The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Robert S Averback - One of the best experts on this subject based on the ideXlab platform.
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nanoscale self organization reaction in cu ag alloys subjected to dry sliding and its impact on wear resistance
Tribology International, 2016Co-Authors: Pascal Bellon, Robert S AverbackAbstract:Abstract Two-phase Cu90–Ag10 alloys are subjected to dry-sliding wear using pin-on-disk testing at room temperature with either a bronze or a martensitic stainless steel as counterface material. Thermal annealing prior to wear testing is used to vary the initial Ag-rich Precipitate Size in the Cu-rich matrix from ≈30 to 260 nm. The wear debris and the sub-surface microstructure are characterized by scanning and transmission electron microscopy. For large enough initial Precipitate Size, wear induces the spontaneous formation of alternating Cu and Ag nanolayers, and this chemical nanolayering correlates with a significant reduction in wear rate. This correlation is analyzed by considering the role of chemical nanolayering on third bodies and on the mechanical properties of the near-surface microstructure.
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Dependence of shear-induced mixing on length scale
Scripta Materialia, 2013Co-Authors: Salman N. Arshad, Pascal Bellon, Timothy G. Lach, Mohsen Pouryazdan, Horst Hahn, Shen J. Dillon, Robert S AverbackAbstract:The critical strain for mixing was determined as a function of Precipitate Size in two-phase Cu90Ag10 alloys using high-pressure torsion experiments. X-ray diffraction, Z-contrast transmission electron microscopy and atom probe tomography were employed to characterize the mixing behavior. For Precipitates ranging from 16 to 131 nm in radius, the critical strain increased linearly with the initial Precipitate Size, with the proportionality constant at ≈5.2 nm−1. These results are in agreement with model predictions based on random dislocation glide
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Microstructural stability of nanostructured Cu-Nb-W alloys during high-temperature annealing and irradiation
Acta Materialia, 2011Co-Authors: Xuan Zhang, Pascal Bellon, Robert S AverbackAbstract:Abstract The microstructural evolution of dilute Cu-based ternary Cu–Nb alloys during high-temperature annealing was investigated using a combination of transmission electron microscopy, X-ray diffraction and kinetic Monte Carlo (KMC) simulations. The experiments showed that, during annealing, the Cu 90 Nb 10 binary alloy undergoes extensive coarsening at 600 °C, with Precipitate Sizes increasing to >40 nm. Additions of just 1.5 at.% W to this alloy, however, dramatically suppresses the growth; the average Precipitate Size in the ternary alloy now increases to only ∼10 nm at 600 °C, and only to 18 nm at 700 °C. On annealing at still higher temperatures, the Precipitate Size then, surprisingly, decreases. The Precipitate Size distribution at the higher temperatures, moreover, is bimodal. It is also observed that irradiation has no effect on the microstructure of the ternary alloys above 600 °C. KMC simulations indicate that the saturation of the average Precipitate Size, followed by its decrease as the annealing temperature is increased and the development of a bimodal Size distribution can be explained by competition between thermodynamic and kinetic effects during precipitation in this ternary alloy.
Runkun Chen - One of the best experts on this subject based on the ideXlab platform.
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effect of initial temper on the creep behavior of precipitation hardened we43 alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: Yonghai Kang, X X Wang, N Zhang, H Yan, Runkun ChenAbstract:Abstract The effect of initial tempers with different characteristics of Precipitates and contents of supersaturated solute atoms, including the homogenized, peak–aged and over–aged conditions, on the tensile creep behavior of WE43 alloy has been investigated at 523 K. Results show that the peak–aged alloy at 523 K obtained superior creep resistance than the homogenized, peak–aged at 498 K and over–aged at 523 K alloy. A uniform dispersion of β Precipitates was dynamically formed within steady–stage creep microstructure of the homogenized WE43 alloy after creep deformation of 200 h. It is found that the Precipitate Size and distribution is similar with the alloy aged equal time without the applied stress. In addition, the WE43 alloy in all tempers obtains similar Precipitate Size and distribution in their steady–stage creep microstructures. Therefore, it is inferred that the various initial tempers mainly affect the primary creep stage. Furthermore, numerous dislocations were detected between Precipitates and the stress exponent n is 4.5, which is close to 5. Thereby, dislocation climb is suggested to be the creep mechanism. The reason for the peak–aged alloy at 523 K obtained superior creep resistance is that the initial uniform dispersion of β″ and β′ Precipitates have smaller Precipitate Size and higher Precipitate density than that of the homogenized and over–aged alloy, which are more effectively to hider dislocation climb. However, a deterioration of creep resistance was occurred in the peak−aged alloy at 498 K due to Precipitate recovery when crept at 523 K. As a consequence, WE43 alloy in peak–aged temper at 523 K achieves the highest creep resistance.
