Intragranular ferrite was formed at inclusions in a vanadium microalloyed steel with excess amount of sulfur. The chemical composition of inclusions in the steel was analyzed by SEM-EDS. The inclusions were mainly com...Intragranular ferrite was formed at inclusions in a vanadium microalloyed steel with excess amount of sulfur. The chemical composition of inclusions in the steel was analyzed by SEM-EDS. The inclusions were mainly composed of MnS and aluminum oxides. The precipitation of MnS at aluminum oxides might result in Mn depletion, which, in turn, pro- motes the formation of intragranular ferrite. Optical and SEM observations and three- dimensional (3D) reconstruction demonstrated that intragranular ferrite was formed at inclusions. The morphology of intragranular ferrite changed with undercooling. At higher temperatures intragranular ferrite was nearly equiaxed whereas it was plate-like or lath-like at lower temperatures.展开更多
The evolution of degenerate ferrite in an Fe-0.28wt%C-3.0wt%Mo alloy isothermally reacted for 10ks at 20℃ below TTT diagram bay temperature have been revealed utilizing serial sectioning in conjunction with computer ...The evolution of degenerate ferrite in an Fe-0.28wt%C-3.0wt%Mo alloy isothermally reacted for 10ks at 20℃ below TTT diagram bay temperature have been revealed utilizing serial sectioning in conjunction with computer reconstruction and visualization. The degenerate ferrite is initially formed at prior austenite boundary and then grows toward grain interior rather than along the grain boundary. The degenerate morphology of ferrite may be attributed to repeated nucleation, growth and coalescence of adjacent ferrite crystals. The shape of individual ferrite crystals appears to be rod-like.展开更多
In recent years,China has been using its soft power(most notably,the establishment of Confucius Institutes)to influence public opinion in foreign countries.However,the literature on soft power has yet to provide a def...In recent years,China has been using its soft power(most notably,the establishment of Confucius Institutes)to influence public opinion in foreign countries.However,the literature on soft power has yet to provide a definitive answer about whether that has led to a positive image of China in the foreign audience.Additionally,it is not clear if a positive image would influence public attitudes concerning foreign policies in those countries,such as policies related to trade and military conflicts.Based on an online survey experiment in June 2018,this research shows that soft power information(about positive contributions of Confucius Institutes to the American society)does make the US public feel warmer towards China and become more willing to support trade negotiations.However,the warm feeling does not alter public attitudes towards a potential military conflict with China over disputed islands in the South China Sea.Our study provides both empirical support and advice to policymakers interested in the influence of China’s soft power on US public opinion.展开更多
Full understanding of the thermomechanical behaviors of materials at high strain rates and high temperatures are of great importance from not only scientific meaning but also practical value in engineering structure d...Full understanding of the thermomechanical behaviors of materials at high strain rates and high temperatures are of great importance from not only scientific meaning but also practical value in engineering structure design and safety assessment.Great efforts have been made for abilities of operation the split Hopkinson bars,the most popular technique for experimental determination of mechanical behaviors of materials over the strain rates from 10^2 to 10^4 s^−1 over the past 70 years,at high temperatures since 1960s.A review of experiment work is presented in this paper to give an overview of the development of experimental techniques at high temperatures based on Hopkinson bar systems.The principles of the split Hopkinson bar requires the loading bars avoiding temperature gradient or keeping relatively low temperature when performing high temperature testing.Techniques such as performing temperature gradient corrections,rapid heating or using special designed automatically assembled systems were proposed by researchers to enable the operation of the split Hopkinson bars at temperature as high as possible.Moreover,to the application of high speed photographic technique for capturing the dynamic deformation process of the specimen in high temperature Hopkinson bar testing,some key issues of eliminating the strong thermal radiation induced lights oversaturation and de-blurring of images due to insufficient exposure at high temperature and high strain rate condition,as well as fabrication of high contrast speckle pattern for high temperature digital image correlation measurement were also proposed.The technique can now enable the split Hopkinson bar testing to be performed at high temperature up to 1873 K under the loading conditions of compression or tension with the in situ observation and full field measurement of deformation as well.The paper concludes with summaries of the most important achievements and highlighting of the prospects,trends and remaining challenges for future research.展开更多
