Heat-resistant aluminum alloys are widely used in aerospace and automotive fields for manufacturing hot components due to their advantages in lightweight design and energy conservation.However,the high-temperature str...Heat-resistant aluminum alloys are widely used in aerospace and automotive fields for manufacturing hot components due to their advantages in lightweight design and energy conservation.However,the high-temperature strength of existing cast aluminum alloys is always limited to about 100 MPa at 350℃due to coarsening and transformation of strengthening phases.Here,we reveal that the yield strength and ultimate tensile strength of the T6 state Al-8.4Cu-2.3Ce-1.0Mn-0.5Ni-0.2Zr alloy at 400◦C increase by 34%and 44%after re-aging at 300℃for 100 h,and its thermal strength exhibits distinguished ad-vantage over traditional heat-resistant aluminum alloys.The enhanced elevated-temperature strength is attributed to the reprecipitation of the Ni-bearing T-Al_(20)Cu_(2)Mn_(3)phase,whose number density increases over one time.The significant segregation of Ni,Ce,and Zr elements at the interfaces helps improve the thermal stability of the T phase.The thermostable T phase effectively strengthens the matrix by in-hibiting dislocation motion.Meanwhile,a highly interconnected 3D intermetallic network along the grain boundaries can still remain after long-term re-aging at 300℃,which is conducive to imposing a drag on the grain boundaries at high temperatures.This finding offers a viable route for enhancing the elevated-temperature strength of heat-resistant aluminum alloys,which could provide expanded opportunities for higher-temperature applications.展开更多
Recently,researchers have explored the use of precipitation strengthening and finer microstructures with high-density dislocations in additive manufacturing to produce high-entropy alloys(HEAs)with adjustable properti...Recently,researchers have explored the use of precipitation strengthening and finer microstructures with high-density dislocations in additive manufacturing to produce high-entropy alloys(HEAs)with adjustable properties.However,the inherent surface roughness and lack of machinability research in AMed HEAs limit their engineering applications.In this study,we systematically investigated the microstructural characteristics,mechanical properties,and machinability of Fe_(29.3)Co_(28.7)Ni_(28.6)Al_(6.8)Ti_(6.6)(at.%)HEAs with three different structures:single FCC phase cellular(SPC),dual precipitation-strengthened(DPS),and single precipitation-strengthened(SPS).These structures were fabricated by selective laser melting and isothermally annealing at 780 and 940℃.Compared to SPC HEA,DPS HEA exhibits a significant increase in yield strength and ultimate tensile strength but with a dramatic sacrifice in ductility.SPS HEA exhibits similar mechanical properties to SPC HEA due to the pronounced coarsening of L21 precipitates.The ultraprecision machining micro-cutting test showed that SPC HEA had a significant mechanochem-ical effect,as evidenced by a sharp drop in cutting force for inked workpieces,but not DPS HEA.An abnormal finding was that the negligible reflection of cutting force for SPS HEAs suggested a negative mechanochemical effect,even though SPS HEA had equally excellent plasticity like SPC HEA.It was found that nanocrystallization-induced strength enhancement and ductility reduction of SPS HEA lead to chips’deformation dominated by shear avalanche rather than chip folding of SPC HEA,which involves the reduction of surface energy and friction of chips’interfaces.Overall,these results and our research findings may guide the machining of AMed precipitation-strengthened HEAs and accelerate their engineering ap-plication.展开更多
The influence of different cryogenic sequences on the rolling contact fatigue(RCF)life of M50-bearing steel has been studied.The results show that direct cryogenic treatment after quenching can effectively improve RCF...The influence of different cryogenic sequences on the rolling contact fatigue(RCF)life of M50-bearing steel has been studied.The results show that direct cryogenic treatment after quenching can effectively improve RCF life.The L_(10)life is strikingly 5 times longer than that with cryogenic treatment after tem-pering.This is caused by the distinct lattice construction of martensite and the transformation of retained austenite.More secondary nanocarbides and fine twins are formed via cryogenic treatment before tem-pering compared with cryogenic treatment after tempering.The improvement in the RCF life of the steel is attributed to the joint effects of the secondary nanocarbides and twin boundaries with a width of 5-13 nm,which delays significantly crack initiation and propagation.This study highlights a common method to improve the service life of high-carbon and high-alloy steels by adjusting the cryogenic se-quence.展开更多
Hydrogen as an interstitial solute at grain boundaries(GBs)can have a catastrophic impact on the mechanical properties of many metals.Despite the global research effort,the underlying hydrogen-GB interactions in polyc...Hydrogen as an interstitial solute at grain boundaries(GBs)can have a catastrophic impact on the mechanical properties of many metals.Despite the global research effort,the underlying hydrogen-GB interactions in polycrystals remain inadequately understood.In this study,using Voronoi tessellations and atomistic simulations,we elucidate the hydrogen segregation energy spectrum at the GBs of polycrystalline nickel by exploring all the topologically favorable segregation sites.Three distinct peaks in the energy spectrum are identified,corresponding to different structural fingerprints.The first peak(-0.205 eV)represents the most favorable segregation sites at GB core,while the second and third peaks account for the sites at GB surface.By incorporating a thermodynamic model,the spectrum enables the determination of the equilibrium hydrogen concentrations at GBs,unveiling a remarkable two to three orders of magnitude increase compared to the bulk hydrogen concentration reported in experimental studies.The identified structures from the GB spectrum exhibit vastly different behaviors in hydrogen segregation and diffusion,with the low-barrier channels inside GB core contributing to short-circuit diffusion,while the high energy gaps between GB and neighboring lattice serving as on-plane diffusion barriers.Mean square displacement analysis further confirms the findings,and shows that the calculated GB diffusion coefficient is three orders of magnitude greater than that of lattice.The present study has a significant implication for practical applications since it offers a tool to bridge the gap between atomic-scale interactions and macroscopic behaviors in engineering materials.展开更多
Reducing the exploration of multi-principal element alloy space is a key challenge to design high-performance U-based high-entropy alloy(UHEA).Here,the best combination of multi-principal element can be efficiently ac...Reducing the exploration of multi-principal element alloy space is a key challenge to design high-performance U-based high-entropy alloy(UHEA).Here,the best combination of multi-principal element can be efficiently acquired because proposed alloying strategy and screening criteria can substantially reduce the space of alloy and thus accelerate alloy design,rather than enormous random combinations through a trial-and-error approach.To choose the best seed alloy and suitable dopants,the screening criteria include small anisotropy,high specific modulus,high dynamical stability,and high ductility.We therefore find a shortcut to design UHEA from typical binary(UTi and UNb)to ternary(UTiNb),qua-ternary(UTiNbTa),and quinary(UTiNbTaFe).Finally,we find a best bcc senary UHEA(UTiNbTaFeMo),which has highest hardness and yield strength,while maintains good ductility among all the candidates.Compared to overestimation from empirical strength-hardness relationship,improved strength prediction can be achieved using a parameter-free theory considering volume mismatch and temperature effect on yield strength.This finding indicates that larger volume mismatch corresponds to higher yield strength,agreeing with the available measurements.Moreover,the dynamical stability and mechanical properties of candidates are greatly enhanced with increasing the number of multi-principal element,indicating the feasibility and effectiveness of adopted alloying strategy.The increasing of multi-principal element cor-responds to the increasing valence electron concentration(VEC).Alternatively,the mechanical properties significantly improve as increasing VEC,agreeing with measurements for other various bcc HEAs.This work can speed up research and development of advanced UHEA by greatly reducing the space of alloy composition.展开更多
