The growing demand for material properties in challenging environments has led to a surge of interest in rapid composition design. Given the great potential composition space, the field of high/medium entropy alloys (...The growing demand for material properties in challenging environments has led to a surge of interest in rapid composition design. Given the great potential composition space, the field of high/medium entropy alloys (H/MEAs) still lacks effective atomic-scale composition design and screening schemes, which hinders the accurate prediction of desired composition and properties. This study proposes a novel approach for rapidly designing the composition of materials with the aim of overcoming the trade-off between strength and ductility in metal matrix composites. The effect of chemical composition on stacking fault energy (SFE), shear modulus, and phase stability was investigated through the use of molecular dynamics (MD) and thermodynamic calculation software. The alloy's low SFE, highest shear modulus, and stable face-centered cubic (FCC) phase have been identified as three standard physical quantities for rapid screening to characterize the deformation mechanism, ultimate tensile strength, phase stability, and ductility of the alloy. The calculation results indicate that the optimal composition space is expected to fall within the ranges of 17 %–34 % Ni, 33 %–50 % Co, and 25 %–33 % Mn. The comparison of stress-strain curves for various predicted components using simulated and experimental results serves to reinforce the efficacy of the method. This indicates that the screening criteria offer a necessary design concept, deviating from traditional strategies and providing crucial guidance for the rapid development and application of MEAs.展开更多
Low-concentration coal mine methane(LC-CMM),which is predominantly composed of methane,serves as a clean and low-carbon energy resource with significant potential for utilization.Utilizing LC-CMM as fuel for solid oxi...Low-concentration coal mine methane(LC-CMM),which is predominantly composed of methane,serves as a clean and low-carbon energy resource with significant potential for utilization.Utilizing LC-CMM as fuel for solid oxide fuel cells(SOFCs)represents an efficient and promising strategy for its effective utilization.However,direct application in Ni-based anodes induces carbon deposition,which severely degrades cell performance.Herein,a medium-entropy oxide Sr_(2)FeNi_(0.1)Cr_(0.3)Mn_(0.3)Mo_(0.3)O_(6−δ)(SFNCMM)was developed as an anode internal reforming catalyst.Following reduction treatment,FeNi_(3) nano-alloy particles precipitate on the surface of the material,thereby significantly enhancing its catalytic activity for LC-CMM reforming process.The catalyst achieved a methane conversion rate of 53.3%,demonstrating excellent catalytic performance.Electrochemical evaluations revealed that SFNCMM-Gd_(0.1)Ce_(0.9)O_(2−δ)(GDC)with a weight ratio of 7:3 exhibited superior electrochemical performance when employed as the anodic catalytic layer.With H_(2) and LC-CMM as fuels,the single cell achieved maximum power densities of 1467.32 and 1116.97 mW·cm^(−2) at 800℃,respectively,with corresponding polarization impedances of 0.17 and 1.35Ω·cm^(2).Furthermore,the single cell maintained stable operation for over 100 h under LC-CMM fueling without significant carbon deposition,confirming its robust resistance to carbon formation.These results underscore the potential of medium-entropy oxides as highly effective catalytic layers for mitigating carbon deposition in SOFCs.展开更多
In recent years,medium entropy alloys have become a research hotspot due to their excellent physical and chemical performances.By controlling reasonable elemental composition and processing parameters,the medium entro...In recent years,medium entropy alloys have become a research hotspot due to their excellent physical and chemical performances.By controlling reasonable elemental composition and processing parameters,the medium entropy alloys can exhibit similar properties to high entropy alloys and have lower costs.In this paper,a FeCoNi medium entropy alloy precursor was prepared via sol-gel and coprecipitation methods,respectively,and FeCoNi medium entropy alloys were prepared by carbothermal and hydrogen reduction.The phases and magnetic properties of FeCoNi medium entropy alloy were investigated.Results showed that FeCoNi medium entropy alloy was produced by carbothermal and hydrogen reduction at 1500℃.Some carbon was detected in the FeCoNi medium entropy alloy prepared by carbothermal reduction.The alloy prepared by hydrogen reduction was uniform and showed a relatively high purity.Moreover,the hydrogen reduction product exhibited better saturation magnetization and lower coercivity.展开更多
Sodium superionic conductors(NASICONs)have attracted enormous attention owing to their excellent ionic diffusion and structural stability.However,the high cost of vanadium,limited capacity due to fewer redox reactions...Sodium superionic conductors(NASICONs)have attracted enormous attention owing to their excellent ionic diffusion and structural stability.However,the high cost of vanadium,limited capacity due to fewer redox reactions,and low electronic conductivity restrict their practical application.Herein,we designed Na_(3.5)V_(0.5)Mn_(0.5)Fe_(0.5)Ti_(0.5)(PO_(4))3 (NVMFTP)medium entropy NASICON with multi-electron reactions as a fast sodium storage cathode for sodium-ion batteries(SIBs).The incorporation of Fe,Mn and Ti not only reduces the cost but also activates multi-redox reactions of V^(2+)/V^(3+),Ti^(3+)/Ti^(4+),Fe^(2+)/Fe^(3+),V^(3+)/V^(4+),Mn^(2+)/Mn^(3+),V^(4+)/V^(5+).Owing to distinctive structural design with medium entropy,the NVMFTP delivered 168 mAh·g^(−1) at 0.5C with a remarkable rate capability of 93.51 mAh·g^(−1) at 60C and steady long-term cycling performance till 5000 cycles.More importantly,NVMFTP takes only 11 min to achieve 80%SOC at 5C.The in-situ and ex-situ X-ray diffraction(XRD)further demonstrate reversible multi-electron reaction mechanisms of slow charging and fast charging.NVMFTP/HC full cell shows 110 mAh·g^(−1) capacity and 208 Wh·kg^(−1) energy density.This study will provide comprehensive insight into developing low-cost,cutting-edge materials for SIBs.展开更多
