The equiatomic and equimass TiHfMo,TiHfMoNb and TiHfMoNbZr alloys were prepared,and their microstructure,mechanical properties and bio-corrosion behaviors were systematically investigated.The results demonstrated that...The equiatomic and equimass TiHfMo,TiHfMoNb and TiHfMoNbZr alloys were prepared,and their microstructure,mechanical properties and bio-corrosion behaviors were systematically investigated.The results demonstrated that all the multi-principal element alloys(MPEAs)had a single BCC phase structure without any intermetallic compounds.Moreover,the Young’s moduli and hardness of the MPEAs were respectively within the range of 95−126 GPa and 5.5−6.4 GPa,respectively.In simulated body fluids,the MPEAs had excellent resistance to chloride ion attack due to the fact that the passive films consisted of multiple oxides and the surface possessed large contact angles.Compared with CP-Ti and Ti6Al4V alloy,equiatomic TiHfMo and TiHfMoNb alloys had a desirable combination of pitting and corrosion resistance,wettability,and wear resistance,and can be utilized as potential candidates for biomedical metallic implants.展开更多
A novel approach for fabricating multi-principal element alloys with adjustable phase configurations and mechanical properties was developed using laser-aided additive manufacturing(LAAM),combining FCC-structured(face...A novel approach for fabricating multi-principal element alloys with adjustable phase configurations and mechanical properties was developed using laser-aided additive manufacturing(LAAM),combining FCC-structured(face-centered cubic)CoCrNi and BCC-structured(body-centered cubic)CoCrNiAl0.6TiFe feedstocks.During fabrication,CoCrNi powders and CoCrNiAl0.6TiFe powders were simultaneously fed into the melt pool at individually adjustable rates,allowing for controlled phase transitions.The resulting phase evolution demonstrated a gradual transition from a single FCC structure CoCrNi(A10.6TiFe)x(x=0,0.1,0.2,0.3)to a dual FCCB2 structure CoCrNi(Al0.6TiFe)x(x=0.4,0.5)as the proportion of BCC-structured powders increased.The B2 phase,enriched in Ti and Al due to their larger atomic radii and negative segregation enthalpy,precipitated around the FCC matrix,with volume fractions of 0.5%and 5.7%for CoCrNi(A10.6TiFe)0.4 and CoCrNi(A10.6TiFe)0.5,respectively.This phase transition resulted in significant mechanical enhancements.Yield and ultimate tensile strengths increased from 486.0 and 781.2 MPa(CoCrNi)to 887.2 and 1165.2 MPa(CoCrNi(A10.6TiFe)0.5).Dislocation-mediated hardening prevailed in single-phase FCC alloys,exhibiting a characteristic dislocation density of 2.5×10^(15)m^(-2)for CoCrNi(A10.6TiFe)0.3 alloy.Once the B2 phase precipitated,precipitation strengthening became dominant,as observed in transmission electron microscopy(TEM),where dislocations accumulated around B2 precipitates.This study presents an innovative alloy fabrication strategy that enables precise tuning of FCC-BCC dualphase structures,facilitating the direct fabrication of components with spatially customized properties.These findings provide valuable insights for developing multiprincipal element alloys with heterogeneous microstructures for advanced engineering applications.展开更多
To improve strength and ductility of Ti-Zr-Nb lightweight refractory multi-principal element alloys(LRMPEAs)simultaneously,which is difficult for traditional solution strengthening and second-phase/precipitate strengt...To improve strength and ductility of Ti-Zr-Nb lightweight refractory multi-principal element alloys(LRMPEAs)simultaneously,which is difficult for traditional solution strengthening and second-phase/precipitate strengthening,the compositional inhomogeneity in TiZrNb ternary equimolar LRMPEAs with a single-phased body-centered cubic structure is stimulated and tailored by doping V element.When V is introduced,compositional inhomogeneity shows as the segregation of V and Zr elements form.As the value of x for TiZrNbV_(x)LRMPEAs increases from 0.3 to 0.6,the mild compositional fluctuation develops to the spinodal decomposition structured three-dimensional framework with a periodicity of~5 nm.Then the dislocations in TiZrNbV_(0.6)LRMPEA are compactly pinned,a remarkable strengthening effect(~120 MPa)while the Frank-Read sources for dislocation multiplication and cross-slip are stimulated.Thus,an optimal combination of strength and ductility including the yield strength of 883 MPa and the fracture elongation of 26.6%is achieved in TiZrNbV0.6 LRMPEA.This work provides a useful method to enhance the strength of Ti-Zr-Nb LRMPEAs without sacrificing the ductility.This way is expected to be effective for other multi-principal element alloys,including high-entropy alloys and medium-entropy alloys.展开更多
This research focused on the influences of Cr element doping on the microstructure,thermal stability,microhardness,soft magnetic,and anti-corrosion properties of FeCoNiSiB multi-principal element alloys.The as-receive...This research focused on the influences of Cr element doping on the microstructure,thermal stability,microhardness,soft magnetic,and anti-corrosion properties of FeCoNiSiB multi-principal element alloys.The as-received Fe-Co-Ni-Si-B-Cr alloy ribbons made by melt-spinning technique could maintain amorphous nature.The glass-transition temperature and onset crystallization temperature become lower with the addition of Cr,and the highest values are 782.0 K and 821.5 K,respectively.When the Cr content reaches 3at.%,the alloy owns the best soft magnetic performance with the saturation magnetic flux density of~0.578 T and coercivity of~5.5 A·m^(-1)among the studied melt-spun ribbon samples.The microhardness of all alloy ribbons reduces with an increasing Cr content on the whole,and the values are 810 HV_(0.5) or above.The corrosion behavior of these multi-principal element amorphous alloys containing Cr was also investigated in detail.As the Cr content increases,the corrosion resistance becomes superior and the specimens present the obvious passive regions in 3.5wt.%NaCl solution.The glassy ribbons with 8at.%Cr have the highest self-corrosion potential of-0.340 V and pitting potential of 0.288 V as well as the widest passive region of 0.628 V.Besides,the corroded micrographs of alloy ribbons immersed in corrosive environment lasting 100 h are also presented,which further confirms the above-mentioned experimental results.This research deepens the understanding about the role of Cr element in the microstructure and a series of physical and chemical properties of Fe-Co-Ni-Si-B-Cr multi-principal element amorphous alloys.展开更多
Oxygen-induced microstructural evolution critically governs the long-term reliability of refractory multi-principal element alloys(RMPEAs)in extreme environments,where oxygen ingress during prolonged high-temperature ...Oxygen-induced microstructural evolution critically governs the long-term reliability of refractory multi-principal element alloys(RMPEAs)in extreme environments,where oxygen ingress during prolonged high-temperature service can drastically alter micro structural stability and mechanical performance,yet its atomic-scale mechanisms remain poorly understood.Here,oxygen's dual role in NbZrTi-based RMPEAs is systematically revealed through aging experiments at 650℃for 48and 168 h,combined with multiscale characterization.High-oxygen alloys(3 at.%O)exhibited multi-phase precipitation,including Zr-O-enriched hexagonal close-packed and dual body-centered cubic phases(Zr+Ti-O-rich and Nb+Ti-rich),governed by oxygen redistribution and thermodynamic stabilization.Contrary to conventional precipitation hardening,oxygen segregation gradients at the grain boundaries induced lattice distortion mitigation in the matrix,leading to a twostage age-softening behavior:rapid initial hardness reduction(20%within 48 h)followed by a plateau regime.The interplay between oxygen-mediated phase separation and concentration-dependent solute partitioning highlights the delicate balance required to optimize RMPEAs for high-temperature applications.These findings establish oxygen concentration thresholds and grain boundary engineering as critical design parameters for RMPEAs,enabling simultaneous optimization of radiation resistance and century-scale stability in next-generation nuclear reactor structure materials.展开更多
