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
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
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
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
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
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
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
An extremely high-strength TiAl/Ni-based superalloy dissimilar joint was obtained using a designed Ni_(25)Zr_(25)Sn_(20)Cu_(10)Hf_(10)Cr_(5)Fe_(5)multi-principal element interlayer via contact reaction brazing.It was ...An extremely high-strength TiAl/Ni-based superalloy dissimilar joint was obtained using a designed Ni_(25)Zr_(25)Sn_(20)Cu_(10)Hf_(10)Cr_(5)Fe_(5)multi-principal element interlayer via contact reaction brazing.It was found that a joint mainly composed of eutectic structure of(Ni)ss,(Ni,Cr,Fe)ss,and(Cr,Ni,Fe,Mo)ss,as well as micro-nano precipitates of(Ti)ss and(Hf,Zr)ss,could be achieved through the interaction between the interlayer and the base metals.The joint exhibited a shear strength of 498 MPa when brazed at 1190°C for 10 min,while the fracture occurred within the TiAl base metal,and the retention rate of high-temperature(HT)strength(650°C)was∼100%.The strengthening mechanism of the brazed joint was systematically discussed by transmission electron microscopy(TEM).It was shown that high-density dis-locations existed in each phase of the seam as well as twinning and stacking faults existed in the micro-nano precipitates,caused by a mass of solute atoms,greatly strengthened the joint.At HTs,the dislocation strengthening effect weakened due to grain recovery and recrystallization,but the joint could be addi-tionally toughened by multi-cracking.Meanwhile,granular(Ti)ss dispersed through the seam and ductile reticular structure(Ni)ss toughened the joint via the mechanism of crack termination and bridging.The proposed method provides a new approach for high strength and heat resistance joining of TiAl/Ni-based superalloy in aeroengine components.展开更多
Owing to the fine nano-laminated structure,the pearlitic multi-principal element alloy(PMPEA) exhibits excellent mechanical and tribological properties.However,the incomplete understanding of the size effect of its la...Owing to the fine nano-laminated structure,the pearlitic multi-principal element alloy(PMPEA) exhibits excellent mechanical and tribological properties.However,the incomplete understanding of the size effect of its lamella thickness and the unclear understanding of the plasticity-interface interaction mechanism limit further optimization of PMPEAs.In this study,the FeCoNi/Ni_3Ti interface-mediated plastic deformation behavior in PMPEA and the variation of mechanical and tribological properties with lamella thickness within the nanoscale range using molecular dynamics(MD) simulation were explored.The results indicate that the mechanical and tribological properties of the PMPEA with lamella thicknesses below 10 nm have a significant inverse size effect,i.e.,the smaller the lamella thickness,the weaker the properties.This is because the plastic carrier-interface interaction mechanism changes from a strengthening mechanism that hinders dislocations to a weakening mechanism that promotes dislocations with the decreases in the lamella thickness,and the weakening effect becomes more pronounced as the lamella thickness decreases and the number of interfaces increases.In particular,the deformation behavior of Ni_3Ti lamellae changes from crystal-like to amorphous-like with decreasing lamella.Moreover,in the sample with larger lamella thickness,the occurrence of hierarchical slips in the body-centered cubic(BCC) phase due to the multiprincipal elements effect can better alleviate the stress concentration caused by the dislocation accumulation at the interface,so that the phase interface exhibits outstanding load-bearing effects.And the dislocation pattern in BCC phase shows a firm high-density cell,which makes the substrate exhibit a stable tribological response.展开更多
Body-centered cubic Ti-Zr-Nb-Ta-Mo multi-principal element alloys(MPEAs),boasting a yield strength ex-ceeding one gigapascal,emerge as promising candidates for demanding structural applications.However,their limited t...Body-centered cubic Ti-Zr-Nb-Ta-Mo multi-principal element alloys(MPEAs),boasting a yield strength ex-ceeding one gigapascal,emerge as promising candidates for demanding structural applications.However,their limited tensile ductility at room temperature presents a significant challenge to their processability and large-scale implementation.This study identifies phase decomposition as a critical factor influencing the plasticity of these alloys.The microscale phase decomposition in these MPEAs during