Change of shape due to dislocation climb

The geometry of the deformation produced by the climb of edge dislocations is defined and the conditions are determined under which dislocation climb, by itself or in conjunction with glide, can produce a general change of shape. The results are important in understanding the high-temperature deformation (T > 0.5Tm) of single crystals and polycrystals of materials with fewer than five independent slip systems. Some of these are discussed in detail. In particular the high-temperature creep of sapphire single crystals pulled parallel to (0001) is shown to be quantitatively consistent with Nabarro (Phil. Mag., 16, 231, 1967) creep by climbing dislocations.