Tantalum(Ta)alloys have been widely utilized in rocket,air-breathing engines,and airframe applications.However,traditional Ta alloys suffer from insufficient strength at ultra-high temperature,making it challenging to...Tantalum(Ta)alloys have been widely utilized in rocket,air-breathing engines,and airframe applications.However,traditional Ta alloys suffer from insufficient strength at ultra-high temperature,making it challenging to satisfy the design requirements for next-generation aerospace equipment.We report a novel strategy to design Ta alloys with superior mechanical properties by integrating the multi-principal element concept with compositionally complex carbides.By introducing multiple refractory elements and C,the resultant alloys displayed a thermally stable microstructure consisting of two phases.With the increasing C contents,the microstructure evolved from hypoeutectic to eutectic and then to hypereutectic.These varying microstructural characteristics influenced crack blunting and dislocation accumulation behaviors,leading to different softening resistance at 1600℃and plasticity at room temperature.Benefiting from the strengthening effects of solid solution and compositionally complex carbides,these alloys exhibited a high strength of~600 MPa at 1600℃,significantly superior than that of traditional Ta alloys.展开更多
The urgent need to overcome the strength-ductility trade-off of nickel-aluminum bronze(NAB)in deep-sea engineering motivates the design of a Cu-bearing multi-principal element alloy(MPEA),Cu_(35)Ni_(35)Co_(30),via mag...The urgent need to overcome the strength-ductility trade-off of nickel-aluminum bronze(NAB)in deep-sea engineering motivates the design of a Cu-bearing multi-principal element alloy(MPEA),Cu_(35)Ni_(35)Co_(30),via magnetic levitation melting.The as-cast Cu_(35)Ni_(35)Co_(30) MPEA exhibits a dual face-centered cubic(FCC)structure with superior mechanical properties(yield strength:~503 MPa,ultimate tensile strength:~686 MPa,total elongation:~11.0%)over its counterparts fabricated by vacuum arc melting.A single-phase FCC structure was obtained by homogenizing at 1030℃ for 15 h.Cold rolling and postdeformation annealing(PDA)were used to construct heterogeneous grain structures,which were achieved in PDA-treated samples at 1030℃ for 45 s(PDA-1030-45s)and 60 s(PDA-1030-60s).The PDA-1030-45s sample,composed of nano-sized recrystallized grains and residual deformed grains(RDGs),showed the best strength among the PDA-treated samples(a yield strength of~864 MPa,an ultimate tensile strength of~959 MPa,and a total elongation of~13.4%).The PDA-1030-60s sample with micro-sized recrystallized grains and RDGs exhibits an excellent combination of strength and ductility,showing a yield strength of~560 MPa,an ultimate tensile strength of~761 MPa,and a total elongation of~32.9%.These mechanical strengths are superior to those reported by NAB.The dominant strengthening mechanisms of the PDA-1030-45s and the PDA-1030-60s samples are dislocation strengthening and hetero-deformation-induced strengthening,respectively.展开更多
In order to understand the influence of ordering behaviors on the thermodynamic and mechanical properties of multi-principal element alloys(MPEAs),the temperature-dependent thermodynamic properties and mechanical prop...In order to understand the influence of ordering behaviors on the thermodynamic and mechanical properties of multi-principal element alloys(MPEAs),the temperature-dependent thermodynamic properties and mechanical properties of FCC_CoNiV MPEAs were comparatively predicted,where the alloys were modeled as the ordered configurations based on our previously predicted site occupying fractions(SOFs),as well as disordered configuration based on traditional special quasi-random structure(SQS).The ordering behavior not only improves the thermodynamic stability of the structure,but also increases the elastic properties and Vickers hardness.For example,at 973 K,the predicted bulk modulus(B),shear modulus(G),Young’s modulus(E),and Vickers hardness(HV)of FCC_CoNiV MPEA based on SOFs configuration are 187.82,79.03,207.93,and 7.58 GPa,respectively,while the corresponded data are 172.58,57.45,155.14,and 4.64 GPa for the SQS configuration,respectively.The Vickers hardness predicted based on SOFs agrees considerably well with the available experimental data,while it is underestimated obviously based on SQS.展开更多
Chemical short-range order(SRO)in multi-principal element alloys(MPEAs)and its unprecedented benefits on materials performance have been elucidated in recent experimental observations.Hence,manipulating the fine struc...Chemical short-range order(SRO)in multi-principal element alloys(MPEAs)and its unprecedented benefits on materials performance have been elucidated in recent experimental observations.Hence,manipulating the fine structure of SRO and its interaction with other coexisting SROs or defects becomes increasingly crucial for MPEAs design.Here,using TiZrNb,TiZrVNb,and TiZrV as the model systems,SRO and its interaction with surrounding environment,as well as its effects on mechanical properties are comprehensively explored through density functional theory-based Monte Carlo simulations.We find that both TiZrNb and TiZrVNb exhibit Ti-Zr SRO and Nb-Nb short-range clustering(SRC),whereas in TiZrV,Zr-V SRO occurs in addition to Ti-Zr SRO.SRO largely increases the modulus and the unstable stacking fault energy(USFE).At the electronic scale,SRO is found accompanied with a deeper pseudo-energy gap at Fermi level,and with a covalent bonding character between the metallic atoms.Due to the SRO-oxygen attraction,oxygen centered and Ti/Zr enriched octahedron coined as(O,2Ti,4Zr)-octahedron populates in TiZrNb-O and TiZrV-O.In TiZrVNb-O,there mainly exist two types of octahedral:(O,2Ti,4Zr)and(O,3Ti,3Zr).Quantitatively,forming these(O,Ti,Zr)-octahedra,the modulus and USFE of MPEAs are further increased compared to the individual contribution from SRO or oxygen,but the improvement does not surpass the sum of the increments induced by the two individuals.The present findings deepen the understanding of SROs and their interactions with surrounding environments,pushing forward the effective utilization of SRO in materials design.展开更多
Ti-Zr-Nb refractory multi-principal element alloys(RMPEAs)have attracted increased attention due to their excellent mechanical properties.In this study,(TiZr)_(80-x)Nb_(20)Mo_(x)(x=0,5 and 10)alloys were designed,and ...Ti-Zr-Nb refractory multi-principal element alloys(RMPEAs)have attracted increased attention due to their excellent mechanical properties.In this study,(TiZr)_(80-x)Nb_(20)Mo_(x)(x=0,5 and 10)alloys were designed,and the intrinsic conflicts between strength and ductility were overcome via composition optimization and recrystallization.The causes of the superior strength-ductility synergy were investigated in terms of their deformation mechanism and dislocation behavior.The results show that the strength improvement can be attributed to the deformation mechanism transition caused by local chemical fluctuations and lattice distortion.Specifically,the slip band widths decrease after Mo addition,and the measured slip traces in the fracture samples are associated with high-order{112}and{123}slip planes.Furthermore,the grain refinement achieved via recrystallization promotes multi-slip system activation and shortens the slip-band spacing,which reduces the stress concentration and inhibits crack source formation,thereby allowing the alloy to ensure sufficient ductility.Consequently,the Ti_(35)Zr_(35)Nb_(20)Mo_(10)alloy annealed at 900℃ exhibits high yield strength and elongation.These findings provide a new strategy for designing high-strength RMPEAs and addressing room-temperature brittleness.展开更多
