The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction...The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction(ORR)compared to the disordered atomic structures in ordinary solid-solution alloy NPs.Accordingly,through a facile and scalable synthetic method,a series of carbon-supported ultrafine Pt_3Co_(x)Mn_(1-x)ternary INPs are prepared in this work,which possess the"skin-like"ultrathin Pt shells,the ordered L1_(2) atomic structure,and the high-even dispersion on supports(L1_(2)-Pt_3Co_(x)Mn_(1-x)/~SPt INPs/C).Electrochemical results present that the composition-optimized L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C exhibits the highest electrocata lytic activity among the series,which are also much better than those of the pristine ultrafine Pt/C.Besides,it also has a greatly enhanced electrochemical stability.In addition,the effects of annealing temperature and time are further investigated.More importantly,such superior ORR electrocatalytic performance of L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C are also well demonstrated in practical fuel cells.Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocata lytic performance:the Pt-Co-Mn alloy-induced geometric and ligand effects as well as the extremely high L1_(2) atomic-ordering degree.This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst,but also elucidates the corresponding"structure-function"relationship,which can be further applied in designing other intermetallic(electro)catalysts.展开更多
Metallic alloys with high strength and large ductility are required for extreme structural applications.However,the achievement of ultrahigh strength often results in a substantially decreased ductility.Here,we report...Metallic alloys with high strength and large ductility are required for extreme structural applications.However,the achievement of ultrahigh strength often results in a substantially decreased ductility.Here,we report a strategy to achieve the strength-ductility synergy by tailoring the alloy composition to control the local stacking fault energy(SFE)of the face-centered-cubic(fcc)matrix in an L1_(2)-strengthened superlattice alloy.As a proof of concept,based on the thermodynamic calculations,we developed a non-equiatomic CoCrNi_(2)(Al_(0.2)Nb_(0.2))alloy using phase separation to create a near-equiatomic low SFE disordered CoCrNi medium-entropy alloy matrix with in situ formed high-content coherent Ni_(3)(Al,Nb)-type ordered nanoprecipitates(∼12 nm).The alloy achieves a high tensile strength up to 1.6 GPa and a uniform ductility of 33%.The low SFE of the fcc matrix promotes the formation of nanotwins and parallel microbands during plastic deformation which could remarkably enhance the strain hardening capacity.This work provides a strategy for developing ultrahigh-strength alloys with large uniform ductility.展开更多
L1_(2)phase-strengthened Fe-Co-Ni-based high-entropy alloys(HEAs)have attracted considerable attention due to their excellent mechanical properties.Improving the properties of HEAs through conventional experimental me...L1_(2)phase-strengthened Fe-Co-Ni-based high-entropy alloys(HEAs)have attracted considerable attention due to their excellent mechanical properties.Improving the properties of HEAs through conventional experimental methods is costly.Therefore,a new method is needed to predict the properties of alloys quickly and accurately.In this study,a comprehensive prediction model for L1_(2)phase-strengthened Fe-Co-Ni-based HEAs was developed.The existence of the L1_(2)phase in the HEAs was first predicted.A link was then established between the microstructure(L1_(2)phase volume fraction)and properties(hardness)of HEAs,and comprehensive prediction was performed.Finally,two mutually exclusive properties(strength and plasticity)of HEAs were coupled and co-optimized.The Shapley additive explained algorithm was also used to interpret the contribution of each model feature to the comprehensive properties of HEAs.The vast compositional and process search space of HEAs was progressively screened in three stages by applying different prediction models.Finally,four HEAs were screened from hundreds of thousands of possible candidate groups,and the prediction results were verified by experiments.In this work,L1_(2)phase-strengthened Fe-Co-Ni-based HEAs with high strength and plasticity were successfully designed.The new method presented herein has a great cost advantage over traditional experimental methods.It is also expected to be applied in the design of HEAs with various excellent properties or to explore the potential factors affecting the microstructure/properties of alloys.展开更多
