L1_(2)precipitates are known to significantly enhance the strength and ductility of single-phase face-centered cubic(FCC)medium-or high-entropy alloys(M/HEAs).However,further improvements in mechanical properties rema...L1_(2)precipitates are known to significantly enhance the strength and ductility of single-phase face-centered cubic(FCC)medium-or high-entropy alloys(M/HEAs).However,further improvements in mechanical properties remain untapped,as alloy design has historically focused on systems with specific CrCoNi-or FeCoCrNi-based FCC matrix and Ni_(3)Al L1_(2)phase compositions.This study introduces novel Co-Ni-Mo-Al alloys with L1_(2)precipitates by systematically altering Al content,aiming to bridge this research gap by revealing the strengthening mechanisms.The(CoNi)_(81)Mo_(12)Al_(7)alloy achieves yield strength of 1086 MPa,tensile strength of 1520 MPa,and ductility of 35%,demonstrating an impressive synergy of strength,ductility,and strain-hardening capacity.Dislocation analysis via transmission electron microscopy,supported by generalized stacking fault energy(GSFE)calculations using density functional theory(DFT),demonstrates that Mo substitution for Al in the L1_(2)phase alters dislocation behavior,promoting the formation of multiple deformation modes,including stacking faults,super-dislocation pairs,Lomer-Cottrell locks,and unusual nano-twin formation even at low strains.These behaviors are facilitated by the low stacking fault energy(SFE)of the FCC matrix,overlapping of SFs,and dislocation dissociation across anti-phase boundaries(APBs).The increased energy barrier for superlattice intrinsic stacking fault(SISF)formation compared to APBs,due to Mo substitution,further influences dislocation activity.This work demonstrates a novel strategy for designing high-performance M/HEAs by expanding the range of FCC matrix and L1_(2)compositions through precipitation hardening.展开更多
Iridium(Ir)-based superalloys withγ/γ'twophase microstructure are recognized as next-generation high-temperature materials for aerospace engines operating above 1500℃.The strengthening phases can markedly enhan...Iridium(Ir)-based superalloys withγ/γ'twophase microstructure are recognized as next-generation high-temperature materials for aerospace engines operating above 1500℃.The strengthening phases can markedly enhance the mechanical strength of alloys.However,these phases exhibit significant brittleness,and their properties in Ir-based alloys remain insufficiently investigated.Here,the high-throughput calculations were employed to screen the potentialγ'phases for Ir_(3)X(X=Al,Si,Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu,Zn,Y,Zr,Nb,Mo,Tc,Ru,Rh,Pd,Ag,Cd,La,Hf,Ta,W,Re,Os,Pt,Au,Th)through systematic assessment of phase stability,melting points,shear modulus and anti-phase boundary(APB)energies.Subsequently,lattice misfit was further optimized through thirdelement compositional design in Ir_(3)(Ti_(0.5)X_(0.5))(X=Nb,Hf,Zr,Ta).The dependence of yield strength on precipitate size was systematically evaluated through the precipitation strengthening effect.Ir_(3)(Ti_(0.5)Ta_(0.5))displays a reduced lattice misfit(0.63%),accompanied by a higher shear modulus(207 GPa),elevated APB energy(920 mJ m^(-2)),and an increased Poisson's ratio(0.25),demonstrating a synergistic improvement in these interrelated mechanical characteristics.The increase of density of states value at Fermi level and the right-shift of the peak in the bonding region result in the improved ductility.The greatest delocalization degree of electrons around Ta and the shorter Ir-Ta bond lengths are responsible for its higher shear modulus and APB energies.A novel Ir_(3)(Ti_(0.5)Ta_(0.5))composition balancing the trade-off between high strength and ductility is expected to guide the development of Irbased superalloys.展开更多