In this work,C_(f)/(CrZrHfNbTa)C-SiC high-entropy ceramic matrix composites with good load-bearing,elec-tromagnetic shielding and ablation resistance were designed and reported for the first time.The compos-ites were ...In this work,C_(f)/(CrZrHfNbTa)C-SiC high-entropy ceramic matrix composites with good load-bearing,elec-tromagnetic shielding and ablation resistance were designed and reported for the first time.The compos-ites were fabricated by an efficient combined processing of slurry infiltration lamination(SIL)and precur-sor infiltration and pyrolysis(PIP).Density and porosity of the as-fabricated composites are 2.72 g/cm^(3) and 12.44 vol.%,respectively,and the flexural strength is 185±13 MPa.Due to the carbon fiber rein-forcement with high conductivity and strong reflection,and high-entropy(CrZrHfNbTa)C ceramic matrix with strong absorbability,the total Electromagnetic interference shielding efficiency(SET)of the compos-ites with a thickness of 3 mm are as high as 88.2 dB and 90 dB respectively in X-band and Ku-band.This means that higher than 99.999999%electromagnetic shielding is achieved at 8-18 GHz,showing excel-lent electromagnetic shielding performance.The C_(f)/(CrZrHfNbTa)C-SiC composites also present excellent ablation resistance,with the linear and mass ablation rates of 0.9μm/s and 1.82 mg/s after ablation at the heat flux of 5 MW/m^(2) for 300 s(∼2450℃).This work opens a new insight for the synergistic de-sign of structural and functional integrated materials with load-bearing,electromagnetic shielding and ablation resistance,etc.展开更多
17-4 precipitation-hardened(PH)stainless steel(SS)exhibits high strength and good corrosion resistance via Cu-precipitation hardening.Unlike conventional wrought 17-4PH SS,Cu segregation andε-Cu pre-cipitates are obs...17-4 precipitation-hardened(PH)stainless steel(SS)exhibits high strength and good corrosion resistance via Cu-precipitation hardening.Unlike conventional wrought 17-4PH SS,Cu segregation andε-Cu pre-cipitates are observed in additively manufactured(AM)17-4PH SS owing to the repeated rapid cooling after heating,which characterizes the AM process.In this study,solution treatment was conducted under various temperatures(1,000,1,050,1,100,and 1,200℃)and durations(1,2,4,and 8 h)to minimize the negative effects of Cu segregation andε-Cu precipitates on precipitation hardening.The mechanical prop-erties and microstructures of each condition for the Cu precipitation behavior were examined.Although theε-Cu precipitates did not disappear after solution treatment,the average diameter of theε-Cu precipi-tates tended to decrease with increasing solution treatment temperature and duration.Therefore,solution treatment at a temperature of 1,200℃ for 8 h was the best,resulting in improved strength compared to the conventional solution treatment at 1,050℃.Solution treatment on at least 1,100℃ is effective in AM.展开更多
Hydrogen energy,whether in generation plants or utilization facilities,plays a decisive role in the mission to achieve net-zero greenhouse gas emissions,all to minimize pollution.The growing demand for clean energy ca...Hydrogen energy,whether in generation plants or utilization facilities,plays a decisive role in the mission to achieve net-zero greenhouse gas emissions,all to minimize pollution.The growing demand for clean energy carrier steadily accelerates the development of hydrogen production processes,and therein proton exchange membrane(PEM)water electrolysis is deemed a promising long-term strategy for hydrogen preparation and collection.This review retrospects recent developments and applications of bipolar plates(BPs)as key components in PEM fuel cells and water electrolysers.The main content includes multifaceted challenges in the R&D or fabrication of BPs and potential future trends have also been proposed.Specific details cover the BPs matrix(metallic materials and carbon composites)and the surface coating types(metal and compound coatings,carbon-based coatings,and polymer coatings),as well as the influence of flow field design for mass transport.Long-term development and feasible researches of BPs are prospected.Especially in the following aspects:(1)Structural and functional integration of components,such as material fabrication and flow field geometry optimization using 3D printing technology;(2)Introduction of environment-friendly renewable energy for hydrogen production;(3)Research on hydrogen energy reversible systems;(4)Composition optimization of surface coatings based on computational materials science and(5)systematic design expected to evolve into the next generation of BPs.展开更多
To high-power permanent magnetic motors,it is critical for Nd-Fe-B magnets to maintain the desirable coercivity at high-temperature operating conditions.To address this,two approaches have been proven effective:(1)enh...To high-power permanent magnetic motors,it is critical for Nd-Fe-B magnets to maintain the desirable coercivity at high-temperature operating conditions.To address this,two approaches have been proven effective:(1)enhancing the room temperature coercivity;(2)reducing the eddy current loss.However,these two items are difficult to be simultaneously achieved.Here,the grain boundary diffusion(GBD)of the Pr-Tb-Al-Cu-based source is applied to enhance the coercivity and electric resistivity at room temperature from 1101 kA m-1 and 2.13×10–6Ωm to 1917 kA m-1 and 2.60×10–6Ωm,and those at 120°C from 384 kA m-1 and 4.31×10–6Ωm to 783 kA m-1 and 4.86×10–6Ωm,respectively.Such optimization is ascribed to the improved formation depth of Tb-rich 2:14:1 shells with large magnetocrystalline anisotropy and the increased intergranular Pr-based oxides with high electric resistivity,induced by the coordination effects of Tb and Pr,as proven by the atomic-scale observations and the first principles calculations.It thus results in the simultaneously improved output power and energy efficiency of the motor because of the combination of magnetic thermal stability enhancement and eddy current loss reduction,as theoretically confirmed by electromagnetic simulation.展开更多
Understanding the long-term corrosion behavior of neutron absorber materials in H_(3)BO_(3)solution is crucial for the materials applications in spent fuel storage.In this paper,long-term corrosion evolution for 180 d...Understanding the long-term corrosion behavior of neutron absorber materials in H_(3)BO_(3)solution is crucial for the materials applications in spent fuel storage.In this paper,long-term corrosion evolution for 180 d in relation to the structural heterogeneities of an Fe-based amorphous coating(AMC)in H_(3)BO_(3)solution at various temperatures was systematically investigated.Results indicate that the coating corrosion could be divided into three distinct stages.Initially,the corrosion resistance increased owing to the thickening and composition evolution of the passive films.Subsequently,the corrosion rate was kept almost constant in the second stage,which connected with the steady state of the passive film.Finally,the corrosion resistance of coating reduced gradually owing to the initiation and penetration of local-ized corrosion.Interestingly,it was revealed that the localized corrosion was initiated at the relatively Cr-depleted amorphous matrix in the deep pores of the coating.This could be attributed to the synergy of Cr-depletion and occlusive effect in the deep pores during long-term immersion.With the elevation of temperature,the localized corrosion was enhanced due to the accumulation of the H+in the pores to swiftly reach the critical conditions for passive film breakdown.This work provides insights into the long-term corrosion mechanism of Fe-based AMCs in H_(3)BO_(3)solution and offers meaningful contributions to the design of new corrosion resistant neutron absorbing coatings for spent fuel storage applications.展开更多
