Dislocation interactions and dipole formation

Abstract

This paper discusses the formation of dislocation dipoles by the interaction of two dislocations. In particular a mechanism is described whereby two screw dislocations of the same sign can become cross linked to form an edge dislocation dipole at the cross-over point. Subsequently, the trailing segments of the cross-linked pair are held back by the dipole while the leading segments move on ahead stretching the dipole behind them. Evidence is presented for this mechanism based on electron transmission studies on thin films of magnesium oxide and its role in the early stages of work hardening is discussed. In a second mechanism edge dislocations of opposite sign approach and form a dipole along their line of contact.