Aligned Ni-In eutectics

Directional solidification of two eutectic alloys in the Ni-In system results in aligned microstructures. The eutectic at 26.5 at. pct In solidifies as ribbons and lamellae of nickel-base solid solution in a matrix of ε-Ni₂In. Peritectoid formation of Ni₃In on cooling drastically alters the morphology, but this reaction can be suppressed by quenching. The peritectoid reaction can then be studied by isothermal heat treatments. The eutectic at 46.6 at. pct In solidifies partly as rods of ε-Ni₂In in a matrix of β-NiIn, partly in a lamellar morphology. Both phases transform on cooling, but because little composition change is involved, the effect on eutectic morphology is slight.