Dislocation substructure in NiAl single crystals cyclically deformed at ambient temperature

Dislocation structures have been characterised in cyclically deformed NiAl single crystals tested at room temperature. The primary slip system <001>{110} was found to be in operation for the <112> 'soft' orientation. The dislocation structure was found to have a high density of dipoles and point defect clusters. Dislocation cross grids that accommodate the misfit between PSBs (persistent slip bands) and the matrix were observed. Possible cyclic hardening mechanisms at room temperature are discussed. The density of the dipoles was not uniform and was found to be modulated on the slip plane, unlike Ni₃Al which shows a homogeneous distribution. Computer simulation of the microstructure has been carried out, based on the mechanism of dipole diffusion in a stress gradient.