The present work reports characteristics of dislocation slip behavior in an equi-atomic HfNbTiZr refractory medium entropy alloy(RMEA)and its systematic comparison with pure niobium(Nb).Fully-recrystallized specimens ...The present work reports characteristics of dislocation slip behavior in an equi-atomic HfNbTiZr refractory medium entropy alloy(RMEA)and its systematic comparison with pure niobium(Nb).Fully-recrystallized specimens were fabricated by cold rolling and subsequent annealing,and uniaxial tensile deformation was applied at room temperature.Slip trace morphologies on the surfaces of the tensile-deformed ma-terials were quantitatively characterized,and the so-calledψand x relationships of the observed slip traces were evaluated by a newly developed method for polycrystalline specimens.Wavy slip traces were observed in most grains in the pure Nb.They consisted of low-indexed slip planes,such as{110},and{112},and high-indexed(or undetermined)slip planes.Some straight slip traces persisting on the low-indexed slip planes were also found in the pure Nb.In contrast,straight slip traces were dominant in the RMEA.The straight slip traces in the RMEA were not parallel to particular slip planes but mostly distributed along the maximum shear stress plane(MSSP),indicating that frequent cross slip in very short intervals occurred.Large deviations of slip planes from the MSSP in a few grains of the RMEA were attributed to the slip transfer from neighboring grains as a characteristic of polycrystalline materi-als.Frequent cross slip in short intervals,attributed to homogeneous slip resistance distribution for screw dislocations in the RMEA originating from the chemical heterogeneity on an atomic scale,was proposed as a novel mechanism responsible for the unique slip behavior and macroscopic deformation behavior.展开更多
The phase constitution,microstructure,damping capacity,and mechanical properties of as-cast AlxCrFe3Ni(x=0.5,0.52,0.54,and 0.56,respectively)medium entropy alloys were investigated.It is found that the volume fraction...The phase constitution,microstructure,damping capacity,and mechanical properties of as-cast AlxCrFe3Ni(x=0.5,0.52,0.54,and 0.56,respectively)medium entropy alloys were investigated.It is found that the volume fraction of BCC phase increases while that of FCC decreases with increasing the Al content.When the content of Al is 0.54,the alloy is composed of 82.1vol.%BCC matrix and 17.9vol.%FCC phase.Wherein the FCC phase is distributed on the BCC matrix,forming a structure where the hard BCC matrix is surrounded by soft FCC phase.This results in a hindering effect on the propagation process of vibration waves.The damping performance of Al0.54CrFe_(3)Ni alloy,characterized by an internal friction of Q^(-1) is as high as 0.059,is higher than that of most FeCr damping alloys.The volume fraction of the BCC phase and the peculiar distribution of the FCC phase are identified as the key factors affecting the damping capacity.In addition,the Al0.54CrFe3Ni alloy exhibits a high yield strength of 811.16 MPa.展开更多
The concept of grain boundary engineering(GBE)has been successfully applied to L1_(2)-strengthened(CoCrNi)_(94)Al_(3)Ti_(3)medium entropy alloy,with the aim of improving the oxidation resistance by increasing the rati...The concept of grain boundary engineering(GBE)has been successfully applied to L1_(2)-strengthened(CoCrNi)_(94)Al_(3)Ti_(3)medium entropy alloy,with the aim of improving the oxidation resistance by increasing the ratio of special boundaries and suppressing discontinuous precipitation.Surprisingly,our results reveal that GBE treatment not only slows down the oxidation kinetics and but also alters the oxide scale from TiO_(2)and multi-defect Cr_(2)O_(3)to continuous and protective Cr_(2)O_(3)and Al_(2)O_(3),thereby contributing to an enhanced oxidation and anti-spalling resistance.The GBE treatment reduces the oxidation weight gain of the current alloy from 1.950 mg cm^(-2)to 1.211 mg cm^(-2)after 100 h of cyclic oxidation at 800℃.The findings show that the extensive outward diffusion of Ti accelerates ion transport and promotes microporosity,thus leading to more defects being formed in the oxide film.The GBE treatment suppresses the discontinuous precipitation of the Ti-bearing L1_(2)phase and breaks the random large angular grain boundaries network,inhibiting the diffusion of Ti and ultimately enhancing the oxidation properties of the alloy.The current work provides an idea of oxidation resistance enhancement for Ti-bearing LI_(2)-strengthened alloys without changing the alloy composition.展开更多
The effect of Ti content on the microstructure and mechanical properties of as-cast light-weight Ti_(x)(AlVCr)_(100−x)medium entropy alloys was studied by compressive tests,X-ray diffraction,scanning electron microsco...The effect of Ti content on the microstructure and mechanical properties of as-cast light-weight Ti_(x)(AlVCr)_(100−x)medium entropy alloys was studied by compressive tests,X-ray diffraction,scanning electron microscopy and transmission electron microscopy.The results suggest that yield strength increases and then decreases with the increment of Ti content.The Ti_(60)(AlVCr)_(40)alloy has the best combination of high strength of 1204 MPa and uniform plastic strain of 70%,possessing a high specific yield strength of 255 MPa·cm^(3)/g.The enhancement of strength is mainly attributed to the synergic effects of solid-solution and coherent nano-precipitation strengthening,while dislocation motion such as dislocation pinning,entanglement and dislocation cells significantly increases the strain-hardening capacity.展开更多
Modern engineering has long been in demand for high-performance additive manufactured materials for harsh working conditions.The idea of high entropy alloy(HEA),medium entropy alloy(MEA),and multi-principal-element al...Modern engineering has long been in demand for high-performance additive manufactured materials for harsh working conditions.The idea of high entropy alloy(HEA),medium entropy alloy(MEA),and multi-principal-element alloy(MPEA)provides a new way for alloy design.In this work,we develop a Co42 Cr20 Ni30 Ti4 Al4 quinary MEA which exhibits a superiority of mechanical properties over a wide tem-perature ranging from 77 to 873 K via selective laser melting(SLM)and post-heat treatment.The present MEA achieves an excellent ultimate tensile strength(UTS)of 1586 MPa with a total elongation(TE)of 22.7%at 298 K,a UTS of 1944 MPa with a TE of 22.6%at 77 K,and a UTS of 1147 MPa with a TE of 9.1%at 873 K.The excellent mechanical properties stem from the microstructures composed of partially refined grains and heterogeneously precipitated L12 phase due to the concurrence of recrystallization and precipitation.The grain boundary hardening,precipitation hardening,and dislocation hardening con-tribute to the high YS at 298 and 77 K.Interactions of nano-spaced stacking faults(SFs)including SFs networks,Lomer-Cottrell locks(L-C locks),and anti-phase boundaries(APBs)induced by the shearing of L12 phase are responsible for the high strain hardening rate and plasticity at 77 K.Our work provides a new insight for the incorporation of precipitation hardening and additive manufacturing technology,paving the avenue for the development of high-performance structural materials.展开更多
