Generation of slip by pressurization of LiF single crystals containing cavities

Abstract

Single crystals of LiF containing cubical and near-spherical cavities were subjected to hydrostatic pressures of up to 1·5 GNm⁻² and the resultant microstructural changes were studied using the repeated etching technique. Nucleation of dislocations in the vicinities of the holes was observed to result from treatments above a threshold pressure characteristic of the cavity size. On raising the pressure, further dislocations were generated. These arrays were on the twelve 〈110〉{110} slip systems, each being associated with a cavity edge for the case of cubical cavities. An adequate representation of a first glissile half-loop is by the introduction of ’an extra (110) half plane ’connecting the distorted (010) cavity face with the (110) slip plane. This (110) plane is bounded by a glissile edge dislocation in (110) and sessile edge dislocations in (001) terminating at the cavity. By symmetry, twelve pairs of 〈110〉{110} half-loops can be produced and the process may continue to generate further slip. The dislocation behaviour in the pressure-induced arrays resembles that in conventional slip bands. Dislocation interactions and the pressure-dependent probability of cross-slip events are thought to contribute to the stability and the ultimate arrangement of the dislocation structures.