The effect of adding Ta on the changes of microstructure and Ms temperature of a dualphase shape memory alloy with compositions of (Ni51 Ti49)1 -x.Tax. and Ni50-Ti50 -g.Ta.g were systematically studied. An optical mi...The effect of adding Ta on the changes of microstructure and Ms temperature of a dualphase shape memory alloy with compositions of (Ni51 Ti49)1 -x.Tax. and Ni50-Ti50 -g.Ta.g were systematically studied. An optical microscope, SEM, X-ray diffraction and DSC were utilized in this work. The evolution of the microstructure as a function of Ta content was characterized. The variation of the Ni/Ti ratio in the NiTi phase plays an important role in the change of the Ms temperatures due to the addition of Ta. A pseudobinary NiTi-Ta phase diagram was proposed based on these results.展开更多
Novel Ti6Al4V particles-reinforced AZ91 Mg matrix composites were successfully fabricated by stir casting method. The stirring time in semisolid condition directly affected the particle distribution and the quality of...Novel Ti6Al4V particles-reinforced AZ91 Mg matrix composites were successfully fabricated by stir casting method. The stirring time in semisolid condition directly affected the particle distribution and the quality of the ingots. Furthermore, the optimal speed of the heating and the liquid stirring could overcome particle settlement caused by the density difference between the matrix and the particles. Ti6Al4V particles distributed uniformly in the composites with different particle contents. The average grain size decreased with the increase in the particle contents. The Ti6A14V particles bonded pretty well with the alloy matrix. In addition, there were some interfacial reactions in the composites. There were rod-like A13Ti phases at the interface. The precipitates extended from the particle surface to the matrix, and they might improve the interfacial bonding strength. The ultimate tensile strength, yield strength and elastic modulus were enhanced as the particle contents increased, and the elongation was much better than that of the same matrix material reinforced with SiC particles. Thus, the novel composites exhibit better comprehensive mechanical properties.展开更多
The superplastic deformation behavior of SiCw/ZK60 composite was investigated at temperatures ranging from 573K to 723K and at initial strain rates ranging from 8.3x10-4s-1 to 8.3x10-2s-1. A maximum elongation of 200%...The superplastic deformation behavior of SiCw/ZK60 composite was investigated at temperatures ranging from 573K to 723K and at initial strain rates ranging from 8.3x10-4s-1 to 8.3x10-2s-1. A maximum elongation of 200% with a m-value of 0.35 was obtained at 613K and a initial strain rate of 1.67x 10-2s-1. The apparent activation energy (98kJ/mol) approximates that for grain boundary diffusion (92kJ/mol) in magnesium. It is proposed that the dominant mechanism of superplastic deformation in the present composite is grain boundary sliding accommodated by diffusional transport, besides, interfacial sliding plays an important role in the superplastic deformation.展开更多
Carbon nanotubes（CNTs） reinforced Mg matrix composites were fabricated by a novel melt processing.The novel processing consisted of two courses：CNTs pre-dispersion and ultrasonic melt processing.Mechanical ball-mil...Carbon nanotubes（CNTs） reinforced Mg matrix composites were fabricated by a novel melt processing.The novel processing consisted of two courses：CNTs pre-dispersion and ultrasonic melt processing.Mechanical ball-milling was employed to pre-disperse CNTs on Zinc（Zn） flakes.Serious CNT entanglements were well dispersed to single CNT or tiny clusters on Zn flakes.The ultrasonic melt processing further dispersed CNTs in the Mg melt,especially tiny CNT clusters.Thus,a uniform dispersion of CNTs was achieved in the as-cast composites.Hot extrusion further improved the distribution of CNTs.CNTs increased both the strength and elongation of the matrix alloy.Notably,the elongation of the matrix alloy was enhanced by 40%.Grain refinement and the pulling-out of CNTs resulted in the evident improvement of ductility for the composites.展开更多
