The flow stress behavior of OFHC polycrystalline copper

Flinn, J.E.; Field, David P.; Korth, G.E.; Lillo, T.M.; Macheret, J.

doi:10.1016/s1359-6454(01)00102-1

Cited by 68 publications

(22 citation statements)

References 33 publications

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“…Irrespective of the studied material and grain size, the accuracy of the strain measurements shows that tensile hardening behavior before necking can be divided in three stages (I, II, and III), which are less different than those for a monocrystal (except for stage I [43] ). For comparison, a similar observation has been reported for copper, [43,50] nickel, [32,42,44] aluminium, [42] and stainless steel. [34,43,44] The same kind of results can be obtained using the stress as a function of the square root of a plastic-strain plot.…”

Section: A Flow-stress Behaviorsupporting

confidence: 79%

Grain-size effects on tensile behavior of nickel and AISI 316L stainless steel

Feaugas

Haddou

2003

Metall Mater Trans A

129

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The aim of this work is to provide experimental results to understand the grain-size effects on tensile hardening of fcc polycrystalline materials. The contribution of grain size on hardening rate is discussed in terms of backstress (X) and effective-stress (⌺ ef ) evolutions in the different hardening stages. Based on this stress partition, the origin of the classical Hall-Petch relationship is clarified at the different levels of microstructural heterogeneities. If the backstresses and effective stresses verified the Hall-Petch formulation, however, the effective stress is less dependent on grain size than the backstress. The grain-size effect on short-range internal stresses (effective stress) is well explained in terms of a mean path length using classical dislocation modeling. The backstress dependence on grain size seems to be mainly the result of intergranular plastic-strain incompatibilities in relation with the formation of a grain-boundary layer in stage I. In others stages (higher plastic strain), the interactions between intergranular and intragranular long-range internal stresses have been illustrated. The degree of these interactions remains unclear.

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Section: A Flow-stress Behaviorsupporting

confidence: 79%

Grain-size effects on tensile behavior of nickel and AISI 316L stainless steel

Feaugas

Haddou

2003

Metall Mater Trans A

129

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“…These grains have a special orientation relationship to the matrix material (related by a 60 o rotation about the <111> crystallographic direction) and have been shown to influence mechanical properties in other materials (see for example Kumar, et. al., 2000 andFlinn, et. al, 2001).…”

Section: Task 3-1 Characterization Of Creep Deformation Of Ma 754mentioning

confidence: 99%

Development of a Supercritical Carbon Dioxide Brayton Cycle: Improving VHTR Efficiency and Testing Material Compatibility - Final Report

Oh¹

2006

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EXECUTIVE SUMMARYGeneration IV reactors will need to be intrinsically safe, having a proliferation-resistant fuel cycle and several advantages relative to existing light water reactor (LWR). They, however, must still overcome certain technical issues and the cost barrier before it can be built in the U.S. The establishment of a nuclear power cost goal of 3.3 cents/kWh is desirable in order to compete with fossil combined-cycle, gas turbine power generation. This goal requires approximately a 30 percent reduction in power cost for stateof-the-art nuclear plants. It has been demonstrated that this large cost differential can be overcome only by technology improvements that lead to a combination of better efficiency and more compatible reactor materials.The objectives of this research are (1) to develop a supercritical carbon dioxide Brayton cycle in the secondary power conversion side that can be applied to the Very-High-Temperature Gas-Cooled Reactor (VHTR), (2) to improve the plant net efficiency by using the carbon dioxide Brayton cycle, and (3) to test material compatibility at high temperatures and pressures. The reduced volumetric flow rate of carbon dioxide due to higher density compared to helium will reduce compression work, which eventually increase plant net efficiency. Research ObjectivesThe project has two major objectives: The first objective is to develop a supercritical carbon dioxide (S-CO 2 ) Brayton cycle and to improve the VHTR plant efficiency by using supercritical CO 2 . The target of the improved cycle efficiency is close to a 50% that includes the hydrogen plant coupled to the VHTR and power conversion unit through the intermediate heat transfer loop. The second objective is to test material compatibility. The current VHTR reference design has a recommended core outlet temperature of 900 0 C, based on a 600-megawatt thermal. Because of the high temperature in the reactor and an intermediate heat exchanger, a material compatibility could be a technical concern. In order to resolve this concern, we need to investigate the material compatibility by high-temperature exposure to supercritical carbon dioxide. In this study, we propose to characterize the creep deformation of Inconel MA 754, 758, and Inconel 617 over a range of temperatures of 850 to 1050°C and stresses within the power law creep regime. We also propose to investigate the interaction of MA 754, 758, and Inconel 617 in supercritical CO 2 using thermogravimetric analysis combined with surface analysis to examine the iv possible chemical interaction mechanism(s), e.g., breakdown of the passivating chromium (Cr) oxide or carburization, at temperatures and pressures of interest. Report Content and OrganizationThis final report highlights key accomplishments from this project. Section 1 provides introductory information about the project. Detailed information about the objectives and accomplishments may be found in Sections 2 through 4. Section 5 highlights results and conclusions that can be drawn from results obtained from each task....

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“…High densities of dislocations now exist within and outside the annealing twins and some twin boundaries appear to have been penetrated by dislocations, Fig 5d. These observations imply that the annealing twin boundaries were sources of partial and perfect dislocations; a similar suggestion has been made by others. [7,34] To validate this suggestion, in situ straining experiments were performed using preloaded specimens. This study showed that perfect and partial dislocations are emitted from the annealing twins, that the annealing twins can act as barriers to slip and in other cases slip is transmitted across the twin boundary, that deformation twins are produced and annihilated during the straining process, and, a Figure 5.…”

Section: Case1 Dislocation Interactions With Frank Loopsmentioning

confidence: 99%

“…However, despite considerable progress, no clear methodology exists for transferring this information into a predictive macroscopic constitutive relationship. [1][2][3][4][5][6][7] In this paper, we present two examples to illustrate how conventional static transmission electron microscopy and in-situ straining in the transmission electron microscope can be combined to understand microstructural evolution during straining and how this information can be incorporated into plasticity models. The importance of grain and twin boundaries as sources of dislocations is demonstrated.…”

Section: Introductionmentioning

confidence: 99%

Dislocation–obstacle interactions: Dynamic experiments to continuum modeling

Robertson

Beaudoin

Al‐Fadhalah

et al. 2005

Materials Science and Engineering: A

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Incorporating the interaction of dislocations with obstacles remains a challenge in the development of predictive large-scale plasticity models. The need is particularly important in the elastic-plastic transition region where these interactions can dominate the behavior. By combining post-mortem analysis with dynamic straining in the transmission electron microscope, the atomic processes governing glissile dislocation reactions and interactions with obstacles has been determined. This information has been incorporated at least phenomenologically in models to assess the macroscopic stress-strain response. Two examples will be presented to demonstrate the methodology. The first example considers the interaction of dislocations with small vacancy Frank loops and the formation of defect-free channels in copper, and the second with the influence of imperfect annealing twin boundaries on the macroscopic stress-strain response in silver. In both examples, the importance of grain and twin boundaries as dislocation sources will be demonstrated.

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The flow stress behavior of OFHC polycrystalline copper

Cited by 68 publications

References 33 publications

Grain-size effects on tensile behavior of nickel and AISI 316L stainless steel

Grain-size effects on tensile behavior of nickel and AISI 316L stainless steel

Development of a Supercritical Carbon Dioxide Brayton Cycle: Improving VHTR Efficiency and Testing Material Compatibility - Final Report

Dislocation–obstacle interactions: Dynamic experiments to continuum modeling

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