Basic modelling of tertiary creep of copper

Sui, Fangfei; Sandström, Rolf

doi:10.1007/s10853-017-1968-7

Cited by 25 publications

(12 citation statements)

References 60 publications

(97 reference statements)

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“…An improvement was found from phosphorous alloying, which improves the creep ductility of copper significantly [24]. An explanation for the enhanced creep strength and ductility by phosphorous alloying has been given by locking of dislocations by so-called Cottrell atmospheres of phosphorous atoms around the dislocation cores [25] and by reduced creep cavity formation at the grain boundaries [26]- [28]. The former explains the increased strength and the later explains the increased ductility.…”

Section: Creep Of Coppermentioning

confidence: 99%

Hydrogen effects on mechanical performance of nodular cast iron

2019

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The KBS-3 method for long-term disposal of spent nuclear fuel is designed with an external self-standing copper shell, which provides the most important barrier against corrosion and escape of radionuclides, and an internal nodular cast iron insert, which provides the load-bearing structure against external loads. The material intended for the load-bearing insert is ferritic nodular cast iron EN 1563 grade EN-GJS-400-15U. In this paper, hydrogen uptake and sensitivity to hydrogen-induced cracking of the cast iron were studied using tensile testing under continuous electrochemical charging in 1 N H2SO4 solution. Hydrogen uptake was measured by using the thermal desorption method. It was found that the hydrogen desorption profile manifests three distinct peaks at initial locations of 400, 500, and 700 K with a heating rate of 6 K/min. Plastic deformation results in a remarkable increase of the 400 K peak, which indicates hydrogen uptake during deformation. In the constant extension rate tests (CERT) and the constant load tests (CLT), electrochemical hydrogen charging reduced markedly the elongation to fracture and time to fracture, respectively. In CLT, hydrogen charging increased dramatically the creep rate at the applied load of about 0.7 yield stress. Ligaments between the graphite nodules exhibit brittle cleavage facets in the presence of hydrogen, while the ligaments show a characteristic ductile appearance of shear and small dimples when testing in air or distilled water. The obtained results are discussed in terms of the known mechanisms of hydrogen-induced cracking and the role of the graphite nodules in the embrittlement of ductile cast iron.

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Section: Creep Of Coppermentioning

confidence: 99%

Hydrogen effects on mechanical performance of nodular cast iron

2019

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“…ε cr is the creep rate, b is Burgers' vector, and K is the constant related to subgrain size, which is shown in Section 2.2 Brittle creep rupture models, Equation (15). α is a work-hardening constant, and m is the Taylor factor, which is about 3.06 for fcc materials.…”

Section: Ductile Creep Rupture Modelsmentioning

confidence: 99%

“…The critical rupture strain can be predicted with basic models. This has been done for annealed and cold worked copper [15,24] describing primary, secondary, and tertiary creep. In particular, the representation of tertiary creep has turned out to be a challenge.…”

Section: Solid Solution Hardeningmentioning

confidence: 99%

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Application of Fundamental Models for Creep Rupture Prediction of Sanicro 25 (23Cr25NiWCoCu)

Sandström

2019

Crystals

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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.

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“…(4)-(6) are given and none is used as adjustable parameter and fitted to the mechanical test data. Equation (4) is generalized to describe primary and tertiary creep as well [23][24][25] but since only secondary creep will be discussed in the present paper, these extensions will not be considered here. When Eq.…”

Section: Model For Precipitation Hardening Dislocation Creepmentioning

confidence: 99%

Creep strength contribution due to precipitation hardening in copper–cobalt alloys

Sui

Sandström

2018

J Mater Sci

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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.

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Basic modelling of tertiary creep of copper

Cited by 25 publications

References 60 publications

Hydrogen effects on mechanical performance of nodular cast iron

Hydrogen effects on mechanical performance of nodular cast iron

Application of Fundamental Models for Creep Rupture Prediction of Sanicro 25 (23Cr25NiWCoCu)

Creep strength contribution due to precipitation hardening in copper–cobalt alloys

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