Face-centered cubic(FCC)-structured multicomponent alloys typically exhibit good ductility but low strength.To simultaneously improve strength and ductility,a multicomponent alloy,Ni_(43.9)Co_(22.4)Fe_(8.8)Al_(10.7)Ti...Face-centered cubic(FCC)-structured multicomponent alloys typically exhibit good ductility but low strength.To simultaneously improve strength and ductility,a multicomponent alloy,Ni_(43.9)Co_(22.4)Fe_(8.8)Al_(10.7)Ti_(11.7)B_(2.5)(at%)with a unique microstructure was developed in this work.The microstructure,which includes 17.8%nanosized L12 precipitates and 26.6%micron-sized annealing twins distributed within~8μm fine FCC grains,was achieved through cryogenic rolling and subsequent annealing.The alloy exhibits a yield strength(YS)of 1063 MPa,ultimate tensile strength(UTS)of 1696 MPa,and excellent elongation of~26%.The L1_(2) precipitates and high-density grain boundaries act as a barrier to the dislocation movement,resulting in a substantial strengthening effect.In addition,the dislocations can cut through the L1_(2) precipitates that are coherent with the FCC matrix,whereas the twin boundaries can effectively absorb and store dislocations,leading to a high work-hardening rate.Furthermore,the stacking faults,Lomer-Cottrell locks,and 9-layer rhombohedral stacking sequence(9R)structures formed during tensile deformation significantly enhance strain hardening by blocking dislocation movement and accumulating dislocations,resulting in excellent comprehensive tensile properties.Theoretical calculations reveal that the grain boundaries,L1_(2)precipitates,and twin boundaries contribute the strengths of 263.8,412.6,and 68.7 MPa,respectively,accounting for 71.9%of the YS.This study introduces a promising strategy for developing multicomponent alloys with significant strength-ductility synergies.展开更多
Precipitation–strengthened high entropy alloys (HEAs) exhibit excellent strength–ductility combinations due to precipitation hindering dislocation gliding and work hardening ability of the matrix. However, the effec...Precipitation–strengthened high entropy alloys (HEAs) exhibit excellent strength–ductility combinations due to precipitation hindering dislocation gliding and work hardening ability of the matrix. However, the effect of compositions on the microstructure and related deformation mechanism of HEAs is still unclear. In this study, we developed two types of L1_(2)–strengthened Al_(5)Ti_(8)Fe_(x)(CoNi)_(86.9–x)B_(0.1) (x = 17, 28) HEAs to study the effect of Fe content on the deformation mechanism. Our results reveal that an increased Fe concentration substantially increases the strength and ductility of Al_(5)Ti_(8)Fe_(x)(CoNi)_(86.9–x)B_(0.1) HEAs at room temperature. For the Al_(5)Ti_(8)Fe17(CoNi)_(69.9)B_(0.1) HEA, the presence of a large amount of ordered L1_(2) phase leads to strain strengthening governed by dynamically refined slip bands. For the Al_(5)Ti_(8)Fe28(CoNi)58.9B_(0.1) HEA, the increasing Fe content raises the stacking fault energy of the matrix and reduces the stability of the FCC matrix, making it less stable than the BCC structure. Additionally, the reduced volume fraction of the ordered L1_(2) precipitated phase and the increased stack fault energy of the FCC matrix lead to an increase in the cross-slip frequency during deformation, which in turn promotes avalanche glide of dislocations on highly stressed crystallographic slip planes and the generation of microbands. The microbands and phase transformation inside the microbands promote the strain strengthening, resulting in enhanced strength and ductility. These findings clarify the effect of the Fe content on the deformation behaviours and provide new insight into the formation mechanism of microbands in precipitation-strengthened HEAs, which will open new avenues for the design of ultra-strong yet ductile alloys in the future.展开更多
The nano-scale L1_(2)-Ni_(3)Al precipitates significantly contribute to thermal stability of alumina-forming austenitic(AFA)steels.The coarsening behavior of L1_(2)-Ni_(3)Al precipitates in AFA steels during isotherma...The nano-scale L1_(2)-Ni_(3)Al precipitates significantly contribute to thermal stability of alumina-forming austenitic(AFA)steels.The coarsening behavior of L1_(2)-Ni_(3)Al precipitates in AFA steels during isothermal aging with considering the influence of alloying elements was investigated.The results show that the coarsening rate of L1_(2)-Ni_(3)Al precipitates increases with co-additions of Ni and Cu,and especially,the increase of Cu content promotes the nucleation of L1_(2)-Ni_(3)Al precipitates.A dynamic competition exists between Lifshitz-Slyozov-Wagner theory and transient interface diffusion-controlled theory for coarsening behavior of L1_(2)-Ni_(3)Al precipitates with duration of isothermal aging.Additionally,the transition from L1_(2)-Ni_(3)Al precipitates to B2-NiAl precipitates during isothermal aging results in the formation of a depleted zone of L1_(2)-Ni_(3)Al precipitates around B2-NiAl precipitates,which inhibits the growth of L1_(2)-Ni_(3)Al precipitates.The coarsening of L1_(2)-Ni_(3)Al precipitates significantly contributes to the yield strength of AFA steels.展开更多
