Effect of Growth Rate and Composition on the Eutectic Spacing in the Directionally Solidified NiAl-Mo Eutectic Alloys

A series of stoichiometric NiAl alloys contain four different concentrations of Mo (7.8, 9, 13, 16 at.%) were directionally solidified in the Bridgman-type directional solidification furnace for four different growth rates (V = 1.5–6 μm/s) in a constant temperature gradient (G = 334 K/cm). the microstructures of the alloys produced with the different growth rates at a constant temperature gradient tended to form fully fibrous structures. The fiber spacings λ were measured from transverse section of the specimen. The variation of λ with respect to growth rate (V) and composition (C0) were determined by linear regression analysis. It has been found that λ decreases with the increasing values of V and C0. The results are compared with theoretical models and previous experimental published data.