solidification,driven by miscibility gaps,manifests as dendritic structures within grains.Closer examination reveals that the MPEAs with a pronounced thermodynamic propensity for phase decomposition are also suscep-tible to analogous phenomena at the atomic level.The atomic phase decomposition is characterized by the localized aggregation of some elements across nanometric domains,culminating in the establishment of short-range orderings(SROs).It is observed that phase decomposition for these MPEAs,occurring at both microscale and atomic scale,adheres to thermodynamic principles and can be predicted using the CALPHAD approach.The impact of phase decomposition on the plasticity of MPEAs fundamentally stems from the induced heterogeneities at three distinct levels:(1)Fluctuations in mechanical properties at the micron scale;(2)Variations in the strain field at the atomic scale;(3)Bond polarization and bond index fluctuations at the electronic scale.Consequently,the key to designing high-strength and high-plasticity MPEAs lies in maximizing lattice distortion while simultaneously minimizing the adverse effects of phase decomposition on the alloy’s plasticity(grain boundary cohesion).This research not only clarifies the mechanisms underpinning the ductile-to-brittle transition in high-strength Ti-Zr-Nb-Ta-Mo MPEAs but also offers crucial guidelines for developing advanced,high-performance alloys.展开更多
In this work, we utilize atomistic simulations and dislocation mechanics to explore the formation of in-verse pileups in CrCoNi model alloys and elucidate their unique impact on the strength and ductilityof multi-prin...In this work, we utilize atomistic simulations and dislocation mechanics to explore the formation of in-verse pileups in CrCoNi model alloys and elucidate their unique impact on the strength and ductilityof multi-principal element alloys (MPEAs). The present atomistic simulations on single crystals revealthat during the deformation of CrCoNi, stress gradients lead to the formation of novel inverse disloca-tion pileup. We find that this unique dislocation pattern in a confined volume is due to the elevatedlattice friction and significant stress gradient present in the material. Furthermore, this phenomenon canbe notably promoted by lowering the temperature, increasing the loading rate, and introducing chemicalshort-range ordering. Additional simulations on bicrystals show that these inverse pileups play a criticalrole in suppressing dislocation transmission, reflection, and grain boundary (GB) migration. As a result,they effectively mitigate stress concentration and reduce damage accumulation at GBs, lowering the riskof catastrophic failure due to GB damages. In our theoretical analysis, we utilize dislocation mechanics topredict the formation of the inverse pileup and its subsequent strengthening effect, considering scenarioswith and without obstacles. Our investigations encompass various lattice frictions and stress gradients.Remarkably, our results shed light on the prevailing impact of dislocation hardening in the plastic de-formation of CrCoNi even under the presence of a linear stress gradient, while the contribution of GBstrengthening is found to be comparatively limited. These findings provide valuable insights into the de-formation mechanisms of MPEAs in general and significantly aid their applications as promising structuralmaterials.展开更多
Sustainable clean energy is gradually replacing traditional fossil energy sources in important industrial applications and is placing higher demands on the technologies of energy storage and transportation.The develop...Sustainable clean energy is gradually replacing traditional fossil energy sources in important industrial applications and is placing higher demands on the technologies of energy storage and transportation.The development of multi-principal element alloys(MPEAs)offers a new idea for safe solid-state hydrogen storage materials.Owing to the unique characteristics of complex components and severe lattice distortion,MPEAs are predicted to have better hydrogen storage performance and more probability for modulation and enhancement,allowing them to meet the requirements of different hydrogen storage applications.The unique structure characteristic potentially devotes the improvement of thermodynamic and kinetic performance,such as the hydrogen storage capacity and hydrogen adsorption/desorption properties.Recently,several important modulation factors originating from components and structures facilitate the understanding of the correlation between hydrogen storage properties and microstructure.Here,we highlight the correlations of hydrogen storage mechanism,with the degree of lattice distortion,the element variation or segregation and valence electron concentration.Moreover,the development tendency on the hydrogen storage mechanism based on the advanced microscopy and computational approach is proposed.Especially,the chemically short-range ordered structure in MPEAs is predicted as a potential modification factor of the hydrogen/tritium storage properties.展开更多
