DISLOCATION SUBSTRUCTURE IN NIAL SINGLE-CRYSTALS CYCLICALLY DEFORMED AT AMBIENT-TEMPERATURE

Dislocation structures have been characterized in cyclically deformed NiAl single crystals tested at room temperature. The primary slip syst em [001]{110} was found to be in operation for the [112] ''soft'' orie ntation. The dislocation structure was found to have a high density of dipoles and point defect clusters. Dislocation cross grids that accom modate the misfit between PSBs (persistent slip bands) and the matrix were observed. Possible cyclic hardening mechanisms at room temperatur e are discussed. The density of the dipoles was not uniform and was fo und to be modulated on the slip plane, unlike Ni3Al which shows a homo geneous distribution. Computer simulation of the microstructure has be en carried out, based on the mechanism of dipole diffusion in a stress gradient.