HALL-PETCH RELATIONS FOR MULTILAYERED MATERIALS

The present work adopts an embedded layer (two interface) approximation to a two-component multilayered material, and examines how the critical resolved shear stress for slip transmission of a pile-up depends on layer thickness, component moduli, interface slip properties, source properties, and pile-up orientation. At nanometer layer dimensions, small numbers of dislocations in the critical pile-up produce significant departures from continuum Hall-Petch behavior. The multilayer geometry may enhance or suppress source operation, so that a sharp transition and even a peak in the critical transmission stress may occur at a particular layer thickness. The multilayer geometry also displays a large anisotropy that is related to the effective glide distance between layers.