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 proper...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
To evaluate the potential of high entropy alloys for marine applications,a new high entropy alloy coating of AlCrFeNiW_(0.2)Ti_(0.5)was designed and produced on Q235 steel via laser cladding.The microstructure,microha...To evaluate the potential of high entropy alloys for marine applications,a new high entropy alloy coating of AlCrFeNiW_(0.2)Ti_(0.5)was designed and produced on Q235 steel via laser cladding.The microstructure,microhardness and tribological performances sliding against YG6 cemented carbide,GCr15 steel and Si_(3)N_(4)ceramic in seawater were studied in detail.The AlCrFeNiW_(0.2)Ti_(0.5)coating showed an anomalous’sunflower-like’morphology and consisted of BCC and ordered B2 phases.The microhardness was approximately 692.5 HV,which was 5 times higher than substrate.The coating showed more excellent tribological performances than Q235 steel and SUS304,a typical material used in seawater environment,sliding against all three coupled balls in seawater.Besides,the wear and friction of AlCrFeNiW_(0.2)Ti_(0.5)coating sliding against YG6 in seawater were most mild.The main reason was the generation of Mg(OH)_(2),CaCO_(3),metal oxides and hydroxides and the formation of protective tribo-film on the worn surface of AlCrFeNiW_(0.2)Ti_(0.5)coating in the process of reciprocated sliding.This would effectively hinder the direct contact between the worn surfaces of AlCrFeNiW_(0.2)Ti_(0.5)coating and YG6 ball,resulting in a decrease of friction coefficient and wear rate.Thus the YG6 was an ideal coupled material for AlCrFeNiW_(0.2)Ti_(0.5)coating in seawater,and the coating would become a promising wear-resisting material in ocean environment.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
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
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
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
A series of AlxCrFe2 Ni2 Mo0.2 alloy consisting of FCC+BCC phases have been designed,and their as-cast microstructures and mechanical properties were also investigated with x ranging from 0.6 to 0.9.It was found that ...A series of AlxCrFe2 Ni2 Mo0.2 alloy consisting of FCC+BCC phases have been designed,and their as-cast microstructures and mechanical properties were also investigated with x ranging from 0.6 to 0.9.It was found that with the addition of Al element,the solidified structures changed from dendrite to columnar crystal then back to dendrite again.Moreover,the increased amount of BCC phase resulted in finer and more uniform microstructures of FCC[FeCrNi(Mo)]and BCC(Al-Ni)phases.Tensile yield strength and hardness of alloys showed a similar increasing trend as the volume fraction of BCC phase increased.Both strain hardening rate and strain hardening exponent were calculated to assess the tensile properties of the alloys.It was shown that A10.6CrFe2 Ni2 Mo0.2 exhibited the most excellent and comprehensive mechanical properties due to its high work hardening ability and stable strain hardening rate.The product of strength and elongation of Al0.6CrFe2 Ni2 Mo0.2reached up to 38.6 GPa%,which was higher than most of the reported as-cast high-entropy alloys.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 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financially supported by the National Natural Science Foundation of China(Nos.51771041,51774065,51671044 and 51901116)the National Key Research and Development Program of China(No.2017YFA0403803)。
文摘To evaluate the potential of high entropy alloys for marine applications,a new high entropy alloy coating of AlCrFeNiW_(0.2)Ti_(0.5)was designed and produced on Q235 steel via laser cladding.The microstructure,microhardness and tribological performances sliding against YG6 cemented carbide,GCr15 steel and Si_(3)N_(4)ceramic in seawater were studied in detail.The AlCrFeNiW_(0.2)Ti_(0.5)coating showed an anomalous’sunflower-like’morphology and consisted of BCC and ordered B2 phases.The microhardness was approximately 692.5 HV,which was 5 times higher than substrate.The coating showed more excellent tribological performances than Q235 steel and SUS304,a typical material used in seawater environment,sliding against all three coupled balls in seawater.Besides,the wear and friction of AlCrFeNiW_(0.2)Ti_(0.5)coating sliding against YG6 in seawater were most mild.The main reason was the generation of Mg(OH)_(2),CaCO_(3),metal oxides and hydroxides and the formation of protective tribo-film on the worn surface of AlCrFeNiW_(0.2)Ti_(0.5)coating in the process of reciprocated sliding.This would effectively hinder the direct contact between the worn surfaces of AlCrFeNiW_(0.2)Ti_(0.5)coating and YG6 ball,resulting in a decrease of friction coefficient and wear rate.Thus the YG6 was an ideal coupled material for AlCrFeNiW_(0.2)Ti_(0.5)coating in seawater,and the coating would become a promising wear-resisting material in ocean environment.
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 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 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financially supported by the National Key Research and Development Program of China (No. 2017YFA0403803)National Natural Science Foundation of China (Nos. 51771041 and 51901116)。
文摘A series of AlxCrFe2 Ni2 Mo0.2 alloy consisting of FCC+BCC phases have been designed,and their as-cast microstructures and mechanical properties were also investigated with x ranging from 0.6 to 0.9.It was found that with the addition of Al element,the solidified structures changed from dendrite to columnar crystal then back to dendrite again.Moreover,the increased amount of BCC phase resulted in finer and more uniform microstructures of FCC[FeCrNi(Mo)]and BCC(Al-Ni)phases.Tensile yield strength and hardness of alloys showed a similar increasing trend as the volume fraction of BCC phase increased.Both strain hardening rate and strain hardening exponent were calculated to assess the tensile properties of the alloys.It was shown that A10.6CrFe2 Ni2 Mo0.2 exhibited the most excellent and comprehensive mechanical properties due to its high work hardening ability and stable strain hardening rate.The product of strength and elongation of Al0.6CrFe2 Ni2 Mo0.2reached up to 38.6 GPa%,which was higher than most of the reported as-cast high-entropy alloys.
基金supported by the National Natural Science Foundation of China(51671168 and 51871197)the National Key Research and Development Program of China(2017YFA0208200)the National 111 Project(B16042).
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.