High entropy alloys(HEAs)possess good mechanical properties and a wide range of industrial applications.In this paper,phase formation prediction theory,microstructure,properties and preparation methods of light-weight...High entropy alloys(HEAs)possess good mechanical properties and a wide range of industrial applications.In this paper,phase formation prediction theory,microstructure,properties and preparation methods of light-weight HEAs(LWHEAs)were reviewed.The problems and challenges faced by LWHEAs development were analyzed.The results showed that many aspects are still weak and require investigation for future advanced alloys,such as clarification of the role of entropy in phase formation and properties of HEAs,improved definition and different generations division of HEAs,close-packed hexagonal(HCP)phase structure prediction and corresponding alloy design and fabrication.Finally,some suggestions were presented in this paper including in-depth research on formation mechanism of multi-component alloy phase and strengthening of large-scale HEA preparation methods via technology compounding and 3D printing technology.Also,there is a need for more research on the in-situ preparation of HEA coatings and films,as well as developing LWHEAs with superior strength and elevated temperature resistance or ultra-low temperature resistance to meet the requirements of future engineering applications.展开更多
Nanograined(NG)materials often suffer from low thermal stability owing to the high volume fraction of grain boundaries(GBs).Herein,we investigate the possibility of utilizing local chemical ordering(LCO)for improving ...Nanograined(NG)materials often suffer from low thermal stability owing to the high volume fraction of grain boundaries(GBs).Herein,we investigate the possibility of utilizing local chemical ordering(LCO)for improving the thermal stability of NG FeCoNiCrMn highentropy alloys(HE As).NG HE As with two different grain sizes were considered.Tensile tests and creep test simulations were then performed to reveal the influence of LCO on the mechanical properties and thermal stability of NG HE As.After performing hybrid molecular dynamics and Monte Carlo simulations,Cr atoms were found to accumulate at GBs.By analyzing the atomic structure evolution during the deformation process,we found that the formation of LCO effectively stabilized the GBs and inhibited GB movement.In addition,dislocation nucleation from GBs and dislocation movement was also hindered.The inhibiting effect of LCO on GB movement and dislocation activity is more prominent than in the NG model with smaller grain sizes.The current simulation results suggest a possible strategy for enhancing the thermal stability of NG HEAs for service in a high-temperature environment.展开更多
Heavy consumption of fossil fuels has raised concerns over the climate change and energy security in the past decades.In this review,hydrogen economy,as a clean and sustainable energy system,is receiving great attenti...Heavy consumption of fossil fuels has raised concerns over the climate change and energy security in the past decades.In this review,hydrogen economy,as a clean and sustainable energy system,is receiving great attention.The success of future hydrogen economy strongly depends on the storage of renewable energy in hydrogen and hydrogen-rich chemicals through electrolyzers and conversion back to electricity via fuel cells.Electrocatalysts are at the heart of these critical technologies and great efforts have been devoted to preparing highly efficient nanomaterials.High-entropy alloys(HEAs),with their unique structural characteristics and intrinsic properties,have evolved to be one of the most popular catalysts for energy-related applications,especially those associated with hydrogen economy.Herein,recent advances regarding HEAs-based hydrogen economy are comprehensively reviewed.Attention is paid to the discussion of emerged HEAs as a new class of materials in hydrogen energy cycle,carbon-based hydrogen energy cycle,and nitrogen-based hydrogen energy cycle,covering the sustainable electrochemical synthesis of hydrogen and hydrogen-rich fuels and their direct application in fuel cells.Based on this overview,the challenges and promising directions are proposed to guide the development of HEAs research,aiming to achieve significant progress for further accessing hydrogen economy.展开更多