The mechanical,thermodynamic properties and electrical conductivities of L1_(2)-Al_(3)X(X=Zr,Sc,Er,Yb,Hf)structural phases in aluminum conductors were investigated through a first-principles study.The results demonstr...The mechanical,thermodynamic properties and electrical conductivities of L1_(2)-Al_(3)X(X=Zr,Sc,Er,Yb,Hf)structural phases in aluminum conductors were investigated through a first-principles study.The results demonstrate that all structural phases have good alloy-forming ability and structural stability,where Al_(3)Zr is the most superior.Al_(3)Zr,Al_(3)Hf and Al_(3)Sc have enhanced shear and deformation resistance in comparison to other phases.Within the temperature range of 200−600 K,Al_(3)Er and Al_(3)Yb possess the greatest thermodynamic stability,followed by Al_(3)Hf,Al_(3)Zr and Al_(3)Sc.Al_(3)Er and Al_(3)Yb have higher thermodynamic stability than Al_(3)Hf,Al_(3)Zr and Al_(3)Sc.All structural phases exhibit substantial metallic properties,indicating their good electrical conductivity.The electrical conductivities of Al_(3)Hf and Al_(3)Zr are higher than those of Al_(3)Er,Al_(3)Yb and Al_(3)Sc.The covalent bond properties in Al_(3)Sc,Al_(3)Er and Al_(3)Yb enhance the hardness,brittleness and thermodynamic stability of the structural phase.The thermodynamic stability of Al_(3)Sc is significantly reduced by ionic bonds.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
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
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
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
基金financially supported by the National Research Foundation of Korea grant funded by the Korea government(MSIT)(Nos.NRF-2022R1A5A1030054,NRF-RS-2024-00345498,and NRFRS-2023-00281508)by Korea Institute for Advancement of Technology(KIAT)grant funded by the Korea Government(MOTIE)(HRD Program for Industrial Innovation-No P0023676)+1 种基金funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)-No 519607530funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(Grant Agreement No 865855).
文摘L1_(2)precipitates are known to significantly enhance the strength and ductility of single-phase face-centered cubic(FCC)medium-or high-entropy alloys(M/HEAs).However,further improvements in mechanical properties remain untapped,as alloy design has historically focused on systems with specific CrCoNi-or FeCoCrNi-based FCC matrix and Ni_(3)Al L1_(2)phase compositions.This study introduces novel Co-Ni-Mo-Al alloys with L1_(2)precipitates by systematically altering Al content,aiming to bridge this research gap by revealing the strengthening mechanisms.The(CoNi)_(81)Mo_(12)Al_(7)alloy achieves yield strength of 1086 MPa,tensile strength of 1520 MPa,and ductility of 35%,demonstrating an impressive synergy of strength,ductility,and strain-hardening capacity.Dislocation analysis via transmission electron microscopy,supported by generalized stacking fault energy(GSFE)calculations using density functional theory(DFT),demonstrates that Mo substitution for Al in the L1_(2)phase alters dislocation behavior,promoting the formation of multiple deformation modes,including stacking faults,super-dislocation pairs,Lomer-Cottrell locks,and unusual nano-twin formation even at low strains.These behaviors are facilitated by the low stacking fault energy(SFE)of the FCC matrix,overlapping of SFs,and dislocation dissociation across anti-phase boundaries(APBs).The increased energy barrier for superlattice intrinsic stacking fault(SISF)formation compared to APBs,due to Mo substitution,further influences dislocation activity.This work demonstrates a novel strategy for designing high-performance M/HEAs by expanding the range of FCC matrix and L1_(2)compositions through precipitation hardening.
