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We study systematically the nanocutting of an Fe single crystal in dependence of the surface orientation and cut direction. We find that in the general case – where the edge dislocations formed at the cutting edge glide obliquely to it – a complex, three-dimensional dislocation network is created. If, however, the edge dislocations formed align with the cutting edge direction, then a simple (two-dimensional) cutting mechanism is realized, in which dislocations glide consecutively without interaction. The shape of the chip is governed by the direction of the activated glide systems. For strong dislocation interaction, a grain boundary may form separating the chip from the workpiece. A cutting hardness is defined; the calculated values are in good agreement with the ploughing hardness measured in scratching simulations. For selected orientations, we find that instead of dislocation plasticity, twinning is activated. This requires smaller cutting forces and the created chip surfaces are smooth. [ABSTRACT FROM AUTHOR]

Orientation related phase transitions of 0.76Pb(Mg 1/3 Nb 2/3 )O 3 -0.24PbTiO 3 single crystals are studied. Values of the relaxation parameters ( γ = 1.87–1.97) estimated from linear fits of the modified Curie-Weiss law indicate the relaxor nature. For (110) oriented single crystal, typical oxygen vacancies related high temperature dielectric relaxation behaviors are observed and analyzed. Orientations dependent electrocaloric effects of 0.76Pb(Mg 1/3 Nb 2/3 )O 3 -0.24PbTiO 3 single crystals are first studied and reported, large reversible adiabatic temperature change (0.80 K) and isothermal entropy change (0.66 J K −1 kg −1 ) are observed. Giant refrigeration efficiency (43.52) and high electrocaloric coefficient (0.041 K cm kV −1 ) exceed the electrocaloric effect values in most bulk ferroelectrics in previous reports. [ABSTRACT FROM AUTHOR]

We present the orientation dependent indentation response of pure magnesium during single grain indentation. A conical indenter and maximum loads between 50 mN and 900 mN were employed. Indent topographies were acquired by confocal microscopy. The indents were also characterized by electron backscatter orientation microscopy for their microstructures. Pronounced activation of specific twinning systems was observed around the impressions. The resulting data were compiled into the inverse pole figure presentation of indent microstructures and topographies after Zambaldi and Raabe, Acta Mater. (2010). Three-dimensional crystal plasticity finite element simulation of the indentation deformation supports the interpretation of the orientation dependent slip and twinning patterns around the indents. The match between the activation of observed and simulated twinning variants is discussed with respect to the conditions for nucleation and growth of extension twins. Furthermore, the compatibility of the twinning strains with the imposed deformation is discussed based on the expanding cavity model of indentation. The orientation dependent response of magnesium during indentation is compared to the literature data for indentation of alpha-titanium and beryllium. Recommendations are given on how to exploit the characteristic nature of the observed indentation patterns to rapidly assess the relative activity of deformation mechanisms and their critical shear stresses during alloy development. [ABSTRACT FROM AUTHOR]

The early stages of recrystallization have been systematically characterized in single crystal metals of medium and low stacking fault energy. Goss {1 1 0}〈0 0 1〉 and brass {1 1 0}〈1 1 2〉 oriented samples of Ni, Cu and Cu–2 wt.% Al alloy were deformed in a channel die to a logarithmic strain of 0.51 to develop a homogeneous structure composed of two sets of symmetrical primary microbands and then lightly annealed. Scanning electron microscopy/electron backscattered diffraction analyses demonstrate a strong relation between as-deformed orientations and the limited number of recrystallized grain orientations. The disorientation angles across the recrystallization front are mostly grouped in the ranges of 25–35° and 45–55° around axes located near, but not at, the normals of all four {1 1 1} planes. The original nuclei possess disorientation angles of 25–35°. The orientation of the growing new grain quickly transforms through the formation of a first generation twin, leading to disorientations of 45–55°. The most frequent situation occurs when the normal of the twinning face plane is situated near the rotation axis, around which the crystal lattice of the “primary nuclei” rotates. Based on the anisotropy of grain growth, a possible mechanism of orientation generation and grain growth by thermally activated movement of dislocation families on {1 1 1} planes is proposed. [ABSTRACT FROM AUTHOR]

