Magnetism of Antiphase Boundaries in Ordered Alloys Studied using Electron Holography

2021 ◽  
pp. 168406
Author(s):  
Takehiro Tamaoka ◽  
Ryotaro Aso ◽  
Yasukazu Murakami
Keyword(s):  
Electron Holography ◽  
Antiphase Boundaries ◽  
Ordered Alloys

scholarly journals Suppressing Geometric Phase Shift Owing to Antiphase Boundaries in Dark-Field Electron Holography

2019 ◽  
Vol 60 (5) ◽  
pp. 698-703
Author(s):  
Youngji Cho ◽  
Kodai Niitsu ◽  
Yoshihiro Midoh ◽  
Koji Nakamae ◽  
Daisuke Shindo ◽  
...  
Keyword(s):  
Phase Shift ◽  
Geometric Phase ◽  
Dark Field ◽  
Electron Holography ◽  
Antiphase Boundaries ◽  
Field Electron ◽  
Dark Field Electron

Dislocations Motion in Alloys with Periodic Antiphase Boundaries

1985 ◽  
Vol 43 ◽  
pp. 344-345
Author(s):  
G. Vanderschaeve ◽  
A. Faress
Keyword(s):  
Mechanical Properties ◽  
Surface Tension ◽  
Plastic Deformation ◽  
Average Distance ◽  
Antiphase Boundaries ◽  
Effective Surface ◽  
Shockley Partial ◽  
Ordered Alloys ◽  
Pd Alloy

Plastic deformation of L12 ordered alloys (Cu3Au type) occurs by slip of dislocation pairs. In alloys with periodic APB's however, dislocations moving through the crystal are continually crossing APB's and mechanical properties of these alloys are affected by conditions governing the propagation of dislocations through them.This paper describes some peculiarities of the interaction of moving dislocations with periodic APB's in a Cu 20.3at%Pd alloy, where the average distance between periodic APB's is Ma∼7.6a. The frequently observed configuration (Fig. 1) consisting of dislocation pairs followed by alternatively widely extended and unsplit unit dislocations can be understood if one analyzes the effective surface tension acting on each Shockley partial.

Modeling of Antiphase Boundaries in L12 Structures

1986 ◽  
Vol 81 ◽  
Author(s):  
J.M. Sanchez ◽  
S. Eng ◽  
Y.P. Wu ◽  
J.K. Tien
Keyword(s):  
Antiphase Boundary ◽  
Cluster Variation Method ◽  
Variation Method ◽  
Bulk Alloy ◽  
Antiphase Boundaries ◽  
Ordered Structures ◽  
Wetting Transitions ◽  
Ordered Alloys ◽  
Disordered Layer ◽  
Cluster Variation

AbstractThe thermodynamic properties of conservative (111) antiphase boundaries in L12 ordered structures are modeled using the tetrahedron approximation of the cluster variation method. The concentration and long-range order parameter profiles are determined as a function of temperature and composition of the bulk alloy. Characteristic wetting transitions, with a macroscopic disordered layer growing from the antiphase boundary as the transition temperature is approached, are found for all cases investigated. The effectof antiphase boundaries on the disordering of ordered alloys and on the gliding of superdislocations are discussed.

Exsolution and inversion in pigeonite from the Whin Sill, Northern England

1978 ◽  
Vol 36 (1) ◽  
pp. 474-475
Author(s):  
P.P.K. Smith
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Homogeneous Nucleation ◽  
Silicate Mineral ◽  
Antiphase Boundaries ◽  
Two Phase ◽  
Primitive Form ◽  
The Core ◽  
Nucleation Mechanisms ◽  
And Inversion

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.

Electron holography in materials science

1991 ◽  
Vol 49 ◽  
pp. 670-671
Author(s):  
Hannes Lichte ◽  
Edgar Voelkl
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Materials Science ◽  
Fourier Spectrum ◽  
Object Wave ◽  
Electron Holography ◽  
Reconstruction Procedure ◽  
Numerical Reconstruction ◽  
Transmission Electron ◽  
Unique Interpretation

The object wave o(x,y) = a(x,y)exp(iφ(x,y)) at the exit face of the specimen is described by two real functions, i.e. amplitude a(x,y) and phase φ(x,y). In stead of o(x,y), however, in conventional transmission electron microscopy one records only the real intensity I(x,y) of the image wave b(x,y) loosing the image phase. In addition, referred to the object wave, b(x,y) is heavily distorted by the aberrations of the microscope giving rise to loss of resolution. Dealing with strong objects, a unique interpretation of the micrograph in terms of amplitude and phase of the object is not possible. According to Gabor, holography helps in that it records the image wave completely by both amplitude and phase. Subsequently, by means of a numerical reconstruction procedure, b(x,y) is deconvoluted from aberrations to retrieve o(x,y). Likewise, the Fourier spectrum of the object wave is at hand. Without the restrictions sketched above, the investigation of the object can be performed by different reconstruction procedures on one hologram. The holograms were taken by means of a Philips EM420-FEG with an electron biprism at 100 kV.

TEM study of boron additions to cobalt aluminide

1988 ◽  
Vol 46 ◽  
pp. 546-547
Author(s):  
Gerald B. Feldewerth
Keyword(s):  
High Temperature ◽  
Turbine Engines ◽  
Major Drawback ◽  
University Of Missouri ◽  
Specific Strength ◽  
Aerospace Applications ◽  
Wide Range ◽  
Ordered Alloys ◽  
The University ◽  
Very High

In recent years an increasing emphasis has been placed on the study of high temperature intermetallic compounds for possible aerospace applications. One group of interest is the B2 aiuminides. This group of intermetaliics has a very high melting temperature, good high temperature, and excellent specific strength. These qualities make it a candidate for applications such as turbine engines. The B2 aiuminides exist over a wide range of compositions and also have a large solubility for third element substitutional additions, which may allow alloying additions to overcome their major drawback, their brittle nature.One B2 aluminide currently being studied is cobalt aluminide. Optical microscopy of CoAl alloys produced at the University of Missouri-Rolla showed a dramatic decrease in the grain size which affects the yield strength and flow stress of long range ordered alloys, and a change in the grain shape with the addition of 0.5 % boron.

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