Regular rod-like eutectic spacing selection during directional solidified NiAl–9Mo eutectic in situ composite

NiAl–9Mo (at%) eutectic alloy was produced by a Bridgman type crystal growing facility with Zone Melting Liquid Metal Cooling technique at the growth rate range from 60 to 200 μm/s. The variation of rod eutectic spacing with growth rates was characterized. Statistical distributions of spacings at each growth rate were also determined. It was confirmed that the relationship between growth rate V and rod spacing λ follows the Jackson and Hunt equation under high growth rates and can be obtained as λ2V=33.94 μm3/s. In addition, a narrow distribution curve of the rod spacing was obtained for a given growth rate. And the width of the distribution decreases as the growth rate increases. It is probable that the capillarity effect, the high value of entropy of fusion constituent phase NiAl and the convection effect are responsible for the existence of the narrow band of the rod spacing.

► Regular fibrous structure of the NiAl–9Mo eutectic was produced at high growth rates.
► The rod spacing selection is very sharp for high growth rates.
► The relationship between rod spacing and growth rate at high growth rates was analyzed.