How to design ultra-strong,light-weight Cu alloys is a long-term pursuit in materials community,which is technically superior and cost-effective for their promising energy-saving applications.In this work,we prepared ...How to design ultra-strong,light-weight Cu alloys is a long-term pursuit in materials community,which is technically superior and cost-effective for their promising energy-saving applications.In this work,we prepared Cu-Mg alloyed thin films to study light element Mg alloying effects on the microstructure,hardness and strain rate sensitivity(SRS) of nanocrystalline Cu thin films.In the studied Mg concentrationrange spanning from 0 at.% to 16.8 at.%,both the grain size and the twin spacing decrease monotonously with increasing Mg composition while Cu-2.8 at.% Mg sample has the highest twin fraction of ~75%.A combined strengthening model was employed to quantify the Mg concentration-dependent hardness of nanotwinned(NT) Cu-Mg thin films,in which the grain/twin boundary facilitates strengthening while the solute Mg atoms induce softening.Both the constant rate of loading tests and the nanoindentation creep tests uncover that compared with pure Cu samples,the NT Cu-Mg thin films manifest much lower SRS,particularly in the creep tests,owing to the activation of dynamic strain aging effects.展开更多
In the present study,AZ31B magnesium matrix composites reinforced with two volume fractions(3 and 5 vol.%)of micron-SiC particles(1μm)were fabricated by semisolid stirring assisted ultrasonic vibration method.The as-...In the present study,AZ31B magnesium matrix composites reinforced with two volume fractions(3 and 5 vol.%)of micron-SiC particles(1μm)were fabricated by semisolid stirring assisted ultrasonic vibration method.The as-cast ingots were extruded at 350℃ with the extrusion ratio of 15:1 at a constant ram speed of 15 mm/s.The microstructure of the composites was investigated by optical microscopy,scanning electron microscope and transmission electron microscope.Microstructure characterization of the composites showed relative uniform reinforcement distribution and significant grain refinement.The presence of 1μm-SiC particles assisted in improving the elastic modulus and tensile strength.The ultimate tensile strength and yield strength of the 5 vol.%SiCp/AZ31B composites were simultaneously improved.展开更多
In this work,we prepare transformable HEA/Cu nanolaminates(NLs)with equal individual layer thick-ness(h)by the magnetron sputtering technique,i.e.,Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu and Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu,an...In this work,we prepare transformable HEA/Cu nanolaminates(NLs)with equal individual layer thick-ness(h)by the magnetron sputtering technique,i.e.,Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu and Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu,and comparatively study He-ion irradiation effects on their microstructure and mechanical properties.It ap-pears that the as-deposited HEA/Cu NLs manifest two size h-dependent hardness regimes(i.e.,increased hardness at small h and hardness plateau at large h),while the He-implanted ones exhibit monotonically increased hardness.Contrary to the fashion that smaller h renders less irradiation hardening in bimetal NLs,the Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs manifest the trend that smaller h leads to greater irradiation hard-ening.By contrast,the Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu NLs exhibit the maximum irradiation hardening at a critical h=50 nm.Below this critical size,smaller h results in lower radiation hardening(similar to bimetal NLs),while above this size,smaller h results in greater radiation hardening(similar to Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs).Moreover,these transformable HEA/Cu NLs display inverse h-dependent strain rate sensitivity(SRS m)before and after He-ion irradiation.Nevertheless,compared with as-deposited samples,the irradi-ated Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs display reduced SRS,while the irradiated Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu NLs dis-play enhanced SRS.Such unusual size-dependent irradiation strengthening and inverse h effect on SRS in irradiated samples were rationalized by considering the blocking effects of He bubbles on dislocation nucleation and motion,i.e.,dislocations shearing or bypassing He bubbles.展开更多
