One of the challenges in the field of multi-photon 3D laser printing lies in further increasing the print speed in terms of voxels/s.Here,we present a setup based on a 7×7 focus array(rather than 3×3 in our ...One of the challenges in the field of multi-photon 3D laser printing lies in further increasing the print speed in terms of voxels/s.Here,we present a setup based on a 7×7 focus array(rather than 3×3 in our previous work)and using a focus velocity of about 1 m/s(rather than 0.5 m/s in our previous work)at the diffraction limit(40×/NA1.4 microscope objective lens).Combined,this advance leads to a ten times increased print speed of about 108 voxels/s.We demonstrate polymer printing of a chiral metamaterial containing more than 1.7×10^(12) voxels as well as millions of printed microparticles for potential pharmaceutical applications.The critical high-quality micro-optical components of the setup,namely a diffractive optical element generating the 7×7 beamlets and a 7×7 lens array,are manufactured by using a commercial two-photon grayscale 3D laser printer.展开更多
Non-Schmid(NS)effects in body-centered cubic(BCC)single-phase metals have received special attention in recent years.However,a deep understanding of these effects in the BCC phase of dual-phase(DP)steels has not yet b...Non-Schmid(NS)effects in body-centered cubic(BCC)single-phase metals have received special attention in recent years.However,a deep understanding of these effects in the BCC phase of dual-phase(DP)steels has not yet been reached.This study explores the NS effects in ferrite-martensite DP steels,where the ferrite phase has a BCC crystallographic structure and exhibits NS effects.The influences of NS stress components on the mechanical response of DP steels are studied,including stress/strain partitioning,plastic flow,and yield surface.To this end,the mechanical behavior of the two phases is described by dislocation density-based crystal plasticity constitutive models,with the NS effect only incorporated into the ferrite phase modeling.The NS stress contribution is revealed for two types of microstructures commonly observed in DP steels:equiaxed phases with random grain orientations,and elongated phases with preferred grain orientations.Our results show that,in the case of a microstructure with equiaxed phases,the normal NS stress components play significant roles in tension-compression asymmetry.By contrast,in microstructures with elongated phases,a combined influence of crystallographic texture and NS effect is evident.These findings advance our knowledge of the intricate interplay between microstructural features and NS effects and help to elucidate the mechanisms underlying anisotropic-asymmetric plastic behavior of DP steels.展开更多
Carbon dioxide(CO_(2))is often monitored as a convenient yardstick for indoor air safety,yet its ability to stand in for pathogen-laden aerosols has never been settled.To probe the question,we reproduced an open-plan ...Carbon dioxide(CO_(2))is often monitored as a convenient yardstick for indoor air safety,yet its ability to stand in for pathogen-laden aerosols has never been settled.To probe the question,we reproduced an open-plan office at full scale(7.2m×5.2m×2.8m)and introduced a breathing plume that carried 4% CO_(2),together with a polydisperse aerosol spanning 0.5–10μm(1320 particles s^(−1)).Inlet air was supplied at 0.7,1.4,and 2.1 m s^(−1),and the resulting fields were simulated with a Realisable k–εRANS model coupled to Lagrangian particle tracking.Nine strategically placed probes provided validation;the calibrated solution deviated fromthe experiment by 58 ppm for CO_(2)(8.1%RMSE)and 0.008 m s^(−1)for velocity(15.7%RMSE).Despite this agreement,gas and particles behaved in sharply different ways.Room-averaged CO_(2)varied by<15%,whereas the aerosol mass rose to almost three-fold the background within slowmoving corner vortices.Sub-micron particles stayed aloft along streamlines,while those≥5μmpeeled away and settled on nearby surfaces.The divergence shows that neither the CO_(2)level nor themeanageof air,taken in isolation,delineates all high-exposure zones.We therefore recommend that ventilation design be informed by a composite diagnosis that couples gas data,size-resolved particle measurements,and rapid CFD appraisal.展开更多
