Growth mechanism of highly twinned Al13Fe4 dendrites obtained from a rapidly solidified Al-5at.% Fe melt

Abstract

We report the formation of large and highly twinned dendrites of the Al13Fe4 approximant phase embedded in an fcc Al-rich matrix. Using a rapid cooling technique, the approximant appears as a 10-fold dendrite. Within each arm, all grains share a common [010] direction. The grain distributions within the arm are quite complex and a single dendrite arm can contain up to four different orientations. Using several techniques, including Electron Back-Scattered Diffraction (EBSD) and Transmission Electron Microscopy (TEM), it has been possible to identify three types of twins, namely {100}, {001} and {201̄} twins. From these observations and previous reports, we propose a growth mechanism to explain the formation of such specific 10-fold motifs. It corresponds to the heteroepitaxial growth of the Al13Fe4 approximant from a well-facetted decagonal Al–Fe quasicrystalline seed.