Search results for "Location"

Computer Simulations on Dislocation Patterning

1995

Reconstructed bcc Co films on the surface

2007

Abstract Ultrathin epitaxial Co films on Cr ( 1 1 0 ) are examined by scanning tunneling microscopy and spectroscopy (STM and STS). At room temperature Co grows as pseudomorphic bcc layers for the first two monolayers and forms close-packed Co layers with stacking faults for thicker coverages. A periodic lattice distortion appears in two equivalent (3 × 1) reconstruction domains in combination with a regular lattice of dislocation lines oriented along the in-plane close-packed row directions bcc [ 1 1 ¯ 1 ] and bcc [ 1 ¯ 1 1 ] . The reconstruction and the occurrence of dislocation lines are caused by the epitaxial strain. The local density-of-states function is mapped by scanning tunneling …

Mathematical modelling of the industrial growth of large silicon crystals by CZ and FZ process

2003

The present paper gives an overview of the complex mathematical modelling of industrial Czochralski (CZ) and floating‐zone (FZ) processes for the growth of large silicon single crystals from melt. Extensive numerical investigations of turbulent Si‐melt flows in large diameter CZ crucibles, global thermal calculations in growth facilities and analysis of the influence of various electromagnetic fields on CZ process are presented. For FZ process, a complex system of coupled 2D and 3D mathematical models is presented to show the possibilities of modelling from the calculation of the molten zone shape till the resistivity distribution in the grown crystal. A special developed program code is pr…

X-ray diffraction study of crystallographic parameters and debye temperature of c60 single crystals

2002

Abstract The cubic lattice parameter value a =1.41568±0.00006  nm of large size C 60 single crystal has been measured and Debye temperature T D =53.9 K from the X-ray scattering spectrum at a fixed temperature was obtained. The microhardness and dislocation structure of the crystals was examined.

Influence of plastic deformation on the microstructure and corrosion behaviour of Ti–10Mo–4Zr and Ti–6Al–4V alloys in the Ringer’s solution at 37°C

2015

Abstract The influence of plastic deformation on the microstructure and passivity of Ti–6Al–4V and Ti–10Mo–4Zr is studied. The content of titanium-based compounds in the passive film formed on the alloys increases under straining. In the region where necking occurs, the β-phase content drops in Ti–6Al–4V. The grain orientation spread increases with increasing strain. The quality index of EBSD maps is affected on Ti–10Mo–4Zr (dislocation structures along preferential orientations). The corrosion behaviour is investigated in the Ringer’s solution (37 °C). Results obtained in the anodic and cathodic domains are discussed considering changes described previously.

Plastic Deformation of Single Nanometer-Sized Crystals

2008

We report in situ electron microscopy observations of the plastic deformation of individual nanometer-sized Au, Pt, W, and Mo crystals. Specifically designed graphitic cages that contract under electron irradiation are used as nanoscopic deformation cells. The correlation with atomistic simulations shows that the observed slow plastic deformation is due to dislocation activity. Our results also provide evidence that the vacancy concentration in a nanoscale system can be smaller than in the bulk material, an effect which has not been studied experimentally before.

Depth profiles of hardening in lithium fluoride irradiated with swift58Ni ions

2004

The changes of hardness and dislocation formation in LiF crystals irradiated with 630-MeV 58Ni ions up to a dose of 20 MGy were studied by microindentation and dislocation etching techniques. Above the threshold fluence of 2 × 1010 ions/cm2, a marked effect of hardening, which is related mainly to damage processes in the track core, has been observed. Its magnitude depends on ion fluence and energy loss. To investigate the depth distribution of hardening, indentation tests on crystal cross sections cleaved parallel to ion flux were performed. It has been found that the hardness change along the ion path correlates with the ion energy loss and reaches the highest value at the Bragg maximum. …

Effective slippage on superhydrophobic trapezoidal grooves

2013

We study the effective slippage on superhydrophobic grooves with trapezoidal cross-sections of various geometries (including the limiting cases of triangles and rectangular stripes), by using two complementary approaches. First, dissipative particle dynamics (DPD) simulations of a flow past such surfaces have been performed to validate an expression [E.S.Asmolov and O.I.Vinogradova, J. Fluid Mech. \textbf{706}, 108 (2012)] that relates the eigenvalues of the effective slip-length tensor for one-dimensional textures. Second, we propose theoretical estimates for the effective slip length and calculate it numerically by solving the Stokes equation based on a collocation method. The comparison …

Powder metallurgy processing and deformation characteristics of bulk multimodal nickel

2014

cited By 7; International audience; Spark plasma sintering was used to process bulk nickel samples from a blend of three powder types. The resulting multimodal microstructure was made of coarse (average size ∼ 135 μm) spherical microcrystalline entities (the core) surrounded by a fine-grained matrix (average grain size ∼ 1.5 μm) or a thick rim (the shell) distinguishable from the matrix. Tensile tests revealed yield strength of ∼ 470 MPa that was accompanied by limited ductility (∼ 2.8% plastic strain). Microstructure observation after testing showed debonding at interfaces between the matrix and the coarse entities, but in many instances, shallow dimples within the rim were observed indica…

The combined influence of grain size distribution and dislocation density on hardness of interstitial free steel

2020

Abstract Understanding the relationship between microstructure features and mechanical properties is of great significance for the improvement and specific adjustment of steel properties. The relationship between mean grain size and yield strength is established by the well-known Hall-Petch equation. But due to the complexity of the grain configuration within materials, considering only the mean value is unlikely to give a complete representation of the mechanical behavior. The classical Taylor equation is often used to account for the effect of dislocation density, but not thoroughly tested in combination with grain size influence. In the present study, systematic heat treatment routes and…