Behavior of individual dislocations in LiF under alternating stresses

Abstract

The behavior of individual dislocations under alternating stresses has been investigated by the etch pit method in highly pure LiF single crystals. The applied stress level is varied from 1 4 to 1 2 of the macroscopic yield stress. Edge dislocations make jerky motion, and move backward when the stress is reversed, even at a low stress level. On the other hand, screw dislocations make no backward when the stress is reversed if the applied stress level is just above the minimum stress to move screw dislocations. When the stress is increased by 40 ∼ 60 g/mm 2, however, they can move back and forth under alternating stresses without any multiplication of dislocations Such as behaviour of screw dislocations is discussed on a basis of debris dipole formation.