High/medium entropy alloys(HEAs/MEAs)with high electrocatalytic activity have attracted great attention in water electrolysis applications.However,facile synthesis of self-supporting high/medium entropy alloys electro...High/medium entropy alloys(HEAs/MEAs)with high electrocatalytic activity have attracted great attention in water electrolysis applications.However,facile synthesis of self-supporting high/medium entropy alloys electrocatalysts with rich active sites through classical metallurgical methods is still a challenge.Here,a self-supporting porous FeCoNi MEA electrocatalyst with nanosheets-shaped surface for oxygen evolution reaction(OER)was prepared by a one-step electrochemical process from the metal oxides in molten CaCl_(2).The formation of the FeCoNi MEA is attributed to the oxides electro-reduction,high-temperature diffusion and solid solution.Additionally,the morphology and structure of the FeCoNi MEA can be precisely controlled by adjusting the electrolysis time and temperature.The electronic structure regulation and the reduced energy barrier of OER from the“cocktail effect”,the abundant exposed active sites brought by surface ultrathin nanosheets,the good electronic conductivity and electrochemical stability from the self-supporting structure enable the FeCoNi MEA electrode shows high-performance OER electrocatalysis,exhibiting a low overpotential of 233 mV at a current density of 10 mA cm^(-2),a low Tafel slope of 29.8 mV dec^(-1),and an excellent stability for over 500 h without any obvious structural destruction.This work demonstrates a facile one-step electrochemical metallurgical approach for fabricating self-supporting HEAs/MEAs electrocatalysts with nanosized surface for the application in water electrolysis.展开更多
A new metastable dual-phase Fe59 Cr13 Ni18 Al10 medium entropy alloy(MEA)with hierarchically heteroge-neous microstructure from micro-to nano-scale was designed in this work.Partially recrystallized FCC phase and lots...A new metastable dual-phase Fe59 Cr13 Ni18 Al10 medium entropy alloy(MEA)with hierarchically heteroge-neous microstructure from micro-to nano-scale was designed in this work.Partially recrystallized FCC phase and lots of NiAl-rich B2 precipitates are obtained by annealing and aging treatment.The yield strength of the MEA at room temperature(298 K)and liquid nitrogen temperature(77 K)increased from∼910 MPa and∼1250 MPa in the annealed state,respectively,to∼1145 MPa and∼1520 MPa in the aged state,while the uniform elongation maintained more than 15%.The excellent mechanical properties of the MEA both at 298 and 77 K are attributed to the co-activation of multiple strengthening mech-anisms,including fine grain,dislocation,precipitation,transformation-induced plasticity,stacking faults,and nano-twins.展开更多
It is widely recognized that the development of ZABs is impeded by the kinetic bottleneck of oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).The application of conformational entropy strategy to oxide...It is widely recognized that the development of ZABs is impeded by the kinetic bottleneck of oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).The application of conformational entropy strategy to oxides often involves introducing multiple elements with different properties,thereby providing outstanding bifunctional catalytic activity for OER/ORR.Nevertheless,the possible underlying catalytic pathways and potential interactions between various components are still poorly understood.This paper presents an excellent medium-entropy perovskite oxide,Sr(FeCoNiMo)_(1/4)O_(3−δ)(lower overpotential of 301 mV at 10 mA cm^(−2)).Zinc-air batteries employing it as a cathode catalyst demonstrate excellent round-trip efficiency(62%).By combining theoretical calculation with experiments,we aim to establish the link between the electronic structure of perovskite oxides with different elemental compositions and their OER mechanism.Research reveals that the conformational entropy strategy can simultaneously shift the O 2p-band center and metal d-band center of perovskite oxide towards the vicinity of the Fermi energy level,thereby triggering a more favorable lattice oxygen-participated mechanism(LOM)during the OER process.The outcomes of this work provide crucial insights into the role of conformational entropy strategies in oxygen catalysis and offer potential avenues for constructing efficient and stable electrocatalysts.展开更多
High/medium entropy alloys(H/MEAs)are generally possible to exhibit chemical short-range order(SRO).However,the complex role of SRO on mechanical properties from nano-scale to meso-scale is still challenging so far.He...High/medium entropy alloys(H/MEAs)are generally possible to exhibit chemical short-range order(SRO).However,the complex role of SRO on mechanical properties from nano-scale to meso-scale is still challenging so far.Here,we study the strengthening mechanism and deformation behavior in a model body-centered-cubic HfNbTa MEA by using atomic-scale molecular dynamics,micro-scale dislocation dynamics,and meso-scale crystal plasticity finite element.The SRO inhibits dislocation nucleation at the atomic scale,improving the flow stress.The SRO-induced ultrastrong local stress fluctuation greatly improves the micro-scale dislocation-based strength by the significant dislocation forest strengthening.Moreover,the Ta-rich locally ordered structure leads to an obvious heterogeneous strain and stress partitioning,which forms a strong strain gradient in the adjacent grain interiors and contributes to the strong back-stress-induced strain hardening.展开更多
A Co-free as-cast AlCrAlCrFe_(2)Ni_(2)medium entropy alloy(MEA)with multi-phases was remelted by fiber laser in this study.The effect of laser remelting on the microstructure,phase distribution and mechanical properti...A Co-free as-cast AlCrAlCrFe_(2)Ni_(2)medium entropy alloy(MEA)with multi-phases was remelted by fiber laser in this study.The effect of laser remelting on the microstructure,phase distribution and mechanical properties was investigated by characterizing the as-cast and the remelted AlCrAlCrFe_(2)Ni_(2)alloy.The laser remelting process resulted in a significant decrease of grain size from about 780μm to 58.89μm(longitudinal section)and 15.87μm(transverse section)and an increase of hardness from 4.72±0.293 GPa to 6.40±0.147 GPa(longitudinal section)and 7.55±0.360 GPa(transverse section).It was also found that the long side plate-like microstructure composed of FCC phase,ordered B2 phase and disordered BCC phase in the as-cast alloy was transformed into nano-size weave-like microstructure consisting of alternating ordered B2 and disordered BCC phases.The mechanical properties were evaluated by the derived stressstrain relationship obtained from nano-indentation tests data.The results showed that the yield stress increased from 661.9 MPa to 1347.6 MPa(longitudinal section)and 1647.2 MPa(transverse section)after remelting.The individual contribution of four potential strengthening mechanisms to the yield strength of the remelted alloy was quantitatively evaluated,including grain boundary strengthening,dislocation strengthening,solid solution strengthening and precipitation strengthening.The calculation results indicated that dislocation and precipitation are dominant strengthening mechanisms in the laser remelted MEA.展开更多