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Effect of initial temper on the creep behavior of precipitation–hardened WE43 alloy
Materials Science and Engineering: A, 2017Co-Authors: Yonghai Kang, X X Wang, N Zhang, H Yan, Runkun ChenAbstract:Abstract The effect of initial tempers with different characteristics of Precipitates and contents of supersaturated solute atoms, including the homogenized, peak–aged and over–aged conditions, on the tensile creep behavior of WE43 alloy has been investigated at 523 K. Results show that the peak–aged alloy at 523 K obtained superior creep resistance than the homogenized, peak–aged at 498 K and over–aged at 523 K alloy. A uniform dispersion of β Precipitates was dynamically formed within steady–stage creep microstructure of the homogenized WE43 alloy after creep deformation of 200 h. It is found that the Precipitate Size and distribution is similar with the alloy aged equal time without the applied stress. In addition, the WE43 alloy in all tempers obtains similar Precipitate Size and distribution in their steady–stage creep microstructures. Therefore, it is inferred that the various initial tempers mainly affect the primary creep stage. Furthermore, numerous dislocations were detected between Precipitates and the stress exponent n is 4.5, which is close to 5. Thereby, dislocation climb is suggested to be the creep mechanism. The reason for the peak–aged alloy at 523 K obtained superior creep resistance is that the initial uniform dispersion of β″ and β′ Precipitates have smaller Precipitate Size and higher Precipitate density than that of the homogenized and over–aged alloy, which are more effectively to hider dislocation climb. However, a deterioration of creep resistance was occurred in the peak−aged alloy at 498 K due to Precipitate recovery when crept at 523 K. As a consequence, WE43 alloy in peak–aged temper at 523 K achieves the highest creep resistance.
Pascal Bellon - One of the best experts on this subject based on the ideXlab platform.
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nanoscale self organization reaction in cu ag alloys subjected to dry sliding and its impact on wear resistance
Tribology International, 2016Co-Authors: Pascal Bellon, Robert S AverbackAbstract:Abstract Two-phase Cu90–Ag10 alloys are subjected to dry-sliding wear using pin-on-disk testing at room temperature with either a bronze or a martensitic stainless steel as counterface material. Thermal annealing prior to wear testing is used to vary the initial Ag-rich Precipitate Size in the Cu-rich matrix from ≈30 to 260 nm. The wear debris and the sub-surface microstructure are characterized by scanning and transmission electron microscopy. For large enough initial Precipitate Size, wear induces the spontaneous formation of alternating Cu and Ag nanolayers, and this chemical nanolayering correlates with a significant reduction in wear rate. This correlation is analyzed by considering the role of chemical nanolayering on third bodies and on the mechanical properties of the near-surface microstructure.
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Dependence of shear-induced mixing on length scale
Scripta Materialia, 2013Co-Authors: Salman N. Arshad, Pascal Bellon, Timothy G. Lach, Mohsen Pouryazdan, Horst Hahn, Shen J. Dillon, Robert S AverbackAbstract:The critical strain for mixing was determined as a function of Precipitate Size in two-phase Cu90Ag10 alloys using high-pressure torsion experiments. X-ray diffraction, Z-contrast transmission electron microscopy and atom probe tomography were employed to characterize the mixing behavior. For Precipitates ranging from 16 to 131 nm in radius, the critical strain increased linearly with the initial Precipitate Size, with the proportionality constant at ≈5.2 nm−1. These results are in agreement with model predictions based on random dislocation glide
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Microstructural stability of nanostructured Cu-Nb-W alloys during high-temperature annealing and irradiation
Acta Materialia, 2011Co-Authors: Xuan Zhang, Pascal Bellon, Robert S AverbackAbstract:Abstract The microstructural evolution of dilute Cu-based ternary Cu–Nb alloys during high-temperature annealing was investigated using a combination of transmission electron microscopy, X-ray diffraction and kinetic Monte Carlo (KMC) simulations. The experiments showed that, during annealing, the Cu 90 Nb 10 binary alloy undergoes extensive coarsening at 600 °C, with Precipitate Sizes increasing to >40 nm. Additions of just 1.5 at.% W to this alloy, however, dramatically suppresses the growth; the average Precipitate Size in the ternary alloy now increases to only ∼10 nm at 600 °C, and only to 18 nm at 700 °C. On annealing at still higher temperatures, the Precipitate Size then, surprisingly, decreases. The Precipitate Size distribution at the higher temperatures, moreover, is bimodal. It is also observed that irradiation has no effect on the microstructure of the ternary alloys above 600 °C. KMC simulations indicate that the saturation of the average Precipitate Size, followed by its decrease as the annealing temperature is increased and the development of a bimodal Size distribution can be explained by competition between thermodynamic and kinetic effects during precipitation in this ternary alloy.
A Deschamps - One of the best experts on this subject based on the ideXlab platform.
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Precipitate characterisation in metallic systems by small angle x ray or neutron scattering
Comptes Rendus Physique, 2012Co-Authors: Frederic De Geuser, A DeschampsAbstract:Abstract Small-angle scattering enables the extraction of precise, quantitative information about nano-scale Precipitate microstructures. It can be used with X-rays (SAXS) or neutrons (SANS). This paper presents simple methods for extracting information on the Precipitate Size and volume fraction from SAS spectra. The various possibilities for obtaining Precipitate Size are reviewed, and the meaning of their differences is discussed. Examples of applications for complex Precipitate microstructure measurements are given in the following areas: kinetic in-situ measurements in Fe–Cu and Fe–Nb–C alloys, non-stoichiometric precipitation in an Al–Zn–Mg–Cu alloy studied by anomalous SAXS (ASAXS), and precipitation mapping in weld cross-sections.
