Bulk ultrafine-grained(UFG) CoCrFeMnNi high-entropy alloy(HEA) with fully recrystallized microstructure was processed by cold rolling and annealing treatment. The high-cycle fatigue behaviors of the UFG HEA and a coar...Bulk ultrafine-grained(UFG) CoCrFeMnNi high-entropy alloy(HEA) with fully recrystallized microstructure was processed by cold rolling and annealing treatment. The high-cycle fatigue behaviors of the UFG HEA and a coarse-grained(CG) counterpart were investigated under fully reversed cyclic deformation.The fatigue strength of the UFG HEA can be significantly enhanced by refining the grain size. However,no grain coarsening was observed in the UFG HEA during fatigue tests. Mechanisms for the superior mechanical properties of the UFG HEA were explored.展开更多
High entropy alloys(HEAs) have presented potential applications in nuclear power plants owing to their novel atomic structure based high irradiation resistance. However, understanding of He-ion irradiation of HEAs is ...High entropy alloys(HEAs) have presented potential applications in nuclear power plants owing to their novel atomic structure based high irradiation resistance. However, understanding of He-ion irradiation of HEAs is still lacking. In this work, we reveal He-ion irradiation resistance of HEA CrMnFeCoNi by comparison study with a pure Ni and a 304 stainless steel(304SS). It is found that the damage structure in the three materials can be characterized with He bubbles and stacking faults/stacking fault tetrahedrons((SFs/SFTs), which show a similar depth distribution after He-ion irradiation at both RT and 450℃.Although the He bubbles have a similar size about 2nm after irradiation at RT, the He bubble sizes of the HEA, 304SS, and Ni increase to 4.0±0.9,5.3±1.0 and 6.7 ±1.0 nm after irradiation at 450℃, respectively. Moreover, the density of SFs/SFTs displays in an order of Ni < 304 SS < HEA at both RT and 450℃.The He-ion irradiation at RT causes significant hardness enhancement for the three materials, however,compared to RT, after irradiation at 450℃, the Ni presents softening, while the 304SS, especially the HEA,shows further hardening. Thus, the HEA CrMnFeCoNi possesses the smallest He bubble size, the densest SFs/SFTs, and the highest hardening, indicating the best structural stability, as well as the best He-ion irradiation resistance, which can be attributed to its low mobility of He atoms and point defects.展开更多
Tailoring the alloy composition,which induces the hard secondary phase to increase hardness and strength to improve the wear features,is a feasible approach for developing wear-resistant metal materials.Here,a group o...Tailoring the alloy composition,which induces the hard secondary phase to increase hardness and strength to improve the wear features,is a feasible approach for developing wear-resistant metal materials.Here,a group of(AlCoCrFeNi)_(100–x)Sc_(x)(x=0–2.0,at%)high-entropy alloys(HEAs)are designed and the phase compositions and wear behaviors are explored.Sc-doped HEA series contain the primary body-centered cubic(BCC)and eutectic phases,in which the eutectic phase is composed of the alternately grown BCC and Laves phases.Sc addition promotes the diffusion of Ni atoms from BCC phase to form the Sc-rich Laves phase at the grain boundaries.Vickers hardness increases due to solid solution strengthening and second phase strengthening.And the second phase strengthening plays a more significant role relative to solid solution strengthening.Laves phase and the oxides caused by wear heating prevent the direct contact between friction pair and HEAs,thus inducing a decreased wear rate from 6.82×10^(−5) to 3.47×10^(−5)m^(3)·N^(−1)·m^(−1).Moreover,the wear mechanism changes from adhesive wear,abrasive wear and oxidative wear to abrasive wear and oxidative wear.展开更多
Dual-phase high-entropy alloys containing facecentered cubic(fcc) and body-centered cubic(bcc) phases achieve a combination of high strength and high ductility,which attract extensive attention.Compared with singlepha...Dual-phase high-entropy alloys containing facecentered cubic(fcc) and body-centered cubic(bcc) phases achieve a combination of high strength and high ductility,which attract extensive attention.Compared with singlephase high-entropy alloys,the dual-phase structure generates more complex deformation mechanisms such as structural transformation and interactions between grain boundaries and dislocations during deformation.In order to understand the structural transformation of the dual-phase high-entropy alloy during deformation and its effect on mechanical