Solid solution strengthening is one of the most conventional strategies for optimizing alloys strength,while the corresponding mechanisms can be more complicated than we traditionally thought specifically as heterogen...Solid solution strengthening is one of the most conventional strategies for optimizing alloys strength,while the corresponding mechanisms can be more complicated than we traditionally thought specifically as heterogeneity of microstructure is involved.In this work,by comparing the change of chemical distribution,dislocation behaviors and mechanical properties after doping equivalent amount of tungsten(W)atoms in CrCoNi alloy and pure Ni,respectively,it is found that the alloying element W in CrCoNi alloy resulted in much stronger strengthening effect due to the significant increase of heterogeneity in chemical distribution after doping trace amount of W.The large atomic scale concentration fluctuation of all elements in CrCoNi-3W causes dislocation motion via strong nanoscale segment detrapping and severe dislocation pile up which is not the case in Ni-3W.The results revealed the high sensitivity of elements distribution in multi-principle element alloys to composition and the significant consequent influence in tuning the mechanical properties,giving insight for complex alloy design.展开更多
The effect of Mo additions on the microstructures and mechanical properties of CoCrNi alloys was investigated,meanwhile,ab initio calculations are performed to quantitatively evaluate the lattice distortion and stacki...The effect of Mo additions on the microstructures and mechanical properties of CoCrNi alloys was investigated,meanwhile,ab initio calculations are performed to quantitatively evaluate the lattice distortion and stacking fault energy(SFE).The yield strength,ultimate tensile strength,and elongation of(CoCrNi)_(97)Mo_(3)alloy are 475 MPa,983 MPa and 69%,respectively.The yield strength is increased by~30%and high ductility is maintained,in comparison with CoCrNi alloy.Besides the nano-twins and dislocations,the higher density of stacking faults is induced during the tensile deformation for(CoCrNi)_(97)Mo_(3)alloy.Ab initio calculation results indicate the mean square atomic displacement(MSAD)and SFE value of(CoCrNi)_(97)Mo_(3)alloy is 42.6 pm^(2)and-40.4 mJ/m^(2)at 0 K,respectively.The relationship between mechanical properties and MSAD,SFE for various multiple principal element alloys is discussed.展开更多
In order to improve the strength and corrosion resistance of CoCrNi medium entropy alloy,TiC strengthened CoCrNi medium entropy alloy(CoCrNi/(TiC)_(x)(x=0.1,0.2,0.4))was designed by addition of different amounts of Ti...In order to improve the strength and corrosion resistance of CoCrNi medium entropy alloy,TiC strengthened CoCrNi medium entropy alloy(CoCrNi/(TiC)_(x)(x=0.1,0.2,0.4))was designed by addition of different amounts of TiC.The effects of TiC content on the microstructure,mechanical properties,and corrosion resistance of the alloy were investigated.It was found that the precipitation morphologies of TiC changed from lamellar eutectic to needle structure with the increase of TiC content,and finally formed mixed needled and bulk TiC particles.TiC appears as a dissolution−precipitation phenomenon in the CoCrNi alloy,which is important for the mechanical properties and corrosion resistance of the CoCrNi/(TiC)_(x) alloy.The strength of alloy was enhanced obviously after the addition of TiC.The compressive yield strength of CoCrNi/(TiC)_(0.4) alloy reached 746 MPa,much larger than that of the CoCrNi medium entropy alloy,108 MPa.Additionally,the addition of TiC was found to improve the corrosion resistance of CoCrNi medium entropy alloy in the salt solution.展开更多
For developing new binder phase with high performance, Co-Ni-Fe alloy was used as binder in cemented carbides. The mechanical properties of WC-CoNiFe and WC-Co cemented carbides with different grain sizes were studied...For developing new binder phase with high performance, Co-Ni-Fe alloy was used as binder in cemented carbides. The mechanical properties of WC-CoNiFe and WC-Co cemented carbides with different grain sizes were studied. The results show that the reprecipitation of WC-CoNiFe is inhibited compared with that of WC-Co during sintering process, and the grains in WC-CoNiFe cemented carbides are more of smooth shape, resulting in a slightly lower hardness and higher transverse rupture strength. With the increase of the grain size, the hardness of the two cemented carbides decreases, and the transverse rupture strength increases. However, the slope values of K in Hall-Petch relationship are higher in WC-CoNiFe than those in WC-Co, indicating the high toughness of medium entropy alloy Co-Ni-Fe.展开更多
Deformation behavior of a FeCrNi medium entropy alloy(MEA)prepared by powder metallurgy(P/M)method was investigated over a wide range of strain rates.The FeCrNi MEA exhibits high strain-hardening ability,which can be ...Deformation behavior of a FeCrNi medium entropy alloy(MEA)prepared by powder metallurgy(P/M)method was investigated over a wide range of strain rates.The FeCrNi MEA exhibits high strain-hardening ability,which can be attributed to the multiple deformation mechanisms,including dislocation slip,deformation induced stacking fault and mechanical twinning.The shear localization behavior of the FeCrNi MEA was also analyzed by dynamically loading hat-shaped specimens,and the distinct adiabatic shear band cannot be observed until the shear strain reaches~14.5.The microstructures within and outside the shear band exhibit different characteristics:the grains near the shear band are severely elongated and significantly refined by dislocation slip and twinning;inside the shear band,the initial coarse grains completely disappear,and transform into recrystallized ultrafine equiaxed grains by the classical rotational dynamic recrystallization mechanism.Moreover,microvoids preferentially nucleate in the central areas of the shear band where the temperature is very high and the shear stress is highly concentrated.These microvoids will coalesce into microcracks with the increase of strain,which eventually leads to the fracture of the shear band.展开更多
In medium/high entropy alloys, their mechanical properties are strongly dependent on the chemicalelemental composition. Thus, searching for optimum elemental composition remains a critical issue to maximize the mechan...In medium/high entropy alloys, their mechanical properties are strongly dependent on the chemicalelemental composition. Thus, searching for optimum elemental composition remains a critical issue to maximize the mechanical performance. However, this issue solved by traditional optimization process via "trial and error" or experiences of domain experts is extremely difficult. Here we propose an approach based on high-throughput simulation combined machine learning to obtain medium entropy alloys with high strength and low cost. This method not only obtains a large amount of data quickly and accurately,but also helps us to determine the relationship between the composition and mechanical properties.The results reveal a vital importance of high-throughput simulation combined machine learning to find best mechanical properties in a wide range of elemental compositions for development of alloys with expected performance.展开更多
基金funding from the National Natural Science Foundation of China(Nos.52063017 and 52061025)the Major Science and Technology Project of Gansu Province(Nos.22ZD6GA008 and 20ZD7GJ008)+3 种基金the Natural Science Foundation of Gansu Province(No.23JRRA820)The Science and Technology Project of Major Science and Technology Project of Gansu Province(No.22ZD6GA008)the Science and Technology Project of Gansu Province(No.23YFGA0058)the College Industry Support Plan of Gansu Province(No.2023CYZC-27).