Building blocks of quantum computers have been demonstrated in small to intermediate-scale systems.As one of the leading platforms,the trapped ion system has attracted wide attention.A significant challenge in this sy...Building blocks of quantum computers have been demonstrated in small to intermediate-scale systems.As one of the leading platforms,the trapped ion system has attracted wide attention.A significant challenge in this system is to combine fast high-fidelity gates with scalability and convenience in ion trap fabrication.Here we propose an architecture for large-scale quantum computing with a two-dimensional array of atomic ions trapped at such large distance which is convenient for ion-trap fabrication but usually believed to be unsuitable for quantum computing as the conventional gates would be too slow.Using gate operations far outside of the Lamb–Dicke region,we show that fast and robust entangling gates can be realized in any large ion arrays.The gate operations are intrinsically parallel and robust to thermal noise,which,together with their high speed and scalability of the proposed architecture,makes this approach an attractive one for large-scale quantum computing.展开更多
Grain-boundary(GB)precipitation has a significant adverse effect on plasticity of alloys,which easily leads to catastrophic intergranular failure in safety-critical applications under high external loading.Herein,we r...Grain-boundary(GB)precipitation has a significant adverse effect on plasticity of alloys,which easily leads to catastrophic intergranular failure in safety-critical applications under high external loading.Herein,we report a novel strategy that uses the local stress concentration induced by GB precipitates as a driving force to trigger phase transformation of preset non-equiatomic high-entropy solid-solution phase at GBs.This in situ deformation-induced phase transformation at GBs introduces a well-known effect:transformation-induced plasticity(TRIP),which enables an exceptional elongation to fracture(above 38%)at a high strength(above 1.5 GPa)in a GB precipitation-hardened high-entropy alloy(HEA).The present strategy in terms of"local stress concentration-induced phase transformations at GBs"may provide a fundamental approach by taking advantage of(rather than avoiding)the GB precipitation to gain a superior combination of high strength and high ductility in HEAs.展开更多
基金the Nationual Natural Science Foundation of China(No.50471107).
文摘Intragranular ferrite was formed at inclusions in a vanadium microalloyed steel with excess amount of sulfur. The chemical composition of inclusions in the steel was analyzed by SEM-EDS. The inclusions were mainly composed of MnS and aluminum oxides. The precipitation of MnS at aluminum oxides might result in Mn depletion, which, in turn, pro- motes the formation of intragranular ferrite. Optical and SEM observations and three- dimensional (3D) reconstruction demonstrated that intragranular ferrite was formed at inclusions. The morphology of intragranular ferrite changed with undercooling. At higher temperatures intragranular ferrite was nearly equiaxed whereas it was plate-like or lath-like at lower temperatures.
文摘The evolution of degenerate ferrite in an Fe-0.28wt%C-3.0wt%Mo alloy isothermally reacted for 10ks at 20℃ below TTT diagram bay temperature have been revealed utilizing serial sectioning in conjunction with computer reconstruction and visualization. The degenerate ferrite is initially formed at prior austenite boundary and then grows toward grain interior rather than along the grain boundary. The degenerate morphology of ferrite may be attributed to repeated nucleation, growth and coalescence of adjacent ferrite crystals. The shape of individual ferrite crystals appears to be rod-like.
文摘In recent years,China has been using its soft power(most notably,the establishment of Confucius Institutes)to influence public opinion in foreign countries.However,the literature on soft power has yet to provide a definitive answer about whether that has led to a positive image of China in the foreign audience.Additionally,it is not clear if a positive image would influence public attitudes concerning foreign policies in those countries,such as policies related to trade and military conflicts.Based on an online survey experiment in June 2018,this research shows that soft power information(about positive contributions of Confucius Institutes to the American society)does make the US public feel warmer towards China and become more willing to support trade negotiations.However,the warm feeling does not alter public attitudes towards a potential military conflict with China over disputed islands in the South China Sea.Our study provides both empirical support and advice to policymakers interested in the influence of China’s soft power on US public opinion.
