The Experts below are selected from a list of 102 Experts worldwide ranked by ideXlab platform
E P George - One of the best experts on this subject based on the ideXlab platform.
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thermal activation parameters of plastic flow reveal deformation mechanisms in the crmnfeconi high entropy Alloy
Acta Materialia, 2018Co-Authors: Guillaume Laplanche, J. Bonneville, Céline Varvenne, William A. Curtin, E P GeorgeAbstract:Abstract To reveal the operating mechanisms of plastic deformation in an FCC high-entropy Alloy, the activation volumes in CrMnFeCoNi have been measured as a function of plastic strain and temperature between 77 K and 423 K using repeated load relaxation experiments. At the yield stress, σ y , the activation volume varies from ∼60 b3 at 77 K to ∼360 b3 at 293 K and scales inversely with yield stress. With increasing plastic strain, the activation volume decreases and the trends follow the Cottrell-Stokes law, according to which the inverse activation volume should increase linearly with σ − σ y (Haasen plot). This is consistent with the notion that hardening due to an increase in the density of forest dislocations is naturally associated with a decrease in the activation volume because the spacing between dislocations decreases. The values and trends in activation volume agree with theoretical predictions that treat the HEA as a high-concentration solid-Solution-Strengthened Alloy. These results demonstrate that this HEA deforms by the mechanisms typical of solute strengthening in FCC Alloys, and thus indicate that the high compositional/structural complexity does not introduce any new intrinsic deformation mechanisms.
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Thermal activation parameters of plastic flow reveal deformation mechanisms in the CrMnFeCoNi high-entropy Alloy
Acta Materialia, 2018Co-Authors: Guillaume Laplanche, J. Bonneville, Céline Varvenne, William A. Curtin, E P GeorgeAbstract:To reveal the operating mechanisms of plastic deformation in an FCC high-entropy Alloy, the activation volumes in CrMnFeCoNi have been measured as a function of plastic strain and temperature between 77 K and 423 K using repeated load relaxation experiments. At the yield stress, sigma(y), the activation volume varies from similar to 60 b(3) at 77 K to similar to 360 b(3) at 293 K and scales inversely with yield stress. With increasing plastic strain, the activation volume decreases and the trends follow the Cottrell-Stokes law, according to which the inverse activation volume should increase linearly with sigma - sigma(y) (Haasen plot). This is consistent with the notion that hardening due to an increase in the density of forest dislocations is naturally associated with a decrease in the activation volume because the spacing between dislocations decreases. The values and trends in activation volume agree with theoretical predictions that treat the HEA as a high-concentration solid-Solution-Strengthened Alloy. These results demonstrate that this HEA deforms by the mechanisms typical of solute strengthening in FCC Alloys, and thus indicate that the high compositional/structural complexity does not introduce any new intrinsic deformation mechanisms. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Guillaume Laplanche - One of the best experts on this subject based on the ideXlab platform.
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thermal activation parameters of plastic flow reveal deformation mechanisms in the crmnfeconi high entropy Alloy
Acta Materialia, 2018Co-Authors: Guillaume Laplanche, J. Bonneville, Céline Varvenne, William A. Curtin, E P GeorgeAbstract:Abstract To reveal the operating mechanisms of plastic deformation in an FCC high-entropy Alloy, the activation volumes in CrMnFeCoNi have been measured as a function of plastic strain and temperature between 77 K and 423 K using repeated load relaxation experiments. At the yield stress, σ y , the activation volume varies from ∼60 b3 at 77 K to ∼360 b3 at 293 K and scales inversely with yield stress. With increasing plastic strain, the activation volume decreases and the trends follow the Cottrell-Stokes law, according to which the inverse activation volume should increase linearly with σ − σ y (Haasen plot). This is consistent with the notion that hardening due to an increase in the density of forest dislocations is naturally associated with a decrease in the activation volume because the spacing between dislocations decreases. The values and trends in activation volume agree with theoretical predictions that treat the HEA as a high-concentration solid-Solution-Strengthened Alloy. These results demonstrate that this HEA deforms by the mechanisms typical of solute strengthening in FCC Alloys, and thus indicate that the high compositional/structural complexity does not introduce any new intrinsic deformation mechanisms.
