1.Introduction.Twinning is a fundamental mechanism for plastic deformation in many face-centered cubic(FCC)metals having low stacking fault energies(SFEs)[1,2].In particular,twinning-induced plasticity(TWIP)alloys hav...1.Introduction.Twinning is a fundamental mechanism for plastic deformation in many face-centered cubic(FCC)metals having low stacking fault energies(SFEs)[1,2].In particular,twinning-induced plasticity(TWIP)alloys have excellent tensile properties as a result of the intensive twinning activity[3-5].The twin boundaries also have been proven to contribute to an improved strengthening-toughening effect,mechanical stability and even fatigue performance,relative to high-angle grain boundaries and low-angle grain boundaries[6-11].Therefore,it is of major interest to clarify the twinning mechanism and thereby improve the mechanical properties of metallic materials.展开更多
Matter conductivities are crucial physical properties that directly determine the engineering application value of materials.In reality,the majority of materials are multiphase composites.However,there is currently a ...Matter conductivities are crucial physical properties that directly determine the engineering application value of materials.In reality,the majority of materials are multiphase composites.However,there is currently a lack of theoretical models to accurately predict the conductivities of composite materials.In this study,we develop a unified mixed conductivity(UMC)model,achieving unity in three aspects:(1)a unified description and prediction for different conductivities,including elastic modulus,thermal conductivity,electrical conductivity,magnetic permeability,liquid permeability coefficient,and gas diffusion coefficient;(2)a unified-form governing equation for mixed conductivities of various composite structures,conforming to the Riccati equation;(3)a unified-form composite structure,i.e.,a three-dimensional multiphase interpenetrating cuboid structure,encompassing over a dozen of typical composite structures as its specific cases.The UMC model is applicable for predicting the conductivity across six different types of physical fields and over a dozen different composite structures,providing a broad range of applications.Therefore,the current study deepens our understanding of the conduction phenomena and offers a powerful theoretical tool for predicting the conductivities of composite materials and optimizing their structures,which holds significant scientific and engineering implications.展开更多
Composition design is one of the signifcant methods to break the trade-of relation between strength and ductility of medium-/high-entropy alloys(M/HEAs).Herein,we introduced three fundamental principles for the compos...Composition design is one of the signifcant methods to break the trade-of relation between strength and ductility of medium-/high-entropy alloys(M/HEAs).Herein,we introduced three fundamental principles for the composition design:high elastic modulus,low stacking-fault energy(SFE),and appropriate phase stability.Subsequently,based on the three principles of component design and the frst-principles calculation results,we designed and investigated a non-equiatomic Ni28 MEA with a single-phase and uniform microstructure.The Ni28 MEA has great mechanical properties with yield strength of 329.5 MPa,tensile strength of 829.4 MPa,and uniform elongation of 56.9%at ambient temperature,respectively.The high ductility of Ni28 MEA may be attributed to the dynamically refned microstructure composed of hexagonal close-packed(HCP)lamellas and stacking faults(SFs),which provide extremely high work-hardening ability.This work demonstrates the feasibility of the three principles for composition design and can be extended to more M/HEAs in the future.展开更多
The trade-off relation between the strength and the electrical conductivity has been a Iong-standing dilemma in metallic materials. In the study, three key principles, i.e.elongated grains, sharp texture and nano-scal...The trade-off relation between the strength and the electrical conductivity has been a Iong-standing dilemma in metallic materials. In the study, three key principles, i.e.elongated grains, sharp texture and nano-scale precipitates, were presented for preparing Al wire with high strength and high electrical conductivity based on the specially designed experiments for breaking the mutually exclusive relation between the strength and the electrical conductivity. The results show that the elongated grains could lead to a higher electrical conductivity in Al wire without sacrificing the strength;while, the <111> sharp texture can efficiently strengthen the Al wire without influencing the electrical conductivity. Furthermore, nano-scale precipitates with proper size can simultaneously improve the strength and electrical conductivity of Al alloy wire. Under the guidance of the above three key principles, Al wires with high strength and high conductivity were prepared.展开更多
The high cost and low efficiency of fatigue tests are bottleneck problem for the anti-fatigue design of metallic materials.For this problem,a theoretical fatigue model is proposed in this study,the possible applicatio...The high cost and low efficiency of fatigue tests are bottleneck problem for the anti-fatigue design of metallic materials.For this problem,a theoretical fatigue model is proposed in this study,the possible applications have also been discussed.Specific results would be introduced in two serial papers,in which the first paper focuses on the model building and the applications on fatigue strength prediction;the second paper put emphasis on the influencing factors of the model parameters and the applications on fatigue strength improvement.In this first paper,a theoretical model is proposed considering both the strength and plastic restrictions of fatigue strength.As the model builds up a brief relationship among yield strength(Y),tensile strength(T)and fatigue strength(F),it is named as the Y-T-F model.Through the verification with fatigue strength data covering various kinds of metallic materials and loading conditions,this Y-T-F model exhibits both generality and accuracy.With the Y-T-F model,the efficient fatigue strength prediction could be conducted by brief linear fitting and calculation,just through yield strength,tensile strength and several known fatigue strength data.Moreover,through its deduced Y-F model,the analytical formula of fatigue strength continuously changing with materials strengthening can be obtained,as well as the maximum value of fatigue strength and corresponding critical yield strength.In summary,the Y-T-F model would be useful for reducing the fatigue tests,thus providing new possibilities on the efficient anti-fatigue design and selection of metallic materials.展开更多
