Non-uniform Solute Segregation at Semi-Coherent Metal/Oxide Interfaces.

The properties and performance of metal/oxide nanocomposites are governed by the structure and chemistry of the metal/oxide interfaces. Here we report an integrated theoretical and experimental study examining the role of interfacial structure, particularly misfit dislocations, on solute segregation at a metal/oxide interface. We find that the local oxygen environment, which varies significantly between the misfit dislocations and the coherent terraces, dictates the segregation tendency of solutes to the interface.

Deformation twinning in a creep-deformed nanolaminate structure.

The underlying mechanism of deformation twinning occurring in a TiAl-(γ)/Ti(3)Al-(α(2)) nanolaminate creep deformed at elevated temperatures has been studied. Since the multiplication and propagation of lattice dislocations in both γ and α(2) thin lamellae are very limited, the total flow of lattice dislocations becomes insufficient to accommodate the accumulated creep strains. Consequently, the movement of interfacial dislocations along the laminate interfaces, i.

Shock-induced phase transformation in tantalum.

A TEM study of pure tantalum and tantalum-tungsten alloys explosively shocked at a peak pressure of 30 GPa is presented. While no omega phase was found in shock-recovered pure Ta and Ta-5W which mainly contain a cellular dislocation structure, a shock-induced omega phase was found in Ta-10W which contains evenly distributed dislocations with a density higher than 1 × 10(12) cm( - 2). The shock-induced [Formula: see text] (hexagonal) transition occurs when the dynamic recovery of dislocations becomes largely suppressed in Ta-10W shocked under dynamic-pressure conditions.

Depth-dependent mechanical properties of enamel by nanoindentation.

Nanoindentation has recently emerged to be the primary method to study the mechanical behavior and reliability of human enamel. Its hardness and elastic modulus were generally reported as average values with standard deviations that were calculated from the results of multiple nanoindentation testing. In such an approach, it is assumed that the mechanical properties of human enamel are constant, independent of testing parameters, like indent depth and loading rate.

Dislocation multi-junctions and strain hardening.

At the microscopic scale, the strength of a crystal derives from the motion, multiplication and interaction of distinctive line defects called dislocations. First proposed theoretically in 1934 (refs 1-3) to explain low magnitudes of crystal strength observed experimentally, the existence of dislocations was confirmed two decades later. Much of the research in dislocation physics has since focused on dislocation interactions and their role in strain hardening, a common phenomenon in which continued deformation increases a crystal's strength.