<i>Ab initio</i>
 investigation of the atomic volume, thermal expansion, and formation energy of WTi solid solutions

Bodlos, Rishi; Dengg, Thomas; Ruban, Andrei V.; Mohammad, Dehghani; Romaner, Lorenz; Spitaler, Jürgen

doi:10.1103/physrevmaterials.5.043601

Cited by 6 publications

(9 citation statements)

References 78 publications

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“…Previous attempts to explain segregation behaviour in W 1-x Ti x have been made on the basis of an idealized thermodynamic description of the W-Ti alloy 30 , 31 , 35 , 36 . However, recent atomistic calculations of the mixing enthalpy of W-Ti 37 differ qualitatively from the previously assumed shape within the regular nanocrystalline solution model. Furthermore, also the segregation energy of Ti in W, as obtained from the Miedema model 30 is in qualitative disagreement with results from ab-initio simulations 38 – 41 .…”

Section: Introductionmentioning

confidence: 63%

Probing the composition dependence of residual stress distribution in tungsten-titanium nanocrystalline thin films

et al. 2023

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Nanocrystalline alloy thin films offer a variety of attractive properties, such as high hardness, strength and wear resistance. A disadvantage is the large residual stresses that result from their fabrication by deposition, and subsequent susceptibility to defects. Here, we use experimental and modelling methods to understand the impact of minority element concentration on residual stresses that emerge after deposition in a tungsten-titanium film with different titanium concentrations. We perform local residual stress measurements using micro-cantilever samples and employ machine learning for data extraction and stress prediction. The results are correlated with accompanying microstructure and elemental analysis as well as atomistic modelling. We discuss how titanium enrichment significantly affects the stress stored in the nanocrystalline thin film. These findings may be useful for designing stable nanocrystalline thin films.

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Section: Introductionmentioning

confidence: 63%

Probing the composition dependence of residual stress distribution in tungsten-titanium nanocrystalline thin films

et al. 2023

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“…To understand the microstructure and elemental composition data in the context to the observed residual stress we further apply DFT calculations. As shown in Ref 42 , alloying Ti into W leads to a nonlinear change in lattice parameter. While in the concentration range between 0-20 at% Ti, the lattice parameter is remarkably insensitive to the Ti concentration indicative of the fact that the Ti atom is of about the same size of W in this concentration regime.…”

Section: Discussionmentioning

confidence: 83%

“…4b, the bulk formation energy taken from Ref. 42 is negative up to concentrations of about 50 at% Ti with a clear minimum at 12.5 at%. This implies that Ti prefers to be coordinated by W atoms in this concentration range.…”

Section: Atomistic Modelling Of Segregation Behaviormentioning

confidence: 85%

“…Furthermore, formation energies in 7 were taken from a previous CALPHAD assessment 45 , where the formation energy is positive at all concentrations. Also this assumption has been proven wrong by recent ab-initio simulaions 42,46 . Therefore, we argue that our model is based on correct thermodynamic data and reveals the true origin of segregation in the W-Ti system.…”

Section: Discussionmentioning

confidence: 99%

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Machine-learning assisted local stress evaluation and atomistic modelling to inquire Ti-enrichment in W-Ti nanocrystalline films

Sinojiya

Paulachan

Chamasemani

et al. 2022

Preprint

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Nanocrystalline metallic alloy thin films provide a variety of interesting properties. A disadvantage concerns their inherent instability and generation of residual stresses. Here, we present a unique framework incorporating machine learning assisted experimental and modelling methods to perceive the impact of the minority element concentration on the generated residual stresses within a nanocrystalline thin film. As a candidate system we use a W-Ti alloy thin film with different Ti concentrations. We perform machine-learning assisted local residual stress measurements, correlate the results with accompanied microstructure and elemental analysis and apply density functional theory. We inquire why the experimental observed Ti enrichment can be strongly reduced at smaller concentrations and discuss how it significantly effects the stress stored in the nanocrystalline thin film. The presented perception is highly crucial to yield future design guidelines for more stable nanocrystalline thin films.

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“…From this the thermal expansion for these materials can be obtained under this quasi-harmonic approximation. The volume at each minimum indicates the volume (corresponding to that temperature), which by numeric differentiation gives thermal expansion coefficients of each composition, similar to previous work [52]. For comparison, the rule-of-mixtures approach for thermal expansion of HEAs was applied by taking a weighted average (by volume fraction) of pure elemental data from Touloukian et al [35] obtained experimentally via dilatometry.…”

Section: Methodsmentioning

confidence: 99%

Predicting the thermal expansion of body-centred cubic (BCC) high entropy alloys in the Mo–Nb–Ta–Ti–W system

et al. 2022

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In this study, the thermal expansion behaviour of equiatomic alloys in the Mo-Nb-Ta-Ti-W system is studied to provide a predictive method to assess the behaviour of this and other high entropy alloy systems. The simulations used are based on first principles density functional perturbation theory and the quasi-harmonic approximation. Calculations have been used to predict the stability and phonon properties of increasingly complex alloys in the Mo-Nb-Ta-Ti-W system and their thermal expansion coefficients have been predicted. These are benchmarked against rule of mixtures predictions and experimental observations where available. We have shown that atomic scale modelling techniques can be used to reliably predict thermal expansion of a range of BCC high entropy alloys and concentrated solid solutions of relevance to nuclear fusion and fission applications.

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Ab initio investigation of the atomic volume, thermal expansion, and formation energy of WTi solid solutions

Cited by 6 publications

References 78 publications

Probing the composition dependence of residual stress distribution in tungsten-titanium nanocrystalline thin films

Probing the composition dependence of residual stress distribution in tungsten-titanium nanocrystalline thin films

Machine-learning assisted local stress evaluation and atomistic modelling to inquire Ti-enrichment in W-Ti nanocrystalline films

Predicting the thermal expansion of body-centred cubic (BCC) high entropy alloys in the Mo–Nb–Ta–Ti–W system

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