Helium bubble nucleation at low-angle twist boundaries in gold has been investigated. It is found that the helium bubbles preferentially nucleate at screw dislocation nodal points and result in helium bubble superlattice formation, which is completely isomorphic with the screw dislocation network along the twist-grain boundary. Molecular statics calculations reveal that defect formation/solution energies along the screw dislocations, especially at the nodal points, are lower than their bulk counterparts. It is believed that this driving force is responsible for the helium bubble superlattice formation. Our study suggests that grain boundary engineering via adjustable twist angles in parallel boundaries to form tunable 3D bubble superlattices could afford a very promising approach for design of radiation tolerant materials.

While initial interest in nanocomposites was to explore size effects in mechanical behavior, current research is focused around the new paradigm of interface-dominated/enabled mechanical behavior. The use of advanced computational tools to accelerate the discovery, design, and fundamental understanding of behavior is highlighted along with novel synthesis and in situ nanomechanical characterization tools. Designed interfaces can be used as building blocks to create new forms of hierarchical composites with unprecedented mechanical and physical behavior. New frontiers in the field of mechanical behavior of nanocomposites involving metallic, nanocarbon, bioinspired, and biomaterials are reviewed.

As-cast Al–20wt.% Si alloys were processed via laser rapid solidification (LRS) techniques to create eutectic microstructures with nanoscale interconnected, nanotwinned Si fibers. LRS morphologies exhibit higher flow stress, exceeding 800 MPa and uniform plastic deformation above 20% compared to as-cast alloy that fractures at strains below 8% at flow strength of approximately 200 MPa. The strengthening mechanisms of LRS morphologies are interpreted in terms of the interfacial constraints: increase in yield strength as well as strain hardening rate due to nanoscale confined slip in fibrous Al–Si eutectic, and load transfer and eventual plasticity in the nanoscale Si fibers. GRAPHICAL ABSTRACT Impact statement Interconnected, nanotwinned Si fibers in hypereutectic Al–Si alloy achieved by LRS increase the flow stress to over 800 MPa while maintaining homogeneous plastic deformation to over 20% strain, due to confined slip in nanoscale eutectic that increases yield strength and strain hardening with reducing size and promotes plastic co-deformability between disparate phases.