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Chen, K., Pan, S., Chen, X., Wang, Z. & Sandström, R. (2020). Optimisation of deformation properties in as-cast copper by microstructural engineering. Part II. Mechanical properties. Journal of Alloys and Compounds, 812, Article ID 151910.
Open this publication in new window or tab >>Optimisation of deformation properties in as-cast copper by microstructural engineering. Part II. Mechanical properties
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2020 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 812, article id 151910Article in journal (Refereed) Published
Abstract [en]

The microstructure evolution in the as-cast pure Cu and Cu-(1.0–3.0)Fe-0.5Co and Cu-1.5Fe-0.1Sn (wt. %) alloys was characterised in the previous work. Herein, the plastic deformation characteristics were examined by uniaxial tensile tests at room temperature. Along with the microstructure evolution, the yield strength increased with increasing Fe content and reached a peak value at 1.5 wt % Fe, but thereafter decreased with the further addition of Fe in the Cu–Fe–Co alloys. Nevertheless, the tensile strength and elongation synchronously improve with increasing Fe content. In particular, the Cu-1.5Fe-0.1Sn alloy achieved the optimal strength–ductility combination. In terms of the strengthening mechanism, the (Fe, Co)- or (Fe, Sn)-doped copper encouraged impediment, trapping, and storage of dislocations by the iron-rich nanoparticles and grain boundaries, which enhanced the strength and sustained the work hardening and elongation. The evolution of mechanical properties under an alloying effect was quantitatively described by the strengthening models. The results indicate that the optimum balance between strength and ductility was achieved by designing a microstructure containing fine grains, intragranular smaller spherical nanoparticles, and a minor solute element with higher misfit and higher growth restriction effect. The necessities for engineering a microstructure to achieve simultaneously strong and ductile bulk metals were discussed.

Place, publisher, year, edition, pages
Elsevier Ltd, 2020
Keywords
Casting, Copper, Iron-rich nanoparticle, Mechanical behaviour, Microstructure design, Cobalt alloys, Copper alloys, Ductility, Grain boundaries, Microstructure, Nanoparticles, Strain hardening, Strengthening (metal), Tensile strength, Tensile testing, Ternary alloys, Tin alloys, Deformation Characteristics, Iron rich, Micro-structure evolutions, Microstructural engineering, Strength and ductilities, Strengthening mechanisms, Iron alloys
National Category
Metallurgy and Metallic Materials
Research subject
Metallurgical process science
Identifiers
urn:nbn:se:kth:diva-263434 (URN)10.1016/j.jallcom.2019.151910 (DOI)000490423000049 ()2-s2.0-85071875799 (Scopus ID)
Note

QC 20191205

Available from: 2019-12-05 Created: 2019-12-05 Last updated: 2019-12-06Bibliographically approved
Chen, K., Zhang, J., Chen, Y., Chen, X., Wang, Z. & Sandström, R. (2020). Slow strain rate tensile tests on notched specimens of as-cast pure Cu and Cu–Fe–Co alloys. Journal of Alloys and Compounds, 822, Article ID 153647.
Open this publication in new window or tab >>Slow strain rate tensile tests on notched specimens of as-cast pure Cu and Cu–Fe–Co alloys
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2020 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 822, article id 153647Article in journal (Refereed) Published
Abstract [en]

Microstructure evolution in the as-cast pure Cu, Cu-(1.0, 2.0, 3.0)Fe-0.5Co (wt. %) alloys were characterized in the former work. The aim of the present study is to investigate the slow strain rate tensile (SSRT) performance and fracture behavior of the Cu–Fe–Co alloys reinforced with fined grains (FG) and iron-rich nanoparticles (NP), referred as NPFG structure. The plastic deformation and fracture characteristics were examined by multiaxial SSRT tests at 75 and 125 °C on notched specimens. The addition of Fe and Co enhanced the ultimate tensile strength and yield strength almost by double to triple times the properties compare to pure Cu, along with an acceptable reduction in ductility, both at 75 and 125 °C. The SSRT properties of the copper samples varied as a function of temperature and alloying content. The analysis of fracture surface indicates the effect of iron-rich nanoparticles and grain boundaries on the deformation and fracture processes. The Kocks-Mecking model was applied to describe the SSRT experimental results with fitting parameters. The model predicted the dynamic recovery ability of the copper samples with different Fe, Co content and temperature. The evolution mechanism of SSRT properties upon alloying content and temperature was discussed in terms of the microstructure characterization, fractographic observation, deformation modeling, strengthening models as well as the analysis of strain-hardening curves. The results indicate through further microstructural engineering the NPFG Cu–Fe–Co alloy is promising in utilization as the canister for the storage of the nuclear waste.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Copper, Fracture behavior, Microstructure, Slow strain rate tensile test, Strengthening mechanisms
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-267781 (URN)10.1016/j.jallcom.2020.153647 (DOI)000512377800100 ()2-s2.0-85077382528 (Scopus ID)
Note