Designing alloys capable of withstanding irradiation is a crucial aspect of developing materials for nuclear reactors and aerospace applications.Local chemical order(LCO)has recently been recognized as a new microstru...Designing alloys capable of withstanding irradiation is a crucial aspect of developing materials for nuclear reactors and aerospace applications.Local chemical order(LCO)has recently been recognized as a new microstructural parameter to leverage,and its effect on the mechanical properties of body-centered cubic(BCC)multi-principal element alloys(MPEAs)has attracted much attention.However,the impact of LCO on the dynamic evolution of irradiation-induced defects in BCC MPEAs remains much less explored.In this study,we engineered varying degrees of LCO and local lattice distortion in NbZrTi BCC MPEAs by alloying them with different concentrations of interstitial oxygen solutes,and analyzed their effects on the evolution of radiation-induced defects during He irradiation at 673 K to 873 K,with a fluence of 5×10^(16) ions/cm^(2) and a peak dose of approximately 1 DPA.Using first-principles calculations and atomic-scale analysis of microstructures and chemical elements,we discovered that interstitial oxygen atoms enhance LCO and increase local lattice distortion.These heterogeneities increase the formation energy,and localize the diffusion,of vacancies,hence effectively reducing the transport of aggregating helium that causes bubble swelling.The initiation and growth of dislocation loops and precipitates are depressed as well.The manipulation of irradiation defects in BCC MPEAs,through orchestrating interstitial oxygen solutes and the LCO they provoke,adds a practical strategy for designing advanced alloys for nuclear applications.展开更多
Achieving high yield strength and ductility in alloys remains a significant challenge in structural materials.In this study,combined nanoprecipitation and gradient grain structure were introduced into a Co-Cr-Ni-based...Achieving high yield strength and ductility in alloys remains a significant challenge in structural materials.In this study,combined nanoprecipitation and gradient grain structure were introduced into a Co-Cr-Ni-based multi-principal element alloy(MPEA)using surface mechanical attrition treatment(SMAT).The multi-scale composite structure,featuring grain sizes refined from∼43.6μm to∼24.3 nm at the topmost surface and high-density L1_(2)nanoprecipitates within the grains,results in a substantial tensile strength of 1733 MPa and a well-maintained ductility of∼23%.The alloy with low local stacking fault energy provides sufficient flow stress to reach the critical value for twinning,a phenomenon rarely observed in MPEAs with high-density L1_(2)nanoprecipitates under quasi-static tensile conditions.The formation of nanotwins further facilitates additional strain hardening,enhancing mechanical performance at ultrahigh strength levels.This work offers significant insights into the deformation behavior of gradient-structured materials with high-density nanoprecipitates.展开更多
To meet the increasing demand for continuously enhancing engineering performance and energy efficiency in a variety of aerospace and energy applications,structural materials with high strength at ultra-high temperatur...To meet the increasing demand for continuously enhancing engineering performance and energy efficiency in a variety of aerospace and energy applications,structural materials with high strength at ultra-high temperatures are urgently required.In the past decade,refractory multi-principal element alloys(RMPEAs),particularly those containing elements with high melting temperatures(T_(m))such as W and Ta(hereafter denoted as WTa-RMPEAs),have garnered extensive interest due to their exceptional strengths and thermally stability at high temperatures.Characterized by high T_(m),sluggish diffusion,and severe lattice distortion,WTa-RMPEAs exhibit chemical composition fluctuations at different scales,leading to unique mechanical properties and deformation behavior.In this paper,an initial summary is provided of the mechanical properties of typical WTa-RMPEAs at room and high temperatures and the differences in deformation behavior and underlying mechanisms between RMPEAs and conventional alloys are discussed.Additionally,strengthening and toughening strategies and the suggested deformation mechanisms were reviewed.Finally,the challenges in revealing the actual deformation mechanism of WTa-RMPEAs were described,and a brief perspective on the future research of the mechanical behavior of WTa-RMPEAs was proposed.展开更多
Maintaining thermal stability is a key concern for the potential application of multi-principal-element alloys(MPEAs)at elevated temperatures,particularly in the intermediate temperature range.In this regime,the therm...Maintaining thermal stability is a key concern for the potential application of multi-principal-element alloys(MPEAs)at elevated temperatures,particularly in the intermediate temperature range.In this regime,the thermodynamic dominance of the entropy term over enthalpy may diminish,while atomic migration remains kinetically active.In this study,the stability of a series of refractory MPEAs(RMPEAs)from the subsystems of Ti-V-Zr-Nb-Hf-Ta is investigated at 550℃for 2-28 days.Although all eleven alloys exhibit a single solid solution phase with a body-centered cubic structure at their homogenized states,only two alloys,VNbTa and TiVNbTa,remain stable after annealing.Decomposition occurs in the other nine alloys under the spinodal manner or the nucleation and growth mechanism,including all three quinary alloys,demonstrating that configurational entropy is not a dominant factor.The phase stabilities can be well understood from the enthalpy perspectives,by combining first-principles calculations and semi-empirical models.By comparing the different contributors of formation enthalpy,the lattice distortion energy is found to be the most critical factor for this alloy system.Furthermore,the phases formed after long-term annealing are generally located at different regions in the space with the axes of chemical,structural,and lattice distortion energies.This work provides a way to interpret and control the stability of RMPEAs in the intermediate temperature regime.展开更多
The approximately equimolar ratio A1CrNiSiTi multi-principal element alloy （MPEA） coatings were fab- ricated by laser cladding on Ti-6Al-4V （Ti64） alloy. Scanning electron microscopy （SEM）, equipped with an ener...The approximately equimolar ratio A1CrNiSiTi multi-principal element alloy （MPEA） coatings were fab- ricated by laser cladding on Ti-6Al-4V （Ti64） alloy. Scanning electron microscopy （SEM）, equipped with an energy-dispersive spectroscopy （EDS）, and X-ray diffrac- tion （XRD） were used to characterize the microstructure and composition. Investigations show that the coatings consist of （Ti, Cr）5Si3 and NiA1 phases, formed by in situ reaction. The phase composition is initially explicated according to obtainable binary and ternary phase diagrams, and the formation Gibbs energy of TisSi3, VsSi3 and CrsSi3. Dry sliding reciprocating friction and wear tests of the A1CrNiSiTi coating and Ti64 alloy substrate without coating were evaluated. A surface mapping profiler was used to evaluate the wear volume. The worn surface was characterized by SEM-EDS. The hardness and wear resistance of the A1CrNiSiTi coating are well compared with that of the basal material （Ti64）. The main wear mechanism of the AICrNiSiTi coating is slightly adhesive transfer from GCrl5 counterpart, and a mixed layer com- posed of transferred materials and oxide is formed.展开更多
