Size effects on deformation and fracture behavior 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 great challenge for designing microstructure-sensitive materials. The nanostructured metallic multilayers (NMMs) are widely used as essential components of high performance microelectronics and interconnect structures owing to their smart, tunable internal features and their outstanding mechanical properties. The deformation and fracture of NMMs during their service processes has been identified as an important factor influencing their reliability. The present authors had systematically investigated the size and interface effects on the mechanical properties, such as hardness/strength, tensile ductility, fracture toughness, deformation and fracture mechanisms of Cu/X (X=Cr, Nb, Zr) nanolayered films/micropillars, in addition to their microstructure evolution. 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 deformation and fracture behavior of NMMs, the correlation of microstructure- size constraint-mechanical performance in NMMs (and nanolayered micropillars) is reviewed, and the universities in their deformation and fracture modes and the related mechanisms are revealed. Finally, a brief prospect onthe studies of NMMs in future in the light of manipulation of the internal features, origin and dynamics of dislocations and the high performance of NMMs at extreme is discussed.