properties,Al_(0.5)CoCrNiFe high-entropy alloy was prepared and its deformation mechanism was investigated by molecular dynamics simulations combined with experiments.The results show that phase transformation occurred during deformation,and dislocation slip was the main deformation mechanism.In addition,there was significant dislocation pile-up at the interface between fcc and bcc phases after tensile deformation.Temperatures and strain rates significantly affected the mechanical properties and deformation behavior of high-entropy alloys.At low temperature and high strain rate,the dislocation density of the alloy increases after stretching,resulting in the enhancement of tensile strength.展开更多
The corrosion behaviour of a non-equiatomic CoCrFeNiMo high-entropy alloy(HEA)in H_(2)S-containing and H_(2)S-free environments was studied by electrochemical tests,surface characterization,and solution analysis.The r...The corrosion behaviour of a non-equiatomic CoCrFeNiMo high-entropy alloy(HEA)in H_(2)S-containing and H_(2)S-free environments was studied by electrochemical tests,surface characterization,and solution analysis.The results showed that the HEA exhibited primary and secondary passivation in the H_(2)S-free environment,and the transition was owing to the enhanced dissolution of Fe species.Compared with the primary passive film,the Cr/Fe ratio in the secondary passive film increased at the expense of the selective dissolution of Fe.Therefore,the corrosion resistance of HEA decreased with the applied potential.Cr was the most stable element in the film of HEA,regardless of H_(2)S.The presence of H_(2)S accelerated the dissolution of all the cationic elements in the HEA.H_(2)S promoted the formation of thicker but less protective surface film and induced the loss of passivity.展开更多
Cr Fe Ni Cu)_(100-x)Ti_(x)(x=0,3,5,7 and 10;at%)high-entropy alloys have been designed by the consideration of the thermophysical relationship between Ti and other principal elements to investigate the influence of Ti...Cr Fe Ni Cu)_(100-x)Ti_(x)(x=0,3,5,7 and 10;at%)high-entropy alloys have been designed by the consideration of the thermophysical relationship between Ti and other principal elements to investigate the influence of Ti on the microstructural evolution and mechanical properties of(CrFeNiCu)_(100-x)Ti_(x)high-entropy alloys.The addition of Ti content in HEAs leads to a change in phase formation from dual-phase(FCC1 and FCC2,FCC:face-centered cubic)to the mixture of FCC1,FCC2 phases,and an additional body-centered cubic(BCC)phase.The yield strength and Vickers hardness of the alloys are enhanced from 291 to 1511 MPa and HV 134 to HV 531,respectively,which depends strongly on the volume fraction of BCC phase.On the one hand,the plasticity of the alloys reduces from 45.00%to 24.09%,but it could be considered reasonable plasticity.These results revealed that the addition of a minor alloying element in high-entropy alloys with consideration of thermophysical parameters led to the formation of a multiple solid solution structure with excellent mechanical properties.展开更多
High entropy alloys(HEAs)attract remarkable attention due to the excellent mechanical performance.However,the origins of their high strength and toughness compared with those of the traditional alloys are still hardly...High entropy alloys(HEAs)attract remarkable attention due to the excellent mechanical performance.However,the origins of their high strength and toughness compared with those of the traditional alloys are still hardly revealed.Here,using a microstructure-based constitutive model and molecular dynamics(MD)simulation,we investigate the unique mechanical behavior and microstructure evolution of FeCoCrNiCu HEAs during the indentation.Due to the interaction between the dislocation and solution,the high dislocation density in FeCoCrNiCu leads to strong work hardening.Plentiful slip systems are stimulated,leading to the good plasticity of FeCoCrNiCu.The plastic deformation of FeCoCrNiCu is basically affected by the motion of dislocation loops.The prismatic dislocation loops inside FeCoCrNiCu are formed by the dislocations with the Burgers vectors of a/6[112]and a/6[112],which interact with each other,and then emit along the<111>slip direction.In addition,the mechanical properties of FeCoCrNiCu HEA can be predicted by constructing the microstructure-based constitutive model,which is identified according to the evolution of the dislocation density and the stress-strain curve.Strong dislocation strengthening and remarkable lattice distortion strengthening occur in the deformation process of FeCoCrNiCu,and improve the strength.Therefore,the origins of high strength and high toughness in FeCoCrNiCu HEAs come from lattice distortion strengthening and the more activable slip systems compared with Cu.These results accelerate the discovery of HEAs with excellent mechanical properties,and provide a valuable reference for the industrial application of HEAs.展开更多