AlCrFeNiCu high-entropy alloy （THA） was synthesized by the arc melting and casting method. The alloy exhibits simple FCC and BCC solid solution phases rather than intermetallic compounds. The reason is that the Gibb...AlCrFeNiCu high-entropy alloy （THA） was synthesized by the arc melting and casting method. The alloy exhibits simple FCC and BCC solid solution phases rather than intermetallic compounds. The reason is that the Gibbs free energy of mixing of the equimolar A1CrFeNiCu alloy is smaller than that of inter-metallic compounds by calculation according to the Miedema model .展开更多
Precipitation strengthening provides one of the most widely-used mechanisms for strengthen-ing multi-principal-element alloys(MPEAs).Here,we report dual-morphology B2 precipitates in Co_(36)Cr_(15)Fe_(18)Ni_(18)Al_(8)...Precipitation strengthening provides one of the most widely-used mechanisms for strengthen-ing multi-principal-element alloys(MPEAs).Here,we report dual-morphology B2 precipitates in Co_(36)Cr_(15)Fe_(18)Ni_(18)Al_(8)Ti_(4)Mo_(1)MPEA obtained by thermo-mechanical processing.Electron microscopy charac-terization reveals that the dual-morphology B2 precipitates are either recrystallized B2 particles formed at the grain boundaries or triple junctions with recrystallization process,or rod-like within the non-recrystallized FCC matrix.The dual-morphology B2 precipitates enhance the yield strength and ultimate tensile strength up to 1120 MPa and 1480 MPa,respectively.This work suggests the mechanical proper-ties of the alloy can be optimized by B2 precipitation strengthening to meet the needs of engineering applications.展开更多
The evaporation and dilution of substrate seriously limit the performance of laser cladding coatings on magnesium alloys.In order to overcome the above shortcomings,a multi-step ultrasonic assisted laser remelting tec...The evaporation and dilution of substrate seriously limit the performance of laser cladding coatings on magnesium alloys.In order to overcome the above shortcomings,a multi-step ultrasonic assisted laser remelting technology was proposed to improve the performance of the coating.In this work,a novel Cu_(2.3)Al_(1.3)Ni_(1.7)SnCr_(0.3) multi-principal element alloy coating(MPEAC)was prepared on the surface of mag-nesium alloy.Characterization techniques such as transmission electron microscopy(TEM),electron back scatter diffraction(EBSD)and scanning electron microscopy(SEM)were employed to characterize the microstructure and phase composition of the coatings.And the phase structure and morphology at the interface between the coating and the substrate were also studied via focus ion beam(FIB)and TEM method.In addition,the corrosion and wear resistance ability of the coatings were monitored by potentiodynamic polarization(PDP),and electrochemical impedance spectroscopy(EIS),hardness and friction tests.The results show that Cu_(2.3)Al_(1.3)Ni_(1.7)SnCr_(0.3) MPEAC with ultrasonic assisted is composed of FCC phase and eutectic phases(Cu_(10)Sn_(3) and Cu_(2)Ni_(3)Sn_(3)).Due to the forced convection generated by ultrasonic waves,some Cu and Ni phases are precipitated around Cu_(2)Ni_(3)Sn_(3) phases,which is beneficial to enhance the corrosion resistance.Because of the grain refinement effect caused by ultrasonic,the wear resistance of the coating is also improved.Furthermore,ultrasonic vibration can effectively weaken and eliminate the texture density of the Cu_(2.3)Al_(1.3)Ni_(1.7)SnCr_(0.3) MPEAC fabricated by laser cladding.展开更多
Multi-principal element alloys(MPEAs)have attracted much attention as future nuclear materials due to their extraordinary radiation resistances.In this work,we have elucidated the development of local chemical orderin...Multi-principal element alloys(MPEAs)have attracted much attention as future nuclear materials due to their extraordinary radiation resistances.In this work,we have elucidated the development of local chemical orderings(LCOs)and their influences on radiation damage behavior in the typical CrFeNi MPEA by hybrid-molecular dynamics and Monte Carlo simulations.It was found that considerable LCOs consist-ing of the Cr-Cr and Ni-Fe short-range orders existed in the ordered configuration with optimized system energy.Through modeling the accumulation cascades up to 1000 recoils,we revealed that the size of de-fect clusters and dislocation loops is smaller in the ordered configuration than those in the random one,although the former formed more Frenkel pairs(i.e.,self-interstitials and vacancies).In addition,the dis-tribution of dislocation loops is relatively more dispersed in the ordered configuration,and the stair-rod dislocations related to irradiation swelling are also smaller,implying that the existence of LCOs is con-ducive to enhancing radiation damage tolerance.To understand the underlying mechanism,the effects of LCOs on the formation and evolution of defects and radiation resistance were discussed from the aspects of atomic bonding,migration path,and energy of defect diffusion,which provides theoretical guidance for the design of MPEAs with enhanced radiation resistance.展开更多
The corrosion behaviors of selective laser melted(SLMed)FeCoCrNi multi-principal element alloys(MPEAs)with carbon or nitrogen addition in 0.5 M H_(2)SO_(4) solution were investigated.Both C and N ad-dition refined the...The corrosion behaviors of selective laser melted(SLMed)FeCoCrNi multi-principal element alloys(MPEAs)with carbon or nitrogen addition in 0.5 M H_(2)SO_(4) solution were investigated.Both C and N ad-dition refined the grains and introduced a heterogeneous structure in SLMed FeCoCrNi MPEA,but they had opposite effects on the corrosion behavior.The doped carbon participated as nano-sized carbides in SLMed MPEA,and localized galvanic corrosion occurred,degrading the corrosion resistance.The doped nitrogen was gathered with chromium and formed CrN chemical clusters in SLMed MPEA,and a protec-tive passive film with a higher Cr_(2)O_(3)/Cr(OH)_(3) ratio formed,which improved corrosion resistance.展开更多
基金the financial supports from the National Key Research and Development Program of China(No.2022YFB3707501)the National Natural Science Foundation of China(No.51701083)+2 种基金GDAS’Project of Science and Technology Development,China(Nos.2022GDASZH-2022010103,2022GDASZH-2022010107,2020GDASYL-20200102030)the financial support from the National Natural Science Foundation of China(No.52001137)the Basic and Applied Basic Research Foundation of Guangzhou,China(No.202201010206)。
文摘The equiatomic and equimass TiHfMo,TiHfMoNb and TiHfMoNbZr alloys were prepared,and their microstructure,mechanical properties and bio-corrosion behaviors were systematically investigated.The results demonstrated that all the multi-principal element alloys(MPEAs)had a single BCC phase structure without any intermetallic compounds.Moreover,the Young’s moduli and hardness of the MPEAs were respectively within the range of 95−126 GPa and 5.5−6.4 GPa,respectively.In simulated body fluids,the MPEAs had excellent resistance to chloride ion attack due to the fact that the passive films consisted of multiple oxides and the surface possessed large contact angles.Compared with CP-Ti and Ti6Al4V alloy,equiatomic TiHfMo and TiHfMoNb alloys had a desirable combination of pitting and corrosion resistance,wettability,and wear resistance,and can be utilized as potential candidates for biomedical metallic implants.
