X-ray topography study of cleavage surfaces of NaCl and LiF single crystals

Plastic deformation accompanying unsteady cleavage-crack propagation was studied in NaCl and LiF single crystals by X-ray topography. It was found that, for slowly propagating cracks, in both materials the main activated systems are the transverse systems, particularly at the stopped crack fronts. They are remarkably intense in NaCl crystals.