The effect of nitrogen on microstructural evolution and tensile properties of transformation-induced plasticity(TRIP)Fe_(50)Mn_(30)Co_(10)Cr_(10)HEAs was investigated.Nitrogen was fully introduced in solid solution by...The effect of nitrogen on microstructural evolution and tensile properties of transformation-induced plasticity(TRIP)Fe_(50)Mn_(30)Co_(10)Cr_(10)HEAs was investigated.Nitrogen was fully introduced in solid solution by pressure-induced melting technique.Nitrogen addition turned the TRIP alloy to a twinning-induced plasticity(TWIP)alloy,and simultaneously improved the strength and elongation.For the nitrogen-doped HEA,the high yield strength is mainly resulted from the friction stress via interstitial strengthening effect,and the high ductility is originated from retained high strain-hardening capability via the successive onset of dislocation accumulation and deformation twinning.The strain-hardening behavior and microstructural evolution at specified strains were revealed.展开更多
We present a new class of metastable high-entropy alloys(HEAs),triggering deformation-induced martensitic transformation(DIMT)from face-centered-cubic(FCC)to body-centered-cubic(BCC),i.e.,BCC-DIMT.Through the ab-initi...We present a new class of metastable high-entropy alloys(HEAs),triggering deformation-induced martensitic transformation(DIMT)from face-centered-cubic(FCC)to body-centered-cubic(BCC),i.e.,BCC-DIMT.Through the ab-initio calculation based on 1 st order axial interaction model and combined with the Gibbs free energy calculation,the addition of Si is considered as a critical element which enables to reduce the intrinsic stacking fault energy(ISFE)in Si_xV_((9-x))Cr_(10)Mn_5 Fe_(46)Co_(30)(x=2,4,and 7 at.%)alloy system.The ISFE decreases from-30.4 to-35.5 mJ/m^(2)as the Si content increases from 2 to 7 at.%,which well corresponds to the reduced phase stability of FCC against HCP.The BCC-DIMT occurs in all the alloys via intermediate HCP martensite,and the HCP martensite provides nucleation sites of BCC martensite.Therefore,the transformation rate enhances as the Si content increases in an earlier deformation ra nge.However,the BCC-DIMT is also affected by the phase stability of FCC against BCC,and the stability is the highest at the Si content of 7 at.%.Thus,the 7Si alloy presents the moderate transformation rate in the later deformation range.Due to the well-controlled transformation rate and consequent strain-ha rdening rate,the 7Si alloy possesses the superior combination of strength and ductility beyond 1 GPa of tensile strength at room temperature.Our results suggest that the Si addition can be a favorable candidate in various metastable HEAs for the further property improvement.展开更多
A novel Ni_(30)Cr_(25)Al_(15)Co_(15)Mo_(5)Ti_(5)Y_(5) high-entropy alloy(HEA)coating was irradiated to optimize its internal structure via laser after supersonic particle deposition(SPD).Owing to the high energy densi...A novel Ni_(30)Cr_(25)Al_(15)Co_(15)Mo_(5)Ti_(5)Y_(5) high-entropy alloy(HEA)coating was irradiated to optimize its internal structure via laser after supersonic particle deposition(SPD).Owing to the high energy density of the laser and large temperature gradient,the crystallization process of the molecules and atoms in the coating was restrained and supercooling occurred.Experimental results showed that a considerable number of nano-crystal grains precipitated and amorphous structures were formed because of the random orientation of the crystals.The baseline of differential scanning calorimetry scans obtained for the coating started to shift at the Tg of 939.37℃ and a step was observed.Multiple dispersion peaks and lattice fringes indicated that the nucleation of the irradiated laser-induced topology optimized(LTO)coating was incomplete.The laser-induced topology optimizing treatment led to quasi-isotropy in the SPD coating.Furthermore,the LTO coating exhibited a residual stress of 18.4 MPa,stress-strain response,and fatigue limit of 265 MPa.Hence,the LTO coating exhibited higher performance than the unirradiated SPD coating.The Nyquist and Bode electrochemical impedance spectra of the LTO coating,including two relaxation processes,indicated that the corrosion process steadily recovered to the equilibrium state.This implies that the uniform oxidation passivation layer on the surface of the LTO coating insulated the material from the corrosive medium,protecting the substrate from further corrosion,thus enhancing the structural security of the material for use in super-intense laser facility applications.展开更多
