| Abstract Scope |
Icosahedral Short-Ranger Order (ISRO) of atoms in liquid, first conjectured by Frank in 1952 to explain the large undercoolings measured by Turnbull in fcc or hcp metals, has been confirmed by several observations (formation of quasicrystals, atomic structure of many intermetallic phases, neutron small angle scattering) and by atomistic simulations. In contrast to the original idea of Frank, however, ISRO can act as a precursor for the formation of fcc grains, so-called "iQC- or ISRO-mediated nucleation". Localized covalent bonding associated with ISRO can also affect diffusion in the liquid as well as the attachment kinetics of atoms at solid-liquid interfaces. An “ISRO-induced stacking fault” mechanism is believed to be responsible for the formation of twinned dendrites in Al alloys and can compete with solid-liquid interfacial energy anisotropy to modify dendrite growth direction. This keynote presentation will try to summarize the recent findings and open questions on the influence of ISRO on solidification morphologies. |