THE SHAPE OF A BLOCKED DEFORMATION TWIN

In previous work it was found that a fractional entity of the Shockley -type twinning dislocations of a blocked twin lamella is arranged as a dislocation wall, being identical with a disclination dipole. In the present letter, the number of partial dislocations within the dislocat ion wall is estimated. It is found that more than 80% of the twinning dislocations are placed within the wall. It is concluded therefore tha t the disclination dipole representation of a blocked twin lamella can be applied as a proper model which overestimates the actual short-ran ge stresses by less than 20%.