基金This work is financially supported by the National Natural Science Foundation of China(Grants 11772268,11527803,11832015 and 11627901)the National Key R&D Program of China(Grant 2017YFB1103500)the 111 Project(Grant BP0719007).The authors also thanks for Dr.Yinggang Miao for useful discussions.
文摘Full understanding of the thermomechanical behaviors of materials at high strain rates and high temperatures are of great importance from not only scientific meaning but also practical value in engineering structure design and safety assessment.Great efforts have been made for abilities of operation the split Hopkinson bars,the most popular technique for experimental determination of mechanical behaviors of materials over the strain rates from 10^2 to 10^4 s^−1 over the past 70 years,at high temperatures since 1960s.A review of experiment work is presented in this paper to give an overview of the development of experimental techniques at high temperatures based on Hopkinson bar systems.The principles of the split Hopkinson bar requires the loading bars avoiding temperature gradient or keeping relatively low temperature when performing high temperature testing.Techniques such as performing temperature gradient corrections,rapid heating or using special designed automatically assembled systems were proposed by researchers to enable the operation of the split Hopkinson bars at temperature as high as possible.Moreover,to the application of high speed photographic technique for capturing the dynamic deformation process of the specimen in high temperature Hopkinson bar testing,some key issues of eliminating the strong thermal radiation induced lights oversaturation and de-blurring of images due to insufficient exposure at high temperature and high strain rate condition,as well as fabrication of high contrast speckle pattern for high temperature digital image correlation measurement were also proposed.The technique can now enable the split Hopkinson bar testing to be performed at high temperature up to 1873 K under the loading conditions of compression or tension with the in situ observation and full field measurement of deformation as well.The paper concludes with summaries of the most important achievements and highlighting of the prospects,trends and remaining challenges for future research.
文摘The effect of adding Ta on the changes of microstructure and Ms temperature of a dualphase shape memory alloy with compositions of (Ni51 Ti49)1 -x.Tax. and Ni50-Ti50 -g.Ta.g were systematically studied. An optical microscope, SEM, X-ray diffraction and DSC were utilized in this work. The evolution of the microstructure as a function of Ta content was characterized. The variation of the Ni/Ti ratio in the NiTi phase plays an important role in the change of the Ms temperatures due to the addition of Ta. A pseudobinary NiTi-Ta phase diagram was proposed based on these results.
基金This work was supported by the National Natural Science Foundation of China[grant numbers 51671066,51771129,51771128]the“Natural Science Foundation of Shanxi”[grant number 2015021067].
基金supported by the National Natural Science Foundation of China (Grant No. 51471059)the China Postdoctoral Science Foundation (Grant No. 2014T70328)
文摘Novel Ti6Al4V particles-reinforced AZ91 Mg matrix composites were successfully fabricated by stir casting method. The stirring time in semisolid condition directly affected the particle distribution and the quality of the ingots. Furthermore, the optimal speed of the heating and the liquid stirring could overcome particle settlement caused by the density difference between the matrix and the particles. Ti6Al4V particles distributed uniformly in the composites with different particle contents. The average grain size decreased with the increase in the particle contents. The Ti6A14V particles bonded pretty well with the alloy matrix. In addition, there were some interfacial reactions in the composites. There were rod-like A13Ti phases at the interface. The precipitates extended from the particle surface to the matrix, and they might improve the interfacial bonding strength. The ultimate tensile strength, yield strength and elastic modulus were enhanced as the particle contents increased, and the elongation was much better than that of the same matrix material reinforced with SiC particles. Thus, the novel composites exhibit better comprehensive mechanical properties.