基金financially supported by the Major R&D Project of Yunnan Province(Nos.202302AB080021 and 202402AB080007)the Major R&D Project of Yunnan Precious Metals Laboratory Co.,Ltd.(No.YPML-2023050205)+1 种基金Yunnan Major Research and Development Plan(No.202403AA080016)the Open Project of Yunnan Precious Metals Laboratory Co.,Ltd.(No.YPML-20240502066)
文摘Iridium(Ir)-based superalloys withγ/γ'twophase microstructure are recognized as next-generation high-temperature materials for aerospace engines operating above 1500℃.The strengthening phases can markedly enhance the mechanical strength of alloys.However,these phases exhibit significant brittleness,and their properties in Ir-based alloys remain insufficiently investigated.Here,the high-throughput calculations were employed to screen the potentialγ'phases for Ir_(3)X(X=Al,Si,Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu,Zn,Y,Zr,Nb,Mo,Tc,Ru,Rh,Pd,Ag,Cd,La,Hf,Ta,W,Re,Os,Pt,Au,Th)through systematic assessment of phase stability,melting points,shear modulus and anti-phase boundary(APB)energies.Subsequently,lattice misfit was further optimized through thirdelement compositional design in Ir_(3)(Ti_(0.5)X_(0.5))(X=Nb,Hf,Zr,Ta).The dependence of yield strength on precipitate size was systematically evaluated through the precipitation strengthening effect.Ir_(3)(Ti_(0.5)Ta_(0.5))displays a reduced lattice misfit(0.63%),accompanied by a higher shear modulus(207 GPa),elevated APB energy(920 mJ m^(-2)),and an increased Poisson's ratio(0.25),demonstrating a synergistic improvement in these interrelated mechanical characteristics.The increase of density of states value at Fermi level and the right-shift of the peak in the bonding region result in the improved ductility.The greatest delocalization degree of electrons around Ta and the shorter Ir-Ta bond lengths are responsible for its higher shear modulus and APB energies.A novel Ir_(3)(Ti_(0.5)Ta_(0.5))composition balancing the trade-off between high strength and ductility is expected to guide the development of Irbased superalloys.
基金supported by the Major Science and Technology Project of Gansu Province(Nos.23ZDGA010 and 22ZD6GA008)the National Natural Science Foundation of China(No.51564035).
文摘Face-centered cubic(FCC)-structured multicomponent alloys typically exhibit good ductility but low strength.To simultaneously improve strength and ductility,a multicomponent alloy,Ni_(43.9)Co_(22.4)Fe_(8.8)Al_(10.7)Ti_(11.7)B_(2.5)(at%)with a unique microstructure was developed in this work.The microstructure,which includes 17.8%nanosized L12 precipitates and 26.6%micron-sized annealing twins distributed within~8μm fine FCC grains,was achieved through cryogenic rolling and subsequent annealing.The alloy exhibits a yield strength(YS)of 1063 MPa,ultimate tensile strength(UTS)of 1696 MPa,and excellent elongation of~26%.The L1_(2) precipitates and high-density grain boundaries act as a barrier to the dislocation movement,resulting in a substantial strengthening effect.In addition,the dislocations can cut through the L1_(2) precipitates that are coherent with the FCC matrix,whereas the twin boundaries can effectively absorb and store dislocations,leading to a high work-hardening rate.Furthermore,the stacking faults,Lomer-Cottrell locks,and 9-layer rhombohedral stacking sequence(9R)structures formed during tensile deformation significantly enhance strain hardening by blocking dislocation movement and accumulating dislocations,resulting in excellent comprehensive tensile properties.Theoretical calculations reveal that the grain boundaries,L1_(2)precipitates,and twin boundaries contribute the strengths of 263.8,412.6,and 68.7 MPa,respectively,accounting for 71.9%of the YS.This study introduces a promising strategy for developing multicomponent alloys with significant strength-ductility synergies.
基金supported by the National Key Research and Development Program(No.2022YFB3707103)the Natural Science Foundation of China(No.52174375)+2 种基金the Key Research and Development Program of Shaanxi(No.2022JBGS2-04)the Fund of the State Key Laboratory of Solidification Processing in NWPU(No.2023-TS-13)the Training Program of Innovation and Entrepreneurship for Undergraduates(No.S202310699761).
