Defects and Mechanical Properties

Abstract

Abstract This chapter treats the important subject of defects in metals, including vacancies, interstitials, dislocations and grain boundaries. All of these defects, in addition to the bulk elasticity that underpins them, are impacted by quantum mechanics, again confirming the fundamental importance of quantum-based interatomic potentials. The discussion here is mainly focused on the bcc transition metals, where extensive applications have been made using model generalized pseudopotential theory. Calculations of point defect formation and migration energies, ideal shear strength and generalized stacking fault energy surfaces compare favorably with density functional theory results. A special Green’s function method is used to study screw dislocation core structure and mobility, including kink-pair energetics and the Peierls stress. Multiscale modeling of crystal plasticity and strength in Ta and Mo is then made possible via dislocation mobility input into micron-scale dislocation dynamics simulations. Predictions of grain-boundary structure in Nb, Mo and Ta have also been validated by experiment.