In the first paper,a Y-T-F model was proposed based on the restrictions of both strength and plasticity;the corresponding applications on the fatigue strength prediction have also been discussed.In this second paper,t...In the first paper,a Y-T-F model was proposed based on the restrictions of both strength and plasticity;the corresponding applications on the fatigue strength prediction have also been discussed.In this second paper,the emphasis will be put on the issues of fatigue strength improvement.Based on the primary form of the Y-T-F model,the parameters are further analyzed and quantified,to clarify the influences of various factors on fatigue strength.Firstly,the damage capacity C is proved to be sensitive to the elastic modulus E,which could change with the alloying components and nano-scaled grain boundaries;the increase of E would lead to the increasing C,thus increase the fatigue strength.Secondly,the microstructure characteristic coefficient a,as well as the yield strengthσ_(y) and tensile strengthσ_(b) in the crack initiation region could be influenced by the processing mode,grain size and microstructure uniformity of materials;the change of microstructure characteristics would affect the changing tendency of tensile strength--fatigue strength relation via varying the values of a,σ_(y) andσ_(b).Thirdly,the damage weight coefficientωis found to be a reflection of the fatigue strength declination induced by defects;the defect dimension D,the defect shape correlated stress concentration coefficient Kt,as well as the strengthening level of matrix materialsσ_(b) are all corresponding factors.Quantified correlations between the above parameters and corresponding factors are comprehensively built up,hence obtaining the influences of either a single factor or multiple factors on fatigue strength.This further developed Y-T-F model would be helpful to clarify the direction of fatigue strength improvement,and contribute to the anti-fatigue design optimization of metallic materials.展开更多
The variation of stacking fault energy(SFE)in a number of binary Cu alloys is predicted through considering the Suzuki segregation by the full potential linearly augmented plane wave(FPLAPW)method.The calculated resul...The variation of stacking fault energy(SFE)in a number of binary Cu alloys is predicted through considering the Suzuki segregation by the full potential linearly augmented plane wave(FPLAPW)method.The calculated results show that some solute atoms(Mg,Al,Si,Zn,Ga,Ge,Cd,Sn,and Pb),which prefer to form the Suzuki segregation,may decrease the value of SFE;while the others(Ti,Mn,Fe,Ni,Zr,Ag,and Au),which do not cause the Suzuki segregation may not decrease the SFE.Furthermore,it is interesting to find that the former alloying elements are located on the right of Cu group while the latter on the left of Cu group in the periodic table of elements.The intrinsic reasons for the new findings can be traced down to the valences electronic structure of solute and Cu atoms,i.e.,the similarity of valence electronic structure between solute and Cu atoms increases the value of SFE,while the difference decreases the value of SFE.展开更多
The development of multi-principal element alloys(MPEAs,also called as high-or medium-entropy al-loys,HEAs/MEAs)provides tremendous possibilities for materials innovation.However,designing MPEAs with desirable mechani...The development of multi-principal element alloys(MPEAs,also called as high-or medium-entropy al-loys,HEAs/MEAs)provides tremendous possibilities for materials innovation.However,designing MPEAs with desirable mechanical properties confronts great challenges due to their vast composition space.In this work,we provide an essential criterion to efficiently screen the CoCrNi MEAs with outstanding strength-ductility combinations.The negative Gibbs free energy difference△E_(FCC-BCC)between the face-centered cubic(FCC)and body-centered cubic(BCC)phases,the enhancement of shear modulus G and the decline of stacking fault energy(SFE)γ_(isf)are combined as three requisites to improve the FCC phase stability,yield strength,deformation mechanisms,work-hardening ability and ductility in the criterion.The effects of chemical composition on△E_(FCC-BCC),G andγisf were investigated with the first principles calculations for Co_(x)Cr_(33)Ni_(67-x),Co_(33)Cr_(y)Ni_(67-y)and Co_(z)Cr_(66-z)Ni_(34)(0≤x,y≤67 and 0≤z≤66)alloys.Based on the essential criterion and the calculation results,the composition space that displays the neg-ative Gibbs free energy difference△E_(FCC-BCC),highest shear modulus G and lowest SFEγ_(isf)was screened with the target on the combination of high strength and excellent ductility.In this context,the optimal composition space of Co-Cr-Ni alloys was predicted as 60 at.%-67 at.%Co,30 at.%-35 at.%Cr and 0 at.%-6 at.%Ni,which coincides well with the previous experimental evidence for Co_(55)Cr_(40)Ni_(5)alloys.The valid-ity of essential criterion is further proved after systematic comparison with numerous experimental data,which demonstrates that the essential criterion can provide significant guidance for the quick exploitation of strong and ductile MEAs and promote the development and application of MPEAs.展开更多
The evolution of microstructure in the drawing process of commercially pure aluminum wire （CPAW） does not only depend on the nature of materials, but also on the stress profile. In this study, the effect of stress p...The evolution of microstructure in the drawing process of commercially pure aluminum wire （CPAW） does not only depend on the nature of materials, but also on the stress profile. In this study, the effect of stress profile on the texture evolution of the CPAW was systematically investigated by combining the numerical simulation and the microstructure observation. The results show that the tensile stress at the wire center promotes the formation of 〈111〉 texture, whereas the shear stress nearby the rim makes little contribution to the texture formation. Therefore, the 〈111 〉 texture at the wire center is stronger than that in the surface layer, which also results in a higher microhardness at the center of the CPAW under axial loading.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.展开更多
