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Dong, Zhihua
Publications (6 of 6) Show all publications
Dong, Z. & Vitos, L. (2019). Finite temperature magnetic properties of CrxCoyNi100-x-y medium entropy alloys from first principles. Scripta Materialia, 171, 78-82
Open this publication in new window or tab >>Finite temperature magnetic properties of CrxCoyNi100-x-y medium entropy alloys from first principles
2019 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 171, p. 78-82Article in journal (Refereed) Published
Abstract [en]

The magnetic structure of polymorphic Cr-Co-Ni medium entropy alloys is investigated as a function of temperature and chemical composition by ab initio calculations. Besides the thermal lattice expansion, the longitudinal spin fluctuations (LSFs) are accounted for in determining the magnetic state at finite temperature. We show that sizable local magnetic moments persist on all alloy components in the paramagnetic state for both face-centered cubic and hexagonal close-packed structures, and each alloy species exhibits particular temperature and concentration dependencies. The crucial role of LSFs for the finite temperature magnetic state and its impact on the temperature dependent elastic parameters are demonstrated.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Medium entropy alloy, Magnetism, Spin fluctuations, Chemical fluctuations, Ab initio calculation
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-257535 (URN)10.1016/j.scriptamat.2019.06.019 (DOI)000479026100016 ()
Note

QC 20190918

Available from: 2019-09-18 Created: 2019-09-18 Last updated: 2019-09-18Bibliographically approved
Liu, T., Long, M.-j., He, W.-j., Chen, D.-f., Dong, Z., Zhang, X.-g. & Duan, H.-m. (2019). Prediction model for austenite grains growth during reheating process in Ti micro-alloyed cast steel by coupling precipitates dissolution and coarsening behavior. Journal of Iron and Steel Research International, 26(2), 162-172
Open this publication in new window or tab >>Prediction model for austenite grains growth during reheating process in Ti micro-alloyed cast steel by coupling precipitates dissolution and coarsening behavior
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2019 (English)In: Journal of Iron and Steel Research International, ISSN 1006-706X, E-ISSN 2210-3988, Vol. 26, no 2, p. 162-172Article in journal (Refereed) Published
Abstract [en]

A combined model to predict austenite grains growth of titanium micro-alloyed as-cast steel during reheating process was established. The model involves the behaviors of austenite grains growth in continuous heating process and isothermal soaking process, and the variation of boundary pinning efficiency caused by the dissolution and coarsening kinetics of second-phase particles was also considered into the model. Furthermore, the experimental verifications were performed to examine the prediction power of the model. The results revealed that the mean austenite grains size increased with the increase in reheating temperature and soaking time, and the coarsening temperature of austenite grains growth was 1423K under the current titanium content. In addition, the reliability of the predicted results in continuous heating process was validated by continuous heating experiments. Moreover, an optimal regression expression of austenite grains growth in isothermal soaking process was obtained based on the experimental results. The compared results indicated that the combined model in conjunction with precipitates dissolution and coarsening kinetics had good reliability and accuracy to predict the austenite grains growth of titanium micro-alloyed casting steel during reheating process.

Place, publisher, year, edition, pages
SPRINGER, 2019
Keywords
Austenite grains growth, Reheating process, Precipitate dissolution, Precipitate coarsening, Prediction model
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-247846 (URN)10.1007/s42243-018-0187-z (DOI)000460599000007 ()2-s2.0-85062513435 (Scopus ID)
Note

QC 20190326

Available from: 2019-03-26 Created: 2019-03-26 Last updated: 2019-04-04Bibliographically approved
Gui, L., Long, M., Wu, S., Dong, Z., Chen, D., Huang, Y., . . . Vitos, L. (2019). Quantitative effects of phase transition on solute partition coefficient, inclusion precipitation, and microsegregation for high-sulfur steel solidification. Paper presented at YNE TW, 1981, METALLURGICAL TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, V12, P965 jcek Pavel, 2017, JOURNAL OF MATERIALS SCIENCE, V52, P5822. Journal of Materials Science & Technology, 35(10), 2383-2395
Open this publication in new window or tab >>Quantitative effects of phase transition on solute partition coefficient, inclusion precipitation, and microsegregation for high-sulfur steel solidification
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2019 (English)In: Journal of Materials Science & Technology, ISSN 1005-0302, Vol. 35, no 10, p. 2383-2395Article in journal (Refereed) Published
Abstract [en]

