On the mechanistic basis of deformation at the microscale in hexagonal close-packed metals

Britton, T. Ben; Dunne, Fionn P.E.; Wilkinson, Angus J.

doi:10.1098/rspa.2014.0881

Cited by 154 publications

(78 citation statements)

References 145 publications

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“…Increasing Al content in the alloy tends to reduce the ratio of critical resolved shear stress (CRSS) values for basal and prismatic slip. The stress to activate these two systems becomes equal at 5.74 wt% Al [32,33]. This could explain why the correlation between strain localization and both high basal and prismatic Schmid factor can be observed.…”

Section: Discussionmentioning

confidence: 91%

Deformation and failure mechanisms of Ti–6Al–4V as built by selective laser melting

Moridi

Demir

Caprio

et al. 2019

Materials Science and Engineering: A

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Section: Discussionmentioning

confidence: 91%

Deformation and failure mechanisms of Ti–6Al–4V as built by selective laser melting

Moridi

Demir

Caprio

et al. 2019

Materials Science and Engineering: A

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“…(a) 111 peak, (b) 200 peak, (c) 220 peak, and (d) 311 peak. Where the IPF plots are with reference to the axial direction ( [100]) and use a random orientation distribution of 14 000 grains. Note that if the refence was the transverse direction ([001]), the figure would look the same but the icons would be reversed (empty circles would become full circles and vice versa).…”

Section: Plasticity Approachmentioning

confidence: 99%

“…In addition to this, deformation twinning is an important mode of deformation in HCP alloys [95,97]. The result of this is that deformation is more heterogeneous in HCP alloys [98][99][100], where different grains or orientations can have markedly different deformation microstructures. The most successful models to predict the slip systems and changes during deformation are crystal plasticity finite element models [51] and viscoplastic self-consistent models [52].…”

Section: Plasticity Approachmentioning

confidence: 99%

Peak Broadening Anisotropy and the Contrast Factor in Metal Alloys

Simm

2018

Crystals

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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]).

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“…The Burgers orientation relationship between the α (HCP) and β (BCC) phases in a titanium alloy, showing

{(0001)}_{α} / / {101}_{β},

{⟨ 11 \bar{2} 0 ⟩}_{α} / / {⟨ 1 \bar{1} \bar{1} ⟩}_{β}

and the relationship between HCP <a> type directions and the equivalent BCC directions (adapted from Britton et al ., under an open access CC‐BY license).…”

Section: Introductionmentioning

confidence: 99%

Using transmission Kikuchi diffraction to characterise α variants in an α+β titanium alloy

Tong

Joseph

Ackerman

et al. 2017

Journal of Microscopy

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SummaryTwo phase titanium alloys are important for highperformance engineering components, such as aeroengine discs. The microstructures of these alloys are tailored during thermomechanical processing to precisely control phase fractions, morphology and crystallographic orientations. In bimodal two phase (α + β) Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) alloys there are often three microstructural lengthscales to consider: large (ß10 μm) equiaxed primary α; >200 nm thick plate α with a basketweave morphology; and very fine scaled (<50 nm plate thickness) secondary α that grows between the larger α plates surrounded by retained β. In this work, we utilise high spatial resolution transmission Kikuchi diffraction (TKD, also known as transmission-based electron backscatter diffraction, t-EBSD) and scanning electron microscopy (SEM)-based forward scattering electron imaging to resolve the structures and orientations of basketweave and secondary α in Ti-6242. We analyse the α variants formed within one prior β grain, and test whether existing theories of habit planes of the phase transformation are upheld. Our analysis is important in understanding both the thermomechanical processing strategy of new bimodal two-phase titanium alloys, as well as the ultimate performance of these alloys in complex loading regimes such as dwell fatigue. Our paper champions the significant increase in spatial resolution afforded using transmission techniques, combined with the ease of SEM-based analysis using conventional electron backscatter diffraction (EBSD) systems and forescatter detector (FSD) imaging, to study the nanostructure of real-world engineering alloys.

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On the mechanistic basis of deformation at the microscale in hexagonal close-packed metals

Cited by 154 publications

References 145 publications

Deformation and failure mechanisms of Ti–6Al–4V as built by selective laser melting

Deformation and failure mechanisms of Ti–6Al–4V as built by selective laser melting

Peak Broadening Anisotropy and the Contrast Factor in Metal Alloys

Using transmission Kikuchi diffraction to characterise α variants in an α+β titanium alloy

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