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
1.Introduction Additive manufacturing or 3D printing outweighs conventional casting methods in the aspect of complex parts fabrication,which can realize one-step formation without the need of complicated cast dies.3D ...1.Introduction Additive manufacturing or 3D printing outweighs conventional casting methods in the aspect of complex parts fabrication,which can realize one-step formation without the need of complicated cast dies.3D printing significantly promotes industrial production for making near-net shaped components.However,this promising technique is not always ideally applicable for metals and alloys.For example,titanium alloys prepared by 3D printing often suf-fer from poor plasticity,and usually require further complex heat treatment or hot isostatic pressing treatment,in order to remove internal stress and regulate plasticity and strength[1,2],which de-feats the original intention of employing additive manufacturing.One of the fundamental causes for such issues is the low fluidity of the alloys upon melting,leading to great chemical heterogeneity,high porosity content and residual stresses.This limitation hinders further design and fabrication of high-performance printable alloys from large scale production and application.展开更多
Recently, high-entropy alloys(HEAs) or multi-principal-element alloys with unprecedented physical,chemical, and mechanical properties, have been considered as candidate materials used in advanced reactors due to their...Recently, high-entropy alloys(HEAs) or multi-principal-element alloys with unprecedented physical,chemical, and mechanical properties, have been considered as candidate materials used in advanced reactors due to their promising irradiation resistant behavior. Here, we report a new single-phase bodycentered cubic(BCC) structured Ti_2 ZrHfV_(0.5)Mo_(0.2) HEA possessing excellent irradiation resistance, i.e.,scarcely irradiation hardening and abnormal lattice constant reduction after helium-ion irradiation,which is completely different from conventional alloys. This is the first time to report the abnormal XRD phenomenon of metallic alloys and almost no hardening after irradiation. These excellent properties make it to be a potential candidate material used as core components in next-generation nuclear reactors. The particular irradiation tolerance derives from high density lattice vacancies/defects.展开更多
The design of novel high-entropy alloys(HEAs)provides a unique opportunity for the development of structure-function integrated materials with high mechanical and antimicrobial properties.In this study,by employing th...The design of novel high-entropy alloys(HEAs)provides a unique opportunity for the development of structure-function integrated materials with high mechanical and antimicrobial properties.In this study,by employing the antibacterial effect of copper,a novel Al0.4CoCrCuFeNi HEA with broad-spectrum antibacterial and strong mechanical properties was designed.High concentrations of copper ions released from the HEA prevented growth and biofilm formation by biocorrosive marine bacterial species.These findings serve as a proof-of-concept for further development of unique HEA materials with high antimicrobial efficiency and mechanical properties,compared to conventional antibacterial alloys.展开更多
The microstructure and mechanical properties of as-cast and isothermally annealed C_(x)Hf_(0.25)NbTaW_(0.5)(x=0,0.05,0.15,0.25)refractory high-entropy alloys(RHEAs)were studied.Both the as-cast and annealed RHEAs cons...The microstructure and mechanical properties of as-cast and isothermally annealed C_(x)Hf_(0.25)NbTaW_(0.5)(x=0,0.05,0.15,0.25)refractory high-entropy alloys(RHEAs)were studied.Both the as-cast and annealed RHEAs consisted of disordered body-centered cubic solid solution phase and metal carbide(MC)phase with a face-centered cubic crystal structure(Fm-3 m space group).The primary carbides were enriched with Hf and C elements and tended to form lamellar eutectic-like microstructure in the interdendrites.The lamellar eutectic-like structure in the interdendrites would be formed from the decomposition of sub-carbide M_(2)C under the influence of Hf element.After isothermal annealing,slatted carbides were precipitated on the matrix,and the distribution became more uniform with high C content.The formation of carbides strongly influenced the mechanical properties both at room and high temperatures.The yield strength values of C_(x)Hf_(0.25)NbTaW_(0.5) RHEA at 1473 and 1673 K were 792 and 749 MPa,respectively.The result had exceeded the high temperature mechanical properties of currently known RHEAs.Moreover,this RHEA exhibited high-temperature performance stability and excellent plasticity,exceeding 30 and 50%at room and elevated temperatures(above 1273 K),respectively.During thermal deformation,carbon-containing RHEAs obtained more severe work hardening than that of ACHO RHEAs,and required greater dynamic recrystallization to achieve the dynamic equilibrium.展开更多
Contact infection of bacteria and viruses has been a critical threat to human health. The worldwideoutbreak of COVID-19 put forward urgent requirements for the research and development of the selfantibacterial materia...Contact infection of bacteria and viruses has been a critical threat to human health. The worldwideoutbreak of COVID-19 put forward urgent requirements for the research and development of the selfantibacterial materials, especially the antibacterial alloys. Based on the concept of high-entropy alloys, thepresent work designed and prepared a novel Co_(0.4)FeCr_(0.9)Cu_(0.3) antibacterial high-entropy alloy with superior antibacterial properties without intricate or rigorous annealing processes, which outperform the antibacterial stainless steels. The antibacterial tests presented a 99.97% antibacterial rate against Escherichiacoli and a 99.96% antibacterial rate against Staphylococcus aureus after 24 h. In contrast, the classic antibacterial copper-bearing stainless steel only performed the 71.50% and 80.84% antibacterial rate, respectively. The results of the reactive oxygen species analysis indicated that the copper ion release and theimmediate contact with copper-rich phase had a synergistic effect in enhancing antibacterial properties.Moreover, this alloy exhibited excellent corrosion resistance when compared with the classic antibacterialstainless steels, and the compression test indicated the yield strength of the alloy was 1015 MPa. Thesefindings generate fresh insights into guiding the designs of structure-function-integrated antibacterial alloys.展开更多