QC 20200304

Available from: 2020-03-04 Created: 2020-03-04 Last updated: 2020-03-17Bibliographically approved
He, J. & Sandström, R. (2019). Application of Fundamental Models for Creep Rupture Prediction of Sanicro 25 (23Cr25NiWCoCu). Crystals, 9(12), Article ID 638.
Open this publication in new window or tab >>Application of Fundamental Models for Creep Rupture Prediction of Sanicro 25 (23Cr25NiWCoCu)
2019 (English)In: Crystals, ISSN 2073-4352, Vol. 9, no 12, article id 638Article in journal (Refereed) Published
Abstract [en]

Creep rupture prediction is always a critical matter for materials serving at high temperatures and stresses for a long time. Empirical models are frequently used to describe creep rupture, but the parameters of the empirical models do not have any physical meanings, and the model cannot reveal the controlling mechanisms during creep rupture. Fundamental models have been proposed where no fitting parameters are involved. Both for ductile and brittle creep rupture, fundamental creep models have been used for the austenitic stainless steel Sanicro 25 (23Cr25NiWCoCu). For ductile creep rupture, the dislocation contribution, solid solution hardening, precipitation hardening, and splitting of dislocations were considered. For brittle creep rupture, creep cavitation models were used taking grain boundary sliding, formation, and growth of creep cavities into account. All parameters in the models have been well defined and no fitting is involved. MatCalc was used for the calculation of the evolution of precipitates. Some physical parameters were obtained with first-principles methods. By combining the ductile and brittle creep rupture models, the final creep rupture prediction was made for Sanicro 25. The modeling results can predict the experiments at long-term creep exposure times in a reasonable way.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
creep, fundamental models, Sanicro 25, creep cavitation, austenitic stainless steels
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-267183 (URN)10.3390/cryst9120638 (DOI)000506676000033 ()2-s2.0-85075873852 (Scopus ID)
Note

QC 20200204

Available from: 2020-02-04 Created: 2020-02-04 Last updated: 2020-02-19Bibliographically approved
Sui, F. & Sandström, R. (2019). Creep strength contribution due to precipitation hardening in copper-cobalt alloys. Journal of Materials Science, 54(2), 1819-1830
Open this publication in new window or tab >>Creep strength contribution due to precipitation hardening in copper-cobalt alloys
2019 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 54, no 2, p. 1819-1830Article in journal (Refereed) Published
Abstract [en]

In spite of its huge technical significance, there does not seem to be consensus about how to model the precipitation contribution to the creep strength. Most contributions in the literature are based on a constant internal stress (also called back stress or threshold stress) from the precipitation. It is well-known and it will also be demonstrated in the paper that this assumption is at variance with observations except for some ODS alloys. There is, however, one model developed by Eliasson et al. (Key Eng Mater 171-174:277-284, 2000) that seems to be able to represent experimental data without the use of any adjustable parameters. It has successfully been applied to describe the creep strength of austenitic stainless steels. Due to the fact that various mechanisms contribute to the creep strength in these steels, the model has not been fully verified. The purpose of this paper is to apply the model to published creep data for Cu-Co alloys, where the precipitation totally dominates the strength contribution to validate the model. In the paper, it is demonstrated that the model can indeed describe the influence of applied stress, alloy composition and heat treatment for the three analysed Cu-Co alloys.

Place, publisher, year, edition, pages
Springer, 2019
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-239460 (URN)10.1007/s10853-018-2922-z (DOI)000448833200064 ()2-s2.0-85053782001 (Scopus ID)
Note

QC 20181128

Available from: 2018-11-28 Created: 2018-11-28 Last updated: 2020-03-09Bibliographically approved
Zhang, J. & Sandström, R. (2019). Influence of W in solid solution on the creep rate of nickel. In: Qian, H; Brongers, M; Uddin, M (Ed.), PROCEEDINGS OF THE ASME PRESSURE VESSELS AND PIPING CONFERENCE, 2018,: . Paper presented at ASME 2018 Pressure Vessels and Piping Conference, PVP 2018; Prague; Czech Republic; 15 July 2018 through 20 July 2018. AMER SOC MECHANICAL ENGINEERS
Open this publication in new window or tab >>Influence of W in solid solution on the creep rate of nickel
2019 (English)In: PROCEEDINGS OF THE ASME PRESSURE VESSELS AND PIPING CONFERENCE, 2018, / [ed] Qian, H; Brongers, M; Uddin, M, AMER SOC MECHANICAL ENGINEERS , 2019Conference paper, Published paper (Refereed)
Abstract [en]

