The Experts below are selected from a list of 80880 Experts worldwide ranked by ideXlab platform
C T Liu - One of the best experts on this subject based on the ideXlab platform.
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enhancement of strength Ductility trade off in a high entropy alloy through a heterogeneous structure
Acta Materialia, 2019Co-Authors: G Wang, Peter K Liaw, Jiabin Liu, Qijie Zhai, Qi Wang, Y D Jia, B A Sun, Haijian Chu, Jun Shen, C T LiuAbstract:Abstract The improvement in strength is usually accompanied by Ductility loss in structural materials, which is a long-standing conflict referred as the strength-Ductility trade-off. Here we present a heterogeneous-structures-architecting strategy, in which we design bulk high-entropy alloys with the largely-enhanced strength-Ductility trade-off, possessing a yield strength of 711 MPa, a tensile strength of 928 MPa, and a uniform elongation of 30.3%. Such an enhancement of the strength-Ductility trade-off is due to the microstructure comprised with a combination of the non-recrystallized and recrystallized grains arranged in complex heterogeneous structures with a characteristic dimension spanning from the submicron scale to the coarse-sized scale. The heterogeneous structures in the high-entropy alloy are produced by cold-rolling, followed by intermediate-temperature-annealing. Our results demonstrate that heterogeneous designs can be accomplished effectively by simple thermal treatments, which offer a design strategy towards a new generation of high-strength and high-Ductility high-entropy alloys.
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new nial strengthened ferritic steels with balanced creep resistance and Ductility designed by coupling thermodynamic calculations with focused experiments
Intermetallics, 2012Co-Authors: Zhenke Teng, Shenyan Huang, Fengyuan Zhang, M K Miller, C T Liu, Yi Chou, R Tien, Y A Chang, Peter K LiawAbstract:Abstract Two critical issues restricting the applications of NiAl precipitate-strengthened ferritic steels are their poor room temperature Ductility and insufficient creep resistance at temperatures higher than 600 °C. In this study, a thermodynamic modeling approach is integrated with experiments focused on investigating the Ductility and creep resistance of steel alloys based on the Fe–Ni–Al–Cr–Mo multi-component system. The mechanical property studies showed that the creep resistance increases with increasing the volume fraction of B2-ordered precipitates, while the opposite trend was observed for the Ductility. Low solubility of Al in the α-Fe matrix was found to favor a Ductility increase. Thermodynamic calculations were used to predict the volume fraction of B2-ordered precipitate and the elemental partitioning to guide the selection of alloy compositions that might exhibit the balanced creep resistance and Ductility. Key experiments were then conducted to validate the prediction. This integrated approach was found to be very effective in the alloy development.
Terence G Langdon - One of the best experts on this subject based on the ideXlab platform.
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enhanced strength Ductility synergy in nanostructured cu and cu al alloys processed by high pressure torsion and subsequent annealing
Scripta Materialia, 2012Co-Authors: Z F Zhang, Terence G Langdon, Roberto B Figueiredo, Nong GaoAbstract:Nanostructured Cu and Cu-Al alloys processed by high-pressure torsion were isochronally annealed to investigate the effects of the stacking fault energy (SFE) on strength and Ductility. All metals exhibit a similar general trend that the strength decreases and the Ductility improves with increasing annealing temperatures, and a notable enhancement of Ductility was achieved only when the volume fraction of recrystallized grains exceeded similar to 80%. The strength-Ductility synergy improves significantly with decreasing SFE. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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simultaneously increasing the Ductility and strength of ultra fine grained pure copper
Advanced Materials, 2006Co-Authors: Yonghao Zhao, X Z Liao, Terence G Langdon, J F Bingert, Baozhi Cui, Ke Han, A V Sergueeva, A K Mukherjee, R Z Valiev, Y T ZhuAbstract:Bulk ultra-fine-grained (UFG) materials produced by severe plastic deformation (SPD) usually have high strength but relatively low Ductility at ambient temperatures. This low Ductility is attributed to insufficient strain hardening due to an inability to accumulate dislocations. For a singlephased UFG material where dislocation slip is the primary deformation mechanism, a long-standing fundamental question concerns the feasibility of developing microstructures that offer high Ductility without sacrificing strength. The answer appears to be positive because there are some isolated examples where excellent mechanical behavior has been observed. Nevertheless, the structural features contributing to high strength and good Ductility remain undefined, and this lack of understanding has hindered the search for effective procedures to simultaneously improve the strength and Ductility of UFG materials. Here, we report a new process in which high Ductility is achieved without sacrificing strength by plastically deforming UFG Cu in liquid