cu2Fe phase is formed exclusively after heat treatment of crushed Al70Cu20Fe10 powders. Thus, the formation of the i- and ω-phases directly depends on the duration of the grinding process and the annealing temperature.
Author: Yan Wang, Ying Tian, Yi Wang, Haoran Geng, Zhonghua Zhang
Institute:
Key Laboratory of Liquid Structure and Heredity of Materials, Shandong University, 73 Jingshi Road, Jinan 250061, P.R. China, School of Materials Science and Engineering, Jinan University, 106 Jiwei Road, Jinan 250022, P.R. China, School of Materials Science and Engineering, Hefei University of Technology, 193 Tongxi Road, Hefei 230009, P.R. China