Slip systems and dislocation densities in individual grains of polycrystalline aggregates of plastically deformed CoTi and CoZr alloys

Ungár, Tamás; Ribárik, Gabor; Zilahi, Gyula; Mulay, R.P.; Lienert, U.; Balogh, Levente; Agnew, Sean R.

doi:10.1016/j.actamat.2014.03.024

Cited by 21 publications

(33 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The homogeneous contrast factor approach has been widely used to quantify cubic alloys. Including, the amount of edge or screw dislocations [24][25][26][27][28], or the relative quantities of different slip types [29] in cubic crystals.…”

Section: Cubic Alloysmentioning

confidence: 99%

“…This can be seen from Equation (1), which shows a feature of DPPA methods that they can only obtain the product ρC hkl and not the values individually. The homogeneous contrast factor approach has been widely used in HCP alloys to quantify the fraction of dislocations with different Burgers vectors [3,22,[29][30][31][32][33]., or relative amounts of slip systems with different slip planes [3,30].…”

Section: Planar Faultsmentioning

confidence: 99%

See 1 more Smart Citation

Peak Broadening Anisotropy and the Contrast Factor in Metal Alloys

Simm

2018

Crystals

View full text Add to dashboard Cite

Diffraction peak profile analysis (DPPA) is a valuable method to understand the microstructure and defects present in a crystalline material. Peak broadening anisotropy, where broadening of a diffraction peak doesn't change smoothly with 2θ or d-spacing, is an important aspect of these methods. There are numerous approaches to take to deal with this anisotropy in metal alloys, which can be used to gain information about the dislocation types present in a sample and the amount of planar faults. However, there are problems in determining which method to use and the potential errors that can result. This is particularly the case for hexagonal close packed (HCP) alloys. There is though a distinct advantage of broadening anisotropy in that it provides a unique and potentially valuable way to develop crystal plasticity and work-hardening models. In this work we use several practical examples of the use of DPPA to highlight the issues of broadening anisotropy. of 31where, D is the crystal size, K Sch is the Scherrer constant (often taken as 0.9 for spherical crystals), g is the reciprocal of the d-spacing of a peak, f m is a function related to the arrangement of dislocations (and represents how the arrangement of groups of dislocations influence their total strain), ρ is the dislocation density and C hkl is the average contrast factor of dislocations in grains that contribute to the hkl diffraction peak. In Equation 1 and other DPPA approaches, C hkl is assumed to be the only term that accounts for broadening anisotropy and its value is required to be able to obtain the dislocation density.TEM to be able to identify details of dislocations [15,16], especially in cases when g.b=0 does not lead to vanishing contrast or due to practicalities of rotating a sample. In the same manner, the diffraction broadening caused by a dislocation varies depending on the diffraction vector, and can be calculated by modelling the dislocation's displacement field. The contribution of a dislocation's displacement field to the broadening of different diffraction profiles is through what is known as the contrast (or orientation) factor of dislocations. The contrast factor of an individual dislocation is dependent on the angles between the diffraction vector and the vectors that define the dislocation: it's Burgers vector (b), slip plane normal (n), and dislocation line (s). The contrast factor of an individual dislocation can be calculated using the computer program ANIZC [17]. For example, the edge dislocation in Figure 2 has a contrast factor of 0.46 when g is [110] and parallel to the dislocations Burgers vector. The value is 0.00 when g is parallel to the slip line ([11 2]) and 0.05 when g is parallel to the slip plane normal ([1 11]).

show abstract

Section: Cubic Alloysmentioning

confidence: 99%

Section: Planar Faultsmentioning

confidence: 99%

Peak Broadening Anisotropy and the Contrast Factor in Metal Alloys

Simm

2018

Crystals

View full text Add to dashboard Cite

show abstract

“…The density of dislocations and the nano-crystallite sizes were determined using modified Williamson-Hall and Warren-Averbach methods [23]. More advanced post-treatment methods can be used as extended convolutional multiple-whole-profile (eCMWP) [24][25][26], as shown by Li et al [27].…”

mentioning

confidence: 99%

Real-Time Investigation of Recovery, Recrystallization and Austenite Transformation during Annealing of a Cold-Rolled Steel Using High Energy X-ray Diffraction (HEXRD)