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Thermal activation parameters of plastic flow reveal deformation mechanisms in the CrMnFeCoNi high-entropy Alloy
Acta Materialia, 2018Co-Authors: Guillaume Laplanche, J. Bonneville, Céline Varvenne, William A. Curtin, E P GeorgeAbstract:To reveal the operating mechanisms of plastic deformation in an FCC high-entropy Alloy, the activation volumes in CrMnFeCoNi have been measured as a function of plastic strain and temperature between 77 K and 423 K using repeated load relaxation experiments. At the yield stress, sigma(y), the activation volume varies from similar to 60 b(3) at 77 K to similar to 360 b(3) at 293 K and scales inversely with yield stress. With increasing plastic strain, the activation volume decreases and the trends follow the Cottrell-Stokes law, according to which the inverse activation volume should increase linearly with sigma - sigma(y) (Haasen plot). This is consistent with the notion that hardening due to an increase in the density of forest dislocations is naturally associated with a decrease in the activation volume because the spacing between dislocations decreases. The values and trends in activation volume agree with theoretical predictions that treat the HEA as a high-concentration solid-Solution-Strengthened Alloy. These results demonstrate that this HEA deforms by the mechanisms typical of solute strengthening in FCC Alloys, and thus indicate that the high compositional/structural complexity does not introduce any new intrinsic deformation mechanisms. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
J. C. Gibeling - One of the best experts on this subject based on the ideXlab platform.
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Low cycle fatigue of niobium–zirconium and niobium–zirconium–carbon Alloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000Co-Authors: Scott L. Dickerson, J. C. GibelingAbstract:Abstract Constant plastic strain amplitude low cycle fatigue tests were performed on two niobium Alloys at both room temperature and at 573 K. In order to fully explore the influence of strain rate on the cyclic stress–strain response, a new testing procedure was developed to conduct tests at constant true plastic strain rate. The two Alloys tested were a solid Solution Strengthened Alloy (Nb–1Zr) and a precipitation Strengthened Alloy (Nb–1Zr–0.1C, also known by the commercial designation PWC-11). The PWC-11 Alloy was heat treated to produce two different microstructures: fine grained (PWC-11(A), 20–50 μm grain size), and coarse grained (PWC-11(B), 70–100 μm grain size). The Nb–1Zr Alloy generally exhibited hardening to a stable, saturated state in each test. Tests conducted on Nb–1Zr at 573 K at plastic strain rates of 10 −4 s −1 and 10 −3 s −1 had essentially the same saturation stress, confirming that strain rate does not influence the cyclic deformation behavior of this Alloy under these test conditions. The PWC-11 Alloys exhibited stable saturation in room temperature tests, but at 573 K they exhibited continuous softening. Furthermore, at 573 K the cyclic stress–strain curves for the PWC-11 Alloys had shallower slopes than those of Nb–1Zr, while the monotonic stress–strain curves had greater hardening rates than did those of Nb–1Zr. These observations are consistent with precipitate strengthening that is diminished at elevated temperatures and by cyclic deformation. In terms of practical significance, however, these effects are minor, and the PWC-11 Alloys exhibited low cycle fatigue behavior that was very similar to that of Nb–1Zr. Both Alloys exhibited grain shape changes leading to intergranular cracking as the dominant failure mechanism.
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low cycle fatigue of niobium zirconium and niobium zirconium carbon Alloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000Co-Authors: Scott L. Dickerson, J. C. GibelingAbstract:Abstract Constant plastic strain amplitude low cycle fatigue tests were performed on two niobium Alloys at both room temperature and at 573 K. In order to fully explore the influence of strain rate on the cyclic stress–strain response, a new testing procedure was developed to conduct tests at constant true plastic strain rate. The two Alloys tested were a solid Solution Strengthened Alloy (Nb–1Zr) and a precipitation Strengthened Alloy (Nb–1Zr–0.1C, also known by the commercial designation PWC-11). The PWC-11 Alloy was heat treated to produce two different microstructures: fine grained (PWC-11(A), 20–50 μm grain size), and coarse grained (PWC-11(B), 70–100 μm grain size). The Nb–1Zr Alloy generally exhibited hardening to a stable, saturated state in each test. Tests conducted on Nb–1Zr at 573 K at plastic strain rates of 10 −4 s −1 and 10 −3 s −1 had essentially the same saturation stress, confirming that strain rate does not influence the cyclic deformation behavior of this Alloy under these test conditions. The PWC-11 Alloys exhibited stable saturation in room temperature tests, but at 573 K they exhibited continuous softening. Furthermore, at 573 K the cyclic stress–strain curves for the PWC-11 Alloys had shallower slopes than those of Nb–1Zr, while the monotonic stress–strain curves had greater hardening rates than did those of Nb–1Zr. These observations are consistent with precipitate strengthening that is diminished at elevated temperatures and by cyclic deformation. In terms of practical significance, however, these effects are minor, and the PWC-11 Alloys exhibited low cycle fatigue behavior that was very similar to that of Nb–1Zr. Both Alloys exhibited grain shape changes leading to intergranular cracking as the dominant failure mechanism.