An eutectic high-entropy alloy consisting Al, Co, Cr, Fe and Ni elements was prepared by vacuum directional solidification technology. The alloy exhibits excellent comprehensive mechanical performance during tension a...An eutectic high-entropy alloy consisting Al, Co, Cr, Fe and Ni elements was prepared by vacuum directional solidification technology. The alloy exhibits excellent comprehensive mechanical performance during tension at temperature range of 600–700℃. The microstructure reveals the intersection of twintwin is the prevailing deformation mechanism and the twins play a dual role in strengthening and toughening the alloy in the thermomechanical process. The deformation twin variants I and were formed by the edge dislocation 112 and the mixed dislocation 211 on the {111} crystal planes, respectively. Besides, the dislocation jogs and kinks caused by twin intersection on the slip planes can strengthen the alloy, which may contribute to the high strength(the tensile strengths at the 600°and 700°tensile tests are respectively780 MPa and 630 MPa.). Moreover, the coherent twin boundary migration has the function of coordinating deformation and contributes to the high ductility of the alloy.展开更多
Recently,the eutectic high-entropy alloy(EHEA),AlCoCrFeNi_(2.1),can reach a good balance of strength and ductility.The dual-phase alloy exhibits a eutectic lamellar microstructure with large numbers of interfaces.Howe...Recently,the eutectic high-entropy alloy(EHEA),AlCoCrFeNi_(2.1),can reach a good balance of strength and ductility.The dual-phase alloy exhibits a eutectic lamellar microstructure with large numbers of interfaces.However,the role of the interfaces in plastic deformation have not been revealed deeply.In the present work,the orientation relationship(OR)of the interfaces has been clarified as the Kurdjumov-Sachs(KS)interfaces presenting〈111〉_(B2) 〈110〉_(FCC)and {110} _(B2){111}_(FCC) independent of their morphologies.There exist three kinds of interfaces in the EHEA,namely,The dominating interface and the secondary interface are both non-slip planes and atomistic-scale faceted,facilitating the nucleation and slip transmission of the dislocations.The formation mechanism of the preferred interfaces is revealed using the atomistic geometrical analysis according to the criteria of the low interfacial energy based on the coincidence-site lattice(CSL)theory.In particular,the ductility of the dual-phase alloy originates from the KS interface-induced slip continuity across interfaces,which provides a high slip-transfer geometric factor.Moreover,the strengthening effect can be attributed to the interface resistance for the dislocation transmission due to the mismatches of the moduli and lattice parameters at the interfaces.展开更多
In this study,a new Al0.9CoFeNi2 eutectic high entropy alloy(EHEA) was designed,and the microstructures as well as the deformation behavior were investigated.The bulk cast Al0.9CoFeNi2 EHEA exhibited an order face-cen...In this study,a new Al0.9CoFeNi2 eutectic high entropy alloy(EHEA) was designed,and the microstructures as well as the deformation behavior were investigated.The bulk cast Al0.9CoFeNi2 EHEA exhibited an order face-centered cubic FCC(L12) and an order body-centered cubic(B2) dual-phase lamellar eutectic microstructure.The volume fractions of FCC(L12) and B2 phases are measured to be 60 % and 40 %,respectively.The combination of the soft and ductile FCC(L12) phase together with the hard B2 phase resulted in superior strength of 1005 MPa and ductility as high as 6.2 % in tension at room temperature.The Al0.9CoFeNi2 EHEA exhibited obvious three-stage work hardening characteristics and high workhardening ability.The evolving dislocation substructure s during uniaxial tensile deformation found that planar slip dominates in both FCC(L12) and B2 phases,and the FCC(L12) phase is easier to deform than the B2 phase.The post-deformation transmission electron microscopy revealed that the sub-structural evolution of the FCC(L12) phase is from planar dislocations to bending dislocations,high-density dislocations,dislocation network,and then to dislocation walls,and Taylor lattices,while the sub-structural evolution of the B2 phase is from a very small number of short dislocations to a number of planar dislocations.Moreover,obvious ductile fracture in the FCC(L12) phase and a brittle-like fracture in the B2 phase were observed on the fracture surface of the Al0.9CoFeNi2 EHEA.The re search results provide some insight into the microstructure-property relationship.展开更多
High entropy alloy has attracted increasing attentions.However,to enhance the alloy strength often leads to impairment of the ductility,or vice versa.Here we reported a heat treatment approach on AlCrFeNi2Ti0.5 high e...High entropy alloy has attracted increasing attentions.However,to enhance the alloy strength often leads to impairment of the ductility,or vice versa.Here we reported a heat treatment approach on AlCrFeNi2Ti0.5 high entropy alloy,which can elevate the strength and ductility simultaneously.An ingot of AlCrFeNi2Ti0.5 weighing 2.5 kg was firstly fabricated by medium frequency induction melting.Then samples from the same height of the bulk ingot were annealed for 6 h at 600,700,800 and 1000 ℃,respectively.After 1000 ℃ annealing,an optimal microstructure was obtained by using our approach which can make some precipitation particles distribute homogeneously in the dendrite interior while keep the interdendrite structure as a single solid solution phase.The mechanical test on this AlCrFeNi2Ti0.5 alloy sample showed that,the compressive fracture strength σbc was increased by about600 MPa and the plastic strain ep was doubled,compared with those of the as-cast sample.Our approach can be readily adapted to large-scale industrial production of high entropy alloys with high strength and ductility by proper annealing treatment.展开更多
Low-melting-point alloys have an extensive applications in the fields of materials processing, phase change energy storage, electronic and electrical automatic control, continuous casting simulation, welding, etc. Spe...Low-melting-point alloys have an extensive applications in the fields of materials processing, phase change energy storage, electronic and electrical automatic control, continuous casting simulation, welding, etc. Specifically, the eutectic compositions make up a large number of low-melting-point alloys that are ex- ploited because of their desirable features like single melting peaks, excellent operational reliability, and casting fluidity. However, the fundamental physicochemical properties from the current available liter- ature on low-melting-point multi-component eutectic alloys （LMP-MCEAs） are rather rare and lowly accurate, including the exact melting temperatures and compositions, constituent phases, microstruc- tures and morphologies, melting enthalpies, specific heats, densities, and so on. This lack of information seriously limits the development and application of low-melting-point multi-component eutectic alloys. In this paper, the low-melting-point multi-component eutectic alloys composed of Bi, Cd, Sn, Pb, and In elements synthesized by high vacuum induction melting and fundamental data were investigated by scan- ning electron microscopy （SEM）, energy dispersive spectrometry （EDS）, X-ray diffraction （XRD）, differential scanning calorimetry （DSC）, and density analysis instrument. Most of the LMP-MCEAs with complex eu- tectic morphology structures and XRD diffraction patterns could be explained with the fact that they were three-phase eutectic alloys with mixed growth way. Generally, LMP-MCEAs present an extremely low melting point between 48.3 and 124 ℃ and high density between 8 and 10 g/cm3.展开更多