Segregation and inclusion precipitation are the common behaviours of steel solidification, which are resulted from the redistribution and diffusion of the solute elements at the solid-liquid interface. The effect of the phase transition of high-sulfur free-cutting steel is quantified in the present work for the solute partition coefficient (k(i)), inclusion precipitation, and microsegregation by establishing a coupling model of microsegregation and inclusion precipitation, wherein the quantified dependencies of k(i) in terms of temperature, phase and carbon temperature range and phase transition of high-sulfur steel that under different solidification paths and C contents were quite different, leading to differences in k(i) and eventually in microsegregation. k k(p), and k(s) were mainly affected by phase composition and k(si) was primarily by temperature, while k(mn) depended on both phase composition and temperature during solidification. Increasing the C content within the interval 0.07-0.48 wt%, the 'proportion of the delta phase maintained temperature region during solidification' (P-delta), k(p)(ave) and k(s)(ave) (k(i)(ave) the average value of the k(i) across the whole stages of solidification) decreased monotonically, whereas k phase composition and k(i), leading to the change in microsegregation. Such effect of the peritectic reaction was more significant at the last stage of solidification. When the P-delta was between 75% and 100% (corresponding to 0.07-0.16 wt% C), the solidification path resulted in a greater effect on the microsegregation of solutes C, P, and S because of the peritectic reaction. The microsegregation of solutes Mn and S were comprehensively influenced by k(Mn), k(s) and MnS precipitation as well. The studies would help reveal the solute redistribution at the solid-liquid interface, and improve the segregation of high-sulfur steel by controlling the solidification and precipitation in practice.

Place, publisher, year, edition, pages
JOURNAL MATER SCI TECHNOL, 2019
Keywords
Phase transition, Microsegregation, Solute partition coefficient, Inclusion precipitation, High-sulfur steel
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-261004 (URN)10.1016/j.jmst.2019.05.058 (DOI)000484531600035 ()2-s2.0-85070602811 (Scopus ID)
Conference
YNE TW, 1981, METALLURGICAL TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, V12, P965 jcek Pavel, 2017, JOURNAL OF MATERIALS SCIENCE, V52, P5822
Note

QC 20191003

Available from: 2019-10-03 Created: 2019-10-03 Last updated: 2019-10-03Bibliographically approved
Zhang, H., Sun, X., Lu, S., Dong, Z., Ding, X., Wang, Y. & Vitos, L. (2018). Elastic properties of AlxCrMnFeCoNi (0 <= x <= 5) high-entropy alloys from ab initio theory. Acta Materialia, 155, 12-22
Open this publication in new window or tab >>Elastic properties of AlxCrMnFeCoNi (0 <= x <= 5) high-entropy alloys from ab initio theory
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2018 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 155, p. 12-22Article in journal (Refereed) Published
Abstract [en]

Using ab initio calculations, we investigate the elastic properties of paramagnetic AlxCrMnFeCoNi (0 <= x <= 5) high -entropy alloys (HEAs) in both body-centered cubic (bcc) and face-centered cubic (fcc) structures. Comparison with available experimental data demonstrates that the employed approach describes accurately the elastic moduli. The predicted lattice constants increase monotonously with Al addition, whereas the elastic parameters exhibit complex composition dependences. The elastic anisotropy is unusually high for both phases. The brittle/ductile transitions formulated in terms of Cauchy pressure and Pugh ratio become consistent only when the strong elastic anisotropy is accounted for. The negative Cauchy pressure of CrMnFeCoNi is due to the relatively low bulk modulus and C-12 elastic constant, which in turn are consistent with the relatively low cohesive energy. The present findings in combination with the experimental data suggest anomalous metallic character for the HEAs system. 

