Papers by Sergiy Divinski
Acta Materialia, Apr 1, 2022
Springer eBooks, 1998
Atomic mechanisms of selfdiffusion in Ni3A1 are theoretically studied. Available experimental dat... more Atomic mechanisms of selfdiffusion in Ni3A1 are theoretically studied. Available experimental data on Ni diffusion are shown to be generally consistent with a model of Ni vacancy movements in the Ni sublattice. At present, the problem of Al self-diffusion cannot be certainly clarified owing to a lack of reliable experimental data. A model of Al atom diffusion by anti-structure defects via so-called anti-structure bridges is suggested. The contribution of anti-structure defects increases with a deviation from the stoichiometric composition and strongly depends on the long-range order. A modified approach to calculate equilibrium defect concentrations is considered and the effect of ordering on Al diffusion is investigated.
Powerpoint presentation by Gary S. Collins at the 13th International Conference on Diffusion in S... more Powerpoint presentation by Gary S. Collins at the 13th International Conference on Diffusion in Solids and Liquids (DSL 2017), Vienna, June 26-30, 2017. This research was supported in part by the National Science Foundation under grant DMR 14-10159 (Metals Program).
arXiv (Cornell University), Aug 28, 2020
The problem of estimation of the tracer diffusion coefficients is solved by utilizing a novel tra... more The problem of estimation of the tracer diffusion coefficients is solved by utilizing a novel tracerinterdiffusion couple technique even in the absence suitable radioisotope of one of the components and absence of reliable thermodynamic parameters. This is demonstrated by generating reliable and reproducible mobility data in the alloys of the Fe-Ga system with a strong composition dependence of the diffusion coefficients. Tracer-( 59 Fe) and inter-diffusion are simultaneously measured in three couples Fe/Fe-16Ga, Fe/Fe-24Ga and Fe-16Ga/Fe-24Ga at 1143 K. The results obtained for the couples with different end-members are in an excellent agreement with each other for the overlapping composition intervals. The influence of the molar volume on the measured tracer-( 59 Fe) and inter-diffusion coefficients is evaluated. Using thermodynamic calculations, the Ga tracer diffusion coefficient and the vacancy wind factor are determined via the Darken-Manning relation for the composition range of 0-24 at.% Ga. The results confirm the reliability of the tracer-interdiffusion couple technique for producing highly accurate diffusion data, in the present case for optimizing the mobility description of the bcc phase of the Fe-Ga system. The Ga tracer diffusion coefficients are further estimated via experimental determination of the ratio of the Fe and Ga tracer diffusivities at the Kirkendall marker planes and utilizing the Fe tracer diffusion coefficients measured directly by the radiotracer method.
Nano research, Feb 27, 2024
Multi-edge extended X-ray absorption fine structure (EXAFS) spectroscopy combined with reverse Mo... more Multi-edge extended X-ray absorption fine structure (EXAFS) spectroscopy combined with reverse Monte Carlo (RMC) simulations was used to probe the details of element-specific local coordinations and component-dependent structure relaxations in single crystalline equiatomic CrMnFeCoNi high-entropy alloy as a function of the annealing temperature. Two representative states, namely a high-temperature state, created by annealing at 1373 K, and a low-temperature state, produced by long-term annealing at 993 K, were compared in detail. Specific features identified in atomic configurations of particular principal components indicate variations in the local environment distortions connected to different degrees of compositional disorder at the chosen representative temperatures. The detected changes provide new atomistic insights and correlate with the existence of kinks previously observed in the Arrhenius dependencies of component diffusion rates in the CrMnFeCoNi high-entropy alloy. high-entropy alloys, diffusion, short-range order, extended X-ray absorption fine structure (EXAFS), reverse Monte Carlo
Defect and Diffusion Forum, 1997
Recent results on diffusion in nanostructured materials are reviewed. The analysis highlights the... more Recent results on diffusion in nanostructured materials are reviewed. The analysis highlights the importance of the proper account for a hierarchic microstructure which is often formed in nanostructured materials. The diffusion kinetics is such a material requires a special consideration in dependence on the temperature, diffusion time and the segregation level of the solute. Pressure-less sintering results in clustering of nanograins with significantly enhanced diffusivity of the inter-agglomerate boundaries. Severe plastic deformation produces a broad spectrum of high-angle grain boundaries (GBs) with different kinetic properties. The majority of the high-angle GBs reveals diffusivities very similar to those of general high-angle GBs in their well-annealed coarse-grained counterparts. Nevertheless, considerably faster short-circuit diffusion paths are detected, too. The origin, geometric arrangement, structural and kinetic properties of these high-diffusivity paths are comprehensively investigated and discussed.