The coarsening behavior and strengthening effect of L1_(2)-Ni_(3)(Ti,Al)precipitates in a face-centered-cubic(FCC)(FeCoNi)_(92)Al_(2.5)Ti_(5.5) high entropy alloy have been systematically investigated.The coherent L1_...The coarsening behavior and strengthening effect of L1_(2)-Ni_(3)(Ti,Al)precipitates in a face-centered-cubic(FCC)(FeCoNi)_(92)Al_(2.5)Ti_(5.5) high entropy alloy have been systematically investigated.The coherent L1_(2) precipitates,uniformly distributed throughout the FCC matrix,consistently retain a spherical shape.The coarsening rate coefficient of precipitate is determined by employing the Philippe-Voorhees(PV)model,suggesting excellent thermal stability.Furthermore,the elemental partitioning and compositional evolution of the L1_(2) precipitates is analyzed by atom probe tomography,which identify aluminum(Al)as the slowest diffusion species during the coarsening process.In addition,the precipitation strengthening effect is quantified to ascertain the optimal size of the precipitates.Our study enhances the understanding of precipitate coarsening in high entropy alloys,presenting valuable insights into their thermal stability and mechanical properties.展开更多
Multi-principal element alloys(MPEAs)composed of thermally stable high-density cuboidal nanoparticles have revealed great potential for high-temperature applications.In this work,we systematically studied the growth b...Multi-principal element alloys(MPEAs)composed of thermally stable high-density cuboidal nanoparticles have revealed great potential for high-temperature applications.In this work,we systematically studied the growth behavior and coarsening kinetics of the cuboidal nanoparticles in Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA.In the initial stage of isothermal aging,the nanoparticles exhibit growth and split behavior,resulting in the improvement of mechanical performance,then the cuboidal nanoparticles retain superior thermal and mechanical stability during long-term isothermal aging.The 288 kJ/mol activation energy of Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA,which is higher than that in Ni-based superalloys,reveals the obvious elemental sluggish diffusion in Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA.Meanwhile,coarsening rate constant determined by the volume diffusion mechanism in Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA is 1–2 orders of magnitude less than that of the traditional Ni-based superalloys.The shortterm regulation and long-term stability of the cuboidal nanoparticles endow the Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA with superior mechanical performance and thermal stability for high temperature applications.展开更多
The mechanical properties of Al_(3)X(X=Sc,Lu)were studied by density functional theory(DFT).The elastic constants and formation enthalpy indicate that the L1_(2)-Al_(3)X(X=Sc and Lu)are mechanically and thermodynamica...The mechanical properties of Al_(3)X(X=Sc,Lu)were studied by density functional theory(DFT).The elastic constants and formation enthalpy indicate that the L1_(2)-Al_(3)X(X=Sc and Lu)are mechanically and thermodynamically stable.The bulk moduli and shear moduli show that Al_(3)Sc has better resistance to volume and shape changes than AI3 Lu.However,the calculated results show that Al_(3)Lu has better plasticity than Al_(3)Sc.The properties of structural stability and elastic moduli of the crystal containing four major types of point defects in L1_(2)-Al_(3)X(X=Sc and Lu)were calculated.The mechanical properties of point defects show that point defects cause L1_(2)-Al_(3)X lattice distortion and change the corresponding elastic constants.Point defects reduce the Young’s,shear and bulk moduli but have little effects on the crystal brittleness and toughness of Al_(3)Sc and Al_(3)Lu.Therefore,we have found that Lu addition into aluminum alloys is a very good replacement for expensive Sc addition when the L1_(2)structures are desired for nucleation or strengthening precipitates in aluminum alloys.展开更多
基金supported by the National Key Research and Development Program of China(2021YFB4001301)the Science and Technology Commission of Shanghai Municipality(21DZ1208600)the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University(SL2021ZD105)。
文摘The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction(ORR)compared to the disordered atomic structures in ordinary solid-solution alloy NPs.Accordingly,through a facile and scalable synthetic method,a series of carbon-supported ultrafine Pt_3Co_(x)Mn_(1-x)ternary INPs are prepared in this work,which possess the"skin-like"ultrathin Pt shells,the ordered L1_(2) atomic structure,and the high-even dispersion on supports(L1_(2)-Pt_3Co_(x)Mn_(1-x)/~SPt INPs/C).Electrochemical results present that the composition-optimized L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C exhibits the highest electrocata lytic activity among the series,which are also much better than those of the pristine ultrafine Pt/C.Besides,it also has a greatly enhanced electrochemical stability.In addition,the effects of annealing temperature and time are further investigated.More importantly,such superior ORR electrocatalytic performance of L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C are also well demonstrated in practical fuel cells.Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocata lytic performance:the Pt-Co-Mn alloy-induced geometric and ligand effects as well as the extremely high L1_(2) atomic-ordering degree.This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst,but also elucidates the corresponding"structure-function"relationship,which can be further applied in designing other intermetallic(electro)catalysts.