National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-232868 (URN)10.1016/j.actamat.2018.05.050 (DOI)000439675000002 ()2-s2.0-85048515476 (Scopus ID)
Note

QC 20180810

Available from: 2018-08-10 Created: 2018-08-10 Last updated: 2018-10-30Bibliographically approved
Dong, Z., Schönecker, S., Li, W., Kwon, S. K. & Vitos, L. (2018). Plastic deformation modes in paramagnetic gamma-Fe from longitudinal spin fluctuation theory. International journal of plasticity, 109, 43-53
Open this publication in new window or tab >>Plastic deformation modes in paramagnetic gamma-Fe from longitudinal spin fluctuation theory
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2018 (English)In: International journal of plasticity, ISSN 0749-6419, E-ISSN 1879-2154, Vol. 109, p. 43-53Article in journal (Refereed) Published
Abstract [en]

Using an efficient first-principles computational scheme, we calculate the intrinsic stacking fault energy (gamma(isf) ) and the unstable stacking fault energy (gamma(usf)) of paramagnetic gamma-Fe as a function of temperature. The formation energies are derived from free energies accounting for thermal longitudinal spin fluctuations (LSFs). LSFs are demonstrated to be important for the accurate description of the temperature-dependent magnetism, intrinsic and unstable stacking fault energies, and have a comparatively large effect on gamma(isf) of gamma-Fe. Dominated by the magneto-volume coupling at thermal excitations, gamma(isf) of gamma-Fe exhibits a positive correlation with temperature, while gamma(usf )declines with increasing temperature. The predicted stacking fault energy of gamma-Fe is negative at static condition, crosses zero around 540 K, and reaches 71.0 mJ m(-2) at 1373 K, which is in good agreement with the experimental value. According to the plasticity theory formulated in terms of the intrinsic and unstable stacking fault energies, twinning remains a possible deformation mode even at elevated temperatures. Both the large positive temperature slope of gamma(usf) and the predicted high-temperature twinning are observed in the case of austenitic stainless steels.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2018
Keywords
Spin fluctuations, Stacking-fault energy, Paramagnetism, gamma-Fe
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-238143 (URN)10.1016/j.ijplas.2018.05.007 (DOI)000447111500003 ()2-s2.0-85047919924 (Scopus ID)
Funder
Swedish Research Council, 2015-5335Swedish Research Council, 2017-06474Swedish Foundation for Strategic Research , S14-0038Swedish Foundation for Strategic Research , SM16-0036The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), CH2015-6292Carl Tryggers foundation
Note

QC 20181108

Available from: 2018-11-08 Created: 2018-11-08 Last updated: 2018-11-08Bibliographically approved
Dong, Z., Schönecker, S., Li, W., Chen, D. & Vitos, L. (2018). Thermal spin fluctuations in CoCrFeMnNi high entropy alloy. Scientific Reports, 8, Article ID 12211.
Open this publication in new window or tab >>Thermal spin fluctuations in CoCrFeMnNi high entropy alloy
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2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 12211Article in journal (Refereed) Published
Abstract [en]

High entropy alloys based on 3d transition metals display rich and promising magnetic characteristics for various high-technology applications. Understanding their behavior at finite temperature is, however, limited by the incomplete experimental data for single-phase alloys. Here we use first-principles alloy theory to investigate the magnetic structure of polymorphic CoCrFeMnNi in the paramagnetic state by accounting for the longitudinal spin fluctuations (LSFs) as a function of temperature. In both face-centered cubic (fcc) and hexagonal close-packed (hcp) structures, the LSFs induce sizable magnetic moments for Co, Cr and Ni. The impact of LSFs is demonstrated on the phase stability, stacking fault energy and the fcc-hcp interfacial energy. The hcp phase is energetically preferable to the fcc one at cryogenic temperatures, which results in negative stacking fault energy at these conditions. With increasing temperature, the stacking fault energy increases, suppressing the formation of stacking faults and nano-twins. Our predictions are consistent with recent experimental findings.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-234176 (URN)10.1038/s41598-018-30732-y (DOI)000441625500034 ()30111892 (PubMedID)2-s2.0-85051647158 (Scopus ID)
Note

QC 20181009

Available from: 2018-10-09 Created: 2018-10-09 Last updated: 2018-12-10Bibliographically approved
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