In 2018,the STAR collaboration collected data from^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr at√^(S)NN=200 Ge V to search for the presence of the chiral magnetic effect in collisions of nuclei.The isobar ...In 2018,the STAR collaboration collected data from^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr at√^(S)NN=200 Ge V to search for the presence of the chiral magnetic effect in collisions of nuclei.The isobar collision species alternated frequently between 9644 Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr.In order to conduct blind analyses of studies related to the chiral magnetic effect in these isobar data,STAR developed a three-step blind analysis procedure.Analysts are initially provided a"reference sample"of data,comprised of a mix of events from the two species,the order of which respects time-dependent changes in run conditions.After tuning analysis codes and performing time-dependent quality assurance on the reference sample,analysts are provided a species-blind sample suitable for calculating efficiencies and corrections for individual≈30-min data-taking runs.For this sample,species-specific information is disguised,but individual output files contain data from a single isobar species.Only run-by-run corrections and code alteration subsequent to these corrections are allowed at this stage.Following these modifications,the"frozen"code is passed over the fully un-blind data,completing the blind analysis.As a check of the feasibility of the blind analysis procedure,analysts completed a"mock data challenge,"analyzing data from Au+Au collisions at√^(S)NN=27 Ge V,collected in 2018.The Au+Au data were prepared in the same manner intended for the isobar blind data.The details of the blind analysis procedure and results from the mock data challenge are presented.展开更多
Nickel-based single-crystal superalloys are widely used in the manufacture of aeroengine turbine vanes for their excellent high-temperature performance. Low-angle grain boundaries (LAGBs) will be generated inevitably ...Nickel-based single-crystal superalloys are widely used in the manufacture of aeroengine turbine vanes for their excellent high-temperature performance. Low-angle grain boundaries (LAGBs) will be generated inevitably during their manufacture, which are often characterized by grain boundary misorientation (GBM) and will weaken the mechanical properties of superalloys. However, the relationship between GBM and the fatigue properties of superalloys at elevated temperatures has seldom been investigated due to the difficulty in the sample preparation and experiment process. Based on six kinds of bicrystals with different tilt LAGBs made by a second-generation single-crystal superalloy, the effects of misorientation on the grain boundary microstructure and fatigue properties (980 °C) of superalloys were studied systematically in this work. It is found that, with the increase of GBM, the GB precipitates combined with the cast micropores increase monotonically, accordingly both the fatigue life and fatigue strength decrease successively. Fatigue fracture observations show that the cracks of all the bicrystals initiated from the cast micropores at GBs, and then propagated along the GBs. Therefore, the coupling effect of cast micropores and GBM on the fatigue damage mechanisms of the bicrystals are evaluated according to their hindering degrees on the piled-up dislocations. Combining with a hysteresis energy model, a quantitative fatigue strength prediction model of superalloys is established and is well verified by abundant experimental data. This study could provide guidance for fatigue performance prediction and structural design of superalloys.展开更多
A<110>/2 screw dislocation is commonly dissociated into two <112>/6 Shockley partial dislocations on{111} planes in face-centered cubic metals.As the two partials are not purely screw,different mechanisms ...A<110>/2 screw dislocation is commonly dissociated into two <112>/6 Shockley partial dislocations on{111} planes in face-centered cubic metals.As the two partials are not purely screw,different mechanisms of cross-slip could take place,depending on the stacking fault energy,applied stress and tempe rature.It is crucial to classify the mechanisms of cross-slip because each mechanism possesses its own reaction path with a special activation process.In this work,molecular dynamics simulations have been performed systematically to explore the cross-slip mechanism under different stresses and temperatures in three different metals Ag,Cu and Ni that have different stacking fault energies of 17.8,44.4 and 126.8 mJ/m^2,re spectively.In Ag and Cu with low stacking fault energy,it is observed that the cross-slip mechanism of screw dislocations changes from the Fleischer obtuse angle(FLOA),to the Friedel-Escaig(FE),and then to the FL acute angle(FLAA) at low temperatures,with increasing the applied stress.However,when the temperature increases,the FE mechanism gradually becomes dominant,while the FLAA only occurs at the high stress region.In particular,the FLOA has not been observed in Ni because of its high stacking fault energy.展开更多
Carbon nanotubes(CNTs)have been synthesized from Ar-CH_4 mixtures using rf-plasma enhanced chemical vapor deposition(rf-PECVD)at 500oC.Reduction gases such as H_2 and NH_3 were found unnecessary for carbon nanotube fo...Carbon nanotubes(CNTs)have been synthesized from Ar-CH_4 mixtures using rf-plasma enhanced chemical vapor deposition(rf-PECVD)at 500oC.Reduction gases such as H_2 and NH_3 were found unnecessary for carbon nanotube formation compared to thermal CVD.The relationship between the growth of CNTs and the plasma condition in PECVD has been investigated by in situ self bias measurement.Plasma conditions were controlled by changing the interelectrode distance,rf power and the applied substrate negative bias.By increasing the interelectrode distance and rf power,the spatial density of CNTs was on a rise as a result of the increase in ions density and self bias.As the applied substrate negative bias increased,the spatial density of CNTs decreased possibly due to the positive ions over bombarding effect.展开更多
Cu bicrystals of different sizes with a sole twin boundary（TB） inclined at 45？with respect to the loading direction were deformed under unidirectional and cyclic loading, respectively. It is found that the slip ba...Cu bicrystals of different sizes with a sole twin boundary（TB） inclined at 45？with respect to the loading direction were deformed under unidirectional and cyclic loading, respectively. It is found that the slip bands（SBs） parallel to the TB can be activated near the TB at all scales without obeying the Schmid＇s law.It is concerned with the local stress enhancement in the macroscale while it is more closely related to the scarce dislocation sources in the microscale. Moreover, a wedge-shaped zone formed near the TB in the microscale ascribed to the limited specimen size.展开更多