Grain boundary(GB)segregation substantially influences the mechanical properties and performance of magnesium(Mg).Atomic-scale modeling,typically using ab-initio or semi-empirical approaches,has mainly focused on GB s...Grain boundary(GB)segregation substantially influences the mechanical properties and performance of magnesium(Mg).Atomic-scale modeling,typically using ab-initio or semi-empirical approaches,has mainly focused on GB segregation at highly symmetric GBs in Mg alloys,often failing to capture the diversity of local atomic environments and segregation energies,resulting in inaccurate structure-property predictions.This study employs atomistic simulations and machine learning models to systematically investigate the segregation behavior of common solute elements in polycrystalline Mg at both 0 K and finite temperatures.The machine learning models accurately predict segregation thermodynamics by incorporating energetic and structural descriptors.We found that segregation energy and vibrational free energy follow skew-normal distributions,with hydrostatic stress,an indicator of excess free volume,emerging as an important factor influencing segregation tendency.The local atomic environment's flexibility,quantified by flexibility volume,is also crucial in predicting GB segregation.Comparing the grain boundary solute concentrations calculated via the Langmuir-Mc Lean isotherm with experimental data,we identified a pronounced segregation tendency for Nd,highlighting its potential for GB engineering in Mg alloys.This work demonstrates the powerful synergy of atomistic simulations and machine learning,paving the way for designing advanced lightweight Mg alloys with tailored properties.展开更多
1 Foreword The crises produced by the COVID-19 pandemic and the ongoing Russia-Ukraine conflict have starkly highlighted the critical need for scientific innovation and global cooperation.The pandemic underscored the ...1 Foreword The crises produced by the COVID-19 pandemic and the ongoing Russia-Ukraine conflict have starkly highlighted the critical need for scientific innovation and global cooperation.The pandemic underscored the urgency of swift,science-driven responses to worldwide health emergencies,while the war has intensified energy shortages and material scarcities,amplifying the demand for sustainable and resilient solutions.展开更多
1.Introduction With the upgrading of major equipment,the mechanical prop-erty requirements for structural materials are increasingly high.The maraging steel or maraging stainless steel has long repre-sented the highes...1.Introduction With the upgrading of major equipment,the mechanical prop-erty requirements for structural materials are increasingly high.The maraging steel or maraging stainless steel has long repre-sented the highest strength alloy to be developed as reported in recent researches[1-8].The tensile strength of this kind of alloy is usually around 2.0 GPa.The yield strength of a maraging steel re-cently fabricated by laser powder bed fusion can reach as high as about 2.4 GPa,but it is unfortunate that the elongation is merely about 1%[9].So it seems that 2.0 GPa yield strength is an upper limitation for this kind of alloy.To break through this limitation,it is of significance to establish a new composition design strat-egy.For instance,recent work[10]reported a medium Mn steel doped with Al and V elements,which exhibits an ultra-high yield strength of 2.21 GPa with 15%uniform elongation after thermo-mechanical processing.In another aspect,the design using multi-ple principal elements and additional elements to form a high en-tropy alloy(HEA)should be a very promising pathway.展开更多
Brittleness is a bottleneck hindering the applications of fruitful functional properties of Ni–Mn-based multiferroic alloys.Recently,experimental studies on B alloying shed new light on this issue.However,the knowled...Brittleness is a bottleneck hindering the applications of fruitful functional properties of Ni–Mn-based multiferroic alloys.Recently,experimental studies on B alloying shed new light on this issue.However,the knowledge related to B alloying is limited until now.More importantly,the mechanism of the improved ductility,which is intrinsically related to the chemical bond that is difficult to reveal by routine experiments,is still unclear.In this context,by first-principles calculations,the impact and the correlated mechanism of B alloying were systemically studied by investigating four alloying systems,i.e.,(Ni_(2-x)B_(x))MnGa,Ni_(2)(Mn_(1-x)B_(x))Ga,Ni_(2)Mn(Ga_(1-x)B_(x))and(Ni_(2)MnGa)_(1-x)B_(x).Results show that B prefers the direct occupation manner when it replaces Ni,Mn and Ga.For interstitial doping,B tends to locate at octahedral rather than tetrahedral interstice.Calculations show that the replacement of B for Ga can effectively improve(reduce)the inherent ductility(inherent strength)due to the weaker covalent strength of Ni(Mn)–B compared with Ni(Mn)–Ga.In contrast,B staying at octahedral interstice will lead to the formation of new chemical bonds between Ni(Mn)and B,bringing about a significantly improved strength and a greatly reduced ductility.Upon the substitutions for Ni and Mn,they affect both the inherent ductility and strength insignificantly.For phase transition,the replacement of B for Ga tends to destabilize the austenite,which can be understood in the picture of the band Jahn–Teller effect.Besides,the substitution for Ga would not lead to an obvious reduction of magnetization.展开更多
基金funding by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)under Germany’s Excellence Strategy for the Excellence Cluster“3D Matter Made to Order”(2082/1-390761711)by the Carl Zeiss Foundation,and by the Helmholtz program Materials Systems Engineering.
