Plastic Deformation

· The presence of impurity atoms in a lattice both distorts the lattice and alters the local elastic modulus.
· The diagrams illustrates the effect of these terms on the local energy of an edge dislocation and show the total force attracting it to the impurity site.
· Close to the impurity location the force is towards the site (attractive) and will "pin" the dislocation line increasing both the yield stress and the flow stress.

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