The intricate balance between reactor economics and safety necessitates the emergence of new and advanced nuclear systems and,very importantly,advanced materials,which can overcome current shortcomings and bring about...The intricate balance between reactor economics and safety necessitates the emergence of new and advanced nuclear systems and,very importantly,advanced materials,which can overcome current shortcomings and bring about more economic nuclear systems with designed-in inherent safety features.These advances will achieve greater safety and better nuclear reactor economics by reaching longer reactor lives with higher levels neutron irradiation,and by providing higher operation temperatures and resistance to more aggressive corrosive environments.This paper provides a review of the current state of research and development on innovative nuclear fuel materials design and development which have the potential of benefiting simultaneously reactor economics and safety.Our discussion focuses on three areas of research:Accident-tolerant Fuels(ATFs),Oxidation Dispersion Strengthened(ODS)steels and High Entropy Alloys(HEAs).The paper also gives a prospective description of future research activities on these materials.展开更多
研究Co Cr Fe Ni Ti0.5高熵合金在熔融Na2SO4-25%Na Cl(质量分数)中的腐蚀行为,应用TGA获得其在650和750℃空气中的腐蚀动力学曲线;采用XRD、SEM(EDS)和EPMA对腐蚀产物的截面形貌及元素分布进行分析。结果表明:喷涂Na2SO4-25%Na Cl的Co ...研究Co Cr Fe Ni Ti0.5高熵合金在熔融Na2SO4-25%Na Cl(质量分数)中的腐蚀行为,应用TGA获得其在650和750℃空气中的腐蚀动力学曲线;采用XRD、SEM(EDS)和EPMA对腐蚀产物的截面形貌及元素分布进行分析。结果表明:喷涂Na2SO4-25%Na Cl的Co Cr Fe Ni Ti0.5高熵合金在650和750℃时的腐蚀动力学曲线相似,呈"指数"增长规律;腐蚀截面由含较多Ti O2、部分Cr2O3以及微量尖晶石结构氧化物构成的氧化层与含孔隙且贫Cr和Ti、富Fe、Ni和Co的腐蚀影响区两部分构成;延长腐蚀时间或提高腐蚀温度后,氧化层破裂,与基体的结合程度显著下降,发生严重剥离甚至脱落。分析认为:Co Cr Fe Ni Ti0.5高熵合金在Na2SO4-25%Na Cl中的高温腐蚀归因于氧化、硫化以及氯化的综合作用。展开更多
High-entropy materials are mainly composed of high-entropy alloys(HEAs)and their derivates.Among them,HEAs account for a big part.As a new kind of alloy,they are now arousing great interests because of their high mech...High-entropy materials are mainly composed of high-entropy alloys(HEAs)and their derivates.Among them,HEAs account for a big part.As a new kind of alloy,they are now arousing great interests because of their high mechanical strength,extraordinary fracture toughness,corrosion resistance compared with traditional alloys.These characteristics allow the use of HEAs in various fields,including mechanical manufacturing,heat-resistant,radiation-resistant,corrosion-resistant,wear-resistant coatings,energy storage,heterocatalysis,etc.In order to promote the extensive application of HEAs,it is of significance to realize their rational design and preparation.In this paper,a systematic review focusing on the rational design and fabrication of nanosized HEAs is given.The design principles of how to match different elements in HEAs and the premise for the formation of single-phase solid solution HEAs are first illustrated.Computation methods for the prediction of formation conditions and properties of HEAs are also in discussion.Then,a detailed description and comparison of the synthesis methods of HEAs and their derivate,as well as their growing mechanism under various synthetic environments is provided.The commonly used characterization methods for the detection of HEAs,along with the typical cases of the application of HEAs in industrial materials,energy storage materials and catalytic materials are also included.Finally,the challenges and perspectives in the design and synthesis of HEAs would be proposed.We hope this review will give guidance for the future development of HEAs materials.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 51501198 and 51331007)
文摘Bulk ultrafine-grained(UFG) CoCrFeMnNi high-entropy alloy(HEA) with fully recrystallized microstructure was processed by cold rolling and annealing treatment. The high-cycle fatigue behaviors of the UFG HEA and a coarse-grained(CG) counterpart were investigated under fully reversed cyclic deformation.The fatigue strength of the UFG HEA can be significantly enhanced by refining the grain size. However,no grain coarsening was observed in the UFG HEA during fatigue tests. Mechanisms for the superior mechanical properties of the UFG HEA were explored.