nitrogen. The enhanced Ductility is attributed primarily to the presence of a high density of preexisting deformation twins (PDTs) and also possibly to a large fraction of high-angle grain boundaries (HAGBs) formed during cryogenic processing. We conclude that this procedure provides a new strategy for increasing the Ductility of UFG materials without any concurrent loss in strength. Strength and Ductility are often mutually exclusive, i.e., materials may be strong or ductile but are rarely both. This also applies to bulk UFG materials. The low Ductility of UFG materials has invariably limited their practical application and, accordingly, much attention has been paid to the development of strategies for improving this poor Ductility. For singlephase UFG and nanostructured materials, several of the reports documenting high Ductility and strength describe experiments on Cu where the stacking-fault energy is relatively low. In some investigations the high Ductility was attributed to the development of a bimodal grain size distribution or pre-existing growth twins (PGTs), but in other investigations the reasons for the high Ductility were not clearly defined. In practice, however, a bimodal grain size distribution must sacrifice some of the strength gained from nanostructuring. Another challenge is the need to fabricate UFG materials in large bulk form suitable for structural applications. This requirement has been hindered because the evidence suggests that PGTs occur only in electrodeposited thin films of nanostructured Cu, and in nanocrystalline Cu by inert-gas condensation (IGC) followed by compaction. However, the Ductility of IGC-prepared nanocrystalline Cu is very low. The objectives of this study were twofold: First, to develop a procedure for increasing the Ductility of large bulk UFG Cu without incurring any significant loss in strength. Second, to evaluate the mechanism contributing to high Ductility in UFG Cu. A pure Cu (99.99%) bar was initially processed by equalchannel angular pressing (ECAP) to produce a UFG structure (hereafter designated the UFGECAP sample), then cryodrawn (D) to a reduction in area of ca. 95%, followed by cryorolling (R) with a reduction in thickness of ca. 96% (hereafter designated the UFGECAP+D+R sample). Figure 1a shows that the UFGECAP+D+R sample has superior mechanical properties compared to the UFGECAP sample. The UFGECAP Cu sample has a 0.2% yield strength of ca. 410 MPa ( ), which is significantly higher than the value of ca. 40 MPa in coarse-grained (CG) Cu. In addition, necking occurs rapidly after the stress reaches a maximum value, yielding a uniform elongation of only ca. 1.3% and an elongation to failure of only ca. 5.9% in the UFGECAP sample. By contrast, the yield strength is increased to ca. 500 MPa in the UFGECAP+D+R sample, and, more importantly, this sample undergoes strain hardening, giving a uniform elongation of C O M M U N IC A IO N S
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tailoring stacking fault energy for high Ductility and high strength in ultrafine grained cu and its alloy
Applied Physics Letters, 2006Co-Authors: Yonghao Zhao, X Z Liao, Y T Zhu, Zenji Horita, Terence G LangdonAbstract:Bulk ultrafine grained (UFG) materials produced by severe plastic deformation often have low Ductility. Here the authors report that simultaneous increases in Ductility and strength can be achieved by tailoring the stacking fault energy (SFE) via alloying. Specifically, UFG bronze (Cu 10wt.% Zn) with a SFE of 35mJ∕m2 was found to have much higher strength and Ductility than UFG copper with a SFE of 78mJ∕m2. Accumulations of both twins and dislocations during tensile testing play a significant role in enhancing the Ductility of the UFG bronze. This work demonstrates a strategy for designing UFG alloys with superior mechanical properties.
Peter K Liaw - One of the best experts on this subject based on the ideXlab platform.
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enhancement of strength Ductility trade off in a high entropy alloy through a heterogeneous structure
Acta Materialia, 2019Co-Authors: G Wang, Peter K Liaw, Jiabin Liu, Qijie Zhai, Qi Wang, Y D Jia, B A Sun, Haijian Chu, Jun Shen, C T LiuAbstract:Abstract The improvement in strength is usually accompanied by Ductility loss in structural materials, which is a long-standing conflict referred as the strength-Ductility trade-off. Here we present a heterogeneous-structures-architecting strategy, in which we design bulk high-entropy alloys with the largely-enhanced strength-Ductility trade-off, possessing a yield strength of 711 MPa, a tensile strength of 928 MPa, and a uniform elongation of 30.3%. Such an enhancement of the strength-Ductility trade-off is due to the microstructure comprised with a combination of the non-recrystallized and recrystallized grains arranged in complex heterogeneous structures with a characteristic dimension spanning from the submicron scale to the coarse-sized scale. The heterogeneous structures in the high-entropy alloy are produced by cold-rolling, followed by intermediate-temperature-annealing. Our results demonstrate that heterogeneous designs can be accomplished effectively by simple thermal treatments, which offer a design strategy towards a new generation of high-strength and high-Ductility high-entropy alloys.