In the present study,a face-centered cubic non-equiatomic Cr_(26)Mn_(20)Fe_(20)Co20Ni_(14) high-entropy alloy(HEA)with a low stacking fault energy of 17.6 mJ m^(−2) was prepared by vacuum induction melting,forging and...In the present study,a face-centered cubic non-equiatomic Cr_(26)Mn_(20)Fe_(20)Co20Ni_(14) high-entropy alloy(HEA)with a low stacking fault energy of 17.6 mJ m^(−2) was prepared by vacuum induction melting,forging and annealing processes.The recrystallized sample is revealed to exhibit an excellent combination of strength and ductility over a wide temperature range of 4.2–293 K.With decreasing temperature from 293 to 77 K,the ductility and ultimate tensile strength(UTS)gradually increase by 30% to 95% and 137% to 1020 MPa,respectively.At the lowest temperature of 4.2 K,the ductility keeps 65% and the UTS increases by 200% to 1300 MPa,which exceed those published in the literature,including conventional 300 series stainless steels.Detailed microstructural analyses of this alloy reveal a change of deformation mechanisms from dislocation slip and nano-twinning at 293 K to nano-phase transformation at 4.2 K.The cooperation and competition of multiple nano-twinning and nano-phase transformation are responsible for the superior tensile properties at cryogenic temperatures.Our study provides experimental evidence for potential cryogenic applications of HEAs.展开更多
A series of CoCrFeNb_xNi（x values in molar ratio, x = 0, 0.25, 0.45, 0.5, 0.75, 1.0 and 1.2） high entropy alloys（HEAs） was prepared to investigate the alloying effect of Nb on the microstructures and mechanical pr...A series of CoCrFeNb_xNi（x values in molar ratio, x = 0, 0.25, 0.45, 0.5, 0.75, 1.0 and 1.2） high entropy alloys（HEAs） was prepared to investigate the alloying effect of Nb on the microstructures and mechanical properties. The results indicate that the prepared CoCrFeNb_xNi（x 〉 0） HEAs consist of a simple FCC solid solution phase and a Laves phase. The microstructures of the alloys change from an initial single-phase FCC solid solution structure（x = 0） to a hypoeutectic microstructure（x = 0.25）, then to a full eutectic microstructure（x = 0.45） and finally to a hypereutectic microstructure（0.5 〈 x 〈 1.2）. The compressive test results show that the Nb0.45（x = 0.45） alloy with a full eutectic microstructure possesses the highest compressive fracture strength of 2558 MPa and a fracture strain of 27.9%. The CoCrFeNi alloy exhibits an excellent compressive ductility, which can reach 50% height reduction without fracture. The Nb0.25 alloy with a hypoeutectic structure exhibits a larger plastic strain of 34.8%. With the increase of Nb content, increased hard/brittle Laves phase leads to a decrease of the plasticity and increases of the Vickers hardness and the wear resistance. The wear mass loss, width and depth of wear scar of the Nb1.2（x = 1.2） alloy with a hypereutectic structure are the lowest among all alloy systems, indicating that the wear resistance of the Nb1.2 alloy is the best one.展开更多
The eutectic CoFeNi2V0.5Nb0.75 high entropy alloys （HEAs） were heated at 500, 600, 700, 800 and 1000 ℃, respectively for 6 h and subsequently quenched in the water to investigate their thermal stability and phase t...The eutectic CoFeNi2V0.5Nb0.75 high entropy alloys （HEAs） were heated at 500, 600, 700, 800 and 1000 ℃, respectively for 6 h and subsequently quenched in the water to investigate their thermal stability and phase transformation at high temperature. The microstructure and mechanical properties of the samples were investigated by scanning electron microscopy, X-ray diffraction, compressive and hardness tests. It was found that the as-cast CoFeNi2V0.5Nb0.75 HEAs showed a eutectic microstructure with alternating fcc solid solution phase and Fe2Nb-type Laves phase. The NbNi4-type intermetallic phase appeared when the heat-treated temperature was higher than 600 ℃. With increasing quenching temperature, the volume fraction of the NbNi4-type intermetallic phase increased while that of the eutectic regions decreased. The sample quenched at 800 ℃ showed the most excellent comprehensive mechanical properties; its fracture strength, yield strength and plastic strain were as high as 2586.76 MPa, 2075.18 MPa and 16.73%, respectively. Moreover, the eutectic CoFeNi2V0.5Nb0.75 HEAs exhibited apparent age hardening, especially quenched at 700 ℃, the hardness reached up to the maximum value of HV 727.52.展开更多
Semisolid-rolling method was successfully developed to prepare the Ni-coated woven carbon fibers reinforced Al-matrix composite. Due to the appropriate matrix flowability and rolling pressure, the Al-matrix could infi...Semisolid-rolling method was successfully developed to prepare the Ni-coated woven carbon fibers reinforced Al-matrix composite. Due to the appropriate matrix flowability and rolling pressure, the Al-matrix could infiltrate into the woven fibers sufficiently and attach to the reinforcements closely forming a smooth interface. The rolling speed of 4 rad/min offered a subtle equilibrium between the heat transfer and the material deformation. The covering matrix should be controlled at semisolid state to provide a better infiltration behavior and a protective effect on the carbon fibers. With the addition of fibers, an improvement for more than 25% was obtained in the bending strength of the materials. Furthermore, the woven carbon fibers could strengthen the composite in multiple directions, rather than only along the fiber longitudinal directions. The annealing process promoted the Ni coating to react with and to diffuse into the matrix, resulted in an obvious increase of the bending strength.展开更多
Magnesium alloys are the lightest metal structural materials owing to their excellent physical and chemical properties.Microstructural evolution in magnesium alloys under the conditions of casting,thermalmechanical pr...Magnesium alloys are the lightest metal structural materials owing to their excellent physical and chemical properties.Microstructural evolution in magnesium alloys under the conditions of casting,thermalmechanical processing,and in-service environment,play an important role in governing their mechanical properties and reliability/sustainability.A synchrotron light source produces high flux,tunable X-ray energy,high resolution,and high coherence X-ray beams,which can realize in-situ dynamic observation of microstructural evolution in a wide range of alloys during the entire processing chain and in simulated service environments.This article reviews the fundamentals of synchrotron radiation characterization techniques(imaging,diffraction,scattering,and fluorescence holography)and state-of-the-art advanced synchrotron characterization techniques on the microstructure evolution mechanism of magnesium alloys.Case studies span a broad range of solidification,deformation,precipitation,fracture and damage,corrosion,and energy storage.Research opportunities and challenges of physical metallurgy studies of magnesium alloys are highlighted for future studies.展开更多
