[1] We report the influence of shear deformation on the microstructure of water-saturated olivine and clinopyroxene aggregates. Prior to deformation, the aqueous fluid was isolated in pockets along grain corners in the olivine-water aggregates, while it was interconnected by a network of grain-edge tubules in the clinopyroxene-water aggregate. During deformation of both types of aggregates, the...

An overview of micromechanical models of strength and deformation behaviour of nanostructured and ultrafine grained metallic materials is presented. Composite models of nanomaterials, polycrystal plasticity based models, grain boundary sliding, the effect of nonequilibrium grain boundaries and nanoscale properties are discussed and compared. The examples of incorporation of peculiar nanocrystal...

– The ice microstructure (grain boundaries) is a key feature used to study ice evolution and to investigate past climatic changes. We studied a deep ice core, in Dome Concordia, Antarctica, which records past mechanical deformations. We measured a “texture tensor” which characterizes the pattern geometry and reveals local heterogeneities of deformation along the core. These results question key...

The reduction of the grain size down to the nm regime has opened new and fascinating avenues for research in several aspects of materials science, including mechanical properties. In recent years large efforts, both experimental and computational, have been made to understand the deformation mechanisms at the nanoscale. Computer simulations suggest both grain boundary accommodation mechanisms a...

Grain boundary networks should play a dominant role in determining the mechanical properties of nanocrystalline metals. However, these networks are difficult to characterize and their response to deformation is incompletely understood. In this work, we study the grain boundary network of nanocrystalline Ni and explore whether it can be modified by plastic deformation. Mechanical cycling at room...

The aim of this chapter is to shed light on the effects of grain boundary segregation on microstructural evolution in nanostructured metallic materials as well as on their mechanical properties. Several key topics will be covered. First, a brief explanation of mechanical stress-driven grain growth in nanostructured Al, Ni, and Cu thin films will be provided in terms of a deformation mechanism m...

Accumulative roll-bonding (ARB) is a severe plastic deformation process that is using rolling to produce ultrafine grains in coarse grained metallic materials. In this study, ARB has been applied on 70/30 brass up to 6 cycles at ambient temperature and non-lubricated conditions to apply a true strain up to 4.8 Von Mises strain. Microstructures of ARBed brass samples were characterized by scanni...

In crystalline materials, plastic deformation occurs by the motion of dislocations, and the regions between individual crystallites, called grain boundaries, act as obstacles to dislocation motion. Grain boundaries are widely envisaged to be mechanically static structures, but this report outlines an experimental investigation of stress-driven grain boundary migration manifested as grain growth...

As foreseen by Richard Feynman in his famous talk titled There's Plenty of Room at the Bottom in 1959, scientists nowadays are miniaturizing structures in materials to achieve better performance as concerned in technical applications. Reducing grain sizes in polycrystalline materials into the range of less than 100nm, for example, could achieve extraordinary high strength in these so called nan...

Based on electron backscattered diffraction analysis and transmission electron microscopy observation, the mechanism of inhomogeneous grain refinement in a NiTiFe shape memory alloy (SMA) subjected to single-pass equal-channel angular extrusion (ECAE) was investigated. The results show that refined grains are mainly nucleated near grain boundaries and a small fraction of them emerges in the gra...