Ni and Ni-W binary alloys are basis for nickel based superalloys. For most nickel based superalloys, strengthening mechanisms include both solid solution hardening and precipitation hardening. W is a vital element to create solid solution hardening and to improve the creep strength. In spite of its wide usage to strengthening of high temperature alloys, the mechanisms for solid solution hardening are not fully quantified. From the assumption that it is due to the attraction of solute atoms to dislocations and formation of Cottrell atmosphere to slow down the motion of dislocations, a fundamental model has been formulated previously. In the present paper, the model is expanded by taking the stacking fault energy and strain induced vacancies into account. Important parameters in the model are the variation of the lattice constant and the shear modulus with alloying content. Models for these variations have been formulated as a function of solute content. Another important parameter is the maximum interaction energy between the dislocations and the solutes. The model can satisfactorily predict both the large difference in creep rate between pure Ni and Ni-W alloys and the comparatively smaller differences between the three investigated Ni-2W, Ni-4W and Ni-6W alloys.

Place, publisher, year, edition, pages
AMER SOC MECHANICAL ENGINEERS, 2019
Keywords
LATTICE-PARAMETERS; BEHAVIOR; MODELS
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-248107 (URN)10.1115/PVP201884286 (DOI)000460998900048 ()2-s2.0-85056875021 (Scopus ID)
Conference
ASME 2018 Pressure Vessels and Piping Conference, PVP 2018; Prague; Czech Republic; 15 July 2018 through 20 July 2018
Note

QC 20190429

Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2020-03-05Bibliographically approved
Sui, F. & Sandström, R. (2018). Basic modelling of tertiary creep of copper. Journal of Materials Science, 53(9), 6850-6863
Open this publication in new window or tab >>Basic modelling of tertiary creep of copper
2018 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 53, no 9, p. 6850-6863Article in journal (Refereed) Published
Abstract [en]

Mechanisms that are associated with acceleration of the creep rate in the tertiary stage such as microstructure degradation, cavitation, necking instability and recovery have been known for a long time. Numerous empirical models for tertiary creep exist in the literature, not least to describe the development of creep damage, which is vital for understanding creep rupture. Unfortunately, these models almost invariably involve parameters that are not accurately known and have to be fitted to experimental data. Basic models that take all the relevant mechanisms into account which makes them predictive have been missing. Only recently, quantitative basic models have been developed for the recovery of the dislocation structure during tertiary creep and for the formation and growth of creep cavities. These models are employed in the present paper to compute the creep strain versus time curves for copper including tertiary creep without the use of any adjustable parameters. A satisfactory representation of observed tertiary creep has been achieved. In addition, the role of necking is analysed with both uniaxial and multiaxial methods.

Place, publisher, year, edition, pages
SPRINGER, 2018
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-223768 (URN)10.1007/s10853-017-1968-7 (DOI)000424874900048 ()2-s2.0-85040081835 (Scopus ID)
Funder
Swedish Nuclear Fuel and Waste Management Company, SKB, 16884
Note

QC 20180307

Available from: 2018-03-07 Created: 2018-03-07 Last updated: 2018-05-16Bibliographically approved
Sui, F., Sandström, R. & Wu, R. (2018). Creep Tests on Notched Specimens of Copper.
Open this publication in new window or tab >>Creep Tests on Notched Specimens of Copper
2018 (English)Manuscript (preprint) (Other academic)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-228007 (URN)
Note

QC 20180523

Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2018-05-23Bibliographically approved
Sui, F., Sandström, R. & Wu, R. (2018). Creep tests on notched specimens of copper. Journal of Nuclear Materials, 509, 62-72
Open this publication in new window or tab >>Creep tests on notched specimens of copper
2018 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 509, p. 62-72Article in journal (Refereed) Published
Abstract [en]