Hard secondary phases usually strengthen alloys at the expense of ductility.In this work,we made a dual-phase CrCoNi-O alloy containing a face centered cubic matrix and chromium oxide.On one side,the dispersed chromiu...Hard secondary phases usually strengthen alloys at the expense of ductility.In this work,we made a dual-phase CrCoNi-O alloy containing a face centered cubic matrix and chromium oxide.On one side,the dispersed chromium oxide nano-particles impeded dislocation movement and increased the strength of the alloy.On another side,the spreading lattice distortion in CrCoNi-O high entropy solution locally relieved the severe interfacial mismatch and led to nanoscale variation of interfacial strain at the matrix-oxide interface,which facilitated dislocations’transmission from one phase to another.Consequently,unlike the strong but brittle oxide nanoparticles used before,the oxide phase here can afford significant dislocation activities during material’s plastic deformation.Comparing the mechanical properties of CrCoNi-O alloys with and without chromium oxide particles,it was found that the yield strength of the dual-phase samples was twice of the single phase CrCoNi-O alloy and strong strain hardening was obtained with ultra-high deformation stability.High density of nanotwins formed in dual-phase samples under high stress,resulting in significant strain hardening according to the well-known twinning-induced plasticity(TWIP)effect.Our results shed light on optimizing the combination of strength and plasticity of compounds by modulating the variation of interfacial strain field based on the spreading lattice distortion.展开更多
Although tension-compression(T-C)asymmetry in yield strength was rarely documented in coarse-grained face centered cubic(FCC)metals as critical resolved shear stress(CRSS)for dislocation slip differs little between te...Although tension-compression(T-C)asymmetry in yield strength was rarely documented in coarse-grained face centered cubic(FCC)metals as critical resolved shear stress(CRSS)for dislocation slip differs little between tension and compression,the T-C asymmetry in strength,i.e.,higher strength when loaded in compression than in tension,was reported in some FCC high entropy alloys(HEAs)due to twinning and phase transitions activated at high strain regimes in compression.In this paper,we demonstrate a reversed and atypical tension-compression asymmetry(tensile strength markedly exceeds compressive strength)in a non-equiatomic FCC Ni_(2)CoFeV_(0.5)Mo_(0.2) medium entropy alloy(MEA)under dynamic loading,wherein dislocation slip governs dynamic deformation without twins or phase transitions.The asymme-try can be primarily interpreted as higher CRSS and more hard slip modes(lower average Schmid factor)activated in grains under dynamic tension than compression.Besides,larger strain rate sensitivity in dy-namic tension overwhelmingly contributes to the higher flow stress,thanks to the occurrence of more immobile Lomer-locks,narrower spacing of planar slip bands and higher dislocation density.This finding may provide some insights into designing MEAs/HEAs with desired properties under extreme conditions such as blast,impact and crash.展开更多
Interstitial strengthening with nitrogen(N)is one of the effective ways to improve the mechanical properties of HEAs,but the effects of N on the microstructures and mechanical properties of the irradiated HEAs have no...Interstitial strengthening with nitrogen(N)is one of the effective ways to improve the mechanical properties of HEAs,but the effects of N on the microstructures and mechanical properties of the irradiated HEAs have not been studied extensively.Here,the microstructures and mechanical properties of N-free and N-doped Ti_(2)ZrNbV_(0.5)Mo_(0.2)HEAs before and after He irradiation were investigated.The results showed that the solid solution strengthening caused by interstitial N improved the yield strength at room temperature and 1023 K without significantly reducing plasticity.N doping significantly promoted the growth,aggregation and wider spatial distribution of He bubbles by enhancing the mobility of He atoms/He-vacancy complexes,with the average size of He bubbles increasing from 10.4 nm in N-free HEA to 31.0 nm in N-doped HEA.In addition,N-doped HEA showed a much higher irradiation hardness increment and hardening fraction than N-free HEA.Contrary to conventional materials doped with N,the introduction of N into Ti_(2)ZrNbV_(0.5)Mo_(0.2)HEA had adverse effects on its resistance to He bubble growth and irradiation hardening.The results of this study indicated that N doping may not improve the irradiation resistance of HEAs.展开更多
The worldwide outbreak of COVID-19 since December 2019 has caused great challenges to health organizations,and brought tremendous impact on the global economy.There have been over62.3 million confirmed infection cases...The worldwide outbreak of COVID-19 since December 2019 has caused great challenges to health organizations,and brought tremendous impact on the global economy.There have been over62.3 million confirmed infection cases and 1.4 million deaths reported until now(December 1 st,2020),and the numbers are still growing[1].Although not as influential as COVID-19.展开更多
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 by the National Natural Science Foundation of China(Nos.51822402,51971248,52101147 and U20A20278)the National Key Research and Development Program of China(No.2019YFA0209901 and 2018YFA0702901)+2 种基金the Liao Ning Revitalization Talents Program(No.XLYC1807047)the Natural Science Foundation of Jiangsu Province(No.BK20210726)the Fund of the State Key Laboratory of Solidification Process-ing in NWPU(No.SKLSP201902).
文摘1.Introduction Additive manufacturing or 3D printing outweighs conventional casting methods in the aspect of complex parts fabrication,which can realize one-step formation without the need of complicated cast dies.3D printing significantly promotes industrial production for making near-net shaped components.However,this promising technique is not always ideally applicable for metals and alloys.For example,titanium alloys prepared by 3D printing often suf-fer from poor plasticity,and usually require further complex heat treatment or hot isostatic pressing treatment,in order to remove internal stress and regulate plasticity and strength[1,2],which de-feats the original intention of employing additive manufacturing.One of the fundamental causes for such issues is the low fluidity of the alloys upon melting,leading to great chemical heterogeneity,high porosity content and residual stresses.This limitation hinders further design and fabrication of high-performance printable alloys from large scale production and application.
