Tracing the coupled atomic shear and shuffle for a cubic to a hexagonal crystal transition

Wang, H.L.; Hao, Yulin; He, Suyun; Du, Kui; Li, Tong; Obbard, E.G.; Hudspeth, Jessica; Wang, J.G.; Wang, Y.D.; Wang, Yihuan; Prima, Frédéric; Lü, Ning; Kim, M.J.; Cairney, Julie M.; Li, S.J.; Yang, Rui

doi:10.1016/j.scriptamat.2017.02.024

Cited by 47 publications

(7 citation statements)

References 28 publications

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“…5d shows that Sn partitions preferentially in the β phase. Although the partitioning of Sn in the β phase seems weak, it is consistent with the reported literature wherein Sn was observed to partition preferentially in the β phase of Ti alloys (Bahl et al, 2017a;Salvador et al, 2016;Wang et al, 2017). This suggests that Sn acts as a β stabilizer in Ti-Nb-Sn alloy system.…”

Section: Microstructural Stability In Tns Alloyssupporting

confidence: 90%

Engineering the next-generation tin containing β titanium alloys with high strength and low modulus for orthopedic applications

Bahl

Das

Suwas

et al. 2018

Journal of the Mechanical Behavior of Biomedical Materials

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Metastable β Ti alloys are the new emerging class of biomaterial for load bearing orthopedic applications. However, these alloys in the single β phase microstructure have insufficient strength for use in load bearing applications. It is imperative to strengthen these alloys by carefully designed thermo-mechanical processing routes that typically involve aging treatment. In this investigation two newly designed Sn based β Ti alloys of composition Ti-32Nb-(2, 4) Sn are evaluated. The effects of Sn content on the mechanical properties and biological performance of these alloys processed through designed thermo-mechanical processing route are investigated. The increase in the Sn content led to a reduction in the elastic modulus of the alloy. An increase in the Sn content increased the aspect ratio of the α precipitates, which led to a significant strengthening in the alloy while keeping the elastic modulus low. In addition, the corrosion behavior of the alloy was evaluated in simulated body fluid. The Sn containing β alloys have an excellent corrosion resistance as desired for an implant material. The corrosion resistance improved with an increase in Sn content. These alloys were also observed to have excellent cytocompatibility as they not only supported the attachment and proliferation of human mesenchymal stem cells but also their osteogenic differentiation in vitro. The combination of high strength, low elastic modulus, superior corrosion resistance and biocompatibility underscores the promise of Sn containing β Ti alloys for use in orthopedic applications.

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Section: Microstructural Stability In Tns Alloyssupporting

confidence: 90%

Engineering the next-generation tin containing β titanium alloys with high strength and low modulus for orthopedic applications

Bahl

Das

Suwas

et al. 2018

Journal of the Mechanical Behavior of Biomedical Materials

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“…7b). These are similar with the orthorhombic phase produced by the up-hill diffusion of the Nb-lean domains as the decomposition is enhanced by heat treatment [22].…”

Section: Notch Fatigue Propertiessupporting

confidence: 58%

“…This leads to some unprecedented properties such as strong in strength, soft in modulus, ductile in toughness in combination with super-elasticity and entirely tunable thermal expansion from positive, via zero, to negative in a wide temperature range [20,21]. The nanoscale Nb modulation can stabilize the β phase and cause a successive atomic rearrangement via the up-hill Nb diffusion [22,23]. Though the novel nonlinear elasticity induced by the nanoscale Nb modulation has been revealed recently, its effect on fatigue notch resistance of Ti2448 alloy is unclear.…”

Section: Introductionmentioning

confidence: 99%

Weak fatigue notch sensitivity in a biomedical titanium alloy exhibiting nonlinear elasticity

et al. 2017

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It is well known that metallic materials exhibit worse fatigue damage tolerance as they behave stronger in strength and softer in modulus. This raises concern on the long term safety of the recently developed biomechanical compatible titanium alloys with high strength and low modulus. Here we demonstrate via a model alloy, Ti-24Nb-4Zr-8Sn in weight percent, that this group of multifunctional titanium alloys possessing nonlinear elastic deformation behavior is tolerant in fatigue notch damage. The results reveal that the alloy has a high strength-to-modulus (σ/E) ratio reaching 2% but its fatigue notch sensitivity (q) is low, which decreases linearly from 0.45 to 0.25 as stress concentration factor increases from 2 to 4. This exceeds significantly the typical relationship between σ/E and q of other metallic materials exhibiting linear elasticity. Furthermore, fatigue damage is characterized by an extremely deflected mountain-shape fracture surface, resulting in much longer and more tortuous crack growth path as compared to these linear elastic materials. The above phenomena can be explained by the nonlinear elasticity and its induced stress relief at the notch root in an adaptive manner of higher stress stronger relief. This finding provides a new strategy to balance high strength and good damage tolerance property of metallic materials.

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“…It is not surprising that shuffling and distortion are correlated in metals, as experimentally found by Wang et al for the bcc-hcp transformation in titanium [142], because the lattice distortion and the displacement of the atoms in the lattice are intrinsically correlated. Similarly, deformation twinning in hcp crystals imagined as an hcp-hcp transformation involves shuffling.…”

Section: Comparison With the Pure-shuffle Modelmentioning

confidence: 67%

Shifting the Shear Paradigm in the Crystallographic Models of Displacive Transformations in Metals and Alloys

Cayron

2018

Crystals

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Deformation twinning and martensitic transformations are characterized by the collective displacements of atoms, an orientation relationship, and specific morphologies. The current crystallographic models are based on the 150-year-old concept of shear. Simple shear is a deformation mode at constant volume, relevant for deformation twinning. For martensitic transformations, a generalized version called invariant plane strain is used; it is associated with one or two simple shears in the phenomenological theory of martensitic crystallography. As simple shears would involve unrealistic stresses, dislocation/disconnection-mediated versions of the usual models have been developed over the last decades. However, a fundamental question remains unsolved: how do the atoms move? The aim of this paper is to return to a crystallographic approach introduced a few years ago; the approach is based on a hard-sphere assumption and linear algebra. The atomic trajectories, lattice distortion, and shuffling (if required) are expressed as analytical functions of a unique angular parameter; the habit planes are calculated with the simple "untilted plane" criterion; non-Schmid behaviors associated with some twinning modes are also predicted. Examples of steel and magnesium alloys are taken from recent publications. The possibilities offered in mechanics and thermodynamics are briefly discussed.

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Tracing the coupled atomic shear and shuffle for a cubic to a hexagonal crystal transition

Cited by 47 publications

References 28 publications

Engineering the next-generation tin containing β titanium alloys with high strength and low modulus for orthopedic applications

Engineering the next-generation tin containing β titanium alloys with high strength and low modulus for orthopedic applications

Weak fatigue notch sensitivity in a biomedical titanium alloy exhibiting nonlinear elasticity

Shifting the Shear Paradigm in the Crystallographic Models of Displacive Transformations in Metals and Alloys

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