The Beginning of Motion of Dislocations in Highly Perfect Copper Crystals

Abstract

Using an etch pit technique, which is applicable to distinguish between edge and 30°-screw dislocations, the shear stress τ₀ necessary to move grown-in dislocations in highly perfect copper crystals is studied in relation to the condition of the crystal surface. The main results obtained are as follows: (i) Surface removal results in the remarkable reduction of τ₀, which is more conspicuous in 30°-screw dislocation than in the edge one. (ii) Both edge and 30°-screw dislocations become very mobile at low stress levels with the reduction of partial pressure of O₂ in the annealing atmosphere. (iii) Neither the surface-step formation in the motion of dislocations with screw character nor jogs along those with the edge character are found to have an important effect on τ₀.