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new nial strengthened ferritic steels with balanced creep resistance and Ductility designed by coupling thermodynamic calculations with focused experiments
Intermetallics, 2012Co-Authors: Zhenke Teng, Shenyan Huang, Fengyuan Zhang, M K Miller, C T Liu, Yi Chou, R Tien, Y A Chang, Peter K LiawAbstract:Abstract Two critical issues restricting the applications of NiAl precipitate-strengthened ferritic steels are their poor room temperature Ductility and insufficient creep resistance at temperatures higher than 600 °C. In this study, a thermodynamic modeling approach is integrated with experiments focused on investigating the Ductility and creep resistance of steel alloys based on the Fe–Ni–Al–Cr–Mo multi-component system. The mechanical property studies showed that the creep resistance increases with increasing the volume fraction of B2-ordered precipitates, while the opposite trend was observed for the Ductility. Low solubility of Al in the α-Fe matrix was found to favor a Ductility increase. Thermodynamic calculations were used to predict the volume fraction of B2-ordered precipitate and the elemental partitioning to guide the selection of alloy compositions that might exhibit the balanced creep resistance and Ductility. Key experiments were then conducted to validate the prediction. This integrated approach was found to be very effective in the alloy development.
Zhenke Teng - One of the best experts on this subject based on the ideXlab platform.
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new nial strengthened ferritic steels with balanced creep resistance and Ductility designed by coupling thermodynamic calculations with focused experiments
Intermetallics, 2012Co-Authors: Zhenke Teng, Shenyan Huang, Fengyuan Zhang, M K Miller, C T Liu, Yi Chou, R Tien, Y A Chang, Peter K LiawAbstract:Abstract Two critical issues restricting the applications of NiAl precipitate-strengthened ferritic steels are their poor room temperature Ductility and insufficient creep resistance at temperatures higher than 600 °C. In this study, a thermodynamic modeling approach is integrated with experiments focused on investigating the Ductility and creep resistance of steel alloys based on the Fe–Ni–Al–Cr–Mo multi-component system. The mechanical property studies showed that the creep resistance increases with increasing the volume fraction of B2-ordered precipitates, while the opposite trend was observed for the Ductility. Low solubility of Al in the α-Fe matrix was found to favor a Ductility increase. Thermodynamic calculations were used to predict the volume fraction of B2-ordered precipitate and the elemental partitioning to guide the selection of alloy compositions that might exhibit the balanced creep resistance and Ductility. Key experiments were then conducted to validate the prediction. This integrated approach was found to be very effective in the alloy development.
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effects of al on the microstructure and Ductility of nial strengthened ferritic steels at room temperature
Intermetallics, 2010Co-Authors: Zhenke Teng, Gautam Ghosh, P K Liaw, M E FineAbstract:One of the major problems for the development of ferritic steels strengthened by NiAl-type (B2) precipitates is their poor Ductility at room temperature. In conjunction with the computational alloy design, selected experiments are performed to investigate the effect of Al content on the Ductility of prototype Fe–Ni–Cr–Al alloys. The microstructure and composition of the matrix (α-Fe type) and precipitate phases are characterized by transmission electron microscopy (TEM) and analytical electron microscopy (AEM). Three-point-bending experiments show that alloys containing more than 5 mass% Al exhibit poor Ductility (<2%) at room temperature, and their fracture mode is predominantly cleavage type. Two major factors governing the poor Ductility are (i) the volume fraction of NiAl-type precipitates, and (ii) the Al content in the α-Fe matrix. A bend Ductility of more than 5% can be achieved by lowering the Al concentration to 3 mass% in the alloy. The alloy containing about 6.5 mass% Al is found to have an optimal combination of hardness and Ductility.
Y T Zhu - One of the best experts on this subject based on the ideXlab platform.
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Ductility and strain hardening in gradient and lamellar structured materials
Scripta Materialia, 2020Co-Authors: Y T ZhuAbstract:Abstract Low Ductility has long been the bottleneck especially at high strength in metallic structured materials due to conventional forest hardening having little to no effect. Hetero-structuring is an emerging strategy producing superior strength and Ductility combination. This Viewpoint article delineates mechanisms for strain hardening and plastic deformation in gradient and lamellar structured materials. Both have typical trans-scale grain hierarchy, leading to sharp mechanical incompatibility and consequent strain gradient at hetero-interfaces during plastic deformation. This induces heterogeneous deformation-induced hardening, along with recovered forest hardening, jointly to improve Ductility. The heterogeneous deformation-related deformation physics sheds lights on the path to designing novel heterostructures particularly for large Ductility at high strength.
