Correlation Factors for Impurity Diffusion—fcc Lattice

A C15 Laves phase, HfV2+Nb, shows promising mechanical properties and here we describe the structure of its grain boundaries. The C15 Laves phase has a fcc lattice with a=7.4Å. An alloy of composition Hf14V64Nb22 (including a C15 matrix and a second phase of V-rich bcc solution) was made by arc-melting. The alloy was homogenized at 1200°C for 120h. Preliminary study concentrated on Σ3{<110>/70.53°} grain boundaries in the C15 phase using Philips 400T and CM 30 microscopes.The most-commonly observed morphology of Σ3{<110>/70.53°} grain boundaries in the C15 phase is a faceted boundary. A bright field image (BFI) of the faceted boundary and the corresponding diffraction patterns with the grain boundary edge-on are shown in Fig. 1(a). From the diffraction patterns using a <110> zone axis for both grains, it is obvious that this is a Σ3{<110>/70.53°} grain boundary. Crystallographic analysis shows that the Σ3{<110>/70.53°} grain boundaries selectively facet with the following relationships between the two grains: {111}1//{111}2, {112}1//{112}2, {111}1//{115}2, and {001}1//{221}2.

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Interpretation of the Contrast of High-Resolution Electron Microscopy Images of Ni4Mo by Means of Simulated Image Maps

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100178896 ◽

1990 ◽

Vol 48 (1) ◽

pp. 28-29

Author(s):

A. Thust ◽

K. Urban

Keyword(s):

Electron Microscopy ◽

High Resolution ◽

Antiphase Boundary ◽

High Resolution Electron Microscopy ◽

Foil Thickness ◽

Order Structure ◽

Simulated Image ◽

Resolution Electron ◽

Fcc Lattice ◽

Direct Interpretation

The alloy of composition Ni4Mo develops, at temperatures below 860 °C, an ordered Dla-structure which is based on the fcc-lattice. This alloy has been widely investigated with respect to its physical properties and its ordering behaviour. High resolution studies are rare and concentrated mainly on its short-range order structure. The aim of the present work was to develop a detailed understanding of image contrast and to apply the results to antiphase-boundary studies in ordered Ni4Mo by means of a JEOL 4000 EX electron microscope.In high-resolution electron microscopy, depending on defocus and foil thickness, a large variety of different images is obtained. Only a few of these allow a direct interpretation concerning the location and the type of the atoms. By computing a through-focus/through-thickness map (TFTT map) before starting experimental work it is possible to determine the proper conditions at which images can be obtained which are closely related to the projected potential.

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Understanding Correlation: Factors That Affect the Size of r

The Journal of Experimental Education ◽

10.3200/jexe.74.3.249-266 ◽

2006 ◽

Vol 74 (3) ◽

pp. 249-266 ◽

Cited By ~ 155

Author(s):

Laura D. Goodwin ◽

Nancy L. Leech

Keyword(s):

Correlation Factors

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