In the present work, Nb-18.1 Si-1.5Zr alloy rods are produced with a growth rate ranging from 1.5 to about 1500 rmn/h using the optical floating zone (OFZ) furnace. A part of each specimen is heat-treated at 1650 °C for 100 h. The microstructure was observed using SEM and TEM and analyzed using EPMA and EBSD. Eutectic-cells are observed in as-grown specimens with a growth rate of 150 mm/h or higher. It is found by EBSD analysis that the solidification direction of Nb is along <113> and that of Nb3Si is along <001], and {112} of Nb and {110) of Nb3Si are parallel. The present crystallographic orientation relationship between Nb and Nb3Si is different from that found in previous reports by several researchers. It was also confirmed that the heat-treated microstructure in the specimen grown by OFZ with a growth rate of 150 mm/h is similar to that in the heat-treated specimen prepared by arc-melting.^
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