Preparation and characterisation of melt-spun Al–Cu–Fe quasicrystals

Abstract

Three Al–Cu–Fe alloys with compositions of Al 60–65Cu 20–27.5Fe 12.5–15 were prepared by conventional casting and further processed by melt-spinning. The structures formed were examined to get an insight into the interrelated effects of synthesis, processing and microstructure of Al–Cu–Fe alloys. The study aimed at answering the questions such as whether the production of single-phase quasicrystalline ribbons is possible by the melt-spinning process and what is the role of the degree of undercooling in the development of microstructure in melt-spun ribbons. The icosahedral ψ-Al 65Cu 20Fe 15 phase forms by a peritectic reaction between the primary β-AlFe phase and the liquid, as the temperature decreases. At the later stages of cooling, the monoclinic λ-Al 13Fe 4 phase and the tetragonal θ-Al 2Cu phase are formed in the cast alloys, as a result of peritectic reactions. In the rapidly solidified alloys, the formation of the tetragonal θ-Al 2Cu phase and, in the case of alloy Al 60Cu 25Fe 15, the monoclinic λ-Al 13Fe 4 phase is avoided, apparently due to high degree of undercooling. Thus, the production of single-phase quasicrystalline ribbons is not possible by the melt-spinning process, at least by using the cooling rate of 5–7×10 4 °C/s. In addition to phase selection, the degree on undercooling influences, for example, the composition of the ψ-Al 65Cu 20Fe 15 phase and the grain morphology in melt-spun ribbons.