A maximum in ductility and fracture toughness in nanostructured Cu/Cr multilayer films

In Cu/Cr multilayers with modulation period (gamma) ranging from 10 to 250 nm, maxima are observed for both tensile ductility and fracture at a critical lambda similar to 50 nm, different from the monotonic lambda dependence known for monolithic films. This unusual behavior is explained, via quantitative assessments, based on micromechanical model, by considering the competing thickness effects on the size of the microcracks Initiated ill the Cr layers and oil the role of the ductile Cu layer in blocking crack propagation (C) 2009 Acta Materialia Inc Published by Elsevier Ltd All rights reserved