Ab initio calculations of elastic properties of alloys with mechanical instability: Application to BCC Ti-V alloys

Skripnyak, Natalia; Ponomareva, A. V.; Belov, M. P.; Abrikosov, Igor A.

doi:10.1016/j.matdes.2017.11.071

Cited by 24 publications

(13 citation statements)

References 44 publications

(78 reference statements)

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“…Since the CPA is a single-site approximation, short-range order effects and local-lattice relaxation were not considered. The accuracy of the EMTO-CPA method for the elastic properties and planar fault energies of multi-component alloy systems was demonstrated in previous works [52,[63][64][65][66][67][68][69][70][71]].…”

Section: Electronic Structure Calculationsmentioning

confidence: 93%

Understanding the mechanical properties of reduced activation steels

Schönecker

et al. 2018

Materials & Design

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Reduced activation ferritic/martensitic (RAFM) steels are structural materials with potential application in Generation-IV fission and fusion reactors. We use density-functional theory to scrutinize the micro-mechanical properties of the main alloy phases of three RAFM steels based on the bodycentered cubic FeCrWVMn solid solution. We assess the lattice parameters and elastic properties of ferromagnetic α-Fe and Fe 91 Cr 9 , which are the main building blocks of the RAFM steels, and present a detailed analysis of the calculated alloying effects of V, Cr, Mn, and W on the mechanical properties of Fe 91 Cr 9 . The composition dependence of the elastic parameters is decomposed into electronic and volumetric contributions and studied for alloying levels that cover the typical intervals in RAFM steels. A linear superposition of the individual solute effects on the properties of Fe 91 Cr 9 is shown to provide an excellent approximation for the ab initio values obtained for the RAFM steels. The intrinsic ductility is evaluated through Rice's phenomenological theory using the surface and unstable stacking fault energies, and the predictions are contrasted with those obtained by empirical criteria. Alloying with V or W is found to enhance the ductility, whereas additional Cr or Mn turns the RAFM base alloys more brittle.capable of withstanding a high neutron fluence is one of the most critical challenges in fusion technology research. For instance, the estimated key irradiation parameters of the first wall in DEMO with a fusion power of 2-2.5 GW in operation include a neutron wall loading of < 2 MW/m 2 and a neutron fluence of 5-8 MW-y/m 2 , which would amount to an accumulated dose of 25-30 dpa per year in steels [1].Reduced activation ferritic/martensitic (RAFM) steels based on low-activation elements (e.g., Fe, V, Cr, Mn, Ta, W, Si, C) are currently one of the most promising structural materials for first wall and breeding-blanket applications in fusion reactors [2][3][4][5]. They were selected for the test blanket module for ITER [5][6][7][8] and are considered as a primary candidate structural material for DEMO [9,10]. RAFM steels are essentially modifications of the body-centered cubic (bcc), Fe-rich, Fe-Cr binary alloys and contain minor concentrations of low-activation elements, such as manganese to improve the abrasion and wear resistance as well as tensile properties [11], tungsten and vanadium to maintain a low activation level and to resist irradiation embrittlement [12,13]. The composition of the main alloying elements lies in the range (wt.%) Fe-(7.5-12)Cr-(1.0-2.2)W-(0.15-0.25)V-(0.05-0.6)Mn [14,15].Recent experimental progress has mainly focused on the fabrication, manufacturing, mechanical properties (precipitation behavior, fracture toughness, creep, fatigue, and thermal aging), effects of irradiation, and corrosion analysis of RAFM steels [14,[16][17][18][19][20]. Irradiation damage on the microstructure and mechanical properties, including irradiation hardening and embrittlement by neutrons and helium,...

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Section: Electronic Structure Calculationsmentioning

confidence: 93%

Understanding the mechanical properties of reduced activation steels

Schönecker

et al. 2018

Materials & Design

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“…It is worth to point out that the peculiar behavior of the mixing enthalpy appears at compositions which correspond to the region of dynamical/mechanical instability of the bcc Ti-V alloys at zero temperature. Indeed, the bcc Ti-V alloys become mechanically unstable at V concentrations below ~20 at.%, where the elastic constant C′ becomes negative [10]. One therefore may suspect that it is related to the instability of the alloys, and therefore is unphysical.…”

Section: Theoretical Calculationsmentioning

confidence: 99%

“…In this work we present evidences for failure of the static calculations of mixing enthalpies in alloys with the dynamical instability. As a model system, we consider body-centered cubic (bcc) titanium-vanadium alloys that are dynamically and thermodynamically stable at high temperatures in the whole concentration interval, while at low temperatures they cannot exist because of the dynamical/mechanical instabilities [9][10]. Ti-V alloys with the bcc crystal structure are of practical interest for high-temperature structural components for the aerospace and automotive industries as well as for the development of nuclear reactors.…”

Section: Introductionmentioning

confidence: 99%

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Mixing enthalpies of alloys with dynamical instability: bcc Ti-V system

et al. 2020

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“…analysis of changes in the elastic properties of both, austenite and martensite, upon varying the Ta concentration can improve our understanding of the chemical interplay that may affect the martensitic transformation in shape memory alloys as well as provide useful insights into designing HTSMAs with desired properties. Moreover, trends in elastic properties can be used to determine the conditions of mechanical stability in cubic Ti-based alloys 15 and qualitatively assess the alloy mechanical behavior. A comprehensive investigation of the elastic properties, in particular of the martensite phase, is, to the best of our knowledge, still missing in theory and experiment, motivating the present study.…”

Section: Introductionmentioning

confidence: 99%

Trends in elastic properties of Ti-Ta alloys from first-principles calculations

Chakraborty,

Rogal

2020

Preprint

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The martensitic start temperature (M s ) is a technologically fundamental characteristic of high-temperature shape memory alloys. We have recently shown [Phys. Rev. B 94, 224104 (2016)] that the two key features in describing the composition dependence of M s are the T = 0 K phase stability and the difference in vibrational entropy which, within the Debye model, is directly linked to the elastic properties. Here, we use density functional theory together with special quasi-random structures to study the elastic properties of disordered martensite and austenite Ti-Ta alloys as a function of composition. We observe a softening in the tetragonal shear elastic constant of the austenite phase at low Ta content and a non-linear behavior in the shear elastic constant of the martensite. A minimum of 12.5% Ta is required to stabilize the austenite phase at T = 0 K. Further, the shear elastic constants and Young's modulus of martensite exhibit a maximum for Ta concentrations close to 30%. Phenomenological, elastic-constant-based criteria suggest that the addition of Ta enhances the strength, but reduces the ductile character of the alloys. In addition, the directional elastic stiffness, calculated for both martensite and austenite, becomes more isotropic with increasing Ta content. The reported trends in elastic properties as a function of composition may serve as a guide in the design of alloys with optimized properties in this interesting class of materials.

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Ab initio calculations of elastic properties of alloys with mechanical instability: Application to BCC Ti-V alloys

Cited by 24 publications

References 44 publications

Understanding the mechanical properties of reduced activation steels

Understanding the mechanical properties of reduced activation steels

Mixing enthalpies of alloys with dynamical instability: bcc Ti-V system

Trends in elastic properties of Ti-Ta alloys from first-principles calculations

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