High Temperature Intermetallic Compounds Ni3Al

The paper describes the preparation of Ni3Al intermetallic compounds, and investigations of their structures in the as-cast, remelted, and annealed states. The materials were produced by three techniques : in a high frequency vacuum furnace, by zonal remelting in an electron beam furnace, and by remelting with unidirectional solidification. Those melted in an h. f. vacuum furnace and poured into graphite moulds had well developed dendritic structures, a Ni3Al (γ) phase, with interdendritic spaces formed by Ni5Al3 + [γ']. Many specimens contained shrinkage cavities. Unidirectional solidification allowed casting defects to be eliminated and the grain size to be controlled in dependence on the solidification rate. Rates from 650 to 60 mm per hour were tried to examine their effects on the grain size, homogeneity, and structure. The authors further investigated the influence of B and Zr additions on the solidification process and formation of the structure of Ni3Al. Annealing, in an argon atmosphere at 1100°C for various durations, was tried out for homogenizing the as-cast structures