Magnetocaloric material is the key working substance for magnetic refrigerant technology,for which the low-field and low-temperature magnetocaloric effect(MCE)performance is of great importance for practical applicati...Magnetocaloric material is the key working substance for magnetic refrigerant technology,for which the low-field and low-temperature magnetocaloric effect(MCE)performance is of great importance for practical applications at low temperatures.Here,a giant low-field magnetocaloric effect in ferromagnetically ordered Er_(1-x)Tm_(x)Al_(2)(0≤x≤1)compounds was reported,and the magnetic structure was characterized based on low-temperature neutron powder diffraction.With increasing Tm content from 0 to 1,the Curie temperature of Er_(1-x)Tm_(x)Al_(2)(0≤x≤1)compounds decreases from 16.0 K to 3.6 K.For Er_(0.7)Tm_(0.3)Al_(2) compound,it showed the largest low-field magnetic entropy change(–SM)with the peak value of 17.2 and 25.7 J/(kg K)for 0–1 T and 0–2 T,respectively.The(–SM)max up to 17.2 J/(kg K)of Er0.7Tm0.3Al2 compound for 0–1 T is the largest among the intermetallic magnetocaloric materials ever reported at temperatures below 20 K.The peak value of adiabatic temperature change(Tad)max was determined as 4.13 K and 6.87 K for 0–1 T and 0–2 T,respectively.The characteristic of second-order magnetic transitions was confirmed on basis of Arrott plots,the quantitative criterion of exponent n,rescaled universal curves,and the mean-field theory criterion.The outstanding low-field MCE performance with low working temperatures indicates that Er_(1-x)Tm_(x)Al_(2)(0≤x≤1)compounds are promising candidates for magnetic cooling materials at liquid hydrogen and liquid helium temperatures.展开更多
Achieving high strength,deformability and toughness in polymers is important for practical industrial applications.This has remained challenging because of the mutually opposing effects of improvements to each of thes...Achieving high strength,deformability and toughness in polymers is important for practical industrial applications.This has remained challenging because of the mutually opposing effects of improvements to each of these properties.Here,a self-assembling nacre-like polymer composite is designed to achieve ex-tremely tough with increasing strength.This special design significantly improved polymer’s mechanical properties,including an ultra-high fracture strain of 1180%,a tensile strength of 55.4 MPa and a toughness of 506.9 MJ/m^(3),which far exceed the highest values previously reported for polymer composites.This ex-cellent combination of properties can be attributed to a novel toughening mechanism,achieved by the synergy of the domain-limiting effect of metallic glass fragments with the strain-gradient-induced orien-tation and crystallisation within the polymer during stretching.Our approach opens a promising avenue for designing robust polymer materials in armour and aerospace engineering for a range of innovative applications.展开更多
Reducing grain size(i.e.increasing the fraction of grain boundaries)could effectively strengthen nanograined metals but inevitably sacrifices the ductility and possibly causes a strengthening-softening transition belo...Reducing grain size(i.e.increasing the fraction of grain boundaries)could effectively strengthen nanograined metals but inevitably sacrifices the ductility and possibly causes a strengthening-softening transition below a critical grain size.In this work,a facile laser surface remelting-based technique was employed and optimized to fabricate a∼600μm-thick heterogeneous gradient nanostructured layer on an austenitic Hadfield manganese steel,in which the average grain size is gradually decreased from∼200μm in the matrix to only∼8 nm in the nanocrystalline-amorphous core-shell topmost surface.Atomic-scale microstructural characterizations dissected the gradient refinement processes along the gradient direction,i.e.transiting from the dislocations activities and twinning in sub-region to three kinds of martensitic transformations,and finally a multi-phase nanocrystalline-amorphous core-shell structural surface.Mechanical tests(e.g.nanoindentation,bulk-specimen tensile,and micro-pillar compression)were conducted along the gradient direction.It confirms a tensile strength of∼1055 MPa and ductility of∼10.5%in the laser-processed specimen.Particularly,the core-shell structural surface maintains ultra-strong(tensile strength of∼1.6 GPa,micro-pillar compressive strength of∼4 GPa at a strain of∼8%,and nanoindentation hardness of∼7.7 GPa)to overcome the potential strengthening-softening transition.Such significant strengthening effects are ascribed to the strength-ductility synergetic effects-induced extra work hardening ability in gradient nanostructure and the well-maintained dislocation activities inside extremely refined nanograins in the multi-phase nanocrystalline-amorphous core-shell structural surface,which are evidenced by atomic-scale observations and theoretical analysis.This study provides a unique hetero-nanostructure through a facile laser-related technique for extraordinary mechanical performance.展开更多
Dislocation-mediated plasticity in inorganic semiconductors and oxides has attracted increasing research interest because of the promising mechanical and functional properties tuned by dislocations.In this study,we in...Dislocation-mediated plasticity in inorganic semiconductors and oxides has attracted increasing research interest because of the promising mechanical and functional properties tuned by dislocations.In this study,we investigated the effects of light illumination on the dislocation-mediated plasticity in hexagonal wurtzite ZnO,a representative third-generation semiconductor material.A(0001)45o off sample was specially designed to preferentially activate the basal slip on(0001)plane.Three types of nanoindentation tests were performed under four different light conditions(550 nm,334 nm,405 nm,and darkness),including low-load(60μN)pop-in tests,high-load(500μN)nanoindentation tests,and nanoindentation creep tests.The maximum shear stresses at pop-in were found to approximate the theoretical shear strength regardless of the light conditions.The activation volume at pop-ins was calculated to be larger in light than in darkness.Cross-sectional transmission electron microscope images taken from beneath the indentation imprints showed that all indentation-induced dislocations were located beneath the indentation imprint in a thin-plate shape along one basal slip plane.These indentation-induced dislocations could spread much deeper in darkness than in light,revealing the suppressive effect of light on dislocation behavior.An analytical model was adopted to estimate the elastoplastic stress field beneath the indenter.It was found that dislocation glide ceased at a higher stress level in light,indicating the increase in the Peierls barrier under light illumination.Furthermore,nanoindentation creep tests showed the suppression of both indentation depth and creep rate by light.Nanoindentation creep also yielded a larger activation volume in light than in darkness.展开更多
“Brittle”metallic glass(MG)usually fractures catastrophically in a shattering mode under macroscopic compression,because cleavage cracking of splitting that originates from extrinsic flaws dominates the failure of s...“Brittle”metallic glass(MG)usually fractures catastrophically in a shattering mode under macroscopic compression,because cleavage cracking of splitting that originates from extrinsic flaws dominates the failure of such alloys,which brings challenges for studying yield strength.Here we show that the plastic yielding behavior in a brittle Fe-based MG can be successfully activated by decreasing the sample size to micrometer scale to avoid the possible large tensile stress concentrators.The yield strength was found to be at least 33%higher than the fracture strength measured with bulk samples for the present brittle MG.The results further demonstrate that the critical stresses for shear band initiation and propagation are size-independent,while the required stress for cleavage cracking increases with decreasing sample size.The competition of thermodynamic driving forces between the two processes of shear banding and cleavage cracking hence leads to the size-induced brittle-to ductile-transition.These findings clarify the physical nature of the strength of“brittle”MG,implying the great opportunity for using high-strength brittle MGs in devices with small dimensions.展开更多