基金supported by the National Natural Science Foundation of China (Nos. 11605271, 51471044, 51525401, 51771201 and 51401208)Support Plan for Innovation of High-level Talents (Top and Leading Talents, 2015R013)Support Plan for Innovation of High-level Talents (Youth Technology Stars, 2016RQ005)
文摘Recently, high-entropy alloys(HEAs) or multi-principal-element alloys with unprecedented physical,chemical, and mechanical properties, have been considered as candidate materials used in advanced reactors due to their promising irradiation resistant behavior. Here, we report a new single-phase bodycentered cubic(BCC) structured Ti_2 ZrHfV_(0.5)Mo_(0.2) HEA possessing excellent irradiation resistance, i.e.,scarcely irradiation hardening and abnormal lattice constant reduction after helium-ion irradiation,which is completely different from conventional alloys. This is the first time to report the abnormal XRD phenomenon of metallic alloys and almost no hardening after irradiation. These excellent properties make it to be a potential candidate material used as core components in next-generation nuclear reactors. The particular irradiation tolerance derives from high density lattice vacancies/defects.
基金the National Natural Science Foundation of China(Nos.51822402 and 51871050)the Fundamental Research Funds for the Central Universities(DUT16ZD206)Dalian Support Plan for Innovation of High-level Talents(Youth Technology Stars,2016RQ005)。
文摘The design of novel high-entropy alloys(HEAs)provides a unique opportunity for the development of structure-function integrated materials with high mechanical and antimicrobial properties.In this study,by employing the antibacterial effect of copper,a novel Al0.4CoCrCuFeNi HEA with broad-spectrum antibacterial and strong mechanical properties was designed.High concentrations of copper ions released from the HEA prevented growth and biofilm formation by biocorrosive marine bacterial species.These findings serve as a proof-of-concept for further development of unique HEA materials with high antimicrobial efficiency and mechanical properties,compared to conventional antibacterial alloys.
基金supported by National MCF Energy Research and Development Program(No.2018YFE0312400)National Key Research and Development Program of China(Nos.2019YFA0209901 and 2018YFA0702901)+2 种基金Liao Ning Revitalization Talents Program(No.XLYC1807047)Fund of Science and Technology on Reactor Fuel and Materials Laboratory(No.6142A06190304)Fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP201902)。
文摘The microstructure and mechanical properties of as-cast and isothermally annealed C_(x)Hf_(0.25)NbTaW_(0.5)(x=0,0.05,0.15,0.25)refractory high-entropy alloys(RHEAs)were studied.Both the as-cast and annealed RHEAs consisted of disordered body-centered cubic solid solution phase and metal carbide(MC)phase with a face-centered cubic crystal structure(Fm-3 m space group).The primary carbides were enriched with Hf and C elements and tended to form lamellar eutectic-like microstructure in the interdendrites.The lamellar eutectic-like structure in the interdendrites would be formed from the decomposition of sub-carbide M_(2)C under the influence of Hf element.After isothermal annealing,slatted carbides were precipitated on the matrix,and the distribution became more uniform with high C content.The formation of carbides strongly influenced the mechanical properties both at room and high temperatures.The yield strength values of C_(x)Hf_(0.25)NbTaW_(0.5) RHEA at 1473 and 1673 K were 792 and 749 MPa,respectively.The result had exceeded the high temperature mechanical properties of currently known RHEAs.Moreover,this RHEA exhibited high-temperature performance stability and excellent plasticity,exceeding 30 and 50%at room and elevated temperatures(above 1273 K),respectively.During thermal deformation,carbon-containing RHEAs obtained more severe work hardening than that of ACHO RHEAs,and required greater dynamic recrystallization to achieve the dynamic equilibrium.
基金Supported by the National Key Research and Development Program of China(No.2019YFA0209901)National Natural Science Foundation of China(No.51822402 and U20A20278)+2 种基金Liao Ning Revitalization Talents Program(No.XLYC1807047)Major Special Project of“Scientific and Technological Innovation 2025 in Ningbo(No.2019B10086)Peter K.Liaw thanks the support from the National Science Foundation(DMR-1611180 and 1809640)with the program directors,Drs.Judith Yang,Gary Shiflet,and Diana Farkas.
文摘Contact infection of bacteria and viruses has been a critical threat to human health. The worldwideoutbreak of COVID-19 put forward urgent requirements for the research and development of the selfantibacterial materials, especially the antibacterial alloys. Based on the concept of high-entropy alloys, thepresent work designed and prepared a novel Co_(0.4)FeCr_(0.9)Cu_(0.3) antibacterial high-entropy alloy with superior antibacterial properties without intricate or rigorous annealing processes, which outperform the antibacterial stainless steels. The antibacterial tests presented a 99.97% antibacterial rate against Escherichiacoli and a 99.96% antibacterial rate against Staphylococcus aureus after 24 h. In contrast, the classic antibacterial copper-bearing stainless steel only performed the 71.50% and 80.84% antibacterial rate, respectively. The results of the reactive oxygen species analysis indicated that the copper ion release and theimmediate contact with copper-rich phase had a synergistic effect in enhancing antibacterial properties.Moreover, this alloy exhibited excellent corrosion resistance when compared with the classic antibacterialstainless steels, and the compression test indicated the yield strength of the alloy was 1015 MPa. Thesefindings generate fresh insights into guiding the designs of structure-function-integrated antibacterial alloys.
基金financially supported by the National Natural Science Foundation of China (Nos: 51601192 and 51671188)the High Technology Research and Development Program of China (No. 2014AA041701)the National Key R & D Program of China (2018YFB1106600)
文摘An eutectic high-entropy alloy consisting Al, Co, Cr, Fe and Ni elements was prepared by vacuum directional solidification technology. The alloy exhibits excellent comprehensive mechanical performance during tension at temperature range of 600–700℃. The microstructure reveals the intersection of twintwin is the prevailing deformation mechanism and the twins play a dual role in strengthening and toughening the alloy in the thermomechanical process. The deformation twin variants I and were formed by the edge dislocation 112 and the mixed dislocation 211 on the {111} crystal planes, respectively. Besides, the dislocation jogs and kinks caused by twin intersection on the slip planes can strengthen the alloy, which may contribute to the high strength(the tensile strengths at the 600°and 700°tensile tests are respectively780 MPa and 630 MPa.). Moreover, the coherent twin boundary migration has the function of coordinating deformation and contributes to the high ductility of the alloy.