基金financially supported by the following sources:Guangdong Basic and Applied Basic Research Foundation(No.2023B1515120045)Yangjiang City Key Industry Talent Revitalization Plan Project for Alloy Materials and Hardware Scissors(No.RCZX202302)+7 种基金GDAS'Project of Science and Technology Development(Nos.2022GDASZH-2022010108,2022GD ASZH-2022010107 and 2024GD ASZH-2024010102)GDAS'Young Talent Project(No.2024GDASQNRC-0314)Guangzhou Basic and Applied Basic Research Foundation(No.2023A04J1628)the National Key R&D Program of China(No.2022YFB4600700)National Natural Science Foundation of China(No.52371110)Guangdong Basic and Applied Basic Research Foundation(No.2023A1515011510)Shenzhen Science and Technology Program(Nos.JCYJ20220530115011026 and JCYJ20230807093410021)Shanxi Province Key R&D Project(No.202302050201011)
文摘A novel approach for fabricating multi-principal element alloys with adjustable phase configurations and mechanical properties was developed using laser-aided additive manufacturing(LAAM),combining FCC-structured(face-centered cubic)CoCrNi and BCC-structured(body-centered cubic)CoCrNiAl0.6TiFe feedstocks.During fabrication,CoCrNi powders and CoCrNiAl0.6TiFe powders were simultaneously fed into the melt pool at individually adjustable rates,allowing for controlled phase transitions.The resulting phase evolution demonstrated a gradual transition from a single FCC structure CoCrNi(A10.6TiFe)x(x=0,0.1,0.2,0.3)to a dual FCCB2 structure CoCrNi(Al0.6TiFe)x(x=0.4,0.5)as the proportion of BCC-structured powders increased.The B2 phase,enriched in Ti and Al due to their larger atomic radii and negative segregation enthalpy,precipitated around the FCC matrix,with volume fractions of 0.5%and 5.7%for CoCrNi(A10.6TiFe)0.4 and CoCrNi(A10.6TiFe)0.5,respectively.This phase transition resulted in significant mechanical enhancements.Yield and ultimate tensile strengths increased from 486.0 and 781.2 MPa(CoCrNi)to 887.2 and 1165.2 MPa(CoCrNi(A10.6TiFe)0.5).Dislocation-mediated hardening prevailed in single-phase FCC alloys,exhibiting a characteristic dislocation density of 2.5×10^(15)m^(-2)for CoCrNi(A10.6TiFe)0.3 alloy.Once the B2 phase precipitated,precipitation strengthening became dominant,as observed in transmission electron microscopy(TEM),where dislocations accumulated around B2 precipitates.This study presents an innovative alloy fabrication strategy that enables precise tuning of FCC-BCC dualphase structures,facilitating the direct fabrication of components with spatially customized properties.These findings provide valuable insights for developing multiprincipal element alloys with heterogeneous microstructures for advanced engineering applications.
基金supported by the National Natural Science Foundation of China(Nos.52171166,52471190,and U20A20231)the Natural Science Foundation of Hunan Province,China(Nos.2024JJ2060 and 2024JJ5406)+1 种基金Key Laboratory of Materials in Dynamic Extremes of Sichuan Province(No.2023SCKT1102)supported by Sinoma Institute of Materials Research(Guang Zhou)Co.,Ltd。
文摘To improve strength and ductility of Ti-Zr-Nb lightweight refractory multi-principal element alloys(LRMPEAs)simultaneously,which is difficult for traditional solution strengthening and second-phase/precipitate strengthening,the compositional inhomogeneity in TiZrNb ternary equimolar LRMPEAs with a single-phased body-centered cubic structure is stimulated and tailored by doping V element.When V is introduced,compositional inhomogeneity shows as the segregation of V and Zr elements form.As the value of x for TiZrNbV_(x)LRMPEAs increases from 0.3 to 0.6,the mild compositional fluctuation develops to the spinodal decomposition structured three-dimensional framework with a periodicity of~5 nm.Then the dislocations in TiZrNbV_(0.6)LRMPEA are compactly pinned,a remarkable strengthening effect(~120 MPa)while the Frank-Read sources for dislocation multiplication and cross-slip are stimulated.Thus,an optimal combination of strength and ductility including the yield strength of 883 MPa and the fracture elongation of 26.6%is achieved in TiZrNbV0.6 LRMPEA.This work provides a useful method to enhance the strength of Ti-Zr-Nb LRMPEAs without sacrificing the ductility.This way is expected to be effective for other multi-principal element alloys,including high-entropy alloys and medium-entropy alloys.
基金supported by the National Natural Science Foundation of China(Grant Nos.52401202,62203028,52275225).
文摘This research focused on the influences of Cr element doping on the microstructure,thermal stability,microhardness,soft magnetic,and anti-corrosion properties of FeCoNiSiB multi-principal element alloys.The as-received Fe-Co-Ni-Si-B-Cr alloy ribbons made by melt-spinning technique could maintain amorphous nature.The glass-transition temperature and onset crystallization temperature become lower with the addition of Cr,and the highest values are 782.0 K and 821.5 K,respectively.When the Cr content reaches 3at.%,the alloy owns the best soft magnetic performance with the saturation magnetic flux density of~0.578 T and coercivity of~5.5 A·m^(-1)among the studied melt-spun ribbon samples.The microhardness of all alloy ribbons reduces with an increasing Cr content on the whole,and the values are 810 HV_(0.5) or above.The corrosion behavior of these multi-principal element amorphous alloys containing Cr was also investigated in detail.As the Cr content increases,the corrosion resistance becomes superior and the specimens present the obvious passive regions in 3.5wt.%NaCl solution.The glassy ribbons with 8at.%Cr have the highest self-corrosion potential of-0.340 V and pitting potential of 0.288 V as well as the widest passive region of 0.628 V.Besides,the corroded micrographs of alloy ribbons immersed in corrosive environment lasting 100 h are also presented,which further confirms the above-mentioned experimental results.This research deepens the understanding about the role of Cr element in the microstructure and a series of physical and chemical properties of Fe-Co-Ni-Si-B-Cr multi-principal element amorphous alloys.
