The Experts below are selected from a list of 65397 Experts worldwide ranked by ideXlab platform
Sheng Liu - One of the best experts on this subject based on the ideXlab platform.
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inverse analysis of the stress strain curve to determine the materials models of work hardening and Dynamic Recovery
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Sheng LiuAbstract:Abstract A constitutive equation has been established based on the dislocation theory, the work hardening and Dynamic Recovery theory. The stress–strain curves of bainite steel have been measured by a hot compression experiment at temperatures of 1173, 1273, 1373, and 1473 K with strain rates of 0.01, 0.1, 1, and 10 s−1 on a thermo-mechanical simulator Gleeble-1500. The material constants involved in the constitutive equation have been optimized by an inverse analysis of the stress–strain curves. This information is used to determine the materials models of work hardening and Dynamic Recovery, and the strain–stress relationship of the investigated steel in high temperature deformation. The results are in agreement with those obtained from experimental measurements. They demonstrate that the material constants determined by the stress–strain curves can capture the underlying materials science of high temperature deformation. On this basis, the evolution law of dislocation density has been obtained in work hardening and Dynamic Recovery. A relationship function between the critical dislocation density for Dynamic recrystallization and deformation parameters has been established. And an equation for Recovery kinetics has been proposed with reference referring to the Avrami equation.
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Inverse analysis of the stress–strain curve to determine the materials models of work hardening and Dynamic Recovery
Materials Science and Engineering: A, 2015Co-Authors: Sheng LiuAbstract:Abstract A constitutive equation has been established based on the dislocation theory, the work hardening and Dynamic Recovery theory. The stress–strain curves of bainite steel have been measured by a hot compression experiment at temperatures of 1173, 1273, 1373, and 1473 K with strain rates of 0.01, 0.1, 1, and 10 s−1 on a thermo-mechanical simulator Gleeble-1500. The material constants involved in the constitutive equation have been optimized by an inverse analysis of the stress–strain curves. This information is used to determine the materials models of work hardening and Dynamic Recovery, and the strain–stress relationship of the investigated steel in high temperature deformation. The results are in agreement with those obtained from experimental measurements. They demonstrate that the material constants determined by the stress–strain curves can capture the underlying materials science of high temperature deformation. On this basis, the evolution law of dislocation density has been obtained in work hardening and Dynamic Recovery. A relationship function between the critical dislocation density for Dynamic recrystallization and deformation parameters has been established. And an equation for Recovery kinetics has been proposed with reference referring to the Avrami equation.
Yves Bréchet - One of the best experts on this subject based on the ideXlab platform.
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On the mechanisms of Dynamic Recovery
Scripta Materialia, 2002Co-Authors: Erik Nes, Knut Marthinsen, Yves BréchetAbstract:Abstract The annihilation of dislocations in Dynamic Recovery is analyzed in terms of reactions between mobile dislocations and dislocations stored in a Frank network. An extended model is presented comprising spontaneous dislocation collapse reactions and annihilation by dipole climb collapse.
Oscar Balancin - One of the best experts on this subject based on the ideXlab platform.
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Dynamic Recovery and Dynamic recrystallization competition on a nb and n bearing austenitic stainless steel biomaterial influence of strain rate and temperature
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013Co-Authors: R C Souza, E S Silva, Alberto Moreira Jorge, J M Cabrera, Oscar BalancinAbstract:The objective of this study was to investigate the Dynamic softening behavior of an austenitic stainless steel with high nitrogen (type ISO 5832-9) through hot torsion tests, in the temperature range of 900–1200 °C and in the strain rate range of 0.01–10 s−1. The shape of flow stress curves indicated that the softening was promoted by Dynamic Recovery followed by Dynamic recrystallization with high level of Recovery. The microstructure evolution indicated that even though after large straining as that of the steady state stresses a combination of strained and recrystallized grains was observed. The delay of Dynamic recrystallization, which is a consequence of the intermediate level of stacking fault energy of this steel, and the presence of large recrystallized grains, inside of necklace formed by small grains, were associated with extended Recovery regions.
Wolfgang Blum - One of the best experts on this subject based on the ideXlab platform.
