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screw dislocations

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Published: 01 June 2012
Fig. 6 Schematic illustration of a screw dislocation More
Image
Published: 01 November 2010
Fig. 3 Basic dislocation configuration of a low-angle twist boundary. (a) A single family of parallel screw dislocations results in a shear deformation, but two perpendicular families of dislocations result in a pure rotation. (b) Transmission electron microscopy image of a low-angle twist More
Image
Published: 01 December 2008
with reactive impurities (for example, magnesium-containing Fe-C-Si alloy). Three growth mechanisms are discussed: A, on the step of the defect boundary ( R step ); B, two-dimensional nucleation ( R 2D ); C, screw dislocation ( R screw ). Source: Ref 37 More
Image
Published: 01 December 2009
Fig. 9 Core structures of 〈 110 〉 { 111 } edge and screw dislocations in Ni 3 Al and a comparison with solutions from the Peierls model (courtesy of Professor Gunther Schoeck). Both calculations used the same input of generalized stacking fault energy, γ, and elastic moduli More
Image
Published: 31 August 2017
., magnesium-containing Fe-C-Si alloy). Three growth mechanisms are discussed: A, on the step of the defect boundary; B, two-dimensional nucleation; and C, screw dislocation. Source: Ref 86 More
Series: ASM Handbook
Volume: 10
Publisher: ASM International
Published: 15 December 2019
DOI: 10.31399/asm.hb.v10.a0006644
EISBN: 978-1-62708-213-6
... directions is projected onto the recording plate to produce a defect image due to orientation contrast ( Fig. 3 ). Fig. 3 (a) Schematic showing the overlap and separation of inhomogeneously diffracted x-rays from a screw dislocation. (b) Back-reflection x-ray topograph of a (0001) 4H-SiC wafer showing...
Series: ASM Handbook
Volume: 19
Publisher: ASM International
Published: 01 January 1996
DOI: 10.31399/asm.hb.v19.a0002354
EISBN: 978-1-62708-193-1
... of forming a three-dimensional dislocation arrangement. This idea is based on the assumption that the stacking fault energy determines the possibility of cross slip of screw dislocations. Cross Slip in Pure Metals As a brief review, if a fcc crystal structure is considered, gliding of a dislocation...
Image
Published: 01 January 2005
Fig. 35 Uniform dislocation structure in iron deformed 14% at −195 °C (–320 °F). The dislocations are primarily of the screw type. Thin-foil electron micrograph. Original magnification 40,000× More
Series: ASM Handbook
Volume: 22A
Publisher: ASM International
Published: 01 December 2009
DOI: 10.31399/asm.hb.v22a.a0005455
EISBN: 978-1-62708-196-2
... for the strain fields to be of the same kind, that is, hydrostatic (or dilatational) or shear. In principle, the strain fields associated with screw dislocations are shear in nature, whereas for edge dislocations there are both shear and dilatational distortions, the latter arising from displacements parallel...
Series: ASM Handbook
Volume: 13A
Publisher: ASM International
Published: 01 January 2003
DOI: 10.31399/asm.hb.v13a.a0003616
EISBN: 978-1-62708-182-5
...—edge dislocations and screw dislocations. An edge dislocation ( Fig. 2 ) is the region of imperfection that lies along the internal edge of an incomplete plane of atoms within a crystal. In a screw dislocation ( Fig. 3 ), a portion of the crystal is displaced such that the atom planes no longer have...
Series: ASM Handbook
Volume: 14A
Publisher: ASM International
Published: 01 January 2005
DOI: 10.31399/asm.hb.v14a.a0004018
EISBN: 978-1-62708-185-6
... ). Planar slip refers to slip lines that are straight, indicating slip on a single plane. Wavy slip ( Fig. 29 ) refers to slip lines that are irregular, indicating slip on two or more intersecting planes, such as that caused by repeated cross slip of a screw dislocation. Slip lines are more readily visible...
Series: ASM Handbook
Volume: 23
Publisher: ASM International
Published: 01 June 2012
DOI: 10.31399/asm.hb.v23.a0005669
EISBN: 978-1-62708-198-6
... mechanical forces resulting in irreversible dislocation glide. Dislocations are either pure edge dislocations ( Fig. 5 ) or screw dislocations ( 6 ) or a mixture of these two ( Ref 19 ). The nonequilibrium interatomic spacing of atoms located at a dislocation core represent zones of higher elastic strain...
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003084
EISBN: 978-1-62708-199-3
... also formed another type of dislocation. The part of the slipped region near the right side, where the displacement is parallel to the dislocation, is called a screw dislocation. In this part, the crystal no longer is made of parallel planes of atoms, but instead consists of a single plane...
Series: ASM Handbook
Volume: 22A
Publisher: ASM International
Published: 01 December 2009
DOI: 10.31399/asm.hb.v22a.a0005413
EISBN: 978-1-62708-196-2
... issue in literature. To illustrate the line of discussion some current models will be represented in the following. In the traditional Seeger model ( Ref 21 ), dynamic recovery is governed by massive cross slip of large groups of screw dislocations, which have been stored previously in front...
Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006307
EISBN: 978-1-62708-179-5
...: edge and screw. For a screw dislocation, the direction of motion is perpendicular to the stress direction, but for an edge dislocation, the motion is parallel to the shear stress. Normally, there is a mixture of screw and edge dislocations, which means that the motion of this mixed dislocation line...
Series: ASM Handbook
Volume: 22B
Publisher: ASM International
Published: 01 November 2010
DOI: 10.31399/asm.hb.v22b.a0005507
EISBN: 978-1-62708-197-9
... of two periodic sets of mutually perpendicular screw dislocations, for instance, (100) twist boundaries. Other twist boundaries are typically comprised of hexagonal grids of three sets of screw dislocations. Low-angle mixed boundaries are composed of a network of mixed dislocations. For a low-angle...
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005213
EISBN: 978-1-62708-187-0
...-dimensional nucleation ( Fig. 22 ), step of a defect (twisted) boundary ( Fig. 22 ), and screw dislocation. The first two mechanisms are governed by exponential laws and apply to the ( 10 1 ¯ 0 ) surface, but the third is governed by a parabolic law and applies to the (0001) surface...
Series: ASM Handbook
Volume: 8
Publisher: ASM International
Published: 01 January 2000
DOI: 10.31399/asm.hb.v08.a0003254
EISBN: 978-1-62708-176-4
... the individual grains of different orientations to match. Fig. 5 Schematic of an edge dislocation The nature and quantity of the dislocations become an integral aspect of plastic deformation. There are two generic types of dislocations, edge and screw, which are primarily differentiated...
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005212
EISBN: 978-1-62708-187-0
.... Kitamura et al. argue that screw dislocations, which are prevalent in real crystals, should be accounted for when developing a growth mechanism for faceted crystals such as silicon. Sunagawa and Yasuda ( Ref 26 ) proved by means of x-ray topography that growth in quartz crystals occurs at the re-entrant...
Series: ASM Handbook
Volume: 17
Publisher: ASM International
Published: 01 August 2018
DOI: 10.31399/asm.hb.v17.a0006446
EISBN: 978-1-62708-190-0
... monopoles is: (Eq 5) β mp = D mp Ω R 3 Λ mp   L 4 μ   b 2 σ r Here, the material factor D mp for screw dislocations is: (Eq 6) D mp,s = 6 ( 1 − ν ) 5 ( 1 + 3 ν ) 5 ( 1 + ν ) 4 ( 1 − 2 ν ) 2...