基金supported financially by the "Hundred Talents Project" of Chinese Academy of Sciencesthe "Thousand Youth Talents Plan" of China+1 种基金the National Natural Science Foundation of China (Nos. 51401208 and 51771201)the Shenyang National Laboratory for Materials Science (No. 2017RP17)
文摘High entropy alloys(HEAs) have presented potential applications in nuclear power plants owing to their novel atomic structure based high irradiation resistance. However, understanding of He-ion irradiation of HEAs is still lacking. In this work, we reveal He-ion irradiation resistance of HEA CrMnFeCoNi by comparison study with a pure Ni and a 304 stainless steel(304SS). It is found that the damage structure in the three materials can be characterized with He bubbles and stacking faults/stacking fault tetrahedrons((SFs/SFTs), which show a similar depth distribution after He-ion irradiation at both RT and 450℃.Although the He bubbles have a similar size about 2nm after irradiation at RT, the He bubble sizes of the HEA, 304SS, and Ni increase to 4.0±0.9,5.3±1.0 and 6.7 ±1.0 nm after irradiation at 450℃, respectively. Moreover, the density of SFs/SFTs displays in an order of Ni < 304 SS < HEA at both RT and 450℃.The He-ion irradiation at RT causes significant hardness enhancement for the three materials, however,compared to RT, after irradiation at 450℃, the Ni presents softening, while the 304SS, especially the HEA,shows further hardening. Thus, the HEA CrMnFeCoNi possesses the smallest He bubble size, the densest SFs/SFTs, and the highest hardening, indicating the best structural stability, as well as the best He-ion irradiation resistance, which can be attributed to its low mobility of He atoms and point defects.
基金This work was financially supported by the National Natural Science Foundation of China(No.51825401)the Postdoctoral Foundation of Heilongjiang Province(No.LBH-Z19154)+1 种基金the National Natural Science Foundation of Heilongjiang Province(No.LH2020E031)the Interdisciplinary Research Foundation of HIT.
文摘Tailoring the alloy composition,which induces the hard secondary phase to increase hardness and strength to improve the wear features,is a feasible approach for developing wear-resistant metal materials.Here,a group of(AlCoCrFeNi)_(100–x)Sc_(x)(x=0–2.0,at%)high-entropy alloys(HEAs)are designed and the phase compositions and wear behaviors are explored.Sc-doped HEA series contain the primary body-centered cubic(BCC)and eutectic phases,in which the eutectic phase is composed of the alternately grown BCC and Laves phases.Sc addition promotes the diffusion of Ni atoms from BCC phase to form the Sc-rich Laves phase at the grain boundaries.Vickers hardness increases due to solid solution strengthening and second phase strengthening.And the second phase strengthening plays a more significant role relative to solid solution strengthening.Laves phase and the oxides caused by wear heating prevent the direct contact between friction pair and HEAs,thus inducing a decreased wear rate from 6.82×10^(−5) to 3.47×10^(−5)m^(3)·N^(−1)·m^(−1).Moreover,the wear mechanism changes from adhesive wear,abrasive wear and oxidative wear to abrasive wear and oxidative wear.
