  This work provides unambiguous evidence for the occurrence of icosahedral
quasicrystal (iQC) enhanced nucleation during selective laser melting of gas
atomized commercially-pure Ni powders. This solidification mechanism, which has
only been recently reported in a few alloys and has to date never been observed
in pure metals, consists on the solidification of grains of the primary phase
on the facets of iQCs formed due to the presence of icosahedral short range
order in the liquid. The occurrence of iQC enhanced nucleation has been
inferred from the observation in the SLM processed pure Ni samples of an excess
fraction of partially incoherent twin boundaries and of clusters of twinned
grain pairs sharing common <110> five-fold symmetry axes. This work further
evidences that additive manufacturing methods may constitute an invaluable tool
for investigating the fundamentals of solidification and for the design of
unprecedented grain boundary networks.