基金supported financially by the National Natural Science Foundation of China(No.51771201 and No.51822402)the Key Project of Natural Science Foundation of Liaoning Province+4 种基金China(No.20180510059)the Shenyang National Laboratory for Materials Science(No.2017RP17)the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University(No.SKLSP201902)support of the U.S.Army Research Office Project(W911NF-13-1-0438 and W911NF-19-2-0049)with the program managers,Drs.M.P.Bakas,S.N.Mathaudhu,D.M.Steppsupport from the National Science Foundation(DMR-1611180 and DMR-1809640)with the program directors,Drs.J.Yang,G.Shiflet,D.Farkas。
文摘Recently,the eutectic high-entropy alloy(EHEA),AlCoCrFeNi_(2.1),can reach a good balance of strength and ductility.The dual-phase alloy exhibits a eutectic lamellar microstructure with large numbers of interfaces.However,the role of the interfaces in plastic deformation have not been revealed deeply.In the present work,the orientation relationship(OR)of the interfaces has been clarified as the Kurdjumov-Sachs(KS)interfaces presenting〈111〉_(B2) 〈110〉_(FCC)and {110} _(B2){111}_(FCC) independent of their morphologies.There exist three kinds of interfaces in the EHEA,namely,The dominating interface and the secondary interface are both non-slip planes and atomistic-scale faceted,facilitating the nucleation and slip transmission of the dislocations.The formation mechanism of the preferred interfaces is revealed using the atomistic geometrical analysis according to the criteria of the low interfacial energy based on the coincidence-site lattice(CSL)theory.In particular,the ductility of the dual-phase alloy originates from the KS interface-induced slip continuity across interfaces,which provides a high slip-transfer geometric factor.Moreover,the strengthening effect can be attributed to the interface resistance for the dislocation transmission due to the mismatches of the moduli and lattice parameters at the interfaces.
基金supported financially by the National Natural Science Foundation of China(Nos.51901116,51822402 and 51671044)the National Key Research and Development Program of China(Nos.2019YFA0209901 and 2018YFA0702901)+5 种基金the Fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP201902)the Liao Ning Revitalization TalentsProgram(No.XLYC1807047)the National MCF Energy R&D Program(No.2018YFE0312400)the Fund of Science and Technology on Reactor Fuel and Materials Laboratory(No.STRFML-2020-04)the U.S.Army Research Office for the support of the present work through projects Nos.W911NF-13-1-0438 and W911NF-19-2-0049the National Science Foundation for the support of the present work through projects Nos.DMR1611180 and 1809640。
文摘In this study,a new Al0.9CoFeNi2 eutectic high entropy alloy(EHEA) was designed,and the microstructures as well as the deformation behavior were investigated.The bulk cast Al0.9CoFeNi2 EHEA exhibited an order face-centered cubic FCC(L12) and an order body-centered cubic(B2) dual-phase lamellar eutectic microstructure.The volume fractions of FCC(L12) and B2 phases are measured to be 60 % and 40 %,respectively.The combination of the soft and ductile FCC(L12) phase together with the hard B2 phase resulted in superior strength of 1005 MPa and ductility as high as 6.2 % in tension at room temperature.The Al0.9CoFeNi2 EHEA exhibited obvious three-stage work hardening characteristics and high workhardening ability.The evolving dislocation substructure s during uniaxial tensile deformation found that planar slip dominates in both FCC(L12) and B2 phases,and the FCC(L12) phase is easier to deform than the B2 phase.The post-deformation transmission electron microscopy revealed that the sub-structural evolution of the FCC(L12) phase is from planar dislocations to bending dislocations,high-density dislocations,dislocation network,and then to dislocation walls,and Taylor lattices,while the sub-structural evolution of the B2 phase is from a very small number of short dislocations to a number of planar dislocations.Moreover,obvious ductile fracture in the FCC(L12) phase and a brittle-like fracture in the B2 phase were observed on the fracture surface of the Al0.9CoFeNi2 EHEA.The re search results provide some insight into the microstructure-property relationship.
基金supported by the National Natural Science Foundation of China(Nos.51134013,51071035,51375070 and 51104029)the Fundamental Research Funds for the Central Universities
文摘High entropy alloy has attracted increasing attentions.However,to enhance the alloy strength often leads to impairment of the ductility,or vice versa.Here we reported a heat treatment approach on AlCrFeNi2Ti0.5 high entropy alloy,which can elevate the strength and ductility simultaneously.An ingot of AlCrFeNi2Ti0.5 weighing 2.5 kg was firstly fabricated by medium frequency induction melting.Then samples from the same height of the bulk ingot were annealed for 6 h at 600,700,800 and 1000 ℃,respectively.After 1000 ℃ annealing,an optimal microstructure was obtained by using our approach which can make some precipitation particles distribute homogeneously in the dendrite interior while keep the interdendrite structure as a single solid solution phase.The mechanical test on this AlCrFeNi2Ti0.5 alloy sample showed that,the compressive fracture strength σbc was increased by about600 MPa and the plastic strain ep was doubled,compared with those of the as-cast sample.Our approach can be readily adapted to large-scale industrial production of high entropy alloys with high strength and ductility by proper annealing treatment.
基金supported by the National Natural Science Foundation of China (Nos. 51525401 and 51471044)the Fundamental Research Funds for the Central Universities (No. DUT14LH013)+1 种基金Key Laboratory of Basic Research Projects of Liaoning Province Department of Education (No. LZ2014007)the Natural Science Foundation of Liaoning Province (No. 2014028013)
文摘Low-melting-point alloys have an extensive applications in the fields of materials processing, phase change energy storage, electronic and electrical automatic control, continuous casting simulation, welding, etc. Specifically, the eutectic compositions make up a large number of low-melting-point alloys that are ex- ploited because of their desirable features like single melting peaks, excellent operational reliability, and casting fluidity. However, the fundamental physicochemical properties from the current available liter- ature on low-melting-point multi-component eutectic alloys （LMP-MCEAs） are rather rare and lowly accurate, including the exact melting temperatures and compositions, constituent phases, microstruc- tures and morphologies, melting enthalpies, specific heats, densities, and so on. This lack of information seriously limits the development and application of low-melting-point multi-component eutectic alloys. In this paper, the low-melting-point multi-component eutectic alloys composed of Bi, Cd, Sn, Pb, and In elements synthesized by high vacuum induction melting and fundamental data were investigated by scan- ning electron microscopy （SEM）, energy dispersive spectrometry （EDS）, X-ray diffraction （XRD）, differential scanning calorimetry （DSC）, and density analysis instrument. Most of the LMP-MCEAs with complex eu- tectic morphology structures and XRD diffraction patterns could be explained with the fact that they were three-phase eutectic alloys with mixed growth way. Generally, LMP-MCEAs present an extremely low melting point between 48.3 and 124 ℃ and high density between 8 and 10 g/cm3.