基金financially supported by the National Natural Science Foundation of China (Nos.92166105 and 52005053)the High-Tech Industry Science and TechnologyInnovation Leading Program of Hunan Province (No.2020GK2085)+1 种基金the Science and Technology Innovation Program of Hunan Province (No.2021RC3096)the Open Fund of Key Laboratory of New Processing Technology for Nonferrous Metal & Materials Ministry of Education (No.20KF-24)。
文摘Dual-phase high-entropy alloys containing facecentered cubic(fcc) and body-centered cubic(bcc) phases achieve a combination of high strength and high ductility,which attract extensive attention.Compared with singlephase high-entropy alloys,the dual-phase structure generates more complex deformation mechanisms such as structural transformation and interactions between grain boundaries and dislocations during deformation.In order to understand the structural transformation of the dual-phase high-entropy alloy during deformation and its effect on mechanical properties,Al_(0.5)CoCrNiFe high-entropy alloy was prepared and its deformation mechanism was investigated by molecular dynamics simulations combined with experiments.The results show that phase transformation occurred during deformation,and dislocation slip was the main deformation mechanism.In addition,there was significant dislocation pile-up at the interface between fcc and bcc phases after tensile deformation.Temperatures and strain rates significantly affected the mechanical properties and deformation behavior of high-entropy alloys.At low temperature and high strain rate,the dislocation density of the alloy increases after stretching,resulting in the enhancement of tensile strength.
基金financially supported by the Fundamental Research Funds for the Central Universities(No.FRF-TP-20-098A1)the National Natural Science Foundation of China(No.52101067).
文摘The corrosion behaviour of a non-equiatomic CoCrFeNiMo high-entropy alloy(HEA)in H_(2)S-containing and H_(2)S-free environments was studied by electrochemical tests,surface characterization,and solution analysis.The results showed that the HEA exhibited primary and secondary passivation in the H_(2)S-free environment,and the transition was owing to the enhanced dissolution of Fe species.Compared with the primary passive film,the Cr/Fe ratio in the secondary passive film increased at the expense of the selective dissolution of Fe.Therefore,the corrosion resistance of HEA decreased with the applied potential.Cr was the most stable element in the film of HEA,regardless of H_(2)S.The presence of H_(2)S accelerated the dissolution of all the cationic elements in the HEA.H_(2)S promoted the formation of thicker but less protective surface film and induced the loss of passivity.
基金financially supported by the National Research Foundation of Korea(NRF)grant funded by the Korean Government(Ministry of Science and ICT)(Nos.2018R1A2B3007167 and 2021R1C1C1006279)the Agency for Presidential Educational Institutions of the Republic of Uzbekistan(No.3/2022)。
文摘Cr Fe Ni Cu)_(100-x)Ti_(x)(x=0,3,5,7 and 10;at%)high-entropy alloys have been designed by the consideration of the thermophysical relationship between Ti and other principal elements to investigate the influence of Ti on the microstructural evolution and mechanical properties of(CrFeNiCu)_(100-x)Ti_(x)high-entropy alloys.The addition of Ti content in HEAs leads to a change in phase formation from dual-phase(FCC1 and FCC2,FCC:face-centered cubic)to the mixture of FCC1,FCC2 phases,and an additional body-centered cubic(BCC)phase.The yield strength and Vickers hardness of the alloys are enhanced from 291 to 1511 MPa and HV 134 to HV 531,respectively,which depends strongly on the volume fraction of BCC phase.On the one hand,the plasticity of the alloys reduces from 45.00%to 24.09%,but it could be considered reasonable plasticity.These results revealed that the addition of a minor alloying element in high-entropy alloys with consideration of thermophysical parameters led to the formation of a multiple solid solution structure with excellent mechanical properties.
基金the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.51621004)the National Natural Science Foundation of China(Nos.12072109,51871092,and 11772122)。
文摘High entropy alloys(HEAs)attract remarkable attention due to the excellent mechanical performance.However,the origins of their high strength and toughness compared with those of the traditional alloys are still hardly revealed.Here,using a microstructure-based constitutive model and molecular dynamics(MD)simulation,we investigate the unique mechanical behavior and microstructure evolution of FeCoCrNiCu HEAs during the indentation.Due to the interaction between the dislocation and solution,the high dislocation density in FeCoCrNiCu leads to strong work hardening.Plentiful slip systems are stimulated,leading to the good plasticity of FeCoCrNiCu.The plastic deformation of FeCoCrNiCu is basically affected by the motion of dislocation loops.The prismatic dislocation loops inside FeCoCrNiCu are formed by the dislocations with the Burgers vectors of a/6[112]and a/6[112],which interact with each other,and then emit along the<111>slip direction.In addition,the mechanical properties of FeCoCrNiCu HEA can be predicted by constructing the microstructure-based constitutive model,which is identified according to the evolution of the dislocation density and the stress-strain curve.Strong dislocation strengthening and remarkable lattice distortion strengthening occur in the deformation process of FeCoCrNiCu,and improve the strength.Therefore,the origins of high strength and high toughness in FeCoCrNiCu HEAs come from lattice distortion strengthening and the more activable slip systems compared with Cu.These results accelerate the discovery of HEAs with excellent mechanical properties,and provide a valuable reference for the industrial application of HEAs.