We present the High-Throughput Computing and Statistical Analysis(HCSA)scheme,which efficiently and accurately predicts the stacking fault energies(SFEs)of multi-principal element alloys(MPEAs).Our approach estimates ...We present the High-Throughput Computing and Statistical Analysis(HCSA)scheme,which efficiently and accurately predicts the stacking fault energies(SFEs)of multi-principal element alloys(MPEAs).Our approach estimates the SFE of a single complex supercell by averaging numerous SFEs from small supercells,resulting in superior accuracy compared to traditional density functional theory(DFT)calculations.To validate our scheme,we applied it to NiFe and Ni_(10)Co_(60)Cr_(25)W_(5)alloys,achieving an SFE error of only 11%,in contrast to the 45%error obtained from traditional DFT calculations for NiFe.We observed a strong correlation between the average SFEs of samples with the same valence electron concentration as that of the experimental data.Our scheme provides an efficient and reliable tool for predicting SFEs in MPEAs and holds the potential to significantly accelerate materials design and discovery processes.展开更多
The thermodynamic extremal principle incorporating the constraints from both fluxes and forces pro-posed in part I was applied to isothermal diffusion in multi-principal element alloys(MPEAs)to propose the so-called d...The thermodynamic extremal principle incorporating the constraints from both fluxes and forces pro-posed in part I was applied to isothermal diffusion in multi-principal element alloys(MPEAs)to propose the so-called double-constraint model.The model cannot reduce physically to the previous model con-sidering only the constraint from fluxes(i.e.,the single-constraint model)but in special cases reduces to Fick’s law and Darken’s equation,showing its reliability.Similar to the previous pair-wise model and single-constraint model,the solutes and solvent do not need to be defined in advance in the double-constraint model and the model can be also applied directly to diffusion in MPEAs.Applications to isothermal diffusion in CoCrFeMnNi pseudo-binary diffusion couple and CoCrFeNi,CoCrFeMnNi body-diagonal diffusion couples showed that the present double-constraint model overall predicted better the experimental results than the previous single-constraint model,indicating again the necessity to consider the constraints from both fluxes and forces in the phenomenological theory of Onsager.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 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 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 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the financial support from the“National Natural Science Foundation of China(NSFC,Grant Nos.51974101,51975150,U21A20128,52175302 and U22A20185)”“National MCF Energy R&D Program(No.2019YFE03100100)”+1 种基金“Fundamental Research Funds for the Central Universities(Nos.2022FRFK060009 and HIT.DZJJ.2023011)”“Natural Science Foundation of Heilongjiang Province,China(No.JQ2020E003)”.
文摘An extremely high-strength TiAl/Ni-based superalloy dissimilar joint was obtained using a designed Ni_(25)Zr_(25)Sn_(20)Cu_(10)Hf_(10)Cr_(5)Fe_(5)multi-principal element interlayer via contact reaction brazing.It was found that a joint mainly composed of eutectic structure of(Ni)ss,(Ni,Cr,Fe)ss,and(Cr,Ni,Fe,Mo)ss,as well as micro-nano precipitates of(Ti)ss and(Hf,Zr)ss,could be achieved through the interaction between the interlayer and the base metals.The joint exhibited a shear strength of 498 MPa when brazed at 1190°C for 10 min,while the fracture occurred within the TiAl base metal,and the retention rate of high-temperature(HT)strength(650°C)was∼100%.The strengthening mechanism of the brazed joint was systematically discussed by transmission electron microscopy(TEM).It was shown that high-density dis-locations existed in each phase of the seam as well as twinning and stacking faults existed in the micro-nano precipitates,caused by a mass of solute atoms,greatly strengthened the joint.At HTs,the dislocation strengthening effect weakened due to grain recovery and recrystallization,but the joint could be addi-tionally toughened by multi-cracking.Meanwhile,granular(Ti)ss dispersed through the seam and ductile reticular structure(Ni)ss toughened the joint via the mechanism of crack termination and bridging.The proposed method provides a new approach for high strength and heat resistance joining of TiAl/Ni-based superalloy in aeroengine components.
