THE EFFECT OF STRESS ON THE SHAPE OF A BLOCKED DEFORMATION TWIN

The equilibrium shape of a blocked twin was determined by a calculatio n of the equilibrium positions of the discrete dislocations in the twi n by means of a numerical solution. The critical stress required to pl ace the leading two dislocations in a nascent tilt-wall configuration as well as the fraction of the total dislocations of the same sign in the twin reaching and forming a discontinuous tilt wall were also dete rmined for applied stresses greater than the critical stress. The magn itude of the critical stress was found to be low and under usual defor mation conditions the majority of the dislocations in the blocked twin were found to form a discontinuous tilt wall.