基金financially supported by the National Natural Science Foundation of China(Nos.U1960203,51774074,51434004 and U1435205)the Fundamental Research Funds for the Central Universities(No.N180204015)+1 种基金the Shanxi Municipal Major Science&Technology Project(No.20181101014)the Fundamental Research Funds for the Central Universities(No.N172512033)。
文摘The effect of nitrogen on microstructural evolution and tensile properties of transformation-induced plasticity(TRIP)Fe_(50)Mn_(30)Co_(10)Cr_(10)HEAs was investigated.Nitrogen was fully introduced in solid solution by pressure-induced melting technique.Nitrogen addition turned the TRIP alloy to a twinning-induced plasticity(TWIP)alloy,and simultaneously improved the strength and elongation.For the nitrogen-doped HEA,the high yield strength is mainly resulted from the friction stress via interstitial strengthening effect,and the high ductility is originated from retained high strain-hardening capability via the successive onset of dislocation accumulation and deformation twinning.The strain-hardening behavior and microstructural evolution at specified strains were revealed.
基金the Korea University Grant for the eightth authorCreative Materials Discovery Program through the National Research Foundation of Korea(NRF)funded by Ministry of Science and ICT(NRF-2016M3D1A1023383)+1 种基金the Brain Korea 21 PLUS Project for Center for Creative Industrial MaterialsKorea Institute for Advancement of Technology(KIAT)grant funded by the Korea Government(MOTIE)(P0002019,The Competency Development Program for Industry Specialist)。
文摘We present a new class of metastable high-entropy alloys(HEAs),triggering deformation-induced martensitic transformation(DIMT)from face-centered-cubic(FCC)to body-centered-cubic(BCC),i.e.,BCC-DIMT.Through the ab-initio calculation based on 1 st order axial interaction model and combined with the Gibbs free energy calculation,the addition of Si is considered as a critical element which enables to reduce the intrinsic stacking fault energy(ISFE)in Si_xV_((9-x))Cr_(10)Mn_5 Fe_(46)Co_(30)(x=2,4,and 7 at.%)alloy system.The ISFE decreases from-30.4 to-35.5 mJ/m^(2)as the Si content increases from 2 to 7 at.%,which well corresponds to the reduced phase stability of FCC against HCP.The BCC-DIMT occurs in all the alloys via intermediate HCP martensite,and the HCP martensite provides nucleation sites of BCC martensite.Therefore,the transformation rate enhances as the Si content increases in an earlier deformation ra nge.However,the BCC-DIMT is also affected by the phase stability of FCC against BCC,and the stability is the highest at the Si content of 7 at.%.Thus,the 7Si alloy presents the moderate transformation rate in the later deformation range.Due to the well-controlled transformation rate and consequent strain-ha rdening rate,the 7Si alloy possesses the superior combination of strength and ductility beyond 1 GPa of tensile strength at room temperature.Our results suggest that the Si addition can be a favorable candidate in various metastable HEAs for the further property improvement.
