Rapidly Solidified and Annealed Powders of Ni3Al

Rapidly solidified powders of stoichiometric Ni3Al (B,Ti) were characterized, both as received and after short anneals. Powders generally exhibit spherical morphologies; deviations arise from particle collisions. In the as-received state the stoichiometric Ni3Al exhibits both lamellar and dendritic structures but the Ni3Al (B,Ti) contains only dendrites. Only small compositional variations exist across lamellae or dendrites. The as-received powders are only partially ordered. Annealing homogenizes the microstructure and produces strongly ordered structures in which most particles develop large grains. Hardness decreases during annealing. No cracks were found around microhardness indentations on any powders, indicating that Ni3Al exhibits ductility under compression.