Physica status solidi, Apr 16, 1996
ABSTRACT
Acta Materialia, Jul 1, 2017
Acta Materialia, Jun 1, 2022
Journal of Alloys and Compounds, Oct 1, 2017
Composition-dependent tracer diffusion coefficients in the B2 Ni-Al-Ti alloy via a combination of... more Composition-dependent tracer diffusion coefficients in the B2 Ni-Al-Ti alloy via a combination of radiotracer and diffusion couple techniques,
Physical Review Letters, Jun 18, 2013
Recent experimental measurements of Ag impurity diffusion in the Σ5 (310) grain boundary (GB) in ... more Recent experimental measurements of Ag impurity diffusion in the Σ5 (310) grain boundary (GB) in Cu revealed an unusual non-Arrhenius behavior suggestive of a possible structural transformation [Divinski et al., Phys. Rev. B 85, 144104 (2012)]. On the other hand, atomistic computer simulations have recently discovered phase transformations in high-angle GBs in metals [Frolov et al., arXiv:1211.1756v2 (2013)]. In this paper we report on atomistic simulations of Ag diffusion and segregation in two different structural phases of the Cu Σ5 (310) GB which transform to each other with temperature. The obtained excellent agreement with the experimental data validates the hypothesis that the unusual diffusion behavior seen in the experiment was caused by a phase transformation. The simulations also predict that the low-temperature GB phase exhibits a monolayer segregation pattern while the high-temperature phase features a bilayer segregation. Together, the simulations and experiment provide the first convincing evidence for the existence of structural phase transformations in highangle metallic GBs and demonstrate the possibility of their detection by GB diffusion measurements and atomistic simulations.
2018-Sustainable Industrial Processing Summit, May 4, 2018
The presentation is focused on structure-property relationship for interfaces in severe plastical... more The presentation is focused on structure-property relationship for interfaces in severe plastically deformed (SPD) materials. The results are systematized for different types of SPD treatment, imposed strain, and induced defects, and the deformation parameters used (temperature, total strain and strain rate). The kinetic properties of interfaces in a broad spectrum of severe plastically deformed materials ranging pure metals to alloys, including the high-entropy alloys, are measured. A multi-level hierarchy of short-circuit diffusion paths is shown to be formed in ultrafine grained materials produced by SPD Treatment [1,2]. The key properties of deformation-modified grain boundaries, such as interface width, diffusion rate, free volume excess, are measured and analyzed in detail. A model of the deformation-modified grain boundary state is presented.
The ion-plasma deposition was used to produce intermetallic coatings on Al-based substrates. Stru... more The ion-plasma deposition was used to produce intermetallic coatings on Al-based substrates. Structure and properties of these coatings were investigated. It was found that a specific combination of nano-, quasi-, and amorphous intermetallic phases in coatings along with formation of extended transitional sublayer increases mechanical properties of the material. Simultaneously the higher adhesion can be obtained.
Uspehi fiziki metallov, Mar 1, 2006
* Методы исследования: 1-Резерфордово обратное рассеяние; 2-вторичная ионная масс-спектроскопия; ... more * Методы исследования: 1-Резерфордово обратное рассеяние; 2-вторичная ионная масс-спектроскопия; 3-радиоизотопный анализ; 4-микрорентгеноспектральный анализ; 5-Оже-электронная спектроскопия; 6-измерение ЭДС.
Philosophical Magazine, Apr 7, 2014
arXiv (Cornell University), Jul 23, 2017
Diffusion couple technique is an efficient tool for the estimating the chemical diffusion coeffic... more Diffusion couple technique is an efficient tool for the estimating the chemical diffusion coefficients. Typical experimental uncertainties of the composition profile measurements complicate a correct determination of the interdiffusion coefficients via the standard Boltzmann-Matano, Sauer-Freise or the den Broeder methods, especially for systems with a strong compositional dependence of the interdiffusion coefficient. A new approach for reliable fitting of the experimental profiles with an improved behavior at both ends of the diffusion couple is proposed and tested against the experimental data on chemical diffusion in the system Fe-Ga.