In Sweden, spent nuclear fuel is planned to be disposed off by placing it in canisters which are made of oxygen free copper alloyed with 50 ppm phosphorus. The canisters are expected to stay intact for thousands of years. During the long term disposal, the canisters will be exposed to mechanical pressure from the surroundings at temperatures up to 100 degrees C and this will result in creep. To investigate the role of the complex stress conditions on the canisters, creep tests under multiaxial stress state are needed. In the present work, creep tests under multiaxial stress state with three different notch profiles (acuity 0.5, 2, and 5, respectively) at 75 degrees C with net section stresses ranging from 170 MPa to 245 MPa have been performed. To interpret the experimental results, finite element computations have been conducted. With the help of the reference stress, the rupture lifetime in the multiaxial tests was estimated. The prediction was more precise for the higher acuities than for the lower one. In order to predict the creep deformation of the canisters for the long service period, fundamental creep models are considered. Previously developed basic models are used to compute the creep deformation in the multiaxial tests. Although the scatter is large, the agreement with the experiments is considered as acceptable, indicating that the basic models which have been successfully developed for uniaxial creep tests can also be used to describe multiaxial creep tests. Notch strengthening was observed for copper.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Multiaxial stress state, Creep, Notched specimen, Finite element modelling, Copper
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-234562 (URN)10.1016/j.jnucmat.2018.06.018 (DOI)000442483300007 ()2-s2.0-85048759534 (Scopus ID)
Funder
Swedish Nuclear Fuel and Waste Management Company, SKB
Note

QC 20180919

Available from: 2018-09-19 Created: 2018-09-19 Last updated: 2018-09-19Bibliographically approved
Xia, S., Lousada, C. M., Mao, H., Maier, A. C., Korzhavyi, P. ., Sandström, R., . . . Zhang, Y. (2018). Erratum: Nonlinear oxidation behavior in pure Ni and Ni-containing entropic alloys (Front. Mater., (2018) 5, 53, 10.3389/fmats.2018.00053). Frontiers in Materials, 5, Article ID 73.
Open this publication in new window or tab >>Erratum: Nonlinear oxidation behavior in pure Ni and Ni-containing entropic alloys (Front. Mater., (2018) 5, 53, 10.3389/fmats.2018.00053)
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2018 (English)In: Frontiers in Materials, ISSN 2296-8016, Vol. 5, article id 73Article in journal (Refereed) Published
Abstract [en]

In the original article, there was an error. An explanation should be inserted at the beginning of the section Thermodynamic Calculations, Paragraph 1, line 1: In this as well as the following paragraphs the authors refer to phases such as halite, spinel, corundum etc. It thereby solely referred to the structure type and not the respective mineral. In the original article, there was an error. The word "sfinancial" should be corrected to "financial" in the Acknowledgements section, Paragraph 1: The Carl Tryggers Stiftelse för Vetenskaplig Forskning is gratefully acknowledged for financial support. The authors apologize for these errors and state that they do not change the scientific conclusions of the article in any way. The original article has been updated.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2018
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-252249 (URN)10.1177/0956797615602271 (DOI)2-s2.0-85062450216 (Scopus ID)
Note

QC20190612

Available from: 2019-06-12 Created: 2019-06-12 Last updated: 2019-11-12Bibliographically approved
Sui, F. & Sandström, R. (2018). Fundamental Modelling of Mechanisms Contributing to Tertiary Creep in Copper AT 215 and 250°C. In: Proceedings of the ASME 2018 Pressure Vessels and Piping Conference: . Paper presented at ASME 2018 Pressure Vessels and Piping Conference, July 15-20, 2018, Prague, Czech Republic.
Open this publication in new window or tab >>Fundamental Modelling of Mechanisms Contributing to Tertiary Creep in Copper AT 215 and 250°C
2018 (English)In: Proceedings of the ASME 2018 Pressure Vessels and Piping Conference, 2018Conference paper, Published paper (Refereed)
Abstract [en]

Extensive creep tests have been performed on oxygen free copper with 50 ppm phosphorus at both low and high temperatures. It is the candidate material for storage of spent nuclear fuel in Sweden. Basic models without fitting parameters have been formulated to reproduce primary and secondary creep. For a long time, only empirical models existed for fitting of tertiary creep. To understand the role of creep damage, including recovery, cavitation and necking, basic models that do not involve adjustable parameters are in urgent demand. Only recently, basic models taking the relevant mechanisms into account have been developed. These models were used to predict the tertiary creep for copper at 75°C. The modelled results were compared with experimental creep curves and good agreement has been found. In the present paper, the models are applied to creep tests at higher temperatures (215 and 250°C). A similar representation with good accuracy is obtained. This demonstrates that the fundamental model for back stress is applicable for the higher temperature tests as well. 

National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-228012 (URN)10.1115/PVP201884288 (DOI)2-s2.0-85056835819 (Scopus ID)
Conference
ASME 2018 Pressure Vessels and Piping Conference, July 15-20, 2018, Prague, Czech Republic
Note

QC 20180523

Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2020-03-05Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-8494-3983

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