基金The authors also thank the Microscope and Imaging Center at Southern University of Science and Technology,China.This work was financially supported by the National Natural Science Foundation of China(52122102)Guangdong Innovative&Entrepreneurial Research Team Program(2016ZT06C279)APT research was conducted at the Inter-University 3D APT Unit of City University of Hong Kong(CityU),which is supported by the CityU grant(9360161).
文摘Metallic alloys with high strength and large ductility are required for extreme structural applications.However,the achievement of ultrahigh strength often results in a substantially decreased ductility.Here,we report a strategy to achieve the strength-ductility synergy by tailoring the alloy composition to control the local stacking fault energy(SFE)of the face-centered-cubic(fcc)matrix in an L1_(2)-strengthened superlattice alloy.As a proof of concept,based on the thermodynamic calculations,we developed a non-equiatomic CoCrNi_(2)(Al_(0.2)Nb_(0.2))alloy using phase separation to create a near-equiatomic low SFE disordered CoCrNi medium-entropy alloy matrix with in situ formed high-content coherent Ni_(3)(Al,Nb)-type ordered nanoprecipitates(∼12 nm).The alloy achieves a high tensile strength up to 1.6 GPa and a uniform ductility of 33%.The low SFE of the fcc matrix promotes the formation of nanotwins and parallel microbands during plastic deformation which could remarkably enhance the strain hardening capacity.This work provides a strategy for developing ultrahigh-strength alloys with large uniform ductility.
基金supported by the National Natural Science Foundation of China(Nos.52161011,52373236)the Natural Science Foundation of Guangxi Province(2023GXNSFDA026046)+8 种基金Guangxi Science and Technology Project(Guike AB24010247)the Central Guiding Local Science and Technology Development Fund Projects(Guike ZY23055005)the Scientific Research and Technology Development Program of Guilin(20220110-3)the Scientific Research and Technology Development Program of Nanning Jiangnan district(20230715-02)the Guangxi Key Laboratory of Superhard Material(2022-K-001),the Guangxi Key Laboratory of Information Materials(231003-Z,231013-Z and 231033-K)the Engineering Research Center of Electronic Information Materials and Devices,the Ministry of Education(EIMD-AB202009),the Major Research Plan of the National Natural Science Foundation of China(92166112),the Innovation Project of GUET Graduate Education(2022YCXS200)the Projects of MOE Key Lab of Disaster Forecast and Control in Engineering in Jinan University(20200904006)the Guangdong Province International Science and Technology Cooperation Project(2023A0505050103)the Open Project Program of Wuhan National Laboratory for Optoelectronics(2021WNLOKF010)for the financial support given to this work.
文摘L1_(2)phase-strengthened Fe-Co-Ni-based high-entropy alloys(HEAs)have attracted considerable attention due to their excellent mechanical properties.Improving the properties of HEAs through conventional experimental methods is costly.Therefore,a new method is needed to predict the properties of alloys quickly and accurately.In this study,a comprehensive prediction model for L1_(2)phase-strengthened Fe-Co-Ni-based HEAs was developed.The existence of the L1_(2)phase in the HEAs was first predicted.A link was then established between the microstructure(L1_(2)phase volume fraction)and properties(hardness)of HEAs,and comprehensive prediction was performed.Finally,two mutually exclusive properties(strength and plasticity)of HEAs were coupled and co-optimized.The Shapley additive explained algorithm was also used to interpret the contribution of each model feature to the comprehensive properties of HEAs.The vast compositional and process search space of HEAs was progressively screened in three stages by applying different prediction models.Finally,four HEAs were screened from hundreds of thousands of possible candidate groups,and the prediction results were verified by experiments.In this work,L1_(2)phase-strengthened Fe-Co-Ni-based HEAs with high strength and plasticity were successfully designed.The new method presented herein has a great cost advantage over traditional experimental methods.It is also expected to be applied in the design of HEAs with various excellent properties or to explore the potential factors affecting the microstructure/properties of alloys.
