An overview of interface-dominated deformation mechanisms in metallic multilayers

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 of 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.