Dislocation loops in α-iron

The equilibrium shapes of dislocation loops in α-iron under the action of a given shear stress are computed, taking into account the effects of elastic anisotropy on the line tension. In fair agreement with these calculations, dislocation loops observed by transmission electron microscopy of cyclically deformed α-iron single crystals are found to be approximately elliptical and rotated by a few degrees with respect to the Burgers vector in the predicted sense.