Density and Hardness Changes Produced by Plastic Deformation in KCl Crystals

A study has been made of the density changes which accompany plastic deformation in compression of potassium chloride crystals and of their annealing. Also hardness changes, their annealing, and slip-line formation have been investigated. Up to about 11% deformation, the slip is predominantly simple with some admixture of double slip, and no change of density is observed. At 11% deformation, multiple slip presumably sets in accompanied by a rapid decrease of density. The rate of formation of vacancies is 3.02 ×{} 10¹⁷ cm^-3 per percent deformation. A comparison of this value with the results of the experiments of Ueta and K\"anzig leads to the ratio of about four vacancies per electron trap. Vacancies seem to have no measurable influence on hardness which thus appears to be primarily associated with changes in the dislocation density or their configuration during plastic deformation.