Observation of the undercoolability of quasicrystal-forming alloys by electromagnetic levitation

The electromagnetic levitation technique is applied to undercool melts of quasicrystal-forming alloys of Al-Cu-Co and Al-Cu-Fe. Undercooling with respect to the solidification of the decagonal phase (quasiperiodic in two dimensions) is measured in situ by contactless temperature measurements. The undercoolings are analyzed within nucleation theory. The results indicate that the activation energy for the formation of the nuclei of quasicrystalline phases is lower than that of crystalline phases. The decrease of activation energy is more pronounced for the icosahedral phase than for the decagonal phase.