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Precipitate characterisation in metallic systems by small-angle X-ray or neutron scattering.
Comptes Rendus Physique, 2012Co-Authors: F. De Geuser, A DeschampsAbstract:Small-angle scattering enables the extraction of precise, quantitative information about nano-scale Precipitate microstructures. It can be used with X-rays (SAXS) or neutrons (SANS). This paper presents simple methods for extracting information on the Precipitate Size and volume fraction from SAS spectra. The various possibilities for obtaining Precipitate Size are reviewed, and the meaning of their differences is discussed. Examples of applications for complex Precipitate microstructure measurements are given in the following areas: kinetic in-situ measurements in Fe-Cu and Fe-Nb-C alloys, non-stoichiometric precipitation in an Al-Zn-Mg-Cu alloy studied by anomalous SAXS (ASAXS), and precipitation mapping in weld cross-sections. (C) 2012 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Bai Qing Xiong - One of the best experts on this subject based on the ideXlab platform.
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Microstructural Comparison of an Al-8.0Zn-1.8Mg-2.0Cu Alloy with Typical T6 and T76 Tempers
Materials Science Forum, 2018Co-Authors: Bai Qing Xiong, Kai Wen, Yong An Zhang, Shu Hui Huang, Li Zhen Yan, Hong Wei Yan, Hong Wei LiuAbstract:In order to analyze aging behavior of an Al-8.0Zn-1.8Mg-2.0Cu alloy, the microstructure of the alloy subjected to T6 and T76 states are investigated by transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). Based on the Precipitate observations, Precipitate Size distributions and average Precipitate Size are extracted from bright-field TEM images projected along 〈110〉Alorientation with the aid of an imaging analysis. The results indicate that the main Precipitates are GPI zone, GPII zone and η' phase in the T6 alloy while η' phase and η phase in the T76 alloy. The bright-field TEM observations reveal that the matrix Precipitates for the T6 alloy have small Size and dispersive distribution while that for the T76 alloy has big Size and sparse distribution. Both have discontinuously distributed grain boundary Precipitates. Quantitative structural information including Precipitate Size distribution and average Precipitate Size has been calculated by an image analysis based on the bright-field TEM images projected along 〈110〉Alorientation. The results show that the T6 alloy has a narrower Precipitate Size range than the T76 alloy and thus the T6 alloy possesses a smaller average Precipitate Size than the T76 alloy.
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Aging behavior and Precipitate characterization of a high Zn-containing Al-Zn-Mg-Cu alloy with various tempers
Materials & Design, 2016Co-Authors: Kai Wen, Yong An Zhang, Yunqiang Fan, Guo-jun Wang, Longbin Jin, Bai Qing XiongAbstract:Abstract In the present work, the influence of one-step and two-step aging treatments on hardness, electrical conductivity and mechanical properties of a high Zn-containing Al-Zn-Mg-Cu alloy is investigated and detailed aging parameters subjected to various aging tempers, i.e., T6, T79, T76, T74 and T73, are proposed. The nanoscale Precipitates under different tempers are qualitatively investigated by means of transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HREM) techniques. Based on the Precipitate observations, Precipitate Size distributions and neighbor Precipitates distances are extracted from bright-field TEM images projected along 〈110〉 Al orientation with the aid of an imaging analysis. The results show that with the deepening of aging degree, the conductivity of one-step and two-step aging increase continuously while the hardness increases for one-step aging and decreases for two-step aging at the second preservation. The tensile strength decreases as the aging degree deepens and the yield strength shows a similar trend. In addition, as the degree of over-aging deepens, the Precipitate Size distribution interval becomes broader, the average Precipitate Size turns larger and the average distance of neighbor Precipitates also becomes greater. The influence of Precipitates on mechanical properties is discussed.
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Quantitative Investigation on Nano-Scale Precipitates in an Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr Alloy under Various Aging Tempers
Materials Science Forum, 2014Co-Authors: Bai Qing Xiong, Yong An Zhang, Dong Mei Liu, Feng Wang, Hong Wei LiuAbstract:In the present study, a systematic study of nanoscale Precipitates in an Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr alloy have been carried out for various typical aging tempers, including T6, T76, T74, T73 and RRA treatments, by combining synchrotron-based small-angle x-ray scattering (SAXS) and transmission electron microscopy (TEM) techniques. Based on the TEM observations, quantitative and statistical structural information, including Precipitate Size, volume fraction, number density and inter-Precipitate distance have been extracted from SAXS data through model fitting. The results show that the T6 peak-aged alloy with the smallest Precipitate Size has the highest number density and lowest volume fraction of Precipitates. Under two-step T7X over-aged tempers, with the deepen of aging degree, the Precipitate Size, volume fraction and inter-Precipitate distance increases, but the number density decreases. The Size distribution of Precipitates for the RRA-treated alloy is in between that of T6 and T76. The results also show that as the degree of over-aging deepens, the Precipitate Size distribution interval becomes broader.