The diffusion behavior of Cu and Ni atoms undergoing liquidesolid electromigration（L-S EM） was investigated using Cu/Sn/Ni interconnects under a current density of 5.0 103A/cm2 at 250℃. The flowing direction of ele...The diffusion behavior of Cu and Ni atoms undergoing liquidesolid electromigration（L-S EM） was investigated using Cu/Sn/Ni interconnects under a current density of 5.0 103A/cm2 at 250℃. The flowing direction of electrons significantly influences the cross-solder interaction of Cu and Ni atoms, i.e., under downwind diffusion, both Cu and Ni atoms can diffuse to the opposite interfaces; while under upwind diffusion,Cu atoms but not Ni atoms can diffuse to the opposite interface. When electrons flow from the Cu to the Ni, only Cu atoms diffuse to the opposite anode Ni interface, resulting in the transformation of interfacial intermetallic compound（IMC） from Ni3Sn4into（Cu,Ni）6Sn5and further into [（Cu,Ni）6Sn5t Cu6Sn5], while no Ni atoms diffuse to the opposite cathode Cu interface and thus the interfacial Cu6Sn5 remained.When electrons flow from the Ni to the Cu, both Cu and Ni atoms diffuse to the opposite interfaces,resulting in the interfacial IMC transformation from initial Cu6Sn5into（Cu,Ni）6Sn5and further into[（Cu,Ni）6Sn5t（Ni,Cu）3Sn4] at the anode Cu interface while that from initial Ni3Sn4into（Cu,Ni）6Sn5and further into（Ni,Cu）3Sn4at the cathode Ni interface. It is more damaging with electrons flowing from the Cu to the Ni than the other way.展开更多
A general rule of strength and plasticity was proposed for three typical wrought Al alloys(2xxx,6xxx,and 7xxx)subjected to different aging times.Investigations of the work-hardening processes and dislocation configura...A general rule of strength and plasticity was proposed for three typical wrought Al alloys(2xxx,6xxx,and 7xxx)subjected to different aging times.Investigations of the work-hardening processes and dislocation configurations in tensile and compressive testing reveal that this general rule arises because there is a common mechanism for these three kinds of wrought alloys whereby the tendency for cross-slip increases monotonously with aging time.By analyzing the strain hardening exponent and the stacking fault energy,it is demonstrated that the change in the dislocation slip mode is attributed mainly to the formation of second phases rather than to the matrix composition.Accordingly,a new work-hardening model was proposed for wrought Al alloys containing second phases and this explains the interaction between dislocations and second phases and other relevant experimental phenomena.This work is therefore beneficial for quantitatively investigating and optimizing the strength and plasticity of wrought aluminum alloys.展开更多
The authors are very sorry for their carelessness that there are some problems with Eq.(14)and the fund in the original manuscript.Firstly,Eq.(14)in the original manuscript is:k=k_(s)f^(O)_(sp)/f_(sp)+f^(C)_(sp)/f_(s...The authors are very sorry for their carelessness that there are some problems with Eq.(14)and the fund in the original manuscript.Firstly,Eq.(14)in the original manuscript is:k=k_(s)f^(O)_(sp)/f_(sp)+f^(C)_(sp)/f_(sp)=η(k s−1)+1,the latter step of Eq.(14)is repeated with Eq.(15),thus it should be deleted and Eq.(14)revised to k=k_(s)f^(O)_(sp)/f_(sp)+f^(C)_(sp)/f_(sp).展开更多
This study purposes an in situ testing method on quality assessment of soil improvement.Factual drilling data includes the spatial distribution and in situ strength of untreated and treated soil along three different ...This study purposes an in situ testing method on quality assessment of soil improvement.Factual drilling data includes the spatial distribution and in situ strength of untreated and treated soil along three different drillholes measured by on-site drilling monitoring method.These factual drilling data can characterize the degree of soil improvement by penetration injection with permeable polyurethane.Result from on-site drilling monitoring shows that the linear zones represent constant drilling speeds shown in the plot of drill bit advancement vs.net drilling time,which indicates the spatial distributions of soil profile.The soil profile at the study site is composed of four layers,which includes fill,untreated silty clay,treated silty clay,and mucky soil.The results of soil profile are verified by the parallel site loggings.The constant drilling speeds profile the coring-resistant strength of drilled soils.By comparing with the untreated silty clay,the constant drilling speeds of the treated silty clay have been decreased by 13.0-62.8%.Two drilling-speed-based indices of 61.2%and 65.6%are proposed to assess the decreased average drilling speed and the increased in situ strength of treated silty clay.Laboratory tests,i.e.uniaxial compressive strength(UCS)test,have been performed with core sample to investigate and characterize in situ strength by comparing that with drilling speeds.Results show that the average predicted strengths of treated silty clay are 2.4-6.9 times higher than the average measured strength of untreated silty clay.The UCS-based indices of 374.5%and 344.2%verified the quality assessment(QA)results by this new in situ method.This method provides a cost-effective tool for quality assessment of soil improvement by utilizing the digital drilling data.展开更多
The authors regret to inform that the whole“Acknowledgements”section is missing due to the composing process of the editing.The“Acknowledgements”information that should be added is as follows.
1.Introduction Material fracture is a primary mode of failure for engineer-ing components,often resulting in severe safety incidents due to its sudden nature.Therefore,predicting material fracture becomes crucial both...1.Introduction Material fracture is a primary mode of failure for engineer-ing components,often resulting in severe safety incidents due to its sudden nature.Therefore,predicting material fracture becomes crucial both in science and engineering.Scientists have been con-tinuously engaged in this research field for centuries[1-3],propos-ing fracture criteria with different equation forms[2,3],such as the classical maximum tensile and shear stress criteria,etc.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52001153,52322105,52271121,52130002 and 52321001)the Youth Innovation Promotion Association CAS(No.202119)+2 种基金the IMR Innovation Fund(No.2023-ZD01)the KC Wong Education Foundation(No.GJTD-2020-09)One of the authors was supported by the European Research Council under grant agreement No.267464-SPDMETALS(TGL).
