A 2-dimensional discrete dislocation plasticity framework, which incorporates some three-dimensional mechanisms through constitutive additions, was used to analyze the response to uniaxial tension of nanoscale bilayer thin films. Frank–Read sources, modelled as junction dipoles in 2-dimensions, acted as sources of dislocations. Infinite, homogeneous medium fields of the discrete dislocations were superposed with a non-singular complementary field that enforces the boundary conditions and accounted for image stresses arising from the difference in elastic properties between the layers. The resulting boundary value problem was solved using the finite element method. Analysis was carried out for fully coherent bilayer Al/Cu and Cu/Ni films oriented for double slip. The analysis accounted for the effects of 3 key mechanisms: resistance to dislocation nucleation and motion due to elastic modulus mismatch (e.g. Koehler barrier); single-dislocation bow-out within layers (Orowan process) and slip blocking at interfaces (Hall–Petch mechanism). The relative importance of each mechanism was studied as a function of the bilayer thickness. The results indicated a significant strengthening with decreasing bilayer thickness. Conclusions were drawn regarding the possible causes of the observed strengthening.

A Discrete Dislocation Analysis of Strengthening in Bilayer Thin Films. S.M.Keralavarma, A.A.Benzerga: Modelling and Simulation in Materials Science and Engineering, 2007, 15[1], S239-54