基金financially supported by the National Key R&D Program of China(Nos.2021YFA1200203,2019YFA0209901)the National Natural Science Foundation of China(Nos.51971112,51822402 and 51225102)+1 种基金the Fundamental Research Funds for the Central Universities(No.30919011405)the LiaoNing Revitalization Talents Program(No.XLYC1807047).
文摘In the present study,a face-centered cubic non-equiatomic Cr_(26)Mn_(20)Fe_(20)Co20Ni_(14) high-entropy alloy(HEA)with a low stacking fault energy of 17.6 mJ m^(−2) was prepared by vacuum induction melting,forging and annealing processes.The recrystallized sample is revealed to exhibit an excellent combination of strength and ductility over a wide temperature range of 4.2–293 K.With decreasing temperature from 293 to 77 K,the ductility and ultimate tensile strength(UTS)gradually increase by 30% to 95% and 137% to 1020 MPa,respectively.At the lowest temperature of 4.2 K,the ductility keeps 65% and the UTS increases by 200% to 1300 MPa,which exceed those published in the literature,including conventional 300 series stainless steels.Detailed microstructural analyses of this alloy reveal a change of deformation mechanisms from dislocation slip and nano-twinning at 293 K to nano-phase transformation at 4.2 K.The cooperation and competition of multiple nano-twinning and nano-phase transformation are responsible for the superior tensile properties at cryogenic temperatures.Our study provides experimental evidence for potential cryogenic applications of HEAs.
基金supported by the National Natural Science Foundation of China (Nos. 51134013, and 51471044)funds for the central universities, key laboratory of basic research projects of Liaoning Province Department of Education (No. LZ2014007)the Natural Science Foundation of Liaoning Province (No. 2014028013)
文摘A series of CoCrFeNb_xNi（x values in molar ratio, x = 0, 0.25, 0.45, 0.5, 0.75, 1.0 and 1.2） high entropy alloys（HEAs） was prepared to investigate the alloying effect of Nb on the microstructures and mechanical properties. The results indicate that the prepared CoCrFeNb_xNi（x 〉 0） HEAs consist of a simple FCC solid solution phase and a Laves phase. The microstructures of the alloys change from an initial single-phase FCC solid solution structure（x = 0） to a hypoeutectic microstructure（x = 0.25）, then to a full eutectic microstructure（x = 0.45） and finally to a hypereutectic microstructure（0.5 〈 x 〈 1.2）. The compressive test results show that the Nb0.45（x = 0.45） alloy with a full eutectic microstructure possesses the highest compressive fracture strength of 2558 MPa and a fracture strain of 27.9%. The CoCrFeNi alloy exhibits an excellent compressive ductility, which can reach 50% height reduction without fracture. The Nb0.25 alloy with a hypoeutectic structure exhibits a larger plastic strain of 34.8%. With the increase of Nb content, increased hard/brittle Laves phase leads to a decrease of the plasticity and increases of the Vickers hardness and the wear resistance. The wear mass loss, width and depth of wear scar of the Nb1.2（x = 1.2） alloy with a hypereutectic structure are the lowest among all alloy systems, indicating that the wear resistance of the Nb1.2 alloy is the best one.
基金supported by the National Natural Science Foundation of China (Nos. 51104029, 51134013, 51471044, 51104029 and 51375070)the Fundamental Research Funds for the Central Universitiesthe Natural Science Foundation of Liaoning Province (No. 2014028013)
文摘The eutectic CoFeNi2V0.5Nb0.75 high entropy alloys （HEAs） were heated at 500, 600, 700, 800 and 1000 ℃, respectively for 6 h and subsequently quenched in the water to investigate their thermal stability and phase transformation at high temperature. The microstructure and mechanical properties of the samples were investigated by scanning electron microscopy, X-ray diffraction, compressive and hardness tests. It was found that the as-cast CoFeNi2V0.5Nb0.75 HEAs showed a eutectic microstructure with alternating fcc solid solution phase and Fe2Nb-type Laves phase. The NbNi4-type intermetallic phase appeared when the heat-treated temperature was higher than 600 ℃. With increasing quenching temperature, the volume fraction of the NbNi4-type intermetallic phase increased while that of the eutectic regions decreased. The sample quenched at 800 ℃ showed the most excellent comprehensive mechanical properties; its fracture strength, yield strength and plastic strain were as high as 2586.76 MPa, 2075.18 MPa and 16.73%, respectively. Moreover, the eutectic CoFeNi2V0.5Nb0.75 HEAs exhibited apparent age hardening, especially quenched at 700 ℃, the hardness reached up to the maximum value of HV 727.52.
基金supported by the National Natural Science Foundation of China (Nos. 51271042 and 51501027)the Fundamental Research Funds for the Central Universities, the Key Laboratory of Basic Research Projects of Liaoning Province Department of Education (No. LZ2014007)+1 种基金the Natural Science Foundation of Liaoning Province (No. 2014028013)China Postdoctoral Science Foundation (No. 2015M570246)
文摘Semisolid-rolling method was successfully developed to prepare the Ni-coated woven carbon fibers reinforced Al-matrix composite. Due to the appropriate matrix flowability and rolling pressure, the Al-matrix could infiltrate into the woven fibers sufficiently and attach to the reinforcements closely forming a smooth interface. The rolling speed of 4 rad/min offered a subtle equilibrium between the heat transfer and the material deformation. The covering matrix should be controlled at semisolid state to provide a better infiltration behavior and a protective effect on the carbon fibers. With the addition of fibers, an improvement for more than 25% was obtained in the bending strength of the materials. Furthermore, the woven carbon fibers could strengthen the composite in multiple directions, rather than only along the fiber longitudinal directions. The annealing process promoted the Ni coating to react with and to diffuse into the matrix, resulted in an obvious increase of the bending strength.