文摘One of the challenges in the field of multi-photon 3D laser printing lies in further increasing the print speed in terms of voxels/s.Here,we present a setup based on a 7×7 focus array(rather than 3×3 in our previous work)and using a focus velocity of about 1 m/s(rather than 0.5 m/s in our previous work)at the diffraction limit(40×/NA1.4 microscope objective lens).Combined,this advance leads to a ten times increased print speed of about 108 voxels/s.We demonstrate polymer printing of a chiral metamaterial containing more than 1.7×10^(12) voxels as well as millions of printed microparticles for potential pharmaceutical applications.The critical high-quality micro-optical components of the setup,namely a diffractive optical element generating the 7×7 beamlets and a 7×7 lens array,are manufactured by using a commercial two-photon grayscale 3D laser printer.
基金supported by the National Natural Science Foundation of China(Grant Nos.12202153 and 12072123).
文摘Non-Schmid(NS)effects in body-centered cubic(BCC)single-phase metals have received special attention in recent years.However,a deep understanding of these effects in the BCC phase of dual-phase(DP)steels has not yet been reached.This study explores the NS effects in ferrite-martensite DP steels,where the ferrite phase has a BCC crystallographic structure and exhibits NS effects.The influences of NS stress components on the mechanical response of DP steels are studied,including stress/strain partitioning,plastic flow,and yield surface.To this end,the mechanical behavior of the two phases is described by dislocation density-based crystal plasticity constitutive models,with the NS effect only incorporated into the ferrite phase modeling.The NS stress contribution is revealed for two types of microstructures commonly observed in DP steels:equiaxed phases with random grain orientations,and elongated phases with preferred grain orientations.Our results show that,in the case of a microstructure with equiaxed phases,the normal NS stress components play significant roles in tension-compression asymmetry.By contrast,in microstructures with elongated phases,a combined influence of crystallographic texture and NS effect is evident.These findings advance our knowledge of the intricate interplay between microstructural features and NS effects and help to elucidate the mechanisms underlying anisotropic-asymmetric plastic behavior of DP steels.
文摘Carbon dioxide(CO_(2))is often monitored as a convenient yardstick for indoor air safety,yet its ability to stand in for pathogen-laden aerosols has never been settled.To probe the question,we reproduced an open-plan office at full scale(7.2m×5.2m×2.8m)and introduced a breathing plume that carried 4% CO_(2),together with a polydisperse aerosol spanning 0.5–10μm(1320 particles s^(−1)).Inlet air was supplied at 0.7,1.4,and 2.1 m s^(−1),and the resulting fields were simulated with a Realisable k–εRANS model coupled to Lagrangian particle tracking.Nine strategically placed probes provided validation;the calibrated solution deviated fromthe experiment by 58 ppm for CO_(2)(8.1%RMSE)and 0.008 m s^(−1)for velocity(15.7%RMSE).Despite this agreement,gas and particles behaved in sharply different ways.Room-averaged CO_(2)varied by<15%,whereas the aerosol mass rose to almost three-fold the background within slowmoving corner vortices.Sub-micron particles stayed aloft along streamlines,while those≥5μmpeeled away and settled on nearby surfaces.The divergence shows that neither the CO_(2)level nor themeanageof air,taken in isolation,delineates all high-exposure zones.We therefore recommend that ventilation design be informed by a composite diagnosis that couples gas data,size-resolved particle measurements,and rapid CFD appraisal.
基金Z.X.and T.A.S.acknowledge the financial support by the German Research Foundation(DFG)(Grant Nr.505716422)T.A.S.are grateful for the financial support from the DFG(Grant Nr.AL1343/7-1,AL1343/8-1 and Yi 103/3-1)+4 种基金Z.X.,S.K.K.and U.K.acknowledge financial support by the DFG through the projects A05,A07 and C02 of the SFB1394 StructuralChemical Atomic Complexity-From Defect Phase Diagrams to Material Properties,project ID 409476157Additionally,Z.X.and S.K.K.are grateful for funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(grant agreement No.852096 FunBlocks)J.G.acknowledges funding from the French National Research Agency(ANR),Grant ANR-21-CE08-0001(ATOUUM)and ANR-22-CE92-0058-01(SILA)The authors gratefully acknowledge the computing time provided to them at the NHR Center NHR4CES at RWTH Aachen University(project number p0020431 and p0020267)。
文摘Grain boundary(GB)segregation substantially influences the mechanical properties and performance of magnesium(Mg).Atomic-scale modeling,typically using ab-initio or semi-empirical approaches,has mainly focused on GB segregation at highly symmetric GBs in Mg alloys,often failing to capture the diversity of local atomic environments and segregation energies,resulting in inaccurate structure-property predictions.This study employs atomistic simulations and machine learning models to systematically investigate the segregation behavior of common solute elements in polycrystalline Mg at both 0 K and finite temperatures.The machine learning models accurately predict segregation thermodynamics by incorporating energetic and structural descriptors.We found that segregation energy and vibrational free energy follow skew-normal distributions,with hydrostatic stress,an indicator of excess free volume,emerging as an important factor influencing segregation tendency.The local atomic environment's flexibility,quantified by flexibility volume,is also crucial in predicting GB segregation.Comparing the grain boundary solute concentrations calculated via the Langmuir-Mc Lean isotherm with experimental data,we identified a pronounced segregation tendency for Nd,highlighting its potential for GB engineering in Mg alloys.This work demonstrates the powerful synergy of atomistic simulations and machine learning,paving the way for designing advanced lightweight Mg alloys with tailored properties.