文摘1.Introduction.Twinning is a fundamental mechanism for plastic deformation in many face-centered cubic(FCC)metals having low stacking fault energies(SFEs)[1,2].In particular,twinning-induced plasticity(TWIP)alloys have excellent tensile properties as a result of the intensive twinning activity[3-5].The twin boundaries also have been proven to contribute to an improved strengthening-toughening effect,mechanical stability and even fatigue performance,relative to high-angle grain boundaries and low-angle grain boundaries[6-11].Therefore,it is of major interest to clarify the twinning mechanism and thereby improve the mechanical properties of metallic materials.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.52322105,52321001,52130002,U22A20114,and 52371084)the Youth Innovation Promotion Association CAS(No.2021192)+1 种基金the IMR Innovation Fund(No.2023-ZD01)the IMR Outstanding Scholar Position(No.E451A804).
文摘Matter conductivities are crucial physical properties that directly determine the engineering application value of materials.In reality,the majority of materials are multiphase composites.However,there is currently a lack of theoretical models to accurately predict the conductivities of composite materials.In this study,we develop a unified mixed conductivity(UMC)model,achieving unity in three aspects:(1)a unified description and prediction for different conductivities,including elastic modulus,thermal conductivity,electrical conductivity,magnetic permeability,liquid permeability coefficient,and gas diffusion coefficient;(2)a unified-form governing equation for mixed conductivities of various composite structures,conforming to the Riccati equation;(3)a unified-form composite structure,i.e.,a three-dimensional multiphase interpenetrating cuboid structure,encompassing over a dozen of typical composite structures as its specific cases.The UMC model is applicable for predicting the conductivity across six different types of physical fields and over a dozen different composite structures,providing a broad range of applications.Therefore,the current study deepens our understanding of the conduction phenomena and offers a powerful theoretical tool for predicting the conductivities of composite materials and optimizing their structures,which holds significant scientific and engineering implications.
基金supported by the National Natural Science Foundation of China(Nos.52130002 and 52321001)the National Key Research and Development Program of China(No.2022YFB3708200)the Youth Innovation Promotion Association CAS(No.2018226).
文摘Composition design is one of the signifcant methods to break the trade-of relation between strength and ductility of medium-/high-entropy alloys(M/HEAs).Herein,we introduced three fundamental principles for the composition design:high elastic modulus,low stacking-fault energy(SFE),and appropriate phase stability.Subsequently,based on the three principles of component design and the frst-principles calculation results,we designed and investigated a non-equiatomic Ni28 MEA with a single-phase and uniform microstructure.The Ni28 MEA has great mechanical properties with yield strength of 329.5 MPa,tensile strength of 829.4 MPa,and uniform elongation of 56.9%at ambient temperature,respectively.The high ductility of Ni28 MEA may be attributed to the dynamically refned microstructure composed of hexagonal close-packed(HCP)lamellas and stacking faults(SFs),which provide extremely high work-hardening ability.This work demonstrates the feasibility of the three principles for composition design and can be extended to more M/HEAs in the future.
基金financially supported by the State Grid Corporation of China (No. 52110416001z)the National Natural Science Foundation of China (No. 51331007)
文摘The trade-off relation between the strength and the electrical conductivity has been a Iong-standing dilemma in metallic materials. In the study, three key principles, i.e.elongated grains, sharp texture and nano-scale precipitates, were presented for preparing Al wire with high strength and high electrical conductivity based on the specially designed experiments for breaking the mutually exclusive relation between the strength and the electrical conductivity. The results show that the elongated grains could lead to a higher electrical conductivity in Al wire without sacrificing the strength;while, the <111> sharp texture can efficiently strengthen the Al wire without influencing the electrical conductivity. Furthermore, nano-scale precipitates with proper size can simultaneously improve the strength and electrical conductivity of Al alloy wire. Under the guidance of the above three key principles, Al wires with high strength and high conductivity were prepared.
基金financially supported by the National Key R&D Program of China under grant No.2017YFB0703002the National Natural Science Foundation of China(NSFC)under grant Nos.U1664253,51901230,51871223,51790482,51771208+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences under grant No.XDB22020202the Youth Innovation Promotion Association CAS under grant No.2018226the National Science and Technology Major Project under grant No.2017-VI-0003-0073the LiaoNing Revitalization Talents Program under Grant No.XLYC1808027。
文摘The high cost and low efficiency of fatigue tests are bottleneck problem for the anti-fatigue design of metallic materials.For this problem,a theoretical fatigue model is proposed in this study,the possible applications have also been discussed.Specific results would be introduced in two serial papers,in which the first paper focuses on the model building and the applications on fatigue strength prediction;the second paper put emphasis on the influencing factors of the model parameters and the applications on fatigue strength improvement.In this first paper,a theoretical model is proposed considering both the strength and plastic restrictions of fatigue strength.As the model builds up a brief relationship among yield strength(Y),tensile strength(T)and fatigue strength(F),it is named as the Y-T-F model.Through the verification with fatigue strength data covering various kinds of metallic materials and loading conditions,this Y-T-F model exhibits both generality and accuracy.With the Y-T-F model,the efficient fatigue strength prediction could be conducted by brief linear fitting and calculation,just through yield strength,tensile strength and several known fatigue strength data.Moreover,through its deduced Y-F model,the analytical formula of fatigue strength continuously changing with materials strengthening can be obtained,as well as the maximum value of fatigue strength and corresponding critical yield strength.In summary,the Y-T-F model would be useful for reducing the fatigue tests,thus providing new possibilities on the efficient anti-fatigue design and selection of metallic materials.