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Cyclic deformation of dispersion-Strengthened aluminum Alloys
Materials Science and Engineering: A, 1995Co-Authors: Meredith E. Mercer, Scott L. Dickerson, J. C. GibelingAbstract:Abstract The cyclic deformation behavior of two dispersion-Strengthened aluminum Alloys produced by mechanical Alloying is examined. The materials studied include an AlMg Alloy (IN-9052) and a similar Alloy containing an addition of lithium (IN-905XL). The results of plastic strain-controlled low cycle fatigue tests are compared with those obtained for a conventional AlMg Alloy (AA5083-H321) and a conventional precipitation-Strengthened Alloy (AA7075-T6). The dispersion-Strengthened materials exhibit a small amount of initial cyclic softening followed by moderate hardening to failure. These observations suggest that the residual stresses induced during processing may influence the initial cyclic response, but that the dispersoids are resistant to shear as expected. The dispersion-Strengthened Alloys also exhibit a substantial asymmetry in the tension and compression peak stresses due to the presence of the dispersoids. This result is similar to that for the AA7075-T6, but no such asymmetry was detected in the solid Solution-Strengthened Alloy (AA5083-H321). The cyclic lifetime of IN-9052 is slightly greater than that of the other materials examined in this study. This result is attributed to the role of the dispersoid particles in promoting homogeneous deformation. Finally, the importance of incorporating a non-linear elastic strain calculation in low cycle fatigue testing of high-strength materials is discussed.
T A Lebedkina - One of the best experts on this subject based on the ideXlab platform.
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strain rate fluctuations during macroscopically uniform deformation of a Solution Strengthened Alloy
Scripta Materialia, 2011Co-Authors: Rebecca N Mudrock, M A Lebyodkin, Peter Kurath, Armand Joseph Beaudoin, T A LebedkinaAbstract:Using a work-hardened aluminum Alloy that exhibits dynamic strain aging, oscillations in strain rate transitioning into intermittent local plastic activity are observed through an extended elastoplastic transition, before onset of the Portevin–Le Chatelier effect. Fourier analysis confirms this intermittency spans multiple scales. Wavelet analysis provides a method of quantifying transitions in the deformation behavior in both the time and frequency domains, and reveals a period doubling transition in both the local strain rate and global load signals.
J. Bonneville - One of the best experts on this subject based on the ideXlab platform.
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thermal activation parameters of plastic flow reveal deformation mechanisms in the crmnfeconi high entropy Alloy
Acta Materialia, 2018Co-Authors: Guillaume Laplanche, J. Bonneville, Céline Varvenne, William A. Curtin, E P GeorgeAbstract:Abstract To reveal the operating mechanisms of plastic deformation in an FCC high-entropy Alloy, the activation volumes in CrMnFeCoNi have been measured as a function of plastic strain and temperature between 77 K and 423 K using repeated load relaxation experiments. At the yield stress, σ y , the activation volume varies from ∼60 b3 at 77 K to ∼360 b3 at 293 K and scales inversely with yield stress. With increasing plastic strain, the activation volume decreases and the trends follow the Cottrell-Stokes law, according to which the inverse activation volume should increase linearly with σ − σ y (Haasen plot). This is consistent with the notion that hardening due to an increase in the density of forest dislocations is naturally associated with a decrease in the activation volume because the spacing between dislocations decreases. The values and trends in activation volume agree with theoretical predictions that treat the HEA as a high-concentration solid-Solution-Strengthened Alloy. These results demonstrate that this HEA deforms by the mechanisms typical of solute strengthening in FCC Alloys, and thus indicate that the high compositional/structural complexity does not introduce any new intrinsic deformation mechanisms.
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Thermal activation parameters of plastic flow reveal deformation mechanisms in the CrMnFeCoNi high-entropy Alloy
Acta Materialia, 2018Co-Authors: Guillaume Laplanche, J. Bonneville, Céline Varvenne, William A. Curtin, E P GeorgeAbstract:To reveal the operating mechanisms of plastic deformation in an FCC high-entropy Alloy, the activation volumes in CrMnFeCoNi have been measured as a function of plastic strain and temperature between 77 K and 423 K using repeated load relaxation experiments. At the yield stress, sigma(y), the activation volume varies from similar to 60 b(3) at 77 K to similar to 360 b(3) at 293 K and scales inversely with yield stress. With increasing plastic strain, the activation volume decreases and the trends follow the Cottrell-Stokes law, according to which the inverse activation volume should increase linearly with sigma - sigma(y) (Haasen plot). This is consistent with the notion that hardening due to an increase in the density of forest dislocations is naturally associated with a decrease in the activation volume because the spacing between dislocations decreases. The values and trends in activation volume agree with theoretical predictions that treat the HEA as a high-concentration solid-Solution-Strengthened Alloy. These results demonstrate that this HEA deforms by the mechanisms typical of solute strengthening in FCC Alloys, and thus indicate that the high compositional/structural complexity does not introduce any new intrinsic deformation mechanisms. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.