High-entropy alloys and ceramics containing at least five principal elements have recently received high attention for various mechanical and functional applications.The application of severe plastic deformation(SPD),...High-entropy alloys and ceramics containing at least five principal elements have recently received high attention for various mechanical and functional applications.The application of severe plastic deformation(SPD),particularly the high-pressure torsion method,combined with the CALPHAD(calculation of phase diagram) and first-principles calculations resulted in the development of numerous superfunctional high-entropy materials with superior properties compared to the normal functions of engineering materials.This article reviews the recent advances in the application of SPD to developing superfunctional high-entropy materials.These superfunctional properties include(ⅰ) ultrahigh hardness levels comparable to the hardness of ceramics in high-entropy alloys,(ⅱ) high yield strength and good hydrogen embrittlement resistance in high-entropy alloys;(ⅲ) high strength,low elastic modulus,and high biocompatibility in high-entropy alloys,(ⅳ) fast and reversible hydrogen storage in high-entropy hydrides,(ⅴ) photovoltaic performance and photocurrent generation on high-entropy semiconductors,(ⅵ) photocatalytic oxygen and hydrogen production from water splitting on high-entropy oxides and oxynitrides,and(ⅶ)CO_(2) photoreduction on high-entropy ceramics.These findings introduce SPD as not only a processing tool to improve the properties of existing high-entropy materials but also as a synthesis tool to produce novel high-entropy materials with superior properties compared with conventional engineering materials.展开更多
Face-centered-cubic high-entropy alloys have excellent ductility and great potential for engineering applications.However,few studies have reported on the wear behavior under different loads.This study aimed to invest...Face-centered-cubic high-entropy alloys have excellent ductility and great potential for engineering applications.However,few studies have reported on the wear behavior under different loads.This study aimed to investigate the tribological behavior of CoCrFeNi highentropy alloy under different loads.The wear rate increased with the load,and the main wear behavior was abrasive wear.The cross-sectional microstructure of worn surface consisted of oxide,nanocrystalline,nanolaminated,and deformation layers.Under the higher loads,the deformation mechanism included dislocation slip and deformation twins,and shear bands also appeared.It was unexpectedly found that the wear rate increased sharply under high load,which was attributed to the formation of shear bands and microcracks in the nanocrystalline layer.The results successfully revealed the great influence of microstructure evolution on the wear rate,providing theoretical guidance for improving the wear resistance of face-centered-cubic high-entropy alloys in the future.展开更多
High entropy alloys(HEAs) are of great interest in the community of materials science and engineering due to their unique phase structure. They are constructed with five or more principal alloying elements in equimola...High entropy alloys(HEAs) are of great interest in the community of materials science and engineering due to their unique phase structure. They are constructed with five or more principal alloying elements in equimolar or near-equimolar ratio. Therefore, HEAs can derive their performance from multiple principal elements rather than a single element. In this work, solid-state cold spraying(CS) was applied for the first time to produce FeCoNiCrMn HEA coating. The experimental results confirm that CS can be used to produce a thick HEA coating with low porosity. As a low-temperature deposition process, CS completely retained the HEA phase structure in the coating without any phase transformation. The characterization also reveals that the grains in the CSed HEA coating had experienced significant refinement as compared to those in the as-received HEA powder due the occurrence of dynamic recrystallization at the highly deformed interparticle region. Due to the increased dislocation density and grain boundaries,CSed HEA coating was much harder than the as-received powder. The tribological study shows that the CSed FeCoNiCrMn HEA coating resulted in lower wear rate than laser cladded HEA coatings.展开更多
Various high entropy alloys(HEAs)with improved mechanical properties were developed by reducing the phase stability and then promote the phase transformation.The promotion of deformation-induced ma rtensitic transform...Various high entropy alloys(HEAs)with improved mechanical properties were developed by reducing the phase stability and then promote the phase transformation.The promotion of deformation-induced ma rtensitic transformation from face-centered cubic(fcc)to hexagonal close-packed(hcp)mostly focuses on overcoming the trade-off of strength-ductility of HEAs at room temperature.However,the hcp phase is brittle at cryogenic-temperature,and thus the enhancement of cryogenic ductility of these HEAs still remains a challenge.Here,we present a concept to toughening Fe50Mn30Co10Cr10 HEAs at cryogenictemperature via retarding phase transformation.The retarded but more persistent phase transformation at high strain level was realized via tailoring the grain size.To further verify the effect of phase transformation rate on ductility of HEAs,the mechanical properties of Fe40Mn40Co10Cr10 HEAs with higher stacking fault energy were tested at room and cryogenic temperature,respectively.The present study sheds light on developing high perfo rmance HEAs,especially for alloys with brittle phase transformation products.展开更多