Topologically protected magnetic skyrmions are expected to be used in the next-generation spintronic devices.Realizing their nucleation and manipulation at room temperature is fundamental for future practical applicat...Topologically protected magnetic skyrmions are expected to be used in the next-generation spintronic devices.Realizing their nucleation and manipulation at room temperature is fundamental for future practical applications.Here,using in situ Lorentz transmission electron microscopy and micromagnetic simulation,we demonstrate that magnetic biskyrmions can spontaneously exist at room temperature in Nd_(1-x) Tb_(x)Co_(5)(x=0.3,0.5)alloys.The spontaneous biskyrmions are controllably obtained over a wide temperature range across room temperature by switching atomic chemical environment.Furthermore,the density of biskyrmions can be tuned by a small magnetic field.High-density biskyrmions are stimulated to form in the thinner region at room temperature by introducing an in-plane magnetic field component.These results provide valuable insights into the manipulation of topological states,which is of great significance to their practical applications.展开更多
Nitride-reinforced(HfNbTaTiV)_(90)N_(10) high-entropy alloy aiming at high-temperature applications is de-signed in this paper.Abundant FCC nitride phases are formed in situ in theBCC matrix by arc melt-ing technique,...Nitride-reinforced(HfNbTaTiV)_(90)N_(10) high-entropy alloy aiming at high-temperature applications is de-signed in this paper.Abundant FCC nitride phases are formed in situ in theBCC matrix by arc melt-ing technique,without complex deformation or heat treatment.The(HfNbTaTiV)_(90)N_(10) alloy exhibits a remarkable yield strength of 2716 MPa and ultimate compressive strength of 2833 MPa with a plas-tic strain of 10%at room temperature.Besides,the alloy remains a high yield strength of 279 MPa at 1400℃.The nitride phases play an essential role in maintaining the excellent strength-ductility com-bination at room temperature and enhancing the high-temperature softening resistance.Alternating BCC and FCC phases possess the semi-coherent interface,which not only strengthens the BCC matrix but also promotes the compatible deformation of the duplex microstructure.The lattice coherency structure of the semi-coherent interface is conducive to the slip transfer of partial dislocations through the interface,which facilitates the accommodation of plastic deformation.The cross-slip of the screw dislocations ef-fectively eliminates stress concentration and leads to good ductility of the dual-phase alloy.The results demonstrate that the nitride phases achieve coordinate deformation with the matrix without deteriorat-ing the ductility of the(HfNbTaTiV)_(90)N_(10) alloy.展开更多
Ammonia is a critical feedstock for modern industry and agriculture,which is also a promising carbonfree energy carrier.Electrochemical nitrogen reduction reaction(ENRR)is a sustainable and efficient approach to synth...Ammonia is a critical feedstock for modern industry and agriculture,which is also a promising carbonfree energy carrier.Electrochemical nitrogen reduction reaction(ENRR)is a sustainable and efficient approach to synthesize ammonia under ambient reaction conditions.ENRR relies on the development of highly efficient electrocatalysts.So far various strategies have been applied to enhance the performance of catalysts including tuning the electronic structure,binding strength,coordination configuration as well as the introduction of multiple active sites and defects.In this review,the recent progress of Fe-based electrocatalysts and their coordination effect,syner gistic effect and def ect effect for nitrogen reduction reaction have been summarized.Our critical review focuses on the discussion of theoretical advancement,the performance origin of ENRR activity and selectivity of Fe-based electrocatalysts.展开更多
Ultrafast heating(UFH)at the rates of 10-300℃/s was employed as a new strategy to anneal a coldrolled 7 wt%Mn steel,followed by the immediate cooling.Severely deformed strain-induced martensite and lightly-deformed t...Ultrafast heating(UFH)at the rates of 10-300℃/s was employed as a new strategy to anneal a coldrolled 7 wt%Mn steel,followed by the immediate cooling.Severely deformed strain-induced martensite and lightly-deformed thermal martensite,both had been already enriched with C and Mn before,transformed to fine and coarse austenite grains during the UFH,leading to the bimodal size distribution.Compared with the long intercritical annealing(IA)process,the UFH processes produced larger fraction of RA grains(up to 37%)with a high density of dislocation,leading to the significant increase in yield strength by 270 MPa and the product of strength and elongation up to 55 GPa%due to the enormous work hardening capacity.Such a significant strengthening is first attributed to high density dislocations preserved after UFH and then to the microstructural refinement and the precipitation strengthening;whilst the sustainable work hardening is attributed to the successive TRIP effect during deformation,resulting from the large fraction of RA instantly formed with the bimodal size distribution during UFH.Moreover,the results on the microstructural characterization,thermodynamics calculation on the reverse transformation temperature and the kinetic simulations on the reverse transformation all suggest that the austenitization during UFH is displacive and involves the diffusion and partition of C.Therefore,we propose that it is a bainite-like transformation.展开更多
A series of large-area,flexible and transparent ultraviolet(UV)photodetectors(PDs)based on Ag nanowire(NW)@ZnO nanorods(NRs)are fabricated by an inexpensive,facile and effective approach.These Ag NW@ZnO NRs are succes...A series of large-area,flexible and transparent ultraviolet(UV)photodetectors(PDs)based on Ag nanowire(NW)@ZnO nanorods(NRs)are fabricated by an inexpensive,facile and effective approach.These Ag NW@ZnO NRs are successfully synthesized using a two-step method in an oil bath with a high surface-to-volume ratio and good crystallinity.The PDs are fabricated by drop-coating with different drop-coating times on the surface of polyethylene terephthalate(PET)coupled with Au electrodes.By optimizing the cross-linked network of Ag NW@ZnO NRs,PD2 with a size greater than 25 mm exhibits excellent photoresponse under UV light illumination of 365 nm(1.3 m W cm^(-2))with a bias of 5 V:a high sensitivity of over 10^(3),and a much shorter rise/decay time of 2.6 s/2.3 s.Simultaneously,the detector exhibits an average transmittance of more than 70%in the visible light region,as well as good flexibility and excellent mechanical stability under a bending angle of 120°over 1000 circles bending.These integral advantages have significant potential for practical applications and mass production.展开更多
文摘Heat-resistant aluminum alloys are widely used in aerospace and automotive fields for manufacturing hot components due to their advantages in lightweight design and energy conservation.However,the high-temperature strength of existing cast aluminum alloys is always limited to about 100 MPa at 350℃due to coarsening and transformation of strengthening phases.Here,we reveal that the yield strength and ultimate tensile strength of the T6 state Al-8.4Cu-2.3Ce-1.0Mn-0.5Ni-0.2Zr alloy at 400◦C increase by 34%and 44%after re-aging at 300℃for 100 h,and its thermal strength exhibits distinguished ad-vantage over traditional heat-resistant aluminum alloys.The enhanced elevated-temperature strength is attributed to the reprecipitation of the Ni-bearing T-Al_(20)Cu_(2)Mn_(3)phase,whose number density increases over one time.The significant segregation of Ni,Ce,and Zr elements at the interfaces helps improve the thermal stability of the T phase.The thermostable T phase effectively strengthens the matrix by in-hibiting dislocation motion.Meanwhile,a highly interconnected 3D intermetallic network along the grain boundaries can still remain after long-term re-aging at 300℃,which is conducive to imposing a drag on the grain boundaries at high temperatures.This finding offers a viable route for enhancing the elevated-temperature strength of heat-resistant aluminum alloys,which could provide expanded opportunities for higher-temperature applications.
