Al–Cu–Fe quasicrystals with unique physical properties were successfully obtained by melt pulling. The initial components were fused in an induction furnace in a high-purity argon atmosphere. The resulting melt was pulled at a controlled rate through a cooled crystallizer, which ensured the formation of a homogeneous structure.
X-ray phase analysis confirmed the formation of a highly ordered icosahedral phase. Microstructural studies using scanning electron microscopy revealed characteristic morphological features of the quasi-crystalline structure. Differential scanning calorimetry showed the presence of phase transitions associated with the thermal stability of the quasi-crystalline phase.
Microhardness and electrical resistance measurements revealed high values characteristic of quasi-crystalline materials. The results obtained indicate the potential of the melt-pulling method for producing high-quality Al–Cu–Fe quasicrystals with improved properties.
In this study, three aluminum alloys with the addition of copper and iron were synthesized with the following composition: Al60–65Cu20–27.5Fe12.5–15. The samples were obtained by traditional casting and subsequent processing by melt spinning. The obtained structures were subjected to detailed analysis to establish the relationship between the synthesis conditions, processing and the resulting microstructure of the Al–Cu–Fe alloys. The main objective of the study was to clarify the possibility of obtaining single-phase quasi-crystalline tapes using the melt molding method, as well as to determine the effect of the degree of supercooling on the formation of the microstructure of tapes manufactured by this method.
During the temperature decrease, the icosahedral phase ψ-Al65Cu20Fe15 is formed by a peritectic reaction between the primary phase β-AlFe and the liquid phase. In the final stages of cooling, the monoclinic λ-Al13Fe4 and tetragonal θ-Al2Cu phases are formed in the cast alloys as a result of peritectic transformations. In the alloys obtained by the rapid crystallization method, the formation of the tetragonal θ-Al2Cu phase, as well as the monoclinic λ-Al13Fe4 phase (in the case of the Al60Cu25Fe15 alloy), is not observed, which is probably due to the high degree of supercooling. Thus, the production of single-phase quasi-crystalline tapes by the melt spinning method seems impossible, at least at cooling rates of 5–7×104 °C/s. The degree of supercooling affects not only the choice of phase, but also the composition of the ψ-Al65Cu20Fe15 phase and the morphology of grains in tapes obtained by melt molding.
Author: Elina Huttunen-Saarivirta, Jyrki Vuorinen
Institute: Institute of Materials Science, Tampere University of Technology, P.O. Box 589, FI-33101 Tampere, Finland, Epanet, Southern Ostrobothnia University Network, P.O. Box 151, FI-60101 Seinäjoki, Finland