Recent advances in the fundamental understanding of the deformation  mechanisms in metallic multilayers are reviewed. The strength of metallic multilayers increases with decreasing layer thickness and reaches a maximum at layer thickness of a couple nanometers. The unit processes of slip transmission across the interphase boundary, without the mechanical  advantage of a dislocation pile-up, are critical in determining the maximum flow strengths of multilayers. For the case of non-coherent fcc-bcc nanolayered composites such as Cu-Nb, we show that the atomic structure of  the interface leads to low interface shear strength. The stress field of a  glide dislocation approaching the interface locally shears the interface,  resulting in dislocation core spreading and trapping in the interface plane.  Glide dislocation trapping at the weak interface via core spreading is thus  the key unit process that determines the interface barrier to slip  transmission. The maximum strength achieved in a non-coherent multilayer can  be tailored by the shear strength of the interface. The role of the atomic  structure of the interface in promoting room temperature climb at interfaces  and its implications in dislocation recovery is highlighted. Experimental  validation of the model predictions is discussed.

Keywords: multilayer, interface, dislocation, atomistic simulations,experiments 

Dr. Jian Wang is currently working at Los Alamos National Laboratory. He got  his PH. Ds in Solid Mechanics in 1999 from Xi’an Jiaotong University and the other in Mechanical Engineering from Rensselaer Polytechnic Institute, Troy, NY, USA. He serves on Nanomechnics Committee in TMS as science advisory, and guest editor of JOM. He has more than 80 peer-reviewed  publications in major journals, such as Nano Letters. Phys. Rev. Letters,  Applied Physical Letters, Acta Materialia, and Scripta Materialian etc. He  has one book chapter in Dislocation in Solids. He has been invited to  present his work for 30 times in internatial conferences, TMS, MS&T, MRS,  Int. Plasticity. He has also organize several symposiam on structure/ Properties of Materials.