文摘The growing demand for material properties in challenging environments has led to a surge of interest in rapid composition design. Given the great potential composition space, the field of high/medium entropy alloys (H/MEAs) still lacks effective atomic-scale composition design and screening schemes, which hinders the accurate prediction of desired composition and properties. This study proposes a novel approach for rapidly designing the composition of materials with the aim of overcoming the trade-off between strength and ductility in metal matrix composites. The effect of chemical composition on stacking fault energy (SFE), shear modulus, and phase stability was investigated through the use of molecular dynamics (MD) and thermodynamic calculation software. The alloy's low SFE, highest shear modulus, and stable face-centered cubic (FCC) phase have been identified as three standard physical quantities for rapid screening to characterize the deformation mechanism, ultimate tensile strength, phase stability, and ductility of the alloy. The calculation results indicate that the optimal composition space is expected to fall within the ranges of 17 %–34 % Ni, 33 %–50 % Co, and 25 %–33 % Mn. The comparison of stress-strain curves for various predicted components using simulated and experimental results serves to reinforce the efficacy of the method. This indicates that the screening criteria offer a necessary design concept, deviating from traditional strategies and providing crucial guidance for the rapid development and application of MEAs.
基金supported by the National Key R&D Program of China(No.2024YFB4007501)the Natural Science Foundation of Jiangsu Province(No.BK20240109)the project of Jiangsu Key Laboratory for Clean Utilization of Carbon Resources(No.BM2024007).
文摘Low-concentration coal mine methane(LC-CMM),which is predominantly composed of methane,serves as a clean and low-carbon energy resource with significant potential for utilization.Utilizing LC-CMM as fuel for solid oxide fuel cells(SOFCs)represents an efficient and promising strategy for its effective utilization.However,direct application in Ni-based anodes induces carbon deposition,which severely degrades cell performance.Herein,a medium-entropy oxide Sr_(2)FeNi_(0.1)Cr_(0.3)Mn_(0.3)Mo_(0.3)O_(6−δ)(SFNCMM)was developed as an anode internal reforming catalyst.Following reduction treatment,FeNi_(3) nano-alloy particles precipitate on the surface of the material,thereby significantly enhancing its catalytic activity for LC-CMM reforming process.The catalyst achieved a methane conversion rate of 53.3%,demonstrating excellent catalytic performance.Electrochemical evaluations revealed that SFNCMM-Gd_(0.1)Ce_(0.9)O_(2−δ)(GDC)with a weight ratio of 7:3 exhibited superior electrochemical performance when employed as the anodic catalytic layer.With H_(2) and LC-CMM as fuels,the single cell achieved maximum power densities of 1467.32 and 1116.97 mW·cm^(−2) at 800℃,respectively,with corresponding polarization impedances of 0.17 and 1.35Ω·cm^(2).Furthermore,the single cell maintained stable operation for over 100 h under LC-CMM fueling without significant carbon deposition,confirming its robust resistance to carbon formation.These results underscore the potential of medium-entropy oxides as highly effective catalytic layers for mitigating carbon deposition in SOFCs.
基金financially supported by the National Natural Science Foundation of China(Nos.52074078 and 52374327)the Applied Fundamental Research Program of Liaoning Province,China(No.2023JH2/101600002)+3 种基金the Liaoning Provincial Natural Science Foundation,China(No.2022-YQ-09)the Shenyang Young Middle-Aged Scientific and Technological Innovation Talent Support Program,China(No.RC220491)the Liaoning Province Steel Industry-University-Research Innovation Alliance Cooperation Project of Bensteel Group,China(No.KJBLM202202)the Fundamental Research Funds for the Central Universities,China(Nos.N2201023 and N2325009)。
文摘In recent years,medium entropy alloys have become a research hotspot due to their excellent physical and chemical performances.By controlling reasonable elemental composition and processing parameters,the medium entropy alloys can exhibit similar properties to high entropy alloys and have lower costs.In this paper,a FeCoNi medium entropy alloy precursor was prepared via sol-gel and coprecipitation methods,respectively,and FeCoNi medium entropy alloys were prepared by carbothermal and hydrogen reduction.The phases and magnetic properties of FeCoNi medium entropy alloy were investigated.Results showed that FeCoNi medium entropy alloy was produced by carbothermal and hydrogen reduction at 1500℃.Some carbon was detected in the FeCoNi medium entropy alloy prepared by carbothermal reduction.The alloy prepared by hydrogen reduction was uniform and showed a relatively high purity.Moreover,the hydrogen reduction product exhibited better saturation magnetization and lower coercivity.
基金supported by the National Natural Science Foundation of China(Nos.52027801 and 92263203)the National Key R&D Program of China(Nos.2022YFA1203902 and 2022YFA1200093)and the China-Germany Collaboration Project(No.M-0199)。
文摘Sodium superionic conductors(NASICONs)have attracted enormous attention owing to their excellent ionic diffusion and structural stability.However,the high cost of vanadium,limited capacity due to fewer redox reactions,and low electronic conductivity restrict their practical application.Herein,we designed Na_(3.5)V_(0.5)Mn_(0.5)Fe_(0.5)Ti_(0.5)(PO_(4))3 (NVMFTP)medium entropy NASICON with multi-electron reactions as a fast sodium storage cathode for sodium-ion batteries(SIBs).The incorporation of Fe,Mn and Ti not only reduces the cost but also activates multi-redox reactions of V^(2+)/V^(3+),Ti^(3+)/Ti^(4+),Fe^(2+)/Fe^(3+),V^(3+)/V^(4+),Mn^(2+)/Mn^(3+),V^(4+)/V^(5+).Owing to distinctive structural design with medium entropy,the NVMFTP delivered 168 mAh·g^(−1) at 0.5C with a remarkable rate capability of 93.51 mAh·g^(−1) at 60C and steady long-term cycling performance till 5000 cycles.More importantly,NVMFTP takes only 11 min to achieve 80%SOC at 5C.The in-situ and ex-situ X-ray diffraction(XRD)further demonstrate reversible multi-electron reaction mechanisms of slow charging and fast charging.NVMFTP/HC full cell shows 110 mAh·g^(−1) capacity and 208 Wh·kg^(−1) energy density.This study will provide comprehensive insight into developing low-cost,cutting-edge materials for SIBs.
基金supported by the Elements Strategy Initiative for Structural Materials(ESISM,No.JPMXP0112101000)the JSP EIG CONCERT-Japan(No.JPMJSC21C6)+5 种基金the Grant-in-Aid for Scientific Research on Innovative Area“High Entropy Alloys”(Nos.JP18H05455 and JP18H05451)the Grant-in-Aid for Scientific Re-search(A)(Nos.JP20H00306 and JP23H00234)the Grant-in-Aid for Research Activity Start-up(No.JP21K20487)the Grant-in-Aid for Early-Career Scientists(No.JP22K14501)the Grant-in-Aid for JSPS Research Fellow(No.JP18J20766)supported by China Scholarship Council(CSC),China.