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Strain Rate Contribution due to Dynamic Recovery of Ultrafine-Grained Cu–Zr as Evidenced by Load Reductions during Quasi-Stationary Deformation at 0.5 Tm
Metals, 2019Co-Authors: Wolfgang Blum, Jiří Dvořák, Petr Král, Philip Eisenlohr, Vaclav SklenickaAbstract:During quasi-stationary tensile deformation of ultrafine-grained Cu-0.2 mass%Zr at 673 K and a deformation rate of about e - 4 / s load changes were performed. Reductions of relative load by more than about 25% initiate anelastic back flow. Subsequently, the creep rate turns positive again and goes through a relative maximum. This is interpreted by a strain rate component ϵ ˙ - associated with Dynamic Recovery of dislocations. Back extrapolation indicates that ϵ ˙ - contributes the same fraction of ( 20 ± 10 ) % to the quasi-stationary strain rate that has been reported for coarse-grained materials with high fraction of low-angle boundaries; this suggests that Dynamic Recovery of dislocations is generally mediated by boundaries. The influence of anelastic back flow on ϵ ˙ - is discussed. Comparison of ϵ ˙ - to the quasi-stationary rate points to enhancement of Dynamic Recovery by internal stresses. Subtraction of ϵ ˙ - from the total rate yields the rate component ϵ ˙ + related with generation and storage of dislocations; its activation volume is in the order expected from the classical theory of thermal glide.
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Grain size and alloying effects on Dynamic Recovery in nanocrystalline metals
Acta Materialia, 2016Co-Authors: Z. Sun, Wolfgang Blum, Antonio Cervellino, S. Van Petegem, H. Van SwygenhovenAbstract:Abstract Dynamic Recovery in nanocrystalline Ni and Ni50Fe50 with respective grain sizes of 65 nm and 15 nm is studied using stress reduction tests during in situ X-ray diffraction. The results are compared with a previous study on NC Ni with 35 nm grain size. Defect Recovery by means of grain boundary processes plays an important role in controlling the strength evolution resulting in a constant flow stress during uniaxial deformation. The relative contributions of dislocation and grain boundary accommodation mechanisms are discussed in terms of grain size and alloying.
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Dynamic Recovery in nanocrystalline Ni
Acta Materialia, 2015Co-Authors: S. Van Petegem, Wolfgang Blum, Antonio Cervellino, Karsten Durst, Helena Van SwygenhovenAbstract:The constant flow stress reached during uniaxial deformation of electrodeposited nanocrystalline Ni reflects a quasi-stationary balance between dislocation slip and grain boundary (GB) accommodation mechanisms. Stress reduction tests allow to suppress dislocation slip and bring Recovery mechanisms into the foreground. When combined with in situ X-ray diffraction it can be shown that grain boundary Recovery mechanisms play an important role in producing plastic strain while hardening the microstructure. This result has a significant consequence for the parameters of thermally activated glide of dislocations, such as athermal stress and activation volume, which are traditionally derived from stress/strain rate change tests. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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Dynamic Recovery: sufficient mechanism in the hot deformation of Al (
Materials Science and Engineering: A, 2000Co-Authors: Hugh J. Mcqueen, Wolfgang BlumAbstract:Abstract A recent OIM study of the substructure in hot compressed Al has observed an increase in the fraction of boundaries both of 15–20° and above 20° as strain rises from 0.9 to 1.5. This was interpreted as evidence of continuous Dynamic recrystallization being the mechanism for the steady state deformation. However, when the original grain boundaries and transition boundaries between deformation bands are discounted, the fraction of 15–20° boundaries is reduced to less than 20% and would be much lower if subboundaries less than 0.5° visible in TEM were taken into account. The present authors argue that Dynamic Recovery maintains the subgrains of constant size, low misorientation and equiaxed to produce a steady state and can permit a limited number of discrete segments with higher misorientation notably as temperature falls. Moreover, continuous Dynamic recrystallization is not appropriate terminology because it is far from reaching the completion observed in other instances of continuous recrystallization.
Sirous Asgari - One of the best experts on this subject based on the ideXlab platform.
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Influence of stacking fault energy and short-range ordering on Dynamic Recovery and work hardening behavior of copper alloys
Scripta Materialia, 2010Co-Authors: Farzad Hamdi, Sirous AsgariAbstract:True stress vs. true strain responses of Cu–6 wt.% Al and Cu–12 wt.% Mn alloys are presented. While Cu–6 wt.% Al alloy shows the typical mechanical response of low stacking fault energy alloys, the Cu–12 wt.% Mn alloy behaved similarly to medium to high stacking fault energy alloys. These findings clearly show that while short-range ordering triggers slip planarity, it has a minor effect on total Dynamic Recovery of these copper alloys.