文摘Precipitation–strengthened high entropy alloys (HEAs) exhibit excellent strength–ductility combinations due to precipitation hindering dislocation gliding and work hardening ability of the matrix. However, the effect of compositions on the microstructure and related deformation mechanism of HEAs is still unclear. In this study, we developed two types of L1_(2)–strengthened Al_(5)Ti_(8)Fe_(x)(CoNi)_(86.9–x)B_(0.1) (x = 17, 28) HEAs to study the effect of Fe content on the deformation mechanism. Our results reveal that an increased Fe concentration substantially increases the strength and ductility of Al_(5)Ti_(8)Fe_(x)(CoNi)_(86.9–x)B_(0.1) HEAs at room temperature. For the Al_(5)Ti_(8)Fe17(CoNi)_(69.9)B_(0.1) HEA, the presence of a large amount of ordered L1_(2) phase leads to strain strengthening governed by dynamically refined slip bands. For the Al_(5)Ti_(8)Fe28(CoNi)58.9B_(0.1) HEA, the increasing Fe content raises the stacking fault energy of the matrix and reduces the stability of the FCC matrix, making it less stable than the BCC structure. Additionally, the reduced volume fraction of the ordered L1_(2) precipitated phase and the increased stack fault energy of the FCC matrix lead to an increase in the cross-slip frequency during deformation, which in turn promotes avalanche glide of dislocations on highly stressed crystallographic slip planes and the generation of microbands. The microbands and phase transformation inside the microbands promote the strain strengthening, resulting in enhanced strength and ductility. These findings clarify the effect of the Fe content on the deformation behaviours and provide new insight into the formation mechanism of microbands in precipitation-strengthened HEAs, which will open new avenues for the design of ultra-strong yet ductile alloys in the future.
基金financial supports from the National Natural Science Foundation of China(Nos.52471004,52171107,52201203)the Industry-University-Research Cooperation Project of Hebei Based Universities and Shijiazhuang City(No.241791237A)the Fundamental Research Funds for the Central Universities(No.N2423030)。
文摘The nano-scale L1_(2)-Ni_(3)Al precipitates significantly contribute to thermal stability of alumina-forming austenitic(AFA)steels.The coarsening behavior of L1_(2)-Ni_(3)Al precipitates in AFA steels during isothermal aging with considering the influence of alloying elements was investigated.The results show that the coarsening rate of L1_(2)-Ni_(3)Al precipitates increases with co-additions of Ni and Cu,and especially,the increase of Cu content promotes the nucleation of L1_(2)-Ni_(3)Al precipitates.A dynamic competition exists between Lifshitz-Slyozov-Wagner theory and transient interface diffusion-controlled theory for coarsening behavior of L1_(2)-Ni_(3)Al precipitates with duration of isothermal aging.Additionally,the transition from L1_(2)-Ni_(3)Al precipitates to B2-NiAl precipitates during isothermal aging results in the formation of a depleted zone of L1_(2)-Ni_(3)Al precipitates around B2-NiAl precipitates,which inhibits the growth of L1_(2)-Ni_(3)Al precipitates.The coarsening of L1_(2)-Ni_(3)Al precipitates significantly contributes to the yield strength of AFA steels.
基金National Natural Science Foundation of China (No. 52274403)。
文摘The mechanical,thermodynamic properties and electrical conductivities of L1_(2)-Al_(3)X(X=Zr,Sc,Er,Yb,Hf)structural phases in aluminum conductors were investigated through a first-principles study.The results demonstrate that all structural phases have good alloy-forming ability and structural stability,where Al_(3)Zr is the most superior.Al_(3)Zr,Al_(3)Hf and Al_(3)Sc have enhanced shear and deformation resistance in comparison to other phases.Within the temperature range of 200−600 K,Al_(3)Er and Al_(3)Yb possess the greatest thermodynamic stability,followed by Al_(3)Hf,Al_(3)Zr and Al_(3)Sc.Al_(3)Er and Al_(3)Yb have higher thermodynamic stability than Al_(3)Hf,Al_(3)Zr and Al_(3)Sc.All structural phases exhibit substantial metallic properties,indicating their good electrical conductivity.The electrical conductivities of Al_(3)Hf and Al_(3)Zr are higher than those of Al_(3)Er,Al_(3)Yb and Al_(3)Sc.The covalent bond properties in Al_(3)Sc,Al_(3)Er and Al_(3)Yb enhance the hardness,brittleness and thermodynamic stability of the structural phase.The thermodynamic stability of Al_(3)Sc is significantly reduced by ionic bonds.
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.
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.