文摘The present work reports characteristics of dislocation slip behavior in an equi-atomic HfNbTiZr refractory medium entropy alloy(RMEA)and its systematic comparison with pure niobium(Nb).Fully-recrystallized specimens were fabricated by cold rolling and subsequent annealing,and uniaxial tensile deformation was applied at room temperature.Slip trace morphologies on the surfaces of the tensile-deformed ma-terials were quantitatively characterized,and the so-calledψand x relationships of the observed slip traces were evaluated by a newly developed method for polycrystalline specimens.Wavy slip traces were observed in most grains in the pure Nb.They consisted of low-indexed slip planes,such as{110},and{112},and high-indexed(or undetermined)slip planes.Some straight slip traces persisting on the low-indexed slip planes were also found in the pure Nb.In contrast,straight slip traces were dominant in the RMEA.The straight slip traces in the RMEA were not parallel to particular slip planes but mostly distributed along the maximum shear stress plane(MSSP),indicating that frequent cross slip in very short intervals occurred.Large deviations of slip planes from the MSSP in a few grains of the RMEA were attributed to the slip transfer from neighboring grains as a characteristic of polycrystalline materi-als.Frequent cross slip in short intervals,attributed to homogeneous slip resistance distribution for screw dislocations in the RMEA originating from the chemical heterogeneity on an atomic scale,was proposed as a novel mechanism responsible for the unique slip behavior and macroscopic deformation behavior.
基金supported by the Natural Science Foundation of Liaoning Province(No.2022-BS-181).
文摘The phase constitution,microstructure,damping capacity,and mechanical properties of as-cast AlxCrFe3Ni(x=0.5,0.52,0.54,and 0.56,respectively)medium entropy alloys were investigated.It is found that the volume fraction of BCC phase increases while that of FCC decreases with increasing the Al content.When the content of Al is 0.54,the alloy is composed of 82.1vol.%BCC matrix and 17.9vol.%FCC phase.Wherein the FCC phase is distributed on the BCC matrix,forming a structure where the hard BCC matrix is surrounded by soft FCC phase.This results in a hindering effect on the propagation process of vibration waves.The damping performance of Al0.54CrFe_(3)Ni alloy,characterized by an internal friction of Q^(-1) is as high as 0.059,is higher than that of most FeCr damping alloys.The volume fraction of the BCC phase and the peculiar distribution of the FCC phase are identified as the key factors affecting the damping capacity.In addition,the Al0.54CrFe3Ni alloy exhibits a high yield strength of 811.16 MPa.
基金the National Natural Science Foundation of China(Nos.U1908219,52171163)the Key Research Program of the Chinese Academy of Sciences(No.ZDRW-CN-2021-2-2)+2 种基金the National key Research&Development Program of China(No.2022YFF0609002)the Natural Science Foundation of Liaoning Province(No.2022-BS-001)China Postdoctoral Science Foundation(No.2022M713210)。
文摘The concept of grain boundary engineering(GBE)has been successfully applied to L1_(2)-strengthened(CoCrNi)_(94)Al_(3)Ti_(3)medium entropy alloy,with the aim of improving the oxidation resistance by increasing the ratio of special boundaries and suppressing discontinuous precipitation.Surprisingly,our results reveal that GBE treatment not only slows down the oxidation kinetics and but also alters the oxide scale from TiO_(2)and multi-defect Cr_(2)O_(3)to continuous and protective Cr_(2)O_(3)and Al_(2)O_(3),thereby contributing to an enhanced oxidation and anti-spalling resistance.The GBE treatment reduces the oxidation weight gain of the current alloy from 1.950 mg cm^(-2)to 1.211 mg cm^(-2)after 100 h of cyclic oxidation at 800℃.The findings show that the extensive outward diffusion of Ti accelerates ion transport and promotes microporosity,thus leading to more defects being formed in the oxide film.The GBE treatment suppresses the discontinuous precipitation of the Ti-bearing L1_(2)phase and breaks the random large angular grain boundaries network,inhibiting the diffusion of Ti and ultimately enhancing the oxidation properties of the alloy.The current work provides an idea of oxidation resistance enhancement for Ti-bearing LI_(2)-strengthened alloys without changing the alloy composition.
基金supported by the National Natural Science Foundation of China(Nos.52071176,12072331,51771090,51671103)the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions,China.
文摘The effect of Ti content on the microstructure and mechanical properties of as-cast light-weight Ti_(x)(AlVCr)_(100−x)medium entropy alloys was studied by compressive tests,X-ray diffraction,scanning electron microscopy and transmission electron microscopy.The results suggest that yield strength increases and then decreases with the increment of Ti content.The Ti_(60)(AlVCr)_(40)alloy has the best combination of high strength of 1204 MPa and uniform plastic strain of 70%,possessing a high specific yield strength of 255 MPa·cm^(3)/g.The enhancement of strength is mainly attributed to the synergic effects of solid-solution and coherent nano-precipitation strengthening,while dislocation motion such as dislocation pinning,entanglement and dislocation cells significantly increases the strain-hardening capacity.
基金supported by the National Natural Science Foundation of China(No.52020105013).
文摘Modern engineering has long been in demand for high-performance additive manufactured materials for harsh working conditions.The idea of high entropy alloy(HEA),medium entropy alloy(MEA),and multi-principal-element alloy(MPEA)provides a new way for alloy design.In this work,we develop a Co42 Cr20 Ni30 Ti4 Al4 quinary MEA which exhibits a superiority of mechanical properties over a wide tem-perature ranging from 77 to 873 K via selective laser melting(SLM)and post-heat treatment.The present MEA achieves an excellent ultimate tensile strength(UTS)of 1586 MPa with a total elongation(TE)of 22.7%at 298 K,a UTS of 1944 MPa with a TE of 22.6%at 77 K,and a UTS of 1147 MPa with a TE of 9.1%at 873 K.The excellent mechanical properties stem from the microstructures composed of partially refined grains and heterogeneously precipitated L12 phase due to the concurrence of recrystallization and precipitation.The grain boundary hardening,precipitation hardening,and dislocation hardening con-tribute to the high YS at 298 and 77 K.Interactions of nano-spaced stacking faults(SFs)including SFs networks,Lomer-Cottrell locks(L-C locks),and anti-phase boundaries(APBs)induced by the shearing of L12 phase are responsible for the high strain hardening rate and plasticity at 77 K.Our work provides a new insight for the incorporation of precipitation hardening and additive manufacturing technology,paving the avenue for the development of high-performance structural materials.
基金supported by the National Natural Science Foundation of China(Nos.52022054,51974181,52004155,52004157,52374307,52304331,52334009)the National Key Research and Development Program of China(No.2022YFC2906100)+4 种基金the China Postdoctoral Science Foundation(No.2022M712023)the Science and Technology Commission of Shanghai Municipality(No.21DZ1208900)the Innovation Program of Shanghai Municipal Education Commission(No.2023ZKZD48)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning(No.TP2019041)the“Shuguang Program”supported by the Shanghai Education Development Foundation and the Shanghai Municipal Education Commission(No.21SG42).