基金supported by the National Natural Science Foundation of China(Nos.12305290,U2441258,52231001)the Postdoctoral Fellowship Program of CPSF(No.GZC20232089)+1 种基金the Innovative Scientific Program of China National Nuclear Corporationthe Fundamental Research Funds for the Central Universities。
文摘Oxygen-induced microstructural evolution critically governs the long-term reliability of refractory multi-principal element alloys(RMPEAs)in extreme environments,where oxygen ingress during prolonged high-temperature service can drastically alter micro structural stability and mechanical performance,yet its atomic-scale mechanisms remain poorly understood.Here,oxygen's dual role in NbZrTi-based RMPEAs is systematically revealed through aging experiments at 650℃for 48and 168 h,combined with multiscale characterization.High-oxygen alloys(3 at.%O)exhibited multi-phase precipitation,including Zr-O-enriched hexagonal close-packed and dual body-centered cubic phases(Zr+Ti-O-rich and Nb+Ti-rich),governed by oxygen redistribution and thermodynamic stabilization.Contrary to conventional precipitation hardening,oxygen segregation gradients at the grain boundaries induced lattice distortion mitigation in the matrix,leading to a twostage age-softening behavior:rapid initial hardness reduction(20%within 48 h)followed by a plateau regime.The interplay between oxygen-mediated phase separation and concentration-dependent solute partitioning highlights the delicate balance required to optimize RMPEAs for high-temperature applications.These findings establish oxygen concentration thresholds and grain boundary engineering as critical design parameters for RMPEAs,enabling simultaneous optimization of radiation resistance and century-scale stability in next-generation nuclear reactor structure materials.
基金funded by the National Natural Science Foundation of China(Grant Nos.52201171 and 52225103)the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-IDRY-23-001)the National Key Research and Development Program of China(Grant No.2022YFB4602101).
文摘Tantalum(Ta)alloys have been widely utilized in rocket,air-breathing engines,and airframe applications.However,traditional Ta alloys suffer from insufficient strength at ultra-high temperature,making it challenging to satisfy the design requirements for next-generation aerospace equipment.We report a novel strategy to design Ta alloys with superior mechanical properties by integrating the multi-principal element concept with compositionally complex carbides.By introducing multiple refractory elements and C,the resultant alloys displayed a thermally stable microstructure consisting of two phases.With the increasing C contents,the microstructure evolved from hypoeutectic to eutectic and then to hypereutectic.These varying microstructural characteristics influenced crack blunting and dislocation accumulation behaviors,leading to different softening resistance at 1600℃and plasticity at room temperature.Benefiting from the strengthening effects of solid solution and compositionally complex carbides,these alloys exhibited a high strength of~600 MPa at 1600℃,significantly superior than that of traditional Ta alloys.
基金supports from the National Key Research and Development Program of China(No.2024YFB4608600)the International Science and Technology Cooperation Project of Guangdong Province(No.2023A0505050154)+1 种基金the Fundamental Research Funds for the Central Universities(No.2024ZYGXZR037)the Pearl River Talent Program(No.2021QN02C766)。
文摘The urgent need to overcome the strength-ductility trade-off of nickel-aluminum bronze(NAB)in deep-sea engineering motivates the design of a Cu-bearing multi-principal element alloy(MPEA),Cu_(35)Ni_(35)Co_(30),via magnetic levitation melting.The as-cast Cu_(35)Ni_(35)Co_(30) MPEA exhibits a dual face-centered cubic(FCC)structure with superior mechanical properties(yield strength:~503 MPa,ultimate tensile strength:~686 MPa,total elongation:~11.0%)over its counterparts fabricated by vacuum arc melting.A single-phase FCC structure was obtained by homogenizing at 1030℃ for 15 h.Cold rolling and postdeformation annealing(PDA)were used to construct heterogeneous grain structures,which were achieved in PDA-treated samples at 1030℃ for 45 s(PDA-1030-45s)and 60 s(PDA-1030-60s).The PDA-1030-45s sample,composed of nano-sized recrystallized grains and residual deformed grains(RDGs),showed the best strength among the PDA-treated samples(a yield strength of~864 MPa,an ultimate tensile strength of~959 MPa,and a total elongation of~13.4%).The PDA-1030-60s sample with micro-sized recrystallized grains and RDGs exhibits an excellent combination of strength and ductility,showing a yield strength of~560 MPa,an ultimate tensile strength of~761 MPa,and a total elongation of~32.9%.These mechanical strengths are superior to those reported by NAB.The dominant strengthening mechanisms of the PDA-1030-45s and the PDA-1030-60s samples are dislocation strengthening and hetero-deformation-induced strengthening,respectively.
基金financially supported by the State Administration for Market Regulation,China(No.2021MK050)the National Natural Science Foundation of China(Nos.50971043,51171046,21973012)+3 种基金the Key Research and Development Program of China(Nos.2022YFB3807200,CISRI-21T62450ZD)the Natural Science Foundation of Fujian Province,China(Nos.2021J01590,2020J01351,2018J01754,2020J01474)the Student Research and Training Program(SRTP) of Fuzhou University,China(No.29320)Fujian Provincial Department of Science & Technology,China(No.2021H6011)。
文摘In order to understand the influence of ordering behaviors on the thermodynamic and mechanical properties of multi-principal element alloys(MPEAs),the temperature-dependent thermodynamic properties and mechanical properties of FCC_CoNiV MPEAs were comparatively predicted,where the alloys were modeled as the ordered configurations based on our previously predicted site occupying fractions(SOFs),as well as disordered configuration based on traditional special quasi-random structure(SQS).The ordering behavior not only improves the thermodynamic stability of the structure,but also increases the elastic properties and Vickers hardness.For example,at 973 K,the predicted bulk modulus(B),shear modulus(G),Young’s modulus(E),and Vickers hardness(HV)of FCC_CoNiV MPEA based on SOFs configuration are 187.82,79.03,207.93,and 7.58 GPa,respectively,while the corresponded data are 172.58,57.45,155.14,and 4.64 GPa for the SQS configuration,respectively.The Vickers hardness predicted based on SOFs agrees considerably well with the available experimental data,while it is underestimated obviously based on SQS.
基金financially supported by the National Natural Science Foundation of China(No.52173216)CNPC Science and Technology Project"Research and Development of Corrosion Resistant Materials for Extreme Environments"(No.2023ZZ11-02).
文摘Chemical short-range order(SRO)in multi-principal element alloys(MPEAs)and its unprecedented benefits on materials performance have been elucidated in recent experimental observations.Hence,manipulating the fine structure of SRO and its interaction with other coexisting SROs or defects becomes increasingly crucial for MPEAs design.Here,using TiZrNb,TiZrVNb,and TiZrV as the model systems,SRO and its interaction with surrounding environment,as well as its effects on mechanical properties are comprehensively explored through density functional theory-based Monte Carlo simulations.We find that both TiZrNb and TiZrVNb exhibit Ti-Zr SRO and Nb-Nb short-range clustering(SRC),whereas in TiZrV,Zr-V SRO occurs in addition to Ti-Zr SRO.SRO largely increases the modulus and the unstable stacking fault energy(USFE).At the electronic scale,SRO is found accompanied with a deeper pseudo-energy gap at Fermi level,and with a covalent bonding character between the metallic atoms.Due to the SRO-oxygen attraction,oxygen centered and Ti/Zr enriched octahedron coined as(O,2Ti,4Zr)-octahedron populates in TiZrNb-O and TiZrV-O.In TiZrVNb-O,there mainly exist two types of octahedral:(O,2Ti,4Zr)and(O,3Ti,3Zr).Quantitatively,forming these(O,Ti,Zr)-octahedra,the modulus and USFE of MPEAs are further increased compared to the individual contribution from SRO or oxygen,but the improvement does not surpass the sum of the increments induced by the two individuals.The present findings deepen the understanding of SROs and their interactions with surrounding environments,pushing forward the effective utilization of SRO in materials design.