文摘The superplastic deformation behavior of SiCw/ZK60 composite was investigated at temperatures ranging from 573K to 723K and at initial strain rates ranging from 8.3x10-4s-1 to 8.3x10-2s-1. A maximum elongation of 200% with a m-value of 0.35 was obtained at 613K and a initial strain rate of 1.67x 10-2s-1. The apparent activation energy (98kJ/mol) approximates that for grain boundary diffusion (92kJ/mol) in magnesium. It is proposed that the dominant mechanism of superplastic deformation in the present composite is grain boundary sliding accommodated by diffusional transport, besides, interfacial sliding plays an important role in the superplastic deformation.
基金supported by the National Natural Science Foundation of China(Grant No.51471059 and 51671066)the China Postdoctoral Science Foundation(Grant No.2014T70328)
文摘Carbon nanotubes（CNTs） reinforced Mg matrix composites were fabricated by a novel melt processing.The novel processing consisted of two courses：CNTs pre-dispersion and ultrasonic melt processing.Mechanical ball-milling was employed to pre-disperse CNTs on Zinc（Zn） flakes.Serious CNT entanglements were well dispersed to single CNT or tiny clusters on Zn flakes.The ultrasonic melt processing further dispersed CNTs in the Mg melt,especially tiny CNT clusters.Thus,a uniform dispersion of CNTs was achieved in the as-cast composites.Hot extrusion further improved the distribution of CNTs.CNTs increased both the strength and elongation of the matrix alloy.Notably,the elongation of the matrix alloy was enhanced by 40%.Grain refinement and the pulling-out of CNTs resulted in the evident improvement of ductility for the composites.
基金financially supported by the National Key Research and Development Program of China (No. 2017YFA0700701)the National Natural Science Foundation of China (Nos. 51722104, 51625103, 51790482 and 51761135031)+5 种基金the “111 Project 2.0 of China” (No. BP2018008)the Fok Ying-Tong Education Foundation (No. 161096)the Fundamental Research Funds for the Central Universities for part of the financial supportthe financial support by the Venture & Innovation Support Program for Chongqing Overseas Returnees (cx2018002)the National Defense Basic Scientific Research Programthe Fundamental Research Funds for the Central Universities (2020CDJDCL001)。
文摘How to design ultra-strong,light-weight Cu alloys is a long-term pursuit in materials community,which is technically superior and cost-effective for their promising energy-saving applications.In this work,we prepared Cu-Mg alloyed thin films to study light element Mg alloying effects on the microstructure,hardness and strain rate sensitivity(SRS) of nanocrystalline Cu thin films.In the studied Mg concentrationrange spanning from 0 at.% to 16.8 at.%,both the grain size and the twin spacing decrease monotonously with increasing Mg composition while Cu-2.8 at.% Mg sample has the highest twin fraction of ~75%.A combined strengthening model was employed to quantify the Mg concentration-dependent hardness of nanotwinned(NT) Cu-Mg thin films,in which the grain/twin boundary facilitates strengthening while the solute Mg atoms induce softening.Both the constant rate of loading tests and the nanoindentation creep tests uncover that compared with pure Cu samples,the NT Cu-Mg thin films manifest much lower SRS,particularly in the creep tests,owing to the activation of dynamic strain aging effects.
基金This work was supported by“National Natural Science Foundation of China”(Grant No.51101043)“Key Project of Science and Technology Department of Heilongjiang Province of China”(Grant No.GC12A109)“the Fundamental Research Funds for the Central Universities”(Grant No.HIT.NSRIF.201130).
文摘In the present study,AZ31B magnesium matrix composites reinforced with two volume fractions(3 and 5 vol.%)of micron-SiC particles(1μm)were fabricated by semisolid stirring assisted ultrasonic vibration method.The as-cast ingots were extruded at 350℃ with the extrusion ratio of 15:1 at a constant ram speed of 15 mm/s.The microstructure of the composites was investigated by optical microscopy,scanning electron microscope and transmission electron microscope.Microstructure characterization of the composites showed relative uniform reinforcement distribution and significant grain refinement.The presence of 1μm-SiC particles assisted in improving the elastic modulus and tensile strength.The ultimate tensile strength and yield strength of the 5 vol.%SiCp/AZ31B composites were simultaneously improved.
