APFIM investigations on quasi-binary hypoeutectic NiAl-Re alloys

The micro- and nano-structure of a NiAl-Re alloy with 1 at.% Re has been investigated by means of atom probe field ion microscopy (APFIM) and by scanning electron microscopy. The effect of heat treatments on this alloy were studied for annealing temperatures at 1000 °C in a time interval of 10-1000 h, and at 1300 °C for 1000 h. The results were compared with those from the as-cast samples. Rhenium contents of the NiAl matrix were determined by APFIM. It was found that the Re concentration in the primary NiAl crystals decreases with increasing annealing time. Layer-resolved atom probe measurements were performed in order to determine the site occupancy of Re atoms in the NiAl superlattice. The results clearly showed a site preference for the Ni sublattice.