基金supported by the National Natural Science Foundation of China(Nos.52371005,52022017,51927801,and 51974058)the Fundamental Research for Central Universities.
文摘Magnesium alloys are the lightest metal structural materials owing to their excellent physical and chemical properties.Microstructural evolution in magnesium alloys under the conditions of casting,thermalmechanical processing,and in-service environment,play an important role in governing their mechanical properties and reliability/sustainability.A synchrotron light source produces high flux,tunable X-ray energy,high resolution,and high coherence X-ray beams,which can realize in-situ dynamic observation of microstructural evolution in a wide range of alloys during the entire processing chain and in simulated service environments.This article reviews the fundamentals of synchrotron radiation characterization techniques(imaging,diffraction,scattering,and fluorescence holography)and state-of-the-art advanced synchrotron characterization techniques on the microstructure evolution mechanism of magnesium alloys.Case studies span a broad range of solidification,deformation,precipitation,fracture and damage,corrosion,and energy storage.Research opportunities and challenges of physical metallurgy studies of magnesium alloys are highlighted for future studies.
基金supported by the National Natural Science Foundation of China(Nos.51671168,51871197)National Key Research and Development Program of China(No.2017YFA0208200)National 111 Project(No.B16042).
文摘Hard secondary phases usually strengthen alloys at the expense of ductility.In this work,we made a dual-phase CrCoNi-O alloy containing a face centered cubic matrix and chromium oxide.On one side,the dispersed chromium oxide nano-particles impeded dislocation movement and increased the strength of the alloy.On another side,the spreading lattice distortion in CrCoNi-O high entropy solution locally relieved the severe interfacial mismatch and led to nanoscale variation of interfacial strain at the matrix-oxide interface,which facilitated dislocations’transmission from one phase to another.Consequently,unlike the strong but brittle oxide nanoparticles used before,the oxide phase here can afford significant dislocation activities during material’s plastic deformation.Comparing the mechanical properties of CrCoNi-O alloys with and without chromium oxide particles,it was found that the yield strength of the dual-phase samples was twice of the single phase CrCoNi-O alloy and strong strain hardening was obtained with ultra-high deformation stability.High density of nanotwins formed in dual-phase samples under high stress,resulting in significant strain hardening according to the well-known twinning-induced plasticity(TWIP)effect.Our results shed light on optimizing the combination of strength and plasticity of compounds by modulating the variation of interfacial strain field based on the spreading lattice distortion.
基金the National Key R&D Program of China(No.2017YFA0204403)the National Natural Science Foundation of China(Nos.51971112 and51225102)+2 种基金the Fundamental Research Funds for the Central Universities(No.30919011405)X.Chen would like to acknowledge the finan-cial support from the National Natural Science Foundation of China(Nos.52001165 and 51931003)the Natural Science Foundation of Jiangsu Province,China(No.BK20200475),and the Fundamen-tal Research Funds for the Central Universities(No.30921011215).
文摘Although tension-compression(T-C)asymmetry in yield strength was rarely documented in coarse-grained face centered cubic(FCC)metals as critical resolved shear stress(CRSS)for dislocation slip differs little between tension and compression,the T-C asymmetry in strength,i.e.,higher strength when loaded in compression than in tension,was reported in some FCC high entropy alloys(HEAs)due to twinning and phase transitions activated at high strain regimes in compression.In this paper,we demonstrate a reversed and atypical tension-compression asymmetry(tensile strength markedly exceeds compressive strength)in a non-equiatomic FCC Ni_(2)CoFeV_(0.5)Mo_(0.2) medium entropy alloy(MEA)under dynamic loading,wherein dislocation slip governs dynamic deformation without twins or phase transitions.The asymme-try can be primarily interpreted as higher CRSS and more hard slip modes(lower average Schmid factor)activated in grains under dynamic tension than compression.Besides,larger strain rate sensitivity in dy-namic tension overwhelmingly contributes to the higher flow stress,thanks to the occurrence of more immobile Lomer-locks,narrower spacing of planar slip bands and higher dislocation density.This finding may provide some insights into designing MEAs/HEAs with desired properties under extreme conditions such as blast,impact and crash.
基金supported by the National Key Research and Development Program of China(No.2019YFA0209901)the Liao Ning Revitalization Talents Program(No.XLYC1807047).
文摘Interstitial strengthening with nitrogen(N)is one of the effective ways to improve the mechanical properties of HEAs,but the effects of N on the microstructures and mechanical properties of the irradiated HEAs have not been studied extensively.Here,the microstructures and mechanical properties of N-free and N-doped Ti_(2)ZrNbV_(0.5)Mo_(0.2)HEAs before and after He irradiation were investigated.The results showed that the solid solution strengthening caused by interstitial N improved the yield strength at room temperature and 1023 K without significantly reducing plasticity.N doping significantly promoted the growth,aggregation and wider spatial distribution of He bubbles by enhancing the mobility of He atoms/He-vacancy complexes,with the average size of He bubbles increasing from 10.4 nm in N-free HEA to 31.0 nm in N-doped HEA.In addition,N-doped HEA showed a much higher irradiation hardness increment and hardening fraction than N-free HEA.Contrary to conventional materials doped with N,the introduction of N into Ti_(2)ZrNbV_(0.5)Mo_(0.2)HEA had adverse effects on its resistance to He bubble growth and irradiation hardening.The results of this study indicated that N doping may not improve the irradiation resistance of HEAs.
基金financially supported by the Fundamental Research Funds for the Central Universities(Nos.N2002020 and N2002019)the National Natural Science Foundation of China(Nos.51871050,5184022,and 51901039)+2 种基金the National Key Research and Development Program of China(Nos.2019YFA0209901 and 2018YFA0702901)the fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP201902)the Fund of Science and Technology on Reactor Fuel and Materials Laboratory(STRFML-2020-04)。
文摘The worldwide outbreak of COVID-19 since December 2019 has caused great challenges to health organizations,and brought tremendous impact on the global economy.There have been over62.3 million confirmed infection cases and 1.4 million deaths reported until now(December 1 st,2020),and the numbers are still growing[1].Although not as influential as COVID-19.
