Effects of oxygen on prismatic faults in α-Ti: a combined quantum mechanics/molecular mechanics study

Bhatia, M. A.; Zhang, X.; Azarnoush, M.; Lü, Gang; Solanki, Kiran

doi:10.1016/j.scriptamat.2014.11.008

Cited by 24 publications

(7 citation statements)

References 23 publications

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“…Density functional theory (DFT) calculations by Ghazisaeidi and Trinkle demonstrate that a (1012) twin boundary affects the formation energy of octahedral oxygen interstitials in the immediate vicinity of the twin [16], however the effect of the twin on formation energy of other sites and the activation barriers for diffusion between the sites is not known. Recent DFT calculations reveal that O diffuses readily along the core of a prismatic edge dislocation in α-Ti and that the presence of O increases Peierls stress and modifies dislocation core geometry [17], providing further indication of complicated interactions between Ti deformation mechanisms and O interstitials. In this study we interrogate the effect of (1012) twin boundaries on the formation energies, activation barriers, and diffusion pathways for O.…”

Section: Introductionmentioning

confidence: 99%

Interaction between oxygen interstitials and deformation twins in alpha-titanium

2016

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Twinning is an important deformation mechanism in many hexagonal close packed metals, including α-titanium (Ti) alloys. However, the mechanisms for twin nucleation, growth, and interaction with other defects are not completely understood.In this study we interrogate the behavior of oxygen (O) interstitials near a (1012) twin boundary using a combination of density functional theory (DFT) and modified embedded atom method (MEAM) calculations. The presence of the twin boundary significantly affects both interstitial formation energy as well as the activation barriers for diffusion between sites. We demonstrate that a tetrahedral interstitial is stable in the twin boundary, despite being unstable in bulk Ti, while the formation energies of the octahedral, hexahedral, and crowdion interstitials are all modified by a nearby twin. Further, the activation barriers for diffusion in the region near the twin are uniformly lower than in the bulk. An atom diffusing across the twin boundary moves through several paths with peak energies more than 0.3 eV lower than for comparable diffusion far from the twin, suggesting that the (1012) twin is a fast diffusion pathway and movement of oxygen interstitials across the twin during twin growth is possible.

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Section: Introductionmentioning

confidence: 99%

Interaction between oxygen interstitials and deformation twins in alpha-titanium

2016

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“…The aspect of "covalent-like" chemical bonding of oxygen atoms in a titanium matrix was also mentioned in [53] and later confirmed by simulations [54][55][56]. Interstitial oxygen was accordingly shown to increase the charge density between titanium atoms around the interstitial sites [57,58]. Fig.…”

Section: Influence Of Oxygen and Nitrogen Contentmentioning

confidence: 66%

Tribological behavior of nanosecond-laser surface textured Ti6Al4V

Kümmel

Hamann-Schroer

Hetzner

et al. 2019

Wear

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Titanium alloys are used due to their high specific strength and remarkable corrosion resistance. Their wear resistance however is poor, which in this paper is counteracted by laser surface texturing. Linear textures were created by the use of a nanosecond-pulsed laser, accompanied by melt bulges of resolidified material on the sides. Packing density, finishing procedure and atmosphere during laser texturing were varied between the experiments. Melt bulges lasered in air turned out to be tribologically beneficial in grease-lubricated sliding contact, reducing wear volume on Ti6Al4V significantly by up to a factor of 160, if a packing density of 5% or more was chosen. Further investigations of melt bulges with energy dispersive X-ray spectroscopy (EDX) and scanning transmission electron microscopy (STEM) revealed an increased content in interstitial oxygen and nitrogen and a purely martensitic α'-phase microstructure. Critical limitation of plastic deformation and a saturation of electronic bonds of the titanium atoms by interstitial elements is thought to be responsible for the reduction in adhesive tendency and therefore the pronounced decrease in wear.

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“…The Peierls-Nabarro (PN) model describes the dislocation core structure within a continuum framework and can be used to estimate the critical stress required for dislocation motion, i.e., Peierls stress [7,13,[21][22][23][24]. However, the inconsistent treatment of the elastic energy and the misfit energy results in inaccurate predictions of the dislocation core properties, see detail in [7,19,21].…”

Section: Semi-discrete Variational Peierls-nabarro Modelmentioning

confidence: 99%

“…First introduced by Vitek [27], the GSFE represents the energy cost per unit area for a stacking fault which is generated by shifting the upper half-crystal relative to the lower half by a certain displacement. The GSFE can be computed using DFT [14,24]. The SVPN model provides an expedient scheme to estimate dislocation core structure and Peierls stress [24] based on DFT-determined GSFE.…”

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confidence: 99%

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Dislocation core properties ofβ-tin: a first-principles study

Bhatia

Azarnoush

Adlakha

et al. 2017

Modelling Simul. Mater. Sci. Eng.

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Dislocation core properties of tin (-Sn) were investigated using the semi-discrete variational Peierls-Nabarro model (SVPN). The SVPN model, which connects the continuum elasticity treatment of the long-range strain field around a dislocation with an approximate treatment of the dislocation core, was employed to calculate various core properties, including the core energetics, widths, and Peierls stresses for different dislocation structures. The role of core energetics and properties on dislocation character and subsequent slip behavior in -Sn was investigated. For instance, this work shows that a widely spread dislocation core on the {110} plane as compared to dislocations on the {100} and {101} planes. Physically, the narrowing or widening of the core will significantly affect the mobility of dislocations as the Peierls stress is exponentially related to the dislocation core width in -Sn. In general, the Peierls stress for the screw dislocation was found to be orders of magnitude higher than the edge dislocation, i.e., the more the edge component of a mixed dislocation, the greater the dislocation mobility (lower the Peierls stress). The largest Peierls stress observed was 365 MPa for the dislocation on the {101} plane. Furthermore, from the density plot, we see a double peak for the 0˚ (screw) and 30˚ dislocations which suggests the dissociation of dislocations along these planes. Thus, for the {101} <1 ̅ 01> slip system, we observed dislocation dissociation into three partials with metastable states. Overall, this work provides qualitative insights that aid in understanding the plastic deformation in -Sn.

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Effects of oxygen on prismatic faults in α-Ti: a combined quantum mechanics/molecular mechanics study

Cited by 24 publications

References 23 publications

Interaction between oxygen interstitials and deformation twins in alpha-titanium

Interaction between oxygen interstitials and deformation twins in alpha-titanium

Tribological behavior of nanosecond-laser surface textured Ti6Al4V

Dislocation core properties ofβ-tin: a first-principles study

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