Plastic Deformation

· The force-position curve for a dislocation interacting with a hard atom for which the elastic modulus interaction is greater than the size effect is shown.
· For an edge dislocation to pass this barrier a force greater than F_max must be applied. In this case, the dislocation (moving from left to right)

From: Courtney, "Mechanical Behavior of Materials,"
McGraw Hill (1990)

must be pushed into the barrier, rather than being attracted to the site as in the previous cases.
· For both sets of conditions, attraction or repulsion, the impurity atoms form a barrier to dislocation motion and result in a strengthening effect.