Voids formed in quenched and annealed NiAl

Abstract
Voids formed in quenched and annealed stoichiometrie NiAl single crystals have been investigated by neutron small-angle scattering and transmission electron microscopy. Voids ranging in mean size up to about 1000 A have been observed. For example, 30 min annealing at 650°C after quenching from 1600°C yields faceted voids about 500 Å in diameter. The voids are found to be rhombic dodecahedra formed by faceting on the {110} family of planes. There is some indication of coarsening at intermediate annealing temperatures of about 900°C, but at 1300°C and above, the voids disappear, presumably by emission of vacancies.