文摘High/medium entropy alloys(HEAs/MEAs)with high electrocatalytic activity have attracted great attention in water electrolysis applications.However,facile synthesis of self-supporting high/medium entropy alloys electrocatalysts with rich active sites through classical metallurgical methods is still a challenge.Here,a self-supporting porous FeCoNi MEA electrocatalyst with nanosheets-shaped surface for oxygen evolution reaction(OER)was prepared by a one-step electrochemical process from the metal oxides in molten CaCl_(2).The formation of the FeCoNi MEA is attributed to the oxides electro-reduction,high-temperature diffusion and solid solution.Additionally,the morphology and structure of the FeCoNi MEA can be precisely controlled by adjusting the electrolysis time and temperature.The electronic structure regulation and the reduced energy barrier of OER from the“cocktail effect”,the abundant exposed active sites brought by surface ultrathin nanosheets,the good electronic conductivity and electrochemical stability from the self-supporting structure enable the FeCoNi MEA electrode shows high-performance OER electrocatalysis,exhibiting a low overpotential of 233 mV at a current density of 10 mA cm^(-2),a low Tafel slope of 29.8 mV dec^(-1),and an excellent stability for over 500 h without any obvious structural destruction.This work demonstrates a facile one-step electrochemical metallurgical approach for fabricating self-supporting HEAs/MEAs electrocatalysts with nanosized surface for the application in water electrolysis.
基金supported by the National Natural Science Foundation of China(Nos.52101053 and 52274399)the Henan Provincial Science and Technology Research Project(No.232102231025).
文摘A new metastable dual-phase Fe59 Cr13 Ni18 Al10 medium entropy alloy(MEA)with hierarchically heteroge-neous microstructure from micro-to nano-scale was designed in this work.Partially recrystallized FCC phase and lots of NiAl-rich B2 precipitates are obtained by annealing and aging treatment.The yield strength of the MEA at room temperature(298 K)and liquid nitrogen temperature(77 K)increased from∼910 MPa and∼1250 MPa in the annealed state,respectively,to∼1145 MPa and∼1520 MPa in the aged state,while the uniform elongation maintained more than 15%.The excellent mechanical properties of the MEA both at 298 and 77 K are attributed to the co-activation of multiple strengthening mech-anisms,including fine grain,dislocation,precipitation,transformation-induced plasticity,stacking faults,and nano-twins.
基金the financial support from the National Natural Science Foundation of China (51872067 and 21773048)
文摘It is widely recognized that the development of ZABs is impeded by the kinetic bottleneck of oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).The application of conformational entropy strategy to oxides often involves introducing multiple elements with different properties,thereby providing outstanding bifunctional catalytic activity for OER/ORR.Nevertheless,the possible underlying catalytic pathways and potential interactions between various components are still poorly understood.This paper presents an excellent medium-entropy perovskite oxide,Sr(FeCoNiMo)_(1/4)O_(3−δ)(lower overpotential of 301 mV at 10 mA cm^(−2)).Zinc-air batteries employing it as a cathode catalyst demonstrate excellent round-trip efficiency(62%).By combining theoretical calculation with experiments,we aim to establish the link between the electronic structure of perovskite oxides with different elemental compositions and their OER mechanism.Research reveals that the conformational entropy strategy can simultaneously shift the O 2p-band center and metal d-band center of perovskite oxide towards the vicinity of the Fermi energy level,thereby triggering a more favorable lattice oxygen-participated mechanism(LOM)during the OER process.The outcomes of this work provide crucial insights into the role of conformational entropy strategies in oxygen catalysis and offer potential avenues for constructing efficient and stable electrocatalysts.
基金supported by the National Natural Science Foundation of China(Grant Nos.12372069,12302083,and 12172123)China Postdoctoral Science Foundation(Grant Nos.2023M731061 and BX20230109)+2 种基金the Natural Science Foundation of Hunan Province(Grant No.2022JJ20001)Hunan Provincial Innovation Foundation for Postgraduate(Grant No.CX20220378)Peter K.Liaw very much appreciates the support from the National Science Foundation(Grant Nos.DMR-1611180,1809640,and 2226508).
文摘High/medium entropy alloys(H/MEAs)are generally possible to exhibit chemical short-range order(SRO).However,the complex role of SRO on mechanical properties from nano-scale to meso-scale is still challenging so far.Here,we study the strengthening mechanism and deformation behavior in a model body-centered-cubic HfNbTa MEA by using atomic-scale molecular dynamics,micro-scale dislocation dynamics,and meso-scale crystal plasticity finite element.The SRO inhibits dislocation nucleation at the atomic scale,improving the flow stress.The SRO-induced ultrastrong local stress fluctuation greatly improves the micro-scale dislocation-based strength by the significant dislocation forest strengthening.Moreover,the Ta-rich locally ordered structure leads to an obvious heterogeneous strain and stress partitioning,which forms a strong strain gradient in the adjacent grain interiors and contributes to the strong back-stress-induced strain hardening.
文摘A Co-free as-cast AlCrAlCrFe_(2)Ni_(2)medium entropy alloy(MEA)with multi-phases was remelted by fiber laser in this study.The effect of laser remelting on the microstructure,phase distribution and mechanical properties was investigated by characterizing the as-cast and the remelted AlCrAlCrFe_(2)Ni_(2)alloy.The laser remelting process resulted in a significant decrease of grain size from about 780μm to 58.89μm(longitudinal section)and 15.87μm(transverse section)and an increase of hardness from 4.72±0.293 GPa to 6.40±0.147 GPa(longitudinal section)and 7.55±0.360 GPa(transverse section).It was also found that the long side plate-like microstructure composed of FCC phase,ordered B2 phase and disordered BCC phase in the as-cast alloy was transformed into nano-size weave-like microstructure consisting of alternating ordered B2 and disordered BCC phases.The mechanical properties were evaluated by the derived stressstrain relationship obtained from nano-indentation tests data.The results showed that the yield stress increased from 661.9 MPa to 1347.6 MPa(longitudinal section)and 1647.2 MPa(transverse section)after remelting.The individual contribution of four potential strengthening mechanisms to the yield strength of the remelted alloy was quantitatively evaluated,including grain boundary strengthening,dislocation strengthening,solid solution strengthening and precipitation strengthening.The calculation results indicated that dislocation and precipitation are dominant strengthening mechanisms in the laser remelted MEA.