High-entropy alloys(HEAs)have attracted widespread attention due to their excellent mechanical properties.However,their functional properties arising from the supersaturated solid solution state can be improved.Advanc...High-entropy alloys(HEAs)have attracted widespread attention due to their excellent mechanical properties.However,their functional properties arising from the supersaturated solid solution state can be improved.Advanced oxidation processes(AOPs)are considered to be an effective method for decomposing organic pollutants,and HEAs are proposed as effective candidates for AOP catalysts.Currently,several HEAs used for organic pollutant degradation are prepared through mechanical alloying.In this work,FeAlCoNi and FeAlCoNiB Fenton-like catalysts were prepared by single roll melt spinning and subsequent ball milling techniques.We found that the FeAlCoNiB HEA exhibits highly efficient degradation for p-nitrophenol(p-NP).The degradation efficiency of FeAlCoNiB is 120 times higher than that of FeAlCoNi,which confirms that boron functions effectively during the degradation process.FeAlCoNiB has a better degradation efficiency than pure iron powder and a degradation efficiency comparable to that of the amorphous Fe_(78)Si_(11)B_(11) alloy.Additionally,the degradation efficiency of FeAlCoNiB_(X) increases(k values from 0.13 to 0.55 min^(−1))when the boron content increases from an X value of 0.25 to 1.25.We speculate that Fe_(2)B favors the degradation process and promotes zero-valent iron to decompose organic pollutants through a galvanic cell effect.Possible p-NP degradation pathways are proposed after LC–MS analysis.This study provides a new series of HEA Fenton-like catalysts,which have the potential to be prepared into bulk devices for industrial applications.展开更多
基金funded by Open Research Fund of State Key Laboratory of Precision Manufacturing for Extreme Service Performance, Central South University, China (No. Kfkt2020-01)Hunan Provincial Natural Science Foundation, China (No. 2021JJ40774)the Project of State Key Laboratory of High Performance Complex Manufacturing, Central South University, China (No. ZZYJKT2021-01)。
基金Funded by the National Natural Science Foundation of China(No.51405510)。
文摘High entropy alloys(HEAs)possess good mechanical properties and a wide range of industrial applications.In this paper,phase formation prediction theory,microstructure,properties and preparation methods of light-weight HEAs(LWHEAs)were reviewed.The problems and challenges faced by LWHEAs development were analyzed.The results showed that many aspects are still weak and require investigation for future advanced alloys,such as clarification of the role of entropy in phase formation and properties of HEAs,improved definition and different generations division of HEAs,close-packed hexagonal(HCP)phase structure prediction and corresponding alloy design and fabrication.Finally,some suggestions were presented in this paper including in-depth research on formation mechanism of multi-component alloy phase and strengthening of large-scale HEA preparation methods via technology compounding and 3D printing technology.Also,there is a need for more research on the in-situ preparation of HEA coatings and films,as well as developing LWHEAs with superior strength and elevated temperature resistance or ultra-low temperature resistance to meet the requirements of future engineering applications.
基金financially supported by the National Natural Science Foundation of China(Nos.52101019,52071023,51901013,52122408)the financial support from the Fundamental Research Funds for theCentral Universities(University of Science and Technology Beijing,Nos.FRF-TP-2021-04C1,06500135)supported by USTB MatCom of Beijing Advanced Innovation Center for Materials Genome Engineering。
文摘Nanograined(NG)materials often suffer from low thermal stability owing to the high volume fraction of grain boundaries(GBs).Herein,we investigate the possibility of utilizing local chemical ordering(LCO)for improving the thermal stability of NG FeCoNiCrMn highentropy alloys(HE As).NG HE As with two different grain sizes were considered.Tensile tests and creep test simulations were then performed to reveal the influence of LCO on the mechanical properties and thermal stability of NG HE As.After performing hybrid molecular dynamics and Monte Carlo simulations,Cr atoms were found to accumulate at GBs.By analyzing the atomic structure evolution during the deformation process,we found that the formation of LCO effectively stabilized the GBs and inhibited GB movement.In addition,dislocation nucleation from GBs and dislocation movement was also hindered.The inhibiting effect of LCO on GB movement and dislocation activity is more prominent than in the NG model with smaller grain sizes.The current simulation results suggest a possible strategy for enhancing the thermal stability of NG HEAs for service in a high-temperature environment.