基金financially supported by the National Key R&D Program of China under grant No.2017YFB0703002the National Natural Science Foundation of China(NSFC)under grant Nos.U1664253,51901230,51871223,51790482,51501198,51771208,51331007+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences under grant No.XDB22020202the Youth Innovation Promotion Association CAS under grant No.2018226the National Science and Technology Major Project under grant No.2017-VI-0003-0073the LiaoNing Revitalization Talents Program under Grant No.XLYC1808027。
文摘In the first paper,a Y-T-F model was proposed based on the restrictions of both strength and plasticity;the corresponding applications on the fatigue strength prediction have also been discussed.In this second paper,the emphasis will be put on the issues of fatigue strength improvement.Based on the primary form of the Y-T-F model,the parameters are further analyzed and quantified,to clarify the influences of various factors on fatigue strength.Firstly,the damage capacity C is proved to be sensitive to the elastic modulus E,which could change with the alloying components and nano-scaled grain boundaries;the increase of E would lead to the increasing C,thus increase the fatigue strength.Secondly,the microstructure characteristic coefficient a,as well as the yield strengthσ_(y) and tensile strengthσ_(b) in the crack initiation region could be influenced by the processing mode,grain size and microstructure uniformity of materials;the change of microstructure characteristics would affect the changing tendency of tensile strength--fatigue strength relation via varying the values of a,σ_(y) andσ_(b).Thirdly,the damage weight coefficientωis found to be a reflection of the fatigue strength declination induced by defects;the defect dimension D,the defect shape correlated stress concentration coefficient Kt,as well as the strengthening level of matrix materialsσ_(b) are all corresponding factors.Quantified correlations between the above parameters and corresponding factors are comprehensively built up,hence obtaining the influences of either a single factor or multiple factors on fatigue strength.This further developed Y-T-F model would be helpful to clarify the direction of fatigue strength improvement,and contribute to the anti-fatigue design optimization of metallic materials.
基金financially supported by the National Natural Science Foundation of China(Nos.51871223,51571198 and 51790482)the LiaoNing Revitalization Talents Program(No.XLYC1808027)。
文摘The variation of stacking fault energy(SFE)in a number of binary Cu alloys is predicted through considering the Suzuki segregation by the full potential linearly augmented plane wave(FPLAPW)method.The calculated results show that some solute atoms(Mg,Al,Si,Zn,Ga,Ge,Cd,Sn,and Pb),which prefer to form the Suzuki segregation,may decrease the value of SFE;while the others(Ti,Mn,Fe,Ni,Zr,Ag,and Au),which do not cause the Suzuki segregation may not decrease the SFE.Furthermore,it is interesting to find that the former alloying elements are located on the right of Cu group while the latter on the left of Cu group in the periodic table of elements.The intrinsic reasons for the new findings can be traced down to the valences electronic structure of solute and Cu atoms,i.e.,the similarity of valence electronic structure between solute and Cu atoms increases the value of SFE,while the difference decreases the value of SFE.
基金We sincerely acknowledge the support of the work by the Na-tional Natural Science Foundation of China(NSFC)(Nos.52130002,52071316,51871223,51771206 and 51571198)the Youth Innova-tion Promotion Association CAS(No.2021192)the KC Wong Education Foundation(No.GJTD-2020-09).
文摘The development of multi-principal element alloys(MPEAs,also called as high-or medium-entropy al-loys,HEAs/MEAs)provides tremendous possibilities for materials innovation.However,designing MPEAs with desirable mechanical properties confronts great challenges due to their vast composition space.In this work,we provide an essential criterion to efficiently screen the CoCrNi MEAs with outstanding strength-ductility combinations.The negative Gibbs free energy difference△E_(FCC-BCC)between the face-centered cubic(FCC)and body-centered cubic(BCC)phases,the enhancement of shear modulus G and the decline of stacking fault energy(SFE)γ_(isf)are combined as three requisites to improve the FCC phase stability,yield strength,deformation mechanisms,work-hardening ability and ductility in the criterion.The effects of chemical composition on△E_(FCC-BCC),G andγisf were investigated with the first principles calculations for Co_(x)Cr_(33)Ni_(67-x),Co_(33)Cr_(y)Ni_(67-y)and Co_(z)Cr_(66-z)Ni_(34)(0≤x,y≤67 and 0≤z≤66)alloys.Based on the essential criterion and the calculation results,the composition space that displays the neg-ative Gibbs free energy difference△E_(FCC-BCC),highest shear modulus G and lowest SFEγ_(isf)was screened with the target on the combination of high strength and excellent ductility.In this context,the optimal composition space of Co-Cr-Ni alloys was predicted as 60 at.%-67 at.%Co,30 at.%-35 at.%Cr and 0 at.%-6 at.%Ni,which coincides well with the previous experimental evidence for Co_(55)Cr_(40)Ni_(5)alloys.The valid-ity of essential criterion is further proved after systematic comparison with numerous experimental data,which demonstrates that the essential criterion can provide significant guidance for the quick exploitation of strong and ductile MEAs and promote the development and application of MPEAs.
基金financially supported by the State Grid Corporation of China (No. 52110416001z)the National Natural Science Foundation of China (No. 51331007)
文摘The evolution of microstructure in the drawing process of commercially pure aluminum wire （CPAW） does not only depend on the nature of materials, but also on the stress profile. In this study, the effect of stress profile on the texture evolution of the CPAW was systematically investigated by combining the numerical simulation and the microstructure observation. The results show that the tensile stress at the wire center promotes the formation of 〈111〉 texture, whereas the shear stress nearby the rim makes little contribution to the texture formation. Therefore, the 〈111 〉 texture at the wire center is stronger than that in the surface layer, which also results in a higher microhardness at the center of the CPAW under axial loading.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.