基金financially supported by the National Natural Science Foundation of China(Nos.U2067219,51722104,51790482,51761135031 and 92163201)the National Key Research and Development Program of China(No.2017YFA0700701)+1 种基金the 111 Project 2.0 of China(No.BP2018008)the Fundamental Research Funds for the Central Universities(No.xtr022019004)。
文摘In this work,we prepare transformable HEA/Cu nanolaminates(NLs)with equal individual layer thick-ness(h)by the magnetron sputtering technique,i.e.,Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu and Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu,and comparatively study He-ion irradiation effects on their microstructure and mechanical properties.It ap-pears that the as-deposited HEA/Cu NLs manifest two size h-dependent hardness regimes(i.e.,increased hardness at small h and hardness plateau at large h),while the He-implanted ones exhibit monotonically increased hardness.Contrary to the fashion that smaller h renders less irradiation hardening in bimetal NLs,the Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs manifest the trend that smaller h leads to greater irradiation hard-ening.By contrast,the Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu NLs exhibit the maximum irradiation hardening at a critical h=50 nm.Below this critical size,smaller h results in lower radiation hardening(similar to bimetal NLs),while above this size,smaller h results in greater radiation hardening(similar to Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs).Moreover,these transformable HEA/Cu NLs display inverse h-dependent strain rate sensitivity(SRS m)before and after He-ion irradiation.Nevertheless,compared with as-deposited samples,the irradi-ated Fe_(50)Mn_(30)Co_(10)Cr_(10)/Cu NLs display reduced SRS,while the irradiated Fe_(50)Mn_(30)Co_(10)Ni_(10)/Cu NLs dis-play enhanced SRS.Such unusual size-dependent irradiation strengthening and inverse h effect on SRS in irradiated samples were rationalized by considering the blocking effects of He bubbles on dislocation nucleation and motion,i.e.,dislocations shearing or bypassing He bubbles.
基金supported by the National key Research and Development Program of China(Grant No.2016YFA0301902)the Frontier Science Center for Quantum Information of the Ministry of Education of China,and the Tsinghua University Initiative Scientific Research Programsupport from Shuimu Tsinghua Scholar Program and the International Postdoctoral Exchange Fellowship Program。
文摘Building blocks of quantum computers have been demonstrated in small to intermediate-scale systems.As one of the leading platforms,the trapped ion system has attracted wide attention.A significant challenge in this system is to combine fast high-fidelity gates with scalability and convenience in ion trap fabrication.Here we propose an architecture for large-scale quantum computing with a two-dimensional array of atomic ions trapped at such large distance which is convenient for ion-trap fabrication but usually believed to be unsuitable for quantum computing as the conventional gates would be too slow.Using gate operations far outside of the Lamb–Dicke region,we show that fast and robust entangling gates can be realized in any large ion arrays.The gate operations are intrinsically parallel and robust to thermal noise,which,together with their high speed and scalability of the proposed architecture,makes this approach an attractive one for large-scale quantum computing.
基金supported financially by the National Natural Science Foundation of China(No.51871178)。
文摘Grain-boundary(GB)precipitation has a significant adverse effect on plasticity of alloys,which easily leads to catastrophic intergranular failure in safety-critical applications under high external loading.Herein,we report a novel strategy that uses the local stress concentration induced by GB precipitates as a driving force to trigger phase transformation of preset non-equiatomic high-entropy solid-solution phase at GBs.This in situ deformation-induced phase transformation at GBs introduces a well-known effect:transformation-induced plasticity(TRIP),which enables an exceptional elongation to fracture(above 38%)at a high strength(above 1.5 GPa)in a GB precipitation-hardened high-entropy alloy(HEA).The present strategy in terms of"local stress concentration-induced phase transformations at GBs"may provide a fundamental approach by taking advantage of(rather than avoiding)the GB precipitation to gain a superior combination of high strength and high ductility in HEAs.