基金financially supported by the National Natural Science Foundation of China (Nos.U21A20332,52103226,52202275,52203314 and 12204253)the Distinguished Young Scholars Fund of Jiangsu Province (No.BK20220061)the Fellowship of China Postdoctoral Science Foundation (No.2021M702382)。
文摘Heavy consumption of fossil fuels has raised concerns over the climate change and energy security in the past decades.In this review,hydrogen economy,as a clean and sustainable energy system,is receiving great attention.The success of future hydrogen economy strongly depends on the storage of renewable energy in hydrogen and hydrogen-rich chemicals through electrolyzers and conversion back to electricity via fuel cells.Electrocatalysts are at the heart of these critical technologies and great efforts have been devoted to preparing highly efficient nanomaterials.High-entropy alloys(HEAs),with their unique structural characteristics and intrinsic properties,have evolved to be one of the most popular catalysts for energy-related applications,especially those associated with hydrogen economy.Herein,recent advances regarding HEAs-based hydrogen economy are comprehensively reviewed.Attention is paid to the discussion of emerged HEAs as a new class of materials in hydrogen energy cycle,carbon-based hydrogen energy cycle,and nitrogen-based hydrogen energy cycle,covering the sustainable electrochemical synthesis of hydrogen and hydrogen-rich fuels and their direct application in fuel cells.Based on this overview,the challenges and promising directions are proposed to guide the development of HEAs research,aiming to achieve significant progress for further accessing hydrogen economy.
基金the Hosokawa Powder Technology Foundation of Japan for a grantsupported by the MEXT, Japan through Grants-in-Aid for Scientific Research on Innovative Areas (Nos. JP19H05176 and JP21H00150)in part by the MEXT, Japan through Grant-in-Aid for Challenging Research Exploratory (No. JP22K18737)。
文摘High-entropy alloys and ceramics containing at least five principal elements have recently received high attention for various mechanical and functional applications.The application of severe plastic deformation(SPD),particularly the high-pressure torsion method,combined with the CALPHAD(calculation of phase diagram) and first-principles calculations resulted in the development of numerous superfunctional high-entropy materials with superior properties compared to the normal functions of engineering materials.This article reviews the recent advances in the application of SPD to developing superfunctional high-entropy materials.These superfunctional properties include(ⅰ) ultrahigh hardness levels comparable to the hardness of ceramics in high-entropy alloys,(ⅱ) high yield strength and good hydrogen embrittlement resistance in high-entropy alloys;(ⅲ) high strength,low elastic modulus,and high biocompatibility in high-entropy alloys,(ⅳ) fast and reversible hydrogen storage in high-entropy hydrides,(ⅴ) photovoltaic performance and photocurrent generation on high-entropy semiconductors,(ⅵ) photocatalytic oxygen and hydrogen production from water splitting on high-entropy oxides and oxynitrides,and(ⅶ)CO_(2) photoreduction on high-entropy ceramics.These findings introduce SPD as not only a processing tool to improve the properties of existing high-entropy materials but also as a synthesis tool to produce novel high-entropy materials with superior properties compared with conventional engineering materials.
基金financially supported by the National Key Research and Development Program of China (Nos.2019YFA0209901 and 2018YFA0702901)the National Natural Science Foundation of China (No.U20A20278)+1 种基金Liao Ning Revitalization Talents Program (No.XLYC1807047)Major Special Project of“Scientific and Technological Innovation 2025”in Ningbo (No.2019B10086)。
文摘Face-centered-cubic high-entropy alloys have excellent ductility and great potential for engineering applications.However,few studies have reported on the wear behavior under different loads.This study aimed to investigate the tribological behavior of CoCrFeNi highentropy alloy under different loads.The wear rate increased with the load,and the main wear behavior was abrasive wear.The cross-sectional microstructure of worn surface consisted of oxide,nanocrystalline,nanolaminated,and deformation layers.Under the higher loads,the deformation mechanism included dislocation slip and deformation twins,and shear bands also appeared.It was unexpectedly found that the wear rate increased sharply under high load,which was attributed to the formation of shear bands and microcracks in the nanocrystalline layer.The results successfully revealed the great influence of microstructure evolution on the wear rate,providing theoretical guidance for improving the wear resistance of face-centered-cubic high-entropy alloys in the future.