文摘In 2018,the STAR collaboration collected data from^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr at√^(S)NN=200 Ge V to search for the presence of the chiral magnetic effect in collisions of nuclei.The isobar collision species alternated frequently between 9644 Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr.In order to conduct blind analyses of studies related to the chiral magnetic effect in these isobar data,STAR developed a three-step blind analysis procedure.Analysts are initially provided a"reference sample"of data,comprised of a mix of events from the two species,the order of which respects time-dependent changes in run conditions.After tuning analysis codes and performing time-dependent quality assurance on the reference sample,analysts are provided a species-blind sample suitable for calculating efficiencies and corrections for individual≈30-min data-taking runs.For this sample,species-specific information is disguised,but individual output files contain data from a single isobar species.Only run-by-run corrections and code alteration subsequent to these corrections are allowed at this stage.Following these modifications,the"frozen"code is passed over the fully un-blind data,completing the blind analysis.As a check of the feasibility of the blind analysis procedure,analysts completed a"mock data challenge,"analyzing data from Au+Au collisions at√^(S)NN=27 Ge V,collected in 2018.The Au+Au data were prepared in the same manner intended for the isobar blind data.The details of the blind analysis procedure and results from the mock data challenge are presented.
文摘Nickel-based single-crystal superalloys are widely used in the manufacture of aeroengine turbine vanes for their excellent high-temperature performance. Low-angle grain boundaries (LAGBs) will be generated inevitably during their manufacture, which are often characterized by grain boundary misorientation (GBM) and will weaken the mechanical properties of superalloys. However, the relationship between GBM and the fatigue properties of superalloys at elevated temperatures has seldom been investigated due to the difficulty in the sample preparation and experiment process. Based on six kinds of bicrystals with different tilt LAGBs made by a second-generation single-crystal superalloy, the effects of misorientation on the grain boundary microstructure and fatigue properties (980 °C) of superalloys were studied systematically in this work. It is found that, with the increase of GBM, the GB precipitates combined with the cast micropores increase monotonically, accordingly both the fatigue life and fatigue strength decrease successively. Fatigue fracture observations show that the cracks of all the bicrystals initiated from the cast micropores at GBs, and then propagated along the GBs. Therefore, the coupling effect of cast micropores and GBM on the fatigue damage mechanisms of the bicrystals are evaluated according to their hindering degrees on the piled-up dislocations. Combining with a hysteresis energy model, a quantitative fatigue strength prediction model of superalloys is established and is well verified by abundant experimental data. This study could provide guidance for fatigue performance prediction and structural design of superalloys.
基金financially supported by the Program of “One Hundred Talented People” of the Chinese Academy of Sciences (JBY)the National Natural Science Foundation of China (Nos. 51871223, 51771206, and 51790482)。
文摘A<110>/2 screw dislocation is commonly dissociated into two <112>/6 Shockley partial dislocations on{111} planes in face-centered cubic metals.As the two partials are not purely screw,different mechanisms of cross-slip could take place,depending on the stacking fault energy,applied stress and tempe rature.It is crucial to classify the mechanisms of cross-slip because each mechanism possesses its own reaction path with a special activation process.In this work,molecular dynamics simulations have been performed systematically to explore the cross-slip mechanism under different stresses and temperatures in three different metals Ag,Cu and Ni that have different stacking fault energies of 17.8,44.4 and 126.8 mJ/m^2,re spectively.In Ag and Cu with low stacking fault energy,it is observed that the cross-slip mechanism of screw dislocations changes from the Fleischer obtuse angle(FLOA),to the Friedel-Escaig(FE),and then to the FL acute angle(FLAA) at low temperatures,with increasing the applied stress.However,when the temperature increases,the FE mechanism gradually becomes dominant,while the FLAA only occurs at the high stress region.In particular,the FLOA has not been observed in Ni because of its high stacking fault energy.
基金financial support by the National Natural Science Foundation of China(grant No:10675070.50701026)the National Basic Research Program of China(973 program,2007CB936601)
文摘Carbon nanotubes(CNTs)have been synthesized from Ar-CH_4 mixtures using rf-plasma enhanced chemical vapor deposition(rf-PECVD)at 500oC.Reduction gases such as H_2 and NH_3 were found unnecessary for carbon nanotube formation compared to thermal CVD.The relationship between the growth of CNTs and the plasma condition in PECVD has been investigated by in situ self bias measurement.Plasma conditions were controlled by changing the interelectrode distance,rf power and the applied substrate negative bias.By increasing the interelectrode distance and rf power,the spatial density of CNTs was on a rise as a result of the increase in ions density and self bias.As the applied substrate negative bias increased,the spatial density of CNTs decreased possibly due to the positive ions over bombarding effect.
基金supported by the National Natural Science Foundation of China (NSFC) under grant Nos. 51171194, 51501197, 51571198, 51471170the IMR SYNL-T.S. Kê Research Fellowship
文摘Cu bicrystals of different sizes with a sole twin boundary（TB） inclined at 45？with respect to the loading direction were deformed under unidirectional and cyclic loading, respectively. It is found that the slip bands（SBs） parallel to the TB can be activated near the TB at all scales without obeying the Schmid＇s law.It is concerned with the local stress enhancement in the macroscale while it is more closely related to the scarce dislocation sources in the microscale. Moreover, a wedge-shaped zone formed near the TB in the microscale ascribed to the limited specimen size.
基金financial support of the projects from the National Natural Science Foundation of China (Nos. 51475072 and 51171036)
文摘The diffusion behavior of Cu and Ni atoms undergoing liquidesolid electromigration（L-S EM） was investigated using Cu/Sn/Ni interconnects under a current density of 5.0 103A/cm2 at 250℃. The flowing direction of electrons significantly influences the cross-solder interaction of Cu and Ni atoms, i.e., under downwind diffusion, both Cu and Ni atoms can diffuse to the opposite interfaces; while under upwind diffusion,Cu atoms but not Ni atoms can diffuse to the opposite interface. When electrons flow from the Cu to the Ni, only Cu atoms diffuse to the opposite anode Ni interface, resulting in the transformation of interfacial intermetallic compound（IMC） from Ni3Sn4into（Cu,Ni）6Sn5and further into [（Cu,Ni）6Sn5t Cu6Sn5], while no Ni atoms diffuse to the opposite cathode Cu interface and thus the interfacial Cu6Sn5 remained.When electrons flow from the Ni to the Cu, both Cu and Ni atoms diffuse to the opposite interfaces,resulting in the interfacial IMC transformation from initial Cu6Sn5into（Cu,Ni）6Sn5and further into[（Cu,Ni）6Sn5t（Ni,Cu）3Sn4] at the anode Cu interface while that from initial Ni3Sn4into（Cu,Ni）6Sn5and further into（Ni,Cu）3Sn4at the cathode Ni interface. It is more damaging with electrons flowing from the Cu to the Ni than the other way.