Tracer diffusion in ordered intermetallic compounds is reviewed. The main attention is paid to al... more Tracer diffusion in ordered intermetallic compounds is reviewed. The main attention is paid to aluminides of transition metals like Ni, Ti, and Fe. The available experimental data are analyzed with respect to crystalline lattice, point defects, and probable diffusion mechanisms. Effects of deviation from the stoichiometric composition and alloying on diffusion in ordered intermetallic compounds are considered. Tracer diffusion in ternary alloys is illustrated for the system Ni–Fe–Al.
Materialia, Jun 1, 2019
The alloying of Ti with Cu(Sn) and Nb significantly increases the grain boundary diffusioncontrol... more The alloying of Ti with Cu(Sn) and Nb significantly increases the grain boundary diffusioncontrolled growth kinetics of Nb 3 Sn accompanied with a decrease in the activation energy in the Cu(5.5 at.% Sn, Ti)/Nb and Cu(5.5 at.% Sn)/Nb(Ti) diffusion couples. In either case, the β-(Ti,Nb) precipitates form at the grain boundaries of Nb 3 Sn. On the other hand, the ternary intermetallic phase, Nb 3 Sn 2 Ti 3 , is present in the interior of the Nb 3 Sn phase matrix only when Ti is added to Nb. The pinning forces on the grain boundaries of Nb 3 Sn exhorted by the β-(Ti,Nb) precipitates and related microstructure refinement results in an enhanced growth kinetics of the product phase, Nb 3 Sn. The addition of 0.5 at.% Ti to Cu(Sn) has a stronger influence on the growth kinetics and the activation energy for the growth of Nb 3 Sn compared to 3 at.% Ti to Nb owing to a higher fraction of smaller and equiaxed grains with high angle grain boundaries of Nb 3 Sn. The Ti-free Nb 3 Sn phase layer grows with a weak texture, a commonly observed behavior in other material systems for the product phases grown by diffusion-controlled mechanism in the interdiffusion zone. On the contrary, a very strong crystallographic texture of the Ti-containing product phase, Nb 3 Sn, is reported that has a unique pattern depending on the orientation of the adjacent Nb or Nb(Ti) grains. The Cu atoms segregate to the grain boundaries of Nb 3 Sn over a distance of ~2-5 nm with a depletion of Nb.
Acta Materialia, Aug 1, 2020
Abstract Composition-dependent diffusion coefficients are determined in B2-Ni(CoPt)Al system foll... more Abstract Composition-dependent diffusion coefficients are determined in B2-Ni(CoPt)Al system following the pseudo-binary and pseudo-ternary diffusion couple methods, which would not be possible otherwise in a quaternary inhomogeneous material fulfilling the conditions to solve the equations developed based on the Onsager formalism. The end-member compositions to produce ideal/near-ideal diffusion profiles are chosen based on thermodynamic details. The pseudo-binary interdiffusion coefficients of Ni and Al decrease in the presence of Co but increase in the presence of Pt. The pseudo-ternary interdiffusion coefficients indicate that the main interdiffusion coefficients increase significantly in the presence of Pt. Marginal changes of the cross interdiffusion coefficients substantiate a minor change of the diffusional interactions between the components. The thermodynamic driving forces show opposite trends with respect to composition as compared to the changes of the interdiffusion coefficients advocating a dominating role of the Pt(Co)-induced modifications of point defect concentrations. DFT-based calculations revealed that Pt alloying increases the Ni vacancy concentration and decreases the activation energy for the triple defect diffusion mechanism. These findings explain the increase in the thickness of the interdiffusion zone between the B2-Ni(Pt)Al bond coat and the single crystal superalloy Rene N5 because of Pt addition. Furthermore, the EPMA and TEM analyses reveal the growth of refractory elements-enriched precipitates.
Bulletin of The Russian Academy of Sciences: Physics, Dec 1, 2019
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Papers by Sergiy Divinski