基金supported by the National Key Research and Development Program of China(No.2022YFF0609000)the National Natural Science Foundation of China(Nos.52171034 and 52101037)the Postdoctoral Fellowship Program of CPSF(No.GZB20230944).
文摘Ti-Zr-Nb refractory multi-principal element alloys(RMPEAs)have attracted increased attention due to their excellent mechanical properties.In this study,(TiZr)_(80-x)Nb_(20)Mo_(x)(x=0,5 and 10)alloys were designed,and the intrinsic conflicts between strength and ductility were overcome via composition optimization and recrystallization.The causes of the superior strength-ductility synergy were investigated in terms of their deformation mechanism and dislocation behavior.The results show that the strength improvement can be attributed to the deformation mechanism transition caused by local chemical fluctuations and lattice distortion.Specifically,the slip band widths decrease after Mo addition,and the measured slip traces in the fracture samples are associated with high-order{112}and{123}slip planes.Furthermore,the grain refinement achieved via recrystallization promotes multi-slip system activation and shortens the slip-band spacing,which reduces the stress concentration and inhibits crack source formation,thereby allowing the alloy to ensure sufficient ductility.Consequently,the Ti_(35)Zr_(35)Nb_(20)Mo_(10)alloy annealed at 900℃ exhibits high yield strength and elongation.These findings provide a new strategy for designing high-strength RMPEAs and addressing room-temperature brittleness.
基金financially supported by the National Key Research and Development Program of China(No.2019YFA0209900)the National Natural Science Foundation of China(Nos.12305290,12075179,52231001,and 12105219)+1 种基金the Postdoctoral Fellowship Program of CPSF(No.GZC20232089)the Innovative Scientific Program of China National Nuclear Corporation,and the Fundamental Research Funds for the Central Universities.
文摘Designing alloys capable of withstanding irradiation is a crucial aspect of developing materials for nuclear reactors and aerospace applications.Local chemical order(LCO)has recently been recognized as a new microstructural parameter to leverage,and its effect on the mechanical properties of body-centered cubic(BCC)multi-principal element alloys(MPEAs)has attracted much attention.However,the impact of LCO on the dynamic evolution of irradiation-induced defects in BCC MPEAs remains much less explored.In this study,we engineered varying degrees of LCO and local lattice distortion in NbZrTi BCC MPEAs by alloying them with different concentrations of interstitial oxygen solutes,and analyzed their effects on the evolution of radiation-induced defects during He irradiation at 673 K to 873 K,with a fluence of 5×10^(16) ions/cm^(2) and a peak dose of approximately 1 DPA.Using first-principles calculations and atomic-scale analysis of microstructures and chemical elements,we discovered that interstitial oxygen atoms enhance LCO and increase local lattice distortion.These heterogeneities increase the formation energy,and localize the diffusion,of vacancies,hence effectively reducing the transport of aggregating helium that causes bubble swelling.The initiation and growth of dislocation loops and precipitates are depressed as well.The manipulation of irradiation defects in BCC MPEAs,through orchestrating interstitial oxygen solutes and the LCO they provoke,adds a practical strategy for designing advanced alloys for nuclear applications.
基金financially supported by the National Natural Science Foundation of China(Nos.52122102 and 523B2003).
文摘Achieving high yield strength and ductility in alloys remains a significant challenge in structural materials.In this study,combined nanoprecipitation and gradient grain structure were introduced into a Co-Cr-Ni-based multi-principal element alloy(MPEA)using surface mechanical attrition treatment(SMAT).The multi-scale composite structure,featuring grain sizes refined from∼43.6μm to∼24.3 nm at the topmost surface and high-density L1_(2)nanoprecipitates within the grains,results in a substantial tensile strength of 1733 MPa and a well-maintained ductility of∼23%.The alloy with low local stacking fault energy provides sufficient flow stress to reach the critical value for twinning,a phenomenon rarely observed in MPEAs with high-density L1_(2)nanoprecipitates under quasi-static tensile conditions.The formation of nanotwins further facilitates additional strain hardening,enhancing mechanical performance at ultrahigh strength levels.This work offers significant insights into the deformation behavior of gradient-structured materials with high-density nanoprecipitates.
基金supported by the National Natural Science Foundation of China(Nos.52201171,52225103,12335017)the Fundamental Research Funds for the Central Universities,China(No.FRF-IDRY-23-001)+1 种基金the Funds for Creative Research Groups of China(No.51921001)China United Gas Turbin Technology Co.,Ltd.under the project of J721.
文摘To meet the increasing demand for continuously enhancing engineering performance and energy efficiency in a variety of aerospace and energy applications,structural materials with high strength at ultra-high temperatures are urgently required.In the past decade,refractory multi-principal element alloys(RMPEAs),particularly those containing elements with high melting temperatures(T_(m))such as W and Ta(hereafter denoted as WTa-RMPEAs),have garnered extensive interest due to their exceptional strengths and thermally stability at high temperatures.Characterized by high T_(m),sluggish diffusion,and severe lattice distortion,WTa-RMPEAs exhibit chemical composition fluctuations at different scales,leading to unique mechanical properties and deformation behavior.In this paper,an initial summary is provided of the mechanical properties of typical WTa-RMPEAs at room and high temperatures and the differences in deformation behavior and underlying mechanisms between RMPEAs and conventional alloys are discussed.Additionally,strengthening and toughening strategies and the suggested deformation mechanisms were reviewed.Finally,the challenges in revealing the actual deformation mechanism of WTa-RMPEAs were described,and a brief perspective on the future research of the mechanical behavior of WTa-RMPEAs was proposed.
基金supported by the National Natural Science Foundation of China(Nos.12375266 and 12435016)。
文摘Maintaining thermal stability is a key concern for the potential application of multi-principal-element alloys(MPEAs)at elevated temperatures,particularly in the intermediate temperature range.In this regime,the thermodynamic dominance of the entropy term over enthalpy may diminish,while atomic migration remains kinetically active.In this study,the stability of a series of refractory MPEAs(RMPEAs)from the subsystems of Ti-V-Zr-Nb-Hf-Ta is investigated at 550℃for 2-28 days.Although all eleven alloys exhibit a single solid solution phase with a body-centered cubic structure at their homogenized states,only two alloys,VNbTa and TiVNbTa,remain stable after annealing.Decomposition occurs in the other nine alloys under the spinodal manner or the nucleation and growth mechanism,including all three quinary alloys,demonstrating that configurational entropy is not a dominant factor.The phase stabilities can be well understood from the enthalpy perspectives,by combining first-principles calculations and semi-empirical models.By comparing the different contributors of formation enthalpy,the lattice distortion energy is found to be the most critical factor for this alloy system.Furthermore,the phases formed after long-term annealing are generally located at different regions in the space with the axes of chemical,structural,and lattice distortion energies.This work provides a way to interpret and control the stability of RMPEAs in the intermediate temperature regime.