基金the National Natural Science Foundation of China(Nos.52271149,51971123,and 51925103)the Innovation Program of Shanghai Municipal Edu-cation Commission(No.2021-01-07-00-09-E00114)+4 种基金the financial support from Program 173(No.2020-JCIQ-ZD-186-01)111project(No.D16002)the Space Utilization System of China Manned Space Engineering(No.KJZ-YY-NCL08)the Singapore Ministry of Education Academic Research Funds(Grant Nos.MOE-T2EP50120-0010,MOE-T2EP50220-0010,and A-8001225-00-00)Long Xu thanks the China Scholarship Council(CSC)Scholarship,China(CSC No.202106890047).
文摘Recently,researchers have explored the use of precipitation strengthening and finer microstructures with high-density dislocations in additive manufacturing to produce high-entropy alloys(HEAs)with adjustable properties.However,the inherent surface roughness and lack of machinability research in AMed HEAs limit their engineering applications.In this study,we systematically investigated the microstructural characteristics,mechanical properties,and machinability of Fe_(29.3)Co_(28.7)Ni_(28.6)Al_(6.8)Ti_(6.6)(at.%)HEAs with three different structures:single FCC phase cellular(SPC),dual precipitation-strengthened(DPS),and single precipitation-strengthened(SPS).These structures were fabricated by selective laser melting and isothermally annealing at 780 and 940℃.Compared to SPC HEA,DPS HEA exhibits a significant increase in yield strength and ultimate tensile strength but with a dramatic sacrifice in ductility.SPS HEA exhibits similar mechanical properties to SPC HEA due to the pronounced coarsening of L21 precipitates.The ultraprecision machining micro-cutting test showed that SPC HEA had a significant mechanochem-ical effect,as evidenced by a sharp drop in cutting force for inked workpieces,but not DPS HEA.An abnormal finding was that the negligible reflection of cutting force for SPS HEAs suggested a negative mechanochemical effect,even though SPS HEA had equally excellent plasticity like SPC HEA.It was found that nanocrystallization-induced strength enhancement and ductility reduction of SPS HEA lead to chips’deformation dominated by shear avalanche rather than chip folding of SPC HEA,which involves the reduction of surface energy and friction of chips’interfaces.Overall,these results and our research findings may guide the machining of AMed precipitation-strengthened HEAs and accelerate their engineering ap-plication.
基金supported by the National Natural Science Foun-dation(Grant No.52031013)the National Key Research and Development Program(Grant No.2018YFA0702900).
文摘The influence of different cryogenic sequences on the rolling contact fatigue(RCF)life of M50-bearing steel has been studied.The results show that direct cryogenic treatment after quenching can effectively improve RCF life.The L_(10)life is strikingly 5 times longer than that with cryogenic treatment after tem-pering.This is caused by the distinct lattice construction of martensite and the transformation of retained austenite.More secondary nanocarbides and fine twins are formed via cryogenic treatment before tem-pering compared with cryogenic treatment after tempering.The improvement in the RCF life of the steel is attributed to the joint effects of the secondary nanocarbides and twin boundaries with a width of 5-13 nm,which delays significantly crack initiation and propagation.This study highlights a common method to improve the service life of high-carbon and high-alloy steels by adjusting the cryogenic se-quence.
基金financially supported by the Research Council of Norway under the M-HEAT project(No.294689)the HyLINE Project(No.294739)All simulation resources are provided by the Norwegian Metacenter for Computational Science(Nos.NN9110K and NN9391K).
文摘Hydrogen as an interstitial solute at grain boundaries(GBs)can have a catastrophic impact on the mechanical properties of many metals.Despite the global research effort,the underlying hydrogen-GB interactions in polycrystals remain inadequately understood.In this study,using Voronoi tessellations and atomistic simulations,we elucidate the hydrogen segregation energy spectrum at the GBs of polycrystalline nickel by exploring all the topologically favorable segregation sites.Three distinct peaks in the energy spectrum are identified,corresponding to different structural fingerprints.The first peak(-0.205 eV)represents the most favorable segregation sites at GB core,while the second and third peaks account for the sites at GB surface.By incorporating a thermodynamic model,the spectrum enables the determination of the equilibrium hydrogen concentrations at GBs,unveiling a remarkable two to three orders of magnitude increase compared to the bulk hydrogen concentration reported in experimental studies.The identified structures from the GB spectrum exhibit vastly different behaviors in hydrogen segregation and diffusion,with the low-barrier channels inside GB core contributing to short-circuit diffusion,while the high energy gaps between GB and neighboring lattice serving as on-plane diffusion barriers.Mean square displacement analysis further confirms the findings,and shows that the calculated GB diffusion coefficient is three orders of magnitude greater than that of lattice.The present study has a significant implication for practical applications since it offers a tool to bridge the gap between atomic-scale interactions and macroscopic behaviors in engineering materials.
基金National Natural Science Foundation of China(No.51871175)111 project 2.0(No.BP0618008).
文摘Reducing the exploration of multi-principal element alloy space is a key challenge to design high-performance U-based high-entropy alloy(UHEA).Here,the best combination of multi-principal element can be efficiently acquired because proposed alloying strategy and screening criteria can substantially reduce the space of alloy and thus accelerate alloy design,rather than enormous random combinations through a trial-and-error approach.To choose the best seed alloy and suitable dopants,the screening criteria include small anisotropy,high specific modulus,high dynamical stability,and high ductility.We therefore find a shortcut to design UHEA from typical binary(UTi and UNb)to ternary(UTiNb),qua-ternary(UTiNbTa),and quinary(UTiNbTaFe).Finally,we find a best bcc senary UHEA(UTiNbTaFeMo),which has highest hardness and yield strength,while maintains good ductility among all the candidates.Compared to overestimation from empirical strength-hardness relationship,improved strength prediction can be achieved using a parameter-free theory considering volume mismatch and temperature effect on yield strength.This finding indicates that larger volume mismatch corresponds to higher yield strength,agreeing with the available measurements.Moreover,the dynamical stability and mechanical properties of candidates are greatly enhanced with increasing the number of multi-principal element,indicating the feasibility and effectiveness of adopted alloying strategy.The increasing of multi-principal element cor-responds to the increasing valence electron concentration(VEC).Alternatively,the mechanical properties significantly improve as increasing VEC,agreeing with measurements for other various bcc HEAs.This work can speed up research and development of advanced UHEA by greatly reducing the space of alloy composition.