基金financially supported by the Natural Science Foundation of China (Nos.52361013 and 52001082)Guizhou Provincial Basic Research Program (Natural Science) (No. ZK [2022] general 137)+1 种基金Talent Project of Guizhou University and Natural Science Foundation of Guizhou University (No.202201)Open Foundation of Key Laboratory of Advanced Manufacturing Technology Foundation (No.GZUAMT2022KF[01])。
文摘Owing to the fine nano-laminated structure,the pearlitic multi-principal element alloy(PMPEA) exhibits excellent mechanical and tribological properties.However,the incomplete understanding of the size effect of its lamella thickness and the unclear understanding of the plasticity-interface interaction mechanism limit further optimization of PMPEAs.In this study,the FeCoNi/Ni_3Ti interface-mediated plastic deformation behavior in PMPEA and the variation of mechanical and tribological properties with lamella thickness within the nanoscale range using molecular dynamics(MD) simulation were explored.The results indicate that the mechanical and tribological properties of the PMPEA with lamella thicknesses below 10 nm have a significant inverse size effect,i.e.,the smaller the lamella thickness,the weaker the properties.This is because the plastic carrier-interface interaction mechanism changes from a strengthening mechanism that hinders dislocations to a weakening mechanism that promotes dislocations with the decreases in the lamella thickness,and the weakening effect becomes more pronounced as the lamella thickness decreases and the number of interfaces increases.In particular,the deformation behavior of Ni_3Ti lamellae changes from crystal-like to amorphous-like with decreasing lamella.Moreover,in the sample with larger lamella thickness,the occurrence of hierarchical slips in the body-centered cubic(BCC) phase due to the multiprincipal elements effect can better alleviate the stress concentration caused by the dislocation accumulation at the interface,so that the phase interface exhibits outstanding load-bearing effects.And the dislocation pattern in BCC phase shows a firm high-density cell,which makes the substrate exhibit a stable tribological response.
基金supported by the Guangdong Basic and Applied Basic Research Foundation(Nos.2022A1515220040,2023A1515220021,and 2024A1515012353)the China Postdoctoral Science Foundation(No.2023M741370)+2 种基金the National Natural Sci-ence Foundation of China(No.52005217)the University Re-search Platform and Research Projects of Guangdong Education De-partment(No.2022ZDZX3003)The first-principles research is also supported by the Dongguan AIPU Technology Company Limited.
文摘Body-centered cubic Ti-Zr-Nb-Ta-Mo multi-principal element alloys(MPEAs),boasting a yield strength ex-ceeding one gigapascal,emerge as promising candidates for demanding structural applications.However,their limited tensile ductility at room temperature presents a significant challenge to their processability and large-scale implementation.This study identifies phase decomposition as a critical factor influencing the plasticity of these alloys.The microscale phase decomposition in these MPEAs during solidification,driven by miscibility gaps,manifests as dendritic structures within grains.Closer examination reveals that the MPEAs with a pronounced thermodynamic propensity for phase decomposition are also suscep-tible to analogous phenomena at the atomic level.The atomic phase decomposition is characterized by the localized aggregation of some elements across nanometric domains,culminating in the establishment of short-range orderings(SROs).It is observed that phase decomposition for these MPEAs,occurring at both microscale and atomic scale,adheres to thermodynamic principles and can be predicted using the CALPHAD approach.The impact of phase decomposition on the plasticity of MPEAs fundamentally stems from the induced heterogeneities at three distinct levels:(1)Fluctuations in mechanical properties at the micron scale;(2)Variations in the strain field at the atomic scale;(3)Bond polarization and bond index fluctuations at the electronic scale.Consequently,the key to designing high-strength and high-plasticity MPEAs lies in maximizing lattice distortion while simultaneously minimizing the adverse effects of phase decomposition on the alloy’s plasticity(grain boundary cohesion).This research not only clarifies the mechanisms underpinning the ductile-to-brittle transition in high-strength Ti-Zr-Nb-Ta-Mo MPEAs but also offers crucial guidelines for developing advanced,high-performance alloys.
文摘In this work, we utilize atomistic simulations and dislocation mechanics to explore the formation of in-verse pileups in CrCoNi model alloys and elucidate their unique impact on the strength and ductilityof multi-principal element alloys (MPEAs). The present atomistic simulations on single crystals revealthat during the deformation of CrCoNi, stress gradients lead to the formation of novel inverse disloca-tion pileup. We find that this unique dislocation pattern in a confined volume is due to the elevatedlattice friction and significant stress gradient present in the material. Furthermore, this phenomenon canbe notably promoted by lowering the temperature, increasing the loading rate, and introducing chemicalshort-range ordering. Additional simulations on bicrystals show that these inverse pileups play a criticalrole in suppressing dislocation transmission, reflection, and grain boundary (GB) migration. As a result,they effectively mitigate stress concentration and reduce damage accumulation at GBs, lowering the riskof catastrophic failure due to GB damages. In our theoretical analysis, we utilize dislocation mechanics topredict the formation of the inverse pileup and its subsequent strengthening effect, considering scenarioswith and without obstacles. Our investigations encompass various lattice frictions and stress gradients.Remarkably, our results shed light on the prevailing impact of dislocation hardening in the plastic de-formation of CrCoNi even under the presence of a linear stress gradient, while the contribution of GBstrengthening is found to be comparatively limited. These findings provide valuable insights into the de-formation mechanisms of MPEAs in general and significantly aid their applications as promising structuralmaterials.