Moreno

Teixeira

Géandier

et al. 2018

Metals

View full text Add to dashboard Cite

The annealing process of cold-rolled ferrite/pearlite steel involves numerous metallurgical mechanisms as recovery/recrystallization of deformed phases, ripening of carbide microstructure, and austenite transformation in the intercritical domain. The interactions between these mechanisms govern the morphogenesis of the transformed austenite microstructure and, thus, the final properties of the steel. This paper demonstrates that high energy X-ray diffraction (HEXRD) on synchrotron beamline offers the unique possibility to follow concomitantly these mechanisms in situ during a single experiment. A cold-rolled ferrite-pearlite steel dedicated to the industrial production of Dual-Phase steel serves as case-study. Synchrotron experiments have been conducted in transmission at 100 keV with a 2D detector. Diffraction patterns acquired all along an annealing treatment are first analyzed after circular integration. A Rietveld refinement procedure coupled with a Williamson-Hall approach is used to determine phase transformation and recovery kinetics. In this paper, a new method inspired by the 3D X-ray diffraction tomography is proposed to follow recrystallization kinetics at the same time. It is based on a systematic detection of individual diffraction spots related to newly recrystallized grains appearing on Debye-Scherrer rings. The deduced recrystallization kinetics is compared and validated by more conventional ex situ methods.

show abstract

“…Monochromatic synchrotron diffraction experiments on single grains in bulk polycrystalline specimens have shown that RCB occurs along the Debye-Scherrer lines, where, at the same time, the radial broadening is by orders of magnitude smaller, indicating that RCB is mainly caused by rotation or tilting of subgrains. This also indicates that the subgrains created by plastic deformation are rotated or tilted with rather small changes of their average lattice constants (Nyilas et al, 2004;Jakobsen et al, 2006;Levine et al, 2006;Jakobsen et al, 2007;Ungá r et al, 2014). Following up on this evidence, we apply the method of polar decomposition (Higham, 1986) to separate the effect of deformation into stretching and rigid-body rotation, which finally allows the decomposition of diffraction peak broadening into line profiles and rocking curves, parallel and perpendicular to the diffraction vectors, respectively.…”

Section: Introductionmentioning

confidence: 94%

“…In the case of a texture-free polycrystalline or powder specimen, especially when many grains are illuminated simultaneously by the beam, the RC of any Bragg reflection would be 4. Recently, however, with very fine X-ray beams at a synchrotron, it has become possible to readily measure RCs corresponding to individual crystallites even in polycrystalline specimens (Barabash et al, 2003;Jakobsen et al, 2006;Juul-Jensen et al, 2006;Levine et al, 2006;Oddershede et al, 2010;Ungá r et al, 2014).…”

Section: Rocking-curve Broadeningmentioning

confidence: 99%

A common theory of line broadening and rocking curves

2015

Self Cite

View full text Add to dashboard Cite

X-ray diffraction peak broadening is discussed in terms of line broadening and rocking-curve broadening in a novel theoretical description. The nonlocal strain tensor is factorized by using the method of polar decomposition instead of the more conventional separation into symmetrical and antisymmetrical components. A number of X-ray line-broadening and rocking-curve experiments on the same single crystals or individual grains in bulk polycrystals prove that plastic deformation produces strained subgrains mutually rotated by rigid-body rotations. The novel theoretical description appropriately accounts for the rigidbody rotation and strain at the same time and provides straightforward separation of the two effects of line and rocking-curve broadening in the radial and normal directions of the diffraction vector. The mathematical results are discussed in terms of experiments of X-ray diffraction, Laue asterism and electron backscatter diffraction. From the experimental results it is shown that the simultaneous evaluation of line and rocking-curve broadening provides qualitative information about the redundant and geometrically necessary character of dislocations, not available if only one or the other is accessible.

show abstract

Slip systems and dislocation densities in individual grains of polycrystalline aggregates of plastically deformed CoTi and CoZr alloys

Cited by 21 publications

References 42 publications

Peak Broadening Anisotropy and the Contrast Factor in Metal Alloys

Peak Broadening Anisotropy and the Contrast Factor in Metal Alloys

Real-Time Investigation of Recovery, Recrystallization and Austenite Transformation during Annealing of a Cold-Rolled Steel Using High Energy X-ray Diffraction (HEXRD)

A common theory of line broadening and rocking curves

Contact Info

Product

Resources

About