基金supported by National Natural Science Foundation of China[grant numbers 51671168,51871197]National Key Research and Development Program of China[grant number 2017YFA0208200]+1 种基金111 project[grant number B16042]the State Key Program for Basic Research in China[grant no.2015CB6593001]。
文摘Solid solution strengthening is one of the most conventional strategies for optimizing alloys strength,while the corresponding mechanisms can be more complicated than we traditionally thought specifically as heterogeneity of microstructure is involved.In this work,by comparing the change of chemical distribution,dislocation behaviors and mechanical properties after doping equivalent amount of tungsten(W)atoms in CrCoNi alloy and pure Ni,respectively,it is found that the alloying element W in CrCoNi alloy resulted in much stronger strengthening effect due to the significant increase of heterogeneity in chemical distribution after doping trace amount of W.The large atomic scale concentration fluctuation of all elements in CrCoNi-3W causes dislocation motion via strong nanoscale segment detrapping and severe dislocation pile up which is not the case in Ni-3W.The results revealed the high sensitivity of elements distribution in multi-principle element alloys to composition and the significant consequent influence in tuning the mechanical properties,giving insight for complex alloy design.
基金supported financially by the National Natural Science Foundation of China(Nos.51701061 and 51601020)the Natural Science Foundation of Hebei Province(No.E2019202059)。
文摘The effect of Mo additions on the microstructures and mechanical properties of CoCrNi alloys was investigated,meanwhile,ab initio calculations are performed to quantitatively evaluate the lattice distortion and stacking fault energy(SFE).The yield strength,ultimate tensile strength,and elongation of(CoCrNi)_(97)Mo_(3)alloy are 475 MPa,983 MPa and 69%,respectively.The yield strength is increased by~30%and high ductility is maintained,in comparison with CoCrNi alloy.Besides the nano-twins and dislocations,the higher density of stacking faults is induced during the tensile deformation for(CoCrNi)_(97)Mo_(3)alloy.Ab initio calculation results indicate the mean square atomic displacement(MSAD)and SFE value of(CoCrNi)_(97)Mo_(3)alloy is 42.6 pm^(2)and-40.4 mJ/m^(2)at 0 K,respectively.The relationship between mechanical properties and MSAD,SFE for various multiple principal element alloys is discussed.
基金sponsored by the National Key R&D Program of China (No.2018YFC1902401)the National Natural Science Foundation of China(No.52005053)Open Fund of Key Laboratory of New Processing Technology for Nonferrous Metal & Materials Ministry of Education,China (No.20KF-24)。
文摘In order to improve the strength and corrosion resistance of CoCrNi medium entropy alloy,TiC strengthened CoCrNi medium entropy alloy(CoCrNi/(TiC)_(x)(x=0.1,0.2,0.4))was designed by addition of different amounts of TiC.The effects of TiC content on the microstructure,mechanical properties,and corrosion resistance of the alloy were investigated.It was found that the precipitation morphologies of TiC changed from lamellar eutectic to needle structure with the increase of TiC content,and finally formed mixed needled and bulk TiC particles.TiC appears as a dissolution−precipitation phenomenon in the CoCrNi alloy,which is important for the mechanical properties and corrosion resistance of the CoCrNi/(TiC)_(x) alloy.The strength of alloy was enhanced obviously after the addition of TiC.The compressive yield strength of CoCrNi/(TiC)_(0.4) alloy reached 746 MPa,much larger than that of the CoCrNi medium entropy alloy,108 MPa.Additionally,the addition of TiC was found to improve the corrosion resistance of CoCrNi medium entropy alloy in the salt solution.
基金Project(51671217)supported by the National Natural Science Foundation of ChinaProject(2016YFB0700302)supported by the National Key Research and Development Plan of China。
文摘For developing new binder phase with high performance, Co-Ni-Fe alloy was used as binder in cemented carbides. The mechanical properties of WC-CoNiFe and WC-Co cemented carbides with different grain sizes were studied. The results show that the reprecipitation of WC-CoNiFe is inhibited compared with that of WC-Co during sintering process, and the grains in WC-CoNiFe cemented carbides are more of smooth shape, resulting in a slightly lower hardness and higher transverse rupture strength. With the increase of the grain size, the hardness of the two cemented carbides decreases, and the transverse rupture strength increases. However, the slope values of K in Hall-Petch relationship are higher in WC-CoNiFe than those in WC-Co, indicating the high toughness of medium entropy alloy Co-Ni-Fe.
基金supported by the National Natural Science Foundation of China[Grant numbers 52020105013,51771232]。
文摘Deformation behavior of a FeCrNi medium entropy alloy(MEA)prepared by powder metallurgy(P/M)method was investigated over a wide range of strain rates.The FeCrNi MEA exhibits high strain-hardening ability,which can be attributed to the multiple deformation mechanisms,including dislocation slip,deformation induced stacking fault and mechanical twinning.The shear localization behavior of the FeCrNi MEA was also analyzed by dynamically loading hat-shaped specimens,and the distinct adiabatic shear band cannot be observed until the shear strain reaches~14.5.The microstructures within and outside the shear band exhibit different characteristics:the grains near the shear band are severely elongated and significantly refined by dislocation slip and twinning;inside the shear band,the initial coarse grains completely disappear,and transform into recrystallized ultrafine equiaxed grains by the classical rotational dynamic recrystallization mechanism.Moreover,microvoids preferentially nucleate in the central areas of the shear band where the temperature is very high and the shear stress is highly concentrated.These microvoids will coalesce into microcracks with the increase of strain,which eventually leads to the fracture of the shear band.
基金supported financially by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (No. 51621004)the National Natural Science Foundation of China (Nos. 51871092, 11772122, 51625404, 51771232+5 种基金51671217)the State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body (No. 71865015)the State Key Laboratory of Powder Metallurgythe National Key Research and Development Program of China (Nos. 2016YFB0700300 and 2016YFB1100103)support of the U.S. Army Research Office Project (Nos. W911NF-13-1-0438 and W911NF-19-2-0049) with the program managers,Drs. M.P. Bakas,S.N. Mathaudhusupport from the National Science Foundation (Nos. DMR-1611180 and 1809640)with the program directors,Drs. J. Yang,J.G. Shiflet,and D. Farkas。
文摘In medium/high entropy alloys, their mechanical properties are strongly dependent on the chemicalelemental composition. Thus, searching for optimum elemental composition remains a critical issue to maximize the mechanical performance. However, this issue solved by traditional optimization process via "trial and error" or experiences of domain experts is extremely difficult. Here we propose an approach based on high-throughput simulation combined machine learning to obtain medium entropy alloys with high strength and low cost. This method not only obtains a large amount of data quickly and accurately,but also helps us to determine the relationship between the composition and mechanical properties.The results reveal a vital importance of high-throughput simulation combined machine learning to find best mechanical properties in a wide range of elemental compositions for development of alloys with expected performance.
