Size effects on the strengthening/toughening of nanostructured metallic multilayers

How to defeat the conflict of strength vs toughness and achieve unprecedented levels of damage tolerance within structural materials is a grand challenge for their microstructure-sensitive design of heterogeneous metallic materials. Nanostructured metallic multilayers act as one class of typical heterogeneous materials and manifest great potential to obtain the structural materials with the combination of high strength and superior toughness, due to their tunable dimensional and microstructural length of the constituents as well the great advantage of tunable interfacial structures via introducing different constituents. The present authors had systematically investigated the size and interface effects on the mechanical properties, such as hardness/strength, tensile ductility, fracture toughness, and strengthening/toughening mechanisms of crystalline/crystalline Cu/X (X=Cr, Nb, Zr) and crystalline/amorphous Cu/Cu-Zr nanolayered films/micropillars. In this paper, based on these experimental results achieved by the present authors, as well as the progresses at home and abroad made in the plastic deformation behavior of NMMs, the correlation of microstructure-size constraint-mechanical performance in NMMs (and nanolayered micropillars) is reviewed. Finally, a brief prospect on the studies of NMMs in future is discussed.