基金supported by the National Key R&D Program of China(no.2022YFB3707700)Program of Shang-hai Academic/Technology Research Leader(no.23XD1424300)National Natural Science Foundation of China(no.52332003).
文摘In this work,C_(f)/(CrZrHfNbTa)C-SiC high-entropy ceramic matrix composites with good load-bearing,elec-tromagnetic shielding and ablation resistance were designed and reported for the first time.The compos-ites were fabricated by an efficient combined processing of slurry infiltration lamination(SIL)and precur-sor infiltration and pyrolysis(PIP).Density and porosity of the as-fabricated composites are 2.72 g/cm^(3) and 12.44 vol.%,respectively,and the flexural strength is 185±13 MPa.Due to the carbon fiber rein-forcement with high conductivity and strong reflection,and high-entropy(CrZrHfNbTa)C ceramic matrix with strong absorbability,the total Electromagnetic interference shielding efficiency(SET)of the compos-ites with a thickness of 3 mm are as high as 88.2 dB and 90 dB respectively in X-band and Ku-band.This means that higher than 99.999999%electromagnetic shielding is achieved at 8-18 GHz,showing excel-lent electromagnetic shielding performance.The C_(f)/(CrZrHfNbTa)C-SiC composites also present excellent ablation resistance,with the linear and mass ablation rates of 0.9μm/s and 1.82 mg/s after ablation at the heat flux of 5 MW/m^(2) for 300 s(∼2450℃).This work opens a new insight for the synergistic de-sign of structural and functional integrated materials with load-bearing,electromagnetic shielding and ablation resistance,etc.
基金This work was funded by Yangyoung Foundation and supported by the Technology Innovation Program(grant No.20009815,Development of DfAM-based 3D printing technology for lightweight and integrated aerospace parts)funded by the Ministry of Trade,Industry&Energy(MOTIE,Korea).
文摘17-4 precipitation-hardened(PH)stainless steel(SS)exhibits high strength and good corrosion resistance via Cu-precipitation hardening.Unlike conventional wrought 17-4PH SS,Cu segregation andε-Cu pre-cipitates are observed in additively manufactured(AM)17-4PH SS owing to the repeated rapid cooling after heating,which characterizes the AM process.In this study,solution treatment was conducted under various temperatures(1,000,1,050,1,100,and 1,200℃)and durations(1,2,4,and 8 h)to minimize the negative effects of Cu segregation andε-Cu precipitates on precipitation hardening.The mechanical prop-erties and microstructures of each condition for the Cu precipitation behavior were examined.Although theε-Cu precipitates did not disappear after solution treatment,the average diameter of theε-Cu precipi-tates tended to decrease with increasing solution treatment temperature and duration.Therefore,solution treatment at a temperature of 1,200℃ for 8 h was the best,resulting in improved strength compared to the conventional solution treatment at 1,050℃.Solution treatment on at least 1,100℃ is effective in AM.
基金supported by the National Key Research and Development Program of China(No.2021YFB4000101)the National Natural Science Foundation of China(No.52125102)the Fundamental Research Funds for the Central Universities(No.FRF-TP-2021–02C2).
文摘Hydrogen energy,whether in generation plants or utilization facilities,plays a decisive role in the mission to achieve net-zero greenhouse gas emissions,all to minimize pollution.The growing demand for clean energy carrier steadily accelerates the development of hydrogen production processes,and therein proton exchange membrane(PEM)water electrolysis is deemed a promising long-term strategy for hydrogen preparation and collection.This review retrospects recent developments and applications of bipolar plates(BPs)as key components in PEM fuel cells and water electrolysers.The main content includes multifaceted challenges in the R&D or fabrication of BPs and potential future trends have also been proposed.Specific details cover the BPs matrix(metallic materials and carbon composites)and the surface coating types(metal and compound coatings,carbon-based coatings,and polymer coatings),as well as the influence of flow field design for mass transport.Long-term development and feasible researches of BPs are prospected.Especially in the following aspects:(1)Structural and functional integration of components,such as material fabrication and flow field geometry optimization using 3D printing technology;(2)Introduction of environment-friendly renewable energy for hydrogen production;(3)Research on hydrogen energy reversible systems;(4)Composition optimization of surface coatings based on computational materials science and(5)systematic design expected to evolve into the next generation of BPs.
基金financially supported by the National Natu-ral Science Foundation of China(Nos.U21A205251774146,and 52171175)Jiangxi Provincial Key Science and Technology R&D Project(No.20203ABC28W006)Natural Science Founda-tion of Zhejiang Province(No.LY20E010002,2021C01023,and 2021C01033).
文摘To high-power permanent magnetic motors,it is critical for Nd-Fe-B magnets to maintain the desirable coercivity at high-temperature operating conditions.To address this,two approaches have been proven effective:(1)enhancing the room temperature coercivity;(2)reducing the eddy current loss.However,these two items are difficult to be simultaneously achieved.Here,the grain boundary diffusion(GBD)of the Pr-Tb-Al-Cu-based source is applied to enhance the coercivity and electric resistivity at room temperature from 1101 kA m-1 and 2.13×10–6Ωm to 1917 kA m-1 and 2.60×10–6Ωm,and those at 120°C from 384 kA m-1 and 4.31×10–6Ωm to 783 kA m-1 and 4.86×10–6Ωm,respectively.Such optimization is ascribed to the improved formation depth of Tb-rich 2:14:1 shells with large magnetocrystalline anisotropy and the increased intergranular Pr-based oxides with high electric resistivity,induced by the coordination effects of Tb and Pr,as proven by the atomic-scale observations and the first principles calculations.It thus results in the simultaneously improved output power and energy efficiency of the motor because of the combination of magnetic thermal stability enhancement and eddy current loss reduction,as theoretically confirmed by electromagnetic simulation.
基金supported by the National Natural Science Foundation of China(Nos.U1908219 and 52171163)the Key Research Program of the Chinese Academy of Sciences(NO.ZDRW-CN-2021-2-2).
文摘Understanding the long-term corrosion behavior of neutron absorber materials in H_(3)BO_(3)solution is crucial for the materials applications in spent fuel storage.In this paper,long-term corrosion evolution for 180 d in relation to the structural heterogeneities of an Fe-based amorphous coating(AMC)in H_(3)BO_(3)solution at various temperatures was systematically investigated.Results indicate that the coating corrosion could be divided into three distinct stages.Initially,the corrosion resistance increased owing to the thickening and composition evolution of the passive films.Subsequently,the corrosion rate was kept almost constant in the second stage,which connected with the steady state of the passive film.Finally,the corrosion resistance of coating reduced gradually owing to the initiation and penetration of local-ized corrosion.Interestingly,it was revealed that the localized corrosion was initiated at the relatively Cr-depleted amorphous matrix in the deep pores of the coating.This could be attributed to the synergy of Cr-depletion and occlusive effect in the deep pores during long-term immersion.With the elevation of temperature,the localized corrosion was enhanced due to the accumulation of the H+in the pores to swiftly reach the critical conditions for passive film breakdown.This work provides insights into the long-term corrosion mechanism of Fe-based AMCs in H_(3)BO_(3)solution and offers meaningful contributions to the design of new corrosion resistant neutron absorbing coatings for spent fuel storage applications.