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simultaneously increasing the Ductility and strength of ultra fine grained pure copper
Advanced Materials, 2006Co-Authors: Yonghao Zhao, X Z Liao, Terence G Langdon, J F Bingert, Baozhi Cui, Ke Han, A V Sergueeva, A K Mukherjee, R Z Valiev, Y T ZhuAbstract:Bulk ultra-fine-grained (UFG) materials produced by severe plastic deformation (SPD) usually have high strength but relatively low Ductility at ambient temperatures. This low Ductility is attributed to insufficient strain hardening due to an inability to accumulate dislocations. For a singlephased UFG material where dislocation slip is the primary deformation mechanism, a long-standing fundamental question concerns the feasibility of developing microstructures that offer high Ductility without sacrificing strength. The answer appears to be positive because there are some isolated examples where excellent mechanical behavior has been observed. Nevertheless, the structural features contributing to high strength and good Ductility remain undefined, and this lack of understanding has hindered the search for effective procedures to simultaneously improve the strength and Ductility of UFG materials. Here, we report a new process in which high Ductility is achieved without sacrificing strength by plastically deforming UFG Cu in liquid nitrogen. The enhanced Ductility is attributed primarily to the presence of a high density of preexisting deformation twins (PDTs) and also possibly to a large fraction of high-angle grain boundaries (HAGBs) formed during cryogenic processing. We conclude that this procedure provides a new strategy for increasing the Ductility of UFG materials without any concurrent loss in strength. Strength and Ductility are often mutually exclusive, i.e., materials may be strong or ductile but are rarely both. This also applies to bulk UFG materials. The low Ductility of UFG materials has invariably limited their practical application and, accordingly, much attention has been paid to the development of strategies for improving this poor Ductility. For singlephase UFG and nanostructured materials, several of the reports documenting high Ductility and strength describe experiments on Cu where the stacking-fault energy is relatively low. In some investigations the high Ductility was attributed to the development of a bimodal grain size distribution or pre-existing growth twins (PGTs), but in other investigations the reasons for the high Ductility were not clearly defined. In practice, however, a bimodal grain size distribution must sacrifice some of the strength gained from nanostructuring. Another challenge is the need to fabricate UFG materials in large bulk form suitable for structural applications. This requirement has been hindered because the evidence suggests that PGTs occur only in electrodeposited thin films of nanostructured Cu, and in nanocrystalline Cu by inert-gas condensation (IGC) followed by compaction. However, the Ductility of IGC-prepared nanocrystalline Cu is very low. The objectives of this study were twofold: First, to develop a procedure for increasing the Ductility of large bulk UFG Cu without incurring any significant loss in strength. Second, to evaluate the mechanism contributing to high Ductility in UFG Cu. A pure Cu (99.99%) bar was initially processed by equalchannel angular pressing (ECAP) to produce a UFG structure (hereafter designated the UFGECAP sample), then cryodrawn (D) to a reduction in area of ca. 95%, followed by cryorolling (R) with a reduction in thickness of ca. 96% (hereafter designated the UFGECAP+D+R sample). Figure 1a shows that the UFGECAP+D+R sample has superior mechanical properties compared to the UFGECAP sample. The UFGECAP Cu sample has a 0.2% yield strength of ca. 410 MPa ( ), which is significantly higher than the value of ca. 40 MPa in coarse-grained (CG) Cu. In addition, necking occurs rapidly after the stress reaches a maximum value, yielding a uniform elongation of only ca. 1.3% and an elongation to failure of only ca. 5.9% in the UFGECAP sample. By contrast, the yield strength is increased to ca. 500 MPa in the UFGECAP+D+R sample, and, more importantly, this sample undergoes strain hardening, giving a uniform elongation of C O M M U N IC A IO N S
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tailoring stacking fault energy for high Ductility and high strength in ultrafine grained cu and its alloy
Applied Physics Letters, 2006Co-Authors: Yonghao Zhao, X Z Liao, Y T Zhu, Zenji Horita, Terence G LangdonAbstract:Bulk ultrafine grained (UFG) materials produced by severe plastic deformation often have low Ductility. Here the authors report that simultaneous increases in Ductility and strength can be achieved by tailoring the stacking fault energy (SFE) via alloying. Specifically, UFG bronze (Cu 10wt.% Zn) with a SFE of 35mJ∕m2 was found to have much higher strength and Ductility than UFG copper with a SFE of 78mJ∕m2. Accumulations of both twins and dislocations during tensile testing play a significant role in enhancing the Ductility of the UFG bronze. This work demonstrates a strategy for designing UFG alloys with superior mechanical properties.
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nanostructured metals retaining Ductility
Nature Materials, 2004Co-Authors: Y T Zhu, X Z LiaoAbstract:Structural applications of nanostructured metals often require both high strength and good Ductility. But although these metals usually have high strength, their Ductility is often too low. New experimental work suggests that it is possible to retain the Ductility of metals after nanostructuring by activating certain deformation mechanisms.