基金financially supported by the Youth Innovation Promotion Association CAS(Nos.2021192,2018226,51871223,51790482,52130002)the KC Wong Education Foundation(No.GJTD-2020–09)+1 种基金the Chinese Academy of Sciences(Grants 174321KYSB20210002)One of the authors was supported by the European Research Council(No.267464-SPDMETALS(TGL))。
文摘A general rule of strength and plasticity was proposed for three typical wrought Al alloys(2xxx,6xxx,and 7xxx)subjected to different aging times.Investigations of the work-hardening processes and dislocation configurations in tensile and compressive testing reveal that this general rule arises because there is a common mechanism for these three kinds of wrought alloys whereby the tendency for cross-slip increases monotonously with aging time.By analyzing the strain hardening exponent and the stacking fault energy,it is demonstrated that the change in the dislocation slip mode is attributed mainly to the formation of second phases rather than to the matrix composition.Accordingly,a new work-hardening model was proposed for wrought Al alloys containing second phases and this explains the interaction between dislocations and second phases and other relevant experimental phenomena.This work is therefore beneficial for quantitatively investigating and optimizing the strength and plasticity of wrought aluminum alloys.
基金supported by the Youth Innovation Promotion Association CAS(Grant No.202,1192)the National Natural Science Foundation of China(NSFC)(Nos.51,871,223,51,790,482,52,130,002)+2 种基金the KC Wong Education Foundation(No.GJTD-2020-09)the Chinese Academy of Sciences(Grants 174321KYSB20210002)supported by the European Research Council(No.267,464-SPDMETALS(TGL))。
文摘The authors are very sorry for their carelessness that there are some problems with Eq.(14)and the fund in the original manuscript.Firstly,Eq.(14)in the original manuscript is:k=k_(s)f^(O)_(sp)/f_(sp)+f^(C)_(sp)/f_(sp)=η(k s−1)+1,the latter step of Eq.(14)is repeated with Eq.(15),thus it should be deleted and Eq.(14)revised to k=k_(s)f^(O)_(sp)/f_(sp)+f^(C)_(sp)/f_(sp).
基金supported by grants from the Research Grant Council of the Hong Kong Special Administrative Region,PR China(Project Nos.HKU 17207518 and R5037-18).
文摘This study purposes an in situ testing method on quality assessment of soil improvement.Factual drilling data includes the spatial distribution and in situ strength of untreated and treated soil along three different drillholes measured by on-site drilling monitoring method.These factual drilling data can characterize the degree of soil improvement by penetration injection with permeable polyurethane.Result from on-site drilling monitoring shows that the linear zones represent constant drilling speeds shown in the plot of drill bit advancement vs.net drilling time,which indicates the spatial distributions of soil profile.The soil profile at the study site is composed of four layers,which includes fill,untreated silty clay,treated silty clay,and mucky soil.The results of soil profile are verified by the parallel site loggings.The constant drilling speeds profile the coring-resistant strength of drilled soils.By comparing with the untreated silty clay,the constant drilling speeds of the treated silty clay have been decreased by 13.0-62.8%.Two drilling-speed-based indices of 61.2%and 65.6%are proposed to assess the decreased average drilling speed and the increased in situ strength of treated silty clay.Laboratory tests,i.e.uniaxial compressive strength(UCS)test,have been performed with core sample to investigate and characterize in situ strength by comparing that with drilling speeds.Results show that the average predicted strengths of treated silty clay are 2.4-6.9 times higher than the average measured strength of untreated silty clay.The UCS-based indices of 374.5%and 344.2%verified the quality assessment(QA)results by this new in situ method.This method provides a cost-effective tool for quality assessment of soil improvement by utilizing the digital drilling data.
基金National Science and Technology Major Project(2017-VI-0003-0073)Youth Innovation Promotion Association CAS under grant No.2021192+3 种基金National Natural Science Foundation of China(NSFC)under grant Nos.52130002 and 51901230IMR Innovation Fund(2023-ZD01)Liaoning"Unveiling and Commanding"Science and Technology plan(2022-37)KC Wong Education Foundation(GJTD-2020-09).
文摘The authors regret to inform that the whole“Acknowledgements”section is missing due to the composing process of the editing.The“Acknowledgements”information that should be added is as follows.
基金supported by the National Nat-ural Science Foundation of China(NSFC)under Grant Nos.52130002,52321001,U2241245the KC Wong Education Founda-tion(No.GJTD-2020-09)+2 种基金the Youth Innovation Promotion Asso-ciation CAS(Grant No.2021192)the IMR Innovation Fund(No.2023-ZD01)the National Key R&D Program of China(No.2020YFA0710404).
文摘1.Introduction Material fracture is a primary mode of failure for engineer-ing components,often resulting in severe safety incidents due to its sudden nature.Therefore,predicting material fracture becomes crucial both in science and engineering.Scientists have been con-tinuously engaged in this research field for centuries[1-3],propos-ing fracture criteria with different equation forms[2,3],such as the classical maximum tensile and shear stress criteria,etc.
