DISLOCATION SCREENING AND THE BRITTLE-TO-DUCTILE TRANSITION - A KOSTERLITZ-THOULESS TYPE INSTABILITY

We propose a new model for the brittle-to-ductile transition based on the Kosterlitz-Thouless concept of dislocation screening. In this mode l, thermal fluctuations assisted by the applied stress drive the spont aneous generation of dislocations and the instability occurs well belo w the melting temperature. In the limit of zero stress, our model redu ces to the Kosterlitz-Thouless theory of the melting transition, and, in the opposite limit of zero temperature, we obtain the Rice-Thomson result for the brittle-to-ductile transition.