基金supported by the National Key Research and Development Program of China(No.2022YFE0134400)the State Key Laboratory for Advanced Metals and Materials(No.2023-Z05)+1 种基金the National Key Laboratory Foundation of Science and Technology on Materials under Shock and Impact(No.6142902220101)the Hunan Provincial Postgraduate Scientific Research Innovation Project(No.CX20230181).
文摘The coarsening behavior and strengthening effect of L1_(2)-Ni_(3)(Ti,Al)precipitates in a face-centered-cubic(FCC)(FeCoNi)_(92)Al_(2.5)Ti_(5.5) high entropy alloy have been systematically investigated.The coherent L1_(2) precipitates,uniformly distributed throughout the FCC matrix,consistently retain a spherical shape.The coarsening rate coefficient of precipitate is determined by employing the Philippe-Voorhees(PV)model,suggesting excellent thermal stability.Furthermore,the elemental partitioning and compositional evolution of the L1_(2) precipitates is analyzed by atom probe tomography,which identify aluminum(Al)as the slowest diffusion species during the coarsening process.In addition,the precipitation strengthening effect is quantified to ascertain the optimal size of the precipitates.Our study enhances the understanding of precipitate coarsening in high entropy alloys,presenting valuable insights into their thermal stability and mechanical properties.
基金This work was financially supported by the National Key Research and Development Program(2018YFB0703402)the Chinese Academy of Sciences(ZDBS-LY-JSC023)+1 种基金the Industrialization Innovation Team of the Industrial Technology Research Institute of the Chinese Academy of Sciences in Foshan(ZK-TD-2019-04)the Key Specialized Research and Development Breakthrough-Unveiling and Commanding the Special Project Program in Liaoning Province under Grant(2021JH15).
文摘Multi-principal element alloys(MPEAs)composed of thermally stable high-density cuboidal nanoparticles have revealed great potential for high-temperature applications.In this work,we systematically studied the growth behavior and coarsening kinetics of the cuboidal nanoparticles in Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA.In the initial stage of isothermal aging,the nanoparticles exhibit growth and split behavior,resulting in the improvement of mechanical performance,then the cuboidal nanoparticles retain superior thermal and mechanical stability during long-term isothermal aging.The 288 kJ/mol activation energy of Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA,which is higher than that in Ni-based superalloys,reveals the obvious elemental sluggish diffusion in Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA.Meanwhile,coarsening rate constant determined by the volume diffusion mechanism in Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA is 1–2 orders of magnitude less than that of the traditional Ni-based superalloys.The shortterm regulation and long-term stability of the cuboidal nanoparticles endow the Ni_(44)Co_(22)Cr_(22)Al_(6)Nb_(6) MPEA with superior mechanical performance and thermal stability for high temperature applications.
基金the Ministry of Industry and Information Technology of China(61409220124)。
文摘The mechanical properties of Al_(3)X(X=Sc,Lu)were studied by density functional theory(DFT).The elastic constants and formation enthalpy indicate that the L1_(2)-Al_(3)X(X=Sc and Lu)are mechanically and thermodynamically stable.The bulk moduli and shear moduli show that Al_(3)Sc has better resistance to volume and shape changes than AI3 Lu.However,the calculated results show that Al_(3)Lu has better plasticity than Al_(3)Sc.The properties of structural stability and elastic moduli of the crystal containing four major types of point defects in L1_(2)-Al_(3)X(X=Sc and Lu)were calculated.The mechanical properties of point defects show that point defects cause L1_(2)-Al_(3)X lattice distortion and change the corresponding elastic constants.Point defects reduce the Young’s,shear and bulk moduli but have little effects on the crystal brittleness and toughness of Al_(3)Sc and Al_(3)Lu.Therefore,we have found that Lu addition into aluminum alloys is a very good replacement for expensive Sc addition when the L1_(2)structures are desired for nucleation or strengthening precipitates in aluminum alloys.