基金financially supported by the President's Foundation of the China Academy of Engineering Physics(No.YZJJLX2018003)the Joint Funds of the National Natural Science Foundation of China(No.U1930120)the National Natural Science Foundation of China(No.12275245)。
文摘Sustainable clean energy is gradually replacing traditional fossil energy sources in important industrial applications and is placing higher demands on the technologies of energy storage and transportation.The development of multi-principal element alloys(MPEAs)offers a new idea for safe solid-state hydrogen storage materials.Owing to the unique characteristics of complex components and severe lattice distortion,MPEAs are predicted to have better hydrogen storage performance and more probability for modulation and enhancement,allowing them to meet the requirements of different hydrogen storage applications.The unique structure characteristic potentially devotes the improvement of thermodynamic and kinetic performance,such as the hydrogen storage capacity and hydrogen adsorption/desorption properties.Recently,several important modulation factors originating from components and structures facilitate the understanding of the correlation between hydrogen storage properties and microstructure.Here,we highlight the correlations of hydrogen storage mechanism,with the degree of lattice distortion,the element variation or segregation and valence electron concentration.Moreover,the development tendency on the hydrogen storage mechanism based on the advanced microscopy and computational approach is proposed.Especially,the chemically short-range ordered structure in MPEAs is predicted as a potential modification factor of the hydrogen/tritium storage properties.
基金financially supported by the National Natural Science Foundation of China(Nos.22173047 and 51931003)the Natural Science Foundation of Jiangsu Province(No.BK20211198)+1 种基金the Sino-German Mobility Program of the Sino-German Center for Research Promotion(Grant M-0147)the Fundamental Research Funds for the Central Universities(Nos.30920041116,30919011254,and 30919011405).
文摘We present the High-Throughput Computing and Statistical Analysis(HCSA)scheme,which efficiently and accurately predicts the stacking fault energies(SFEs)of multi-principal element alloys(MPEAs).Our approach estimates the SFE of a single complex supercell by averaging numerous SFEs from small supercells,resulting in superior accuracy compared to traditional density functional theory(DFT)calculations.To validate our scheme,we applied it to NiFe and Ni_(10)Co_(60)Cr_(25)W_(5)alloys,achieving an SFE error of only 11%,in contrast to the 45%error obtained from traditional DFT calculations for NiFe.We observed a strong correlation between the average SFEs of samples with the same valence electron concentration as that of the experimental data.Our scheme provides an efficient and reliable tool for predicting SFEs in MPEAs and holds the potential to significantly accelerate materials design and discovery processes.
基金the Natural Science Foundation of China(Nos.51975474 and 52304414)the Fundamental Research Funds for the Central Universities(No.3102019JC001).
文摘The thermodynamic extremal principle incorporating the constraints from both fluxes and forces pro-posed in part I was applied to isothermal diffusion in multi-principal element alloys(MPEAs)to propose the so-called double-constraint model.The model cannot reduce physically to the previous model con-sidering only the constraint from fluxes(i.e.,the single-constraint model)but in special cases reduces to Fick’s law and Darken’s equation,showing its reliability.Similar to the previous pair-wise model and single-constraint model,the solutes and solvent do not need to be defined in advance in the double-constraint model and the model can be also applied directly to diffusion in MPEAs.Applications to isothermal diffusion in CoCrFeMnNi pseudo-binary diffusion couple and CoCrFeNi,CoCrFeMnNi body-diagonal diffusion couples showed that the present double-constraint model overall predicted better the experimental results than the previous single-constraint model,indicating again the necessity to consider the constraints from both fluxes and forces in the phenomenological theory of Onsager.
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.