基金supported by a grant from the Natural Science Foundation of Jiangsu Province (Grant No.BK20191036)the Foundation of Research Project of China (Grant No.JCKY 61420051911)。
文摘A novel Ni_(30)Cr_(25)Al_(15)Co_(15)Mo_(5)Ti_(5)Y_(5) high-entropy alloy(HEA)coating was irradiated to optimize its internal structure via laser after supersonic particle deposition(SPD).Owing to the high energy density of the laser and large temperature gradient,the crystallization process of the molecules and atoms in the coating was restrained and supercooling occurred.Experimental results showed that a considerable number of nano-crystal grains precipitated and amorphous structures were formed because of the random orientation of the crystals.The baseline of differential scanning calorimetry scans obtained for the coating started to shift at the Tg of 939.37℃ and a step was observed.Multiple dispersion peaks and lattice fringes indicated that the nucleation of the irradiated laser-induced topology optimized(LTO)coating was incomplete.The laser-induced topology optimizing treatment led to quasi-isotropy in the SPD coating.Furthermore,the LTO coating exhibited a residual stress of 18.4 MPa,stress-strain response,and fatigue limit of 265 MPa.Hence,the LTO coating exhibited higher performance than the unirradiated SPD coating.The Nyquist and Bode electrochemical impedance spectra of the LTO coating,including two relaxation processes,indicated that the corrosion process steadily recovered to the equilibrium state.This implies that the uniform oxidation passivation layer on the surface of the LTO coating insulated the material from the corrosive medium,protecting the substrate from further corrosion,thus enhancing the structural security of the material for use in super-intense laser facility applications.
文摘The intricate balance between reactor economics and safety necessitates the emergence of new and advanced nuclear systems and,very importantly,advanced materials,which can overcome current shortcomings and bring about more economic nuclear systems with designed-in inherent safety features.These advances will achieve greater safety and better nuclear reactor economics by reaching longer reactor lives with higher levels neutron irradiation,and by providing higher operation temperatures and resistance to more aggressive corrosive environments.This paper provides a review of the current state of research and development on innovative nuclear fuel materials design and development which have the potential of benefiting simultaneously reactor economics and safety.Our discussion focuses on three areas of research:Accident-tolerant Fuels(ATFs),Oxidation Dispersion Strengthened(ODS)steels and High Entropy Alloys(HEAs).The paper also gives a prospective description of future research activities on these materials.
文摘研究Co Cr Fe Ni Ti0.5高熵合金在熔融Na2SO4-25%Na Cl(质量分数)中的腐蚀行为,应用TGA获得其在650和750℃空气中的腐蚀动力学曲线;采用XRD、SEM(EDS)和EPMA对腐蚀产物的截面形貌及元素分布进行分析。结果表明:喷涂Na2SO4-25%Na Cl的Co Cr Fe Ni Ti0.5高熵合金在650和750℃时的腐蚀动力学曲线相似,呈"指数"增长规律;腐蚀截面由含较多Ti O2、部分Cr2O3以及微量尖晶石结构氧化物构成的氧化层与含孔隙且贫Cr和Ti、富Fe、Ni和Co的腐蚀影响区两部分构成;延长腐蚀时间或提高腐蚀温度后,氧化层破裂,与基体的结合程度显著下降,发生严重剥离甚至脱落。分析认为:Co Cr Fe Ni Ti0.5高熵合金在Na2SO4-25%Na Cl中的高温腐蚀归因于氧化、硫化以及氯化的综合作用。
基金the National Natural Science Foundation of China(Nos.21703149,51872193,21938006,and 5192500409)the National Key Research&Development Program of China(No.2020YFC1808401)+1 种基金Cutting-Edge Technology Basic Research Project of Jiangsu(No.BK20202012)the project supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘High-entropy materials are mainly composed of high-entropy alloys(HEAs)and their derivates.Among them,HEAs account for a big part.As a new kind of alloy,they are now arousing great interests because of their high mechanical strength,extraordinary fracture toughness,corrosion resistance compared with traditional alloys.These characteristics allow the use of HEAs in various fields,including mechanical manufacturing,heat-resistant,radiation-resistant,corrosion-resistant,wear-resistant coatings,energy storage,heterocatalysis,etc.In order to promote the extensive application of HEAs,it is of significance to realize their rational design and preparation.In this paper,a systematic review focusing on the rational design and fabrication of nanosized HEAs is given.The design principles of how to match different elements in HEAs and the premise for the formation of single-phase solid solution HEAs are first illustrated.Computation methods for the prediction of formation conditions and properties of HEAs are also in discussion.Then,a detailed description and comparison of the synthesis methods of HEAs and their derivate,as well as their growing mechanism under various synthetic environments is provided.The commonly used characterization methods for the detection of HEAs,along with the typical cases of the application of HEAs in industrial materials,energy storage materials and catalytic materials are also included.Finally,the challenges and perspectives in the design and synthesis of HEAs would be proposed.We hope this review will give guidance for the future development of HEAs materials.