基金supported by the National Key Research and Development Program of China(Nos.2021YFB3501202 and 2019YFB2005800)the Science Center of the National Science Foundation of China(No.52088101)+1 种基金the National Natural Science Foundation of China(Nos.51871019,52171170,52130103,51961145305,51971026,and 52171169)the Beijing Natural Science Foundation Key Program(Grant Nos.Z190007 and Z200007),and“111 Project”(No.B170003).
文摘Magnetocaloric material is the key working substance for magnetic refrigerant technology,for which the low-field and low-temperature magnetocaloric effect(MCE)performance is of great importance for practical applications at low temperatures.Here,a giant low-field magnetocaloric effect in ferromagnetically ordered Er_(1-x)Tm_(x)Al_(2)(0≤x≤1)compounds was reported,and the magnetic structure was characterized based on low-temperature neutron powder diffraction.With increasing Tm content from 0 to 1,the Curie temperature of Er_(1-x)Tm_(x)Al_(2)(0≤x≤1)compounds decreases from 16.0 K to 3.6 K.For Er_(0.7)Tm_(0.3)Al_(2) compound,it showed the largest low-field magnetic entropy change(–SM)with the peak value of 17.2 and 25.7 J/(kg K)for 0–1 T and 0–2 T,respectively.The(–SM)max up to 17.2 J/(kg K)of Er0.7Tm0.3Al2 compound for 0–1 T is the largest among the intermetallic magnetocaloric materials ever reported at temperatures below 20 K.The peak value of adiabatic temperature change(Tad)max was determined as 4.13 K and 6.87 K for 0–1 T and 0–2 T,respectively.The characteristic of second-order magnetic transitions was confirmed on basis of Arrott plots,the quantitative criterion of exponent n,rescaled universal curves,and the mean-field theory criterion.The outstanding low-field MCE performance with low working temperatures indicates that Er_(1-x)Tm_(x)Al_(2)(0≤x≤1)compounds are promising candidates for magnetic cooling materials at liquid hydrogen and liquid helium temperatures.
基金This work was financially supported by the Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone Shen-zhen Park Project(No.HZQB-KCZYB-2020030)the RGC Gen-eral Research Fund(No.AoE/M-402/20,CityU 11209918)+1 种基金the RGC Theme-based Research Scheme(No.T13-402/17-N)the Ma-jor Program of Changsha Science and Technology Project(No.kh2003023).
文摘Achieving high strength,deformability and toughness in polymers is important for practical industrial applications.This has remained challenging because of the mutually opposing effects of improvements to each of these properties.Here,a self-assembling nacre-like polymer composite is designed to achieve ex-tremely tough with increasing strength.This special design significantly improved polymer’s mechanical properties,including an ultra-high fracture strain of 1180%,a tensile strength of 55.4 MPa and a toughness of 506.9 MJ/m^(3),which far exceed the highest values previously reported for polymer composites.This ex-cellent combination of properties can be attributed to a novel toughening mechanism,achieved by the synergy of the domain-limiting effect of metallic glass fragments with the strain-gradient-induced orien-tation and crystallisation within the polymer during stretching.Our approach opens a promising avenue for designing robust polymer materials in armour and aerospace engineering for a range of innovative applications.
文摘Reducing grain size(i.e.increasing the fraction of grain boundaries)could effectively strengthen nanograined metals but inevitably sacrifices the ductility and possibly causes a strengthening-softening transition below a critical grain size.In this work,a facile laser surface remelting-based technique was employed and optimized to fabricate a∼600μm-thick heterogeneous gradient nanostructured layer on an austenitic Hadfield manganese steel,in which the average grain size is gradually decreased from∼200μm in the matrix to only∼8 nm in the nanocrystalline-amorphous core-shell topmost surface.Atomic-scale microstructural characterizations dissected the gradient refinement processes along the gradient direction,i.e.transiting from the dislocations activities and twinning in sub-region to three kinds of martensitic transformations,and finally a multi-phase nanocrystalline-amorphous core-shell structural surface.Mechanical tests(e.g.nanoindentation,bulk-specimen tensile,and micro-pillar compression)were conducted along the gradient direction.It confirms a tensile strength of∼1055 MPa and ductility of∼10.5%in the laser-processed specimen.Particularly,the core-shell structural surface maintains ultra-strong(tensile strength of∼1.6 GPa,micro-pillar compressive strength of∼4 GPa at a strain of∼8%,and nanoindentation hardness of∼7.7 GPa)to overcome the potential strengthening-softening transition.Such significant strengthening effects are ascribed to the strength-ductility synergetic effects-induced extra work hardening ability in gradient nanostructure and the well-maintained dislocation activities inside extremely refined nanograins in the multi-phase nanocrystalline-amorphous core-shell structural surface,which are evidenced by atomic-scale observations and theoretical analysis.This study provides a unique hetero-nanostructure through a facile laser-related technique for extraordinary mechanical performance.
基金supported by Japan Society for the Promotion of Science KAKENHI(Grant Nos.JP19H05786,JP21H04532,JP21H04618,JP21K20484,JP20H02421,JP22K14143,JP17H01238,and JP17H06094)A.Nakamura and E.Tochigi acknowledge the financial support of JST PRESTO(Grant Nos.JPMJPR199A and JPMJPR1999)X.Fang acknowledges the financial support by the Athene Young Investigator Programme at TU Darmstadt.
文摘Dislocation-mediated plasticity in inorganic semiconductors and oxides has attracted increasing research interest because of the promising mechanical and functional properties tuned by dislocations.In this study,we investigated the effects of light illumination on the dislocation-mediated plasticity in hexagonal wurtzite ZnO,a representative third-generation semiconductor material.A(0001)45o off sample was specially designed to preferentially activate the basal slip on(0001)plane.Three types of nanoindentation tests were performed under four different light conditions(550 nm,334 nm,405 nm,and darkness),including low-load(60μN)pop-in tests,high-load(500μN)nanoindentation tests,and nanoindentation creep tests.The maximum shear stresses at pop-in were found to approximate the theoretical shear strength regardless of the light conditions.The activation volume at pop-ins was calculated to be larger in light than in darkness.Cross-sectional transmission electron microscope images taken from beneath the indentation imprints showed that all indentation-induced dislocations were located beneath the indentation imprint in a thin-plate shape along one basal slip plane.These indentation-induced dislocations could spread much deeper in darkness than in light,revealing the suppressive effect of light on dislocation behavior.An analytical model was adopted to estimate the elastoplastic stress field beneath the indenter.It was found that dislocation glide ceased at a higher stress level in light,indicating the increase in the Peierls barrier under light illumination.Furthermore,nanoindentation creep tests showed the suppression of both indentation depth and creep rate by light.Nanoindentation creep also yielded a larger activation volume in light than in darkness.
基金financially supported by the National Natural Science Foundation of China(NSFC)(Nos.51771205 and 52271072)the Natural Science Foundation of Liaoning Province(No.2020-MS-011)the Start-up Program by Northwestern Polytechnical Uni-versity.