This study reports a direct observation on the crack behavior of lithiated Si wafer. Three different Si wafers with <100>, <110> and <111> axes are investigated, to compare the crack behaviors of different orientation Si wafers. Electrochemically induced cracks in each orientated wafer have dissimilar crack behaviors, because the initiations and propagations of cracks are strongly affected by their orientation and strain energy release rate. It is also found that triangular humps and cracks are formed in the (111) wafer, which are discovered for the first time by in this study. Considering that volume expansion, cracks, and pulverizations of Si are the main issues for the commercial use of Si for Li ion battery, this study provides important insight that is relevant to the design of advanced Si anode materials. [ABSTRACT FROM AUTHOR]

Investigation of polarized IR reflectance spectra of single crystals is important in the course of obtaining vibrational, optical and dielectric properties of solid state samples. Diffraction X-ray methods are usually employed for crystal orientation. In this work, two IR reflectance methods were proposed as a supplement in determining the orientation of the b crystal axis and by that the ac crystal plane, in respect to the morphology of monoclinic single crystals. The methods were tested on two Tutton salt single crystals (K2Ni(SO4)2·6H2O and K2Ni(SeO4)2·6H2O) which were further compared with the cross-polarization IR reflectance method. Both methods relied on the symmetry and optical properties of monoclinic single crystals. One takes into account the fact that one of the principal axes of the dielectric tensor was symmetry fixed, while the other used the conditions for the appearance of an isosbestic-like point/region in the polarized IR reflectance spectra of single crystals with low symmetry. [ABSTRACT FROM AUTHOR]

Highlights: [•] Lozenge shape PS-b-PLLA single crystals with uniform size are prepared. [•] Isotropic–nematic transition occurs at low volume fraction for crystal suspensions. [•] The orientation of crystals in nematic phase varies with crystal size. [•] Ethanol can block the lateral attraction. [•] Composite single crystals lose the highly orientation-dependant lateral attraction. [Copyright &y& Elsevier]

Abstract: By means of the stress–strain finite element method (FEM) in elastic–plastic regime, the influences of the applied stress on the distribution of von Mises stress and evolution of shape regularity of γ′ phase in a [011] oriented single crystal nickel-based superalloy are investigated. Results show that, after full heat treatment, the microstructure of [011] oriented single crystal superalloy consists of the cuboidal γ′ phase embedded coherently in the γ matrix phase, and on (100) plane aligned regularly at angle of 45° relative to the [011] orientation. During compressive creep, the cuboidal γ′ phase is transformed into the mesh-like lamellar rafted structure on (100) plane. Therefore, the changes of the lattice strain, the strain energy density and interfacial energy are thought to be the driving forces of the element diffusion and γ′ phase directional growth. During compressive creep, the lattice contraction occurs on (100) plane of the cuboidal γ′ phase along [001] and [010] directions, whose extruding effect may repel Al, Ti atoms with bigger radius. Therefore, the expanding strain of lattices along [100] direction on (010) and (001) planes of the cuboidal γ′ phase may trap Al, Ti atoms to promote the directional growth of γ′ phase on (100) plane along [001] and [010] directions, which is thought to be the main reason for the γ′ phase growing directionally into the mesh-like lamellar structure. [Copyright &y& Elsevier]

The dependence of the reaction initiation mechanism ofpentaerythritoltetranitrate (PETN) on shock orientation and shock strength is investigatedwith molecular dynamics simulations using a reactive force field andthe multiscale shock technique. In the simulations, a single crystalof PETN is shocked along the [110], [001], and [100] orientationswith shock velocities in the range 3–10 km/s. Reactions occurwith shock velocities of 6 km/s or stronger, and reactions initiatethrough the dissociation of nitro and nitrate groups from the PETNmolecules. The most sensitive orientation is [110], while [100] isthe most insensitive. For the [001] orientation, PETN decompositionvia nitro group dissociation is the dominant reaction initiation mechanism,while for the [110] and [100] orientations the decomposition is viamixed nitro and nitrate group dissociation. For shock along the [001]orientation, we find that CO–NO2bonds initiallyacquire more kinetic energy, facilitating nitro dissociation. Forthe other two orientations, C–ONO2bonds acquiremore kinetic energy, facilitating nitrate group dissociation. [ABSTRACT FROM AUTHOR]