基金the financial support from Irish Research Council Project(GOIPD-2017-912)European Space Agency(4000112844/14/NL/FE)
文摘High entropy alloys(HEAs) are of great interest in the community of materials science and engineering due to their unique phase structure. They are constructed with five or more principal alloying elements in equimolar or near-equimolar ratio. Therefore, HEAs can derive their performance from multiple principal elements rather than a single element. In this work, solid-state cold spraying(CS) was applied for the first time to produce FeCoNiCrMn HEA coating. The experimental results confirm that CS can be used to produce a thick HEA coating with low porosity. As a low-temperature deposition process, CS completely retained the HEA phase structure in the coating without any phase transformation. The characterization also reveals that the grains in the CSed HEA coating had experienced significant refinement as compared to those in the as-received HEA powder due the occurrence of dynamic recrystallization at the highly deformed interparticle region. Due to the increased dislocation density and grain boundaries,CSed HEA coating was much harder than the as-received powder. The tribological study shows that the CSed FeCoNiCrMn HEA coating resulted in lower wear rate than laser cladded HEA coatings.
基金financially supported by the National Natural Science Foundation of China(Nos.U1832203,11975202,U1704159 and 51701183)the China Postdoctoral Science Foundation(No.2018M630834)。
文摘Various high entropy alloys(HEAs)with improved mechanical properties were developed by reducing the phase stability and then promote the phase transformation.The promotion of deformation-induced ma rtensitic transformation from face-centered cubic(fcc)to hexagonal close-packed(hcp)mostly focuses on overcoming the trade-off of strength-ductility of HEAs at room temperature.However,the hcp phase is brittle at cryogenic-temperature,and thus the enhancement of cryogenic ductility of these HEAs still remains a challenge.Here,we present a concept to toughening Fe50Mn30Co10Cr10 HEAs at cryogenictemperature via retarding phase transformation.The retarded but more persistent phase transformation at high strain level was realized via tailoring the grain size.To further verify the effect of phase transformation rate on ductility of HEAs,the mechanical properties of Fe40Mn40Co10Cr10 HEAs with higher stacking fault energy were tested at room and cryogenic temperature,respectively.The present study sheds light on developing high perfo rmance HEAs,especially for alloys with brittle phase transformation products.
基金financially supported by the Shenzhen Science and Technology Research Grant(No.20200812092703001).
文摘High-entropy alloys(HEAs)have attracted widespread attention due to their excellent mechanical properties.However,their functional properties arising from the supersaturated solid solution state can be improved.Advanced oxidation processes(AOPs)are considered to be an effective method for decomposing organic pollutants,and HEAs are proposed as effective candidates for AOP catalysts.Currently,several HEAs used for organic pollutant degradation are prepared through mechanical alloying.In this work,FeAlCoNi and FeAlCoNiB Fenton-like catalysts were prepared by single roll melt spinning and subsequent ball milling techniques.We found that the FeAlCoNiB HEA exhibits highly efficient degradation for p-nitrophenol(p-NP).The degradation efficiency of FeAlCoNiB is 120 times higher than that of FeAlCoNi,which confirms that boron functions effectively during the degradation process.FeAlCoNiB has a better degradation efficiency than pure iron powder and a degradation efficiency comparable to that of the amorphous Fe_(78)Si_(11)B_(11) alloy.Additionally,the degradation efficiency of FeAlCoNiB_(X) increases(k values from 0.13 to 0.55 min^(−1))when the boron content increases from an X value of 0.25 to 1.25.We speculate that Fe_(2)B favors the degradation process and promotes zero-valent iron to decompose organic pollutants through a galvanic cell effect.Possible p-NP degradation pathways are proposed after LC–MS analysis.This study provides a new series of HEA Fenton-like catalysts,which have the potential to be prepared into bulk devices for industrial applications.