文摘1 Foreword The crises produced by the COVID-19 pandemic and the ongoing Russia-Ukraine conflict have starkly highlighted the critical need for scientific innovation and global cooperation.The pandemic underscored the urgency of swift,science-driven responses to worldwide health emergencies,while the war has intensified energy shortages and material scarcities,amplifying the demand for sustainable and resilient solutions.
基金Project(51171120)supported by the National Natural Science Foundation of ChinaProject(N090202001)supported by the Fundamental Research Funds for the Central Universities,China
基金National Natural Science Foundation of Jiangsu Province(BK20160291)the Natural Science Foundation of the Jiangsu Higher Education Institutions(17KJB430013)+1 种基金the fund of the State Key Laboratory of Solidification Processing in NWPU(SKLSP201822)the Fund of the Jiangsu Planned Projects for Postdoctoral Research Funds(1701006B)
基金National Natural Science Foundation of China(No.51371121).
文摘1.Introduction With the upgrading of major equipment,the mechanical prop-erty requirements for structural materials are increasingly high.The maraging steel or maraging stainless steel has long repre-sented the highest strength alloy to be developed as reported in recent researches[1-8].The tensile strength of this kind of alloy is usually around 2.0 GPa.The yield strength of a maraging steel re-cently fabricated by laser powder bed fusion can reach as high as about 2.4 GPa,but it is unfortunate that the elongation is merely about 1%[9].So it seems that 2.0 GPa yield strength is an upper limitation for this kind of alloy.To break through this limitation,it is of significance to establish a new composition design strat-egy.For instance,recent work[10]reported a medium Mn steel doped with Al and V elements,which exhibits an ultra-high yield strength of 2.21 GPa with 15%uniform elongation after thermo-mechanical processing.In another aspect,the design using multi-ple principal elements and additional elements to form a high en-tropy alloy(HEA)should be a very promising pathway.
基金the National Natural Science Foundation of China(Grant No.51801020,51922026,51771044)the Fundamental Research Funds for the Central Universities(Grant No.N2002005,N2002021)+2 种基金the Liao Ning Revitalization Talents Program(Grant No.XLYC1802023)the Ph.D.Starting Foundation of Liaoning Province(Grant No.20180540115)Programme of Introducing Talents of Discipline Innovation to Universities(the 111 Project of China,No.BP0719037,B20029)。
文摘Brittleness is a bottleneck hindering the applications of fruitful functional properties of Ni–Mn-based multiferroic alloys.Recently,experimental studies on B alloying shed new light on this issue.However,the knowledge related to B alloying is limited until now.More importantly,the mechanism of the improved ductility,which is intrinsically related to the chemical bond that is difficult to reveal by routine experiments,is still unclear.In this context,by first-principles calculations,the impact and the correlated mechanism of B alloying were systemically studied by investigating four alloying systems,i.e.,(Ni_(2-x)B_(x))MnGa,Ni_(2)(Mn_(1-x)B_(x))Ga,Ni_(2)Mn(Ga_(1-x)B_(x))and(Ni_(2)MnGa)_(1-x)B_(x).Results show that B prefers the direct occupation manner when it replaces Ni,Mn and Ga.For interstitial doping,B tends to locate at octahedral rather than tetrahedral interstice.Calculations show that the replacement of B for Ga can effectively improve(reduce)the inherent ductility(inherent strength)due to the weaker covalent strength of Ni(Mn)–B compared with Ni(Mn)–Ga.In contrast,B staying at octahedral interstice will lead to the formation of new chemical bonds between Ni(Mn)and B,bringing about a significantly improved strength and a greatly reduced ductility.Upon the substitutions for Ni and Mn,they affect both the inherent ductility and strength insignificantly.For phase transition,the replacement of B for Ga tends to destabilize the austenite,which can be understood in the picture of the band Jahn–Teller effect.Besides,the substitution for Ga would not lead to an obvious reduction of magnetization.
