The influence of interface structure on nanocrystalline deformation of a layered and nanostructured steel

The structural reliability of many brittle materials can rely on the occurrence of intergranular, as opposed to transgranular, fracture in order to maintain high toughness by crack bridging. The current work examines effects of interface structure and grain size distribution on promoting intergranular fracture of nanostructured materials. A layered and nanostructured (LaNa) stainless steel was produced by combination of surface mechanical attrition treatment with warm co-rolling. The microstructure of LaNa steel is characterized by periodic distribution of nanocrystalline layer, ultrafine grained layer and micron grained layer, where the grain size exhibits a graded transition. The large ductility of LaNa steel is achieved by an interlaminar multiple cracking, which is induced by interface debonding and crack deflection at the weak and strong interface bonding zones, respectively. The size-dependent deformation of nanocrystalline is discussed.