基金supported by the Chongqing Research Program of Basic Research and Frontier Technology(No.CSTC2013jcyjA50016)the National Natural Science Foundation of China(Nos.51401039,51571037 and 51204110)the Scientific and Technological Research Program of Chongqing Municipal Education Commission(No.KJ1709204).
文摘The approximately equimolar ratio A1CrNiSiTi multi-principal element alloy （MPEA） coatings were fab- ricated by laser cladding on Ti-6Al-4V （Ti64） alloy. Scanning electron microscopy （SEM）, equipped with an energy-dispersive spectroscopy （EDS）, and X-ray diffrac- tion （XRD） were used to characterize the microstructure and composition. Investigations show that the coatings consist of （Ti, Cr）5Si3 and NiA1 phases, formed by in situ reaction. The phase composition is initially explicated according to obtainable binary and ternary phase diagrams, and the formation Gibbs energy of TisSi3, VsSi3 and CrsSi3. Dry sliding reciprocating friction and wear tests of the A1CrNiSiTi coating and Ti64 alloy substrate without coating were evaluated. A surface mapping profiler was used to evaluate the wear volume. The worn surface was characterized by SEM-EDS. The hardness and wear resistance of the A1CrNiSiTi coating are well compared with that of the basal material （Ti64）. The main wear mechanism of the AICrNiSiTi coating is slightly adhesive transfer from GCrl5 counterpart, and a mixed layer com- posed of transferred materials and oxide is formed.
基金financial support for this research by Natural Science Foundation of Guangxi Province (0575-18)Guangxi Technology Research Project (0639003)Guangxi University Scientific Research Foundation (x071066)
文摘AlCrFeNiCu high-entropy alloy （THA） was synthesized by the arc melting and casting method. The alloy exhibits simple FCC and BCC solid solution phases rather than intermetallic compounds. The reason is that the Gibbs free energy of mixing of the equimolar A1CrFeNiCu alloy is smaller than that of inter-metallic compounds by calculation according to the Miedema model .
基金supported by the Central Guidance on Local Science and Technology Development Fund of Hebei Province(No.216Z1012G)the National Natural Science Foundation of China(No.12174274).
文摘Precipitation strengthening provides one of the most widely-used mechanisms for strengthen-ing multi-principal-element alloys(MPEAs).Here,we report dual-morphology B2 precipitates in Co_(36)Cr_(15)Fe_(18)Ni_(18)Al_(8)Ti_(4)Mo_(1)MPEA obtained by thermo-mechanical processing.Electron microscopy charac-terization reveals that the dual-morphology B2 precipitates are either recrystallized B2 particles formed at the grain boundaries or triple junctions with recrystallization process,or rod-like within the non-recrystallized FCC matrix.The dual-morphology B2 precipitates enhance the yield strength and ultimate tensile strength up to 1120 MPa and 1480 MPa,respectively.This work suggests the mechanical proper-ties of the alloy can be optimized by B2 precipitation strengthening to meet the needs of engineering applications.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51975137 and 52175163)the Equipment Pre-research Field Foundation(No.80923010602)the Fundamental Research Funds for the Central University(No.3072021CFT1008).
文摘The evaporation and dilution of substrate seriously limit the performance of laser cladding coatings on magnesium alloys.In order to overcome the above shortcomings,a multi-step ultrasonic assisted laser remelting technology was proposed to improve the performance of the coating.In this work,a novel Cu_(2.3)Al_(1.3)Ni_(1.7)SnCr_(0.3) multi-principal element alloy coating(MPEAC)was prepared on the surface of mag-nesium alloy.Characterization techniques such as transmission electron microscopy(TEM),electron back scatter diffraction(EBSD)and scanning electron microscopy(SEM)were employed to characterize the microstructure and phase composition of the coatings.And the phase structure and morphology at the interface between the coating and the substrate were also studied via focus ion beam(FIB)and TEM method.In addition,the corrosion and wear resistance ability of the coatings were monitored by potentiodynamic polarization(PDP),and electrochemical impedance spectroscopy(EIS),hardness and friction tests.The results show that Cu_(2.3)Al_(1.3)Ni_(1.7)SnCr_(0.3) MPEAC with ultrasonic assisted is composed of FCC phase and eutectic phases(Cu_(10)Sn_(3) and Cu_(2)Ni_(3)Sn_(3)).Due to the forced convection generated by ultrasonic waves,some Cu and Ni phases are precipitated around Cu_(2)Ni_(3)Sn_(3) phases,which is beneficial to enhance the corrosion resistance.Because of the grain refinement effect caused by ultrasonic,the wear resistance of the coating is also improved.Furthermore,ultrasonic vibration can effectively weaken and eliminate the texture density of the Cu_(2.3)Al_(1.3)Ni_(1.7)SnCr_(0.3) MPEAC fabricated by laser cladding.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51671021,11790293,51871016,52071024,and 51961160729)the Funds for Creative Research Groups of China(No.51921001)+1 种基金the 111 Project(No.B07003)the Fundamental Research Funds for the Central Universities.
文摘Multi-principal element alloys(MPEAs)have attracted much attention as future nuclear materials due to their extraordinary radiation resistances.In this work,we have elucidated the development of local chemical orderings(LCOs)and their influences on radiation damage behavior in the typical CrFeNi MPEA by hybrid-molecular dynamics and Monte Carlo simulations.It was found that considerable LCOs consist-ing of the Cr-Cr and Ni-Fe short-range orders existed in the ordered configuration with optimized system energy.Through modeling the accumulation cascades up to 1000 recoils,we revealed that the size of de-fect clusters and dislocation loops is smaller in the ordered configuration than those in the random one,although the former formed more Frenkel pairs(i.e.,self-interstitials and vacancies).In addition,the dis-tribution of dislocation loops is relatively more dispersed in the ordered configuration,and the stair-rod dislocations related to irradiation swelling are also smaller,implying that the existence of LCOs is con-ducive to enhancing radiation damage tolerance.To understand the underlying mechanism,the effects of LCOs on the formation and evolution of defects and radiation resistance were discussed from the aspects of atomic bonding,migration path,and energy of defect diffusion,which provides theoretical guidance for the design of MPEAs with enhanced radiation resistance.
基金the sponsorship from City University of Hong Kong(Grant Nos.9380088,9360157,9231348 and 7005078).
文摘The corrosion behaviors of selective laser melted(SLMed)FeCoCrNi multi-principal element alloys(MPEAs)with carbon or nitrogen addition in 0.5 M H_(2)SO_(4) solution were investigated.Both C and N ad-dition refined the grains and introduced a heterogeneous structure in SLMed FeCoCrNi MPEA,but they had opposite effects on the corrosion behavior.The doped carbon participated as nano-sized carbides in SLMed MPEA,and localized galvanic corrosion occurred,degrading the corrosion resistance.The doped nitrogen was gathered with chromium and formed CrN chemical clusters in SLMed MPEA,and a protec-tive passive film with a higher Cr_(2)O_(3)/Cr(OH)_(3) ratio formed,which improved corrosion resistance.
