Probing the dynamics of quasicrystal growth using synchrotron live imaging
Résumé
Quasicrystals constitute a distinct class of solids as they differ both from crystals, because they are not periodic, and from glasses, because they have long-range orientation order. The main challenge of quasicrystal physics is certainly to elucidate how the quasiperiodic order can extend up to the centimetre size of the single grains routinely grown nowadays. In particular, the dynamics of quasicrystal growth remains an unsolved problem in condensed matter. Here, owing to the incisiveness of synchrotron live imaging, we show evidences that the solidification front of icosahedral AlPdMn quasicrystal is facetted all along the growth which proceeds by the tangential motion of ledges at the solid-melt interface, with a measurable effect of interface kinetics. Increasing the applied solidification rate, the kinetic undercooling becomes large enough for the nucleation and free growth of new facetted grains in the melt. The evolution of these grains is explained in details, which reveals the crucial role of aluminium rejection, both in the poisoning of grain growth and driving fluid flow.