Plastic Deformation

· When a unit dislocation dissociates into two Shockley partial dislocations, they repel each other with a repulsive force given by:
F_R = G(b₁·b₂)/2πD per unit length
where D is the width of the stacking fault between the two dislocations.
· Because the stacking fault region increases the total energy of the sample an attractive force is associated with increasing its width:
F_Α = d(γ x)/dx = γ per unit length
where γ is the stacking fault energy.
· The dislocations and stacking fault reach an equilibrium width when these two forces are equal, the separation of the partial dislocations being:
D_E = G(b₁·b₂)/2πγ
· Low stacking fault energies give wide regions of stacking fault, and vice versa.