文摘“Brittle”metallic glass(MG)usually fractures catastrophically in a shattering mode under macroscopic compression,because cleavage cracking of splitting that originates from extrinsic flaws dominates the failure of such alloys,which brings challenges for studying yield strength.Here we show that the plastic yielding behavior in a brittle Fe-based MG can be successfully activated by decreasing the sample size to micrometer scale to avoid the possible large tensile stress concentrators.The yield strength was found to be at least 33%higher than the fracture strength measured with bulk samples for the present brittle MG.The results further demonstrate that the critical stresses for shear band initiation and propagation are size-independent,while the required stress for cleavage cracking increases with decreasing sample size.The competition of thermodynamic driving forces between the two processes of shear banding and cleavage cracking hence leads to the size-induced brittle-to ductile-transition.These findings clarify the physical nature of the strength of“brittle”MG,implying the great opportunity for using high-strength brittle MGs in devices with small dimensions.
基金supported by the Science Center of the Na-tional Science Foundation of China(Grant No.52088101)the Na-tional Natural Science Foundation of China(Grant Nos.52121001,52001019,52271195,52101210,and 52130103)+2 种基金the National Key and Development Program of China(Grant Nos.2021YFB3501600,2022YFB3505302)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant Nos.XDB33030100,XDB33030200)Youth Innovation Promotion Association(No.CAS Y201903).
文摘Topologically protected magnetic skyrmions are expected to be used in the next-generation spintronic devices.Realizing their nucleation and manipulation at room temperature is fundamental for future practical applications.Here,using in situ Lorentz transmission electron microscopy and micromagnetic simulation,we demonstrate that magnetic biskyrmions can spontaneously exist at room temperature in Nd_(1-x) Tb_(x)Co_(5)(x=0.3,0.5)alloys.The spontaneous biskyrmions are controllably obtained over a wide temperature range across room temperature by switching atomic chemical environment.Furthermore,the density of biskyrmions can be tuned by a small magnetic field.High-density biskyrmions are stimulated to form in the thinner region at room temperature by introducing an in-plane magnetic field component.These results provide valuable insights into the manipulation of topological states,which is of great significance to their practical applications.
基金supported by the National Natural Science Foun-dation of China(No.51975582)the Jiangsu Provincial Key Re-search and Development Program(No.BE2021088).
文摘Nitride-reinforced(HfNbTaTiV)_(90)N_(10) high-entropy alloy aiming at high-temperature applications is de-signed in this paper.Abundant FCC nitride phases are formed in situ in theBCC matrix by arc melt-ing technique,without complex deformation or heat treatment.The(HfNbTaTiV)_(90)N_(10) alloy exhibits a remarkable yield strength of 2716 MPa and ultimate compressive strength of 2833 MPa with a plas-tic strain of 10%at room temperature.Besides,the alloy remains a high yield strength of 279 MPa at 1400℃.The nitride phases play an essential role in maintaining the excellent strength-ductility com-bination at room temperature and enhancing the high-temperature softening resistance.Alternating BCC and FCC phases possess the semi-coherent interface,which not only strengthens the BCC matrix but also promotes the compatible deformation of the duplex microstructure.The lattice coherency structure of the semi-coherent interface is conducive to the slip transfer of partial dislocations through the interface,which facilitates the accommodation of plastic deformation.The cross-slip of the screw dislocations ef-fectively eliminates stress concentration and leads to good ductility of the dual-phase alloy.The results demonstrate that the nitride phases achieve coordinate deformation with the matrix without deteriorat-ing the ductility of the(HfNbTaTiV)_(90)N_(10) alloy.
基金supported by the Science and Tech-nology Commission of Shanghai Municipality(No.19ZR1418400)Xiaoli Zhang acknowledges financial supports from the National Natural Science Foundation of China(No.51602291).
文摘Ammonia is a critical feedstock for modern industry and agriculture,which is also a promising carbonfree energy carrier.Electrochemical nitrogen reduction reaction(ENRR)is a sustainable and efficient approach to synthesize ammonia under ambient reaction conditions.ENRR relies on the development of highly efficient electrocatalysts.So far various strategies have been applied to enhance the performance of catalysts including tuning the electronic structure,binding strength,coordination configuration as well as the introduction of multiple active sites and defects.In this review,the recent progress of Fe-based electrocatalysts and their coordination effect,syner gistic effect and def ect effect for nitrogen reduction reaction have been summarized.Our critical review focuses on the discussion of theoretical advancement,the performance origin of ENRR activity and selectivity of Fe-based electrocatalysts.
基金financial support from National Natural Science Foundation of China[Nos.51831002 and 51861135302]the Fundamental Research Funds for the Central Universities(No.FRF-TP-18-002C2)。
文摘Ultrafast heating(UFH)at the rates of 10-300℃/s was employed as a new strategy to anneal a coldrolled 7 wt%Mn steel,followed by the immediate cooling.Severely deformed strain-induced martensite and lightly-deformed thermal martensite,both had been already enriched with C and Mn before,transformed to fine and coarse austenite grains during the UFH,leading to the bimodal size distribution.Compared with the long intercritical annealing(IA)process,the UFH processes produced larger fraction of RA grains(up to 37%)with a high density of dislocation,leading to the significant increase in yield strength by 270 MPa and the product of strength and elongation up to 55 GPa%due to the enormous work hardening capacity.Such a significant strengthening is first attributed to high density dislocations preserved after UFH and then to the microstructural refinement and the precipitation strengthening;whilst the sustainable work hardening is attributed to the successive TRIP effect during deformation,resulting from the large fraction of RA instantly formed with the bimodal size distribution during UFH.Moreover,the results on the microstructural characterization,thermodynamics calculation on the reverse transformation temperature and the kinetic simulations on the reverse transformation all suggest that the austenitization during UFH is displacive and involves the diffusion and partition of C.Therefore,we propose that it is a bainite-like transformation.
基金supported by the National Natural Science Foundation of China(No.51775140)partially supported by the Shenzhen Science and Technology Plan(No.JCYJ20180507183511908)+2 种基金the National Science and Technology Major Project(No.2017-VⅠ-0009-0080)the Key-Area Research and Development Program of Guangdong Province(No.2019B010935001)the Industry and Information Technology Bureau of Shenzhen Municipality(No.201806071354163490)。
文摘A series of large-area,flexible and transparent ultraviolet(UV)photodetectors(PDs)based on Ag nanowire(NW)@ZnO nanorods(NRs)are fabricated by an inexpensive,facile and effective approach.These Ag NW@ZnO NRs are successfully synthesized using a two-step method in an oil bath with a high surface-to-volume ratio and good crystallinity.The PDs are fabricated by drop-coating with different drop-coating times on the surface of polyethylene terephthalate(PET)coupled with Au electrodes.By optimizing the cross-linked network of Ag NW@ZnO NRs,PD2 with a size greater than 25 mm exhibits excellent photoresponse under UV light illumination of 365 nm(1.3 m W cm^(-2))with a bias of 5 V:a high sensitivity of over 10^(3),and a much shorter rise/decay time of 2.6 s/2.3 s.Simultaneously,the detector exhibits an average transmittance of more than 70%in the visible light region,as well as good flexibility and excellent mechanical stability under a bending angle of 120°over 1000 circles bending.These integral advantages have significant potential for practical applications and mass production.