The effect of dislocations is especially pronounced on the
strength of crystals. The experimentally measured yield strength
of metals turns out to be the only one-thousandth of its theoretical
value, the loss being mainly attributed to the effect of mobile
dislocations. By increasing substantially the dislocation density
and decreasing the dislocation mobility, the strength of a metal
can be raised several times compared with its strength in the
annealed state. Faultless pieces of metals (in particular, long and
thin ‘whiskers’ obtained by crystallization from the gaseous
phase) exhibit a strength approaching the theoretical value