Flexible pressure sensors show great promise for applications in such fields as electronic skin,healthcare,and intelligent robotics.Traditional capacitive pressure sensors,however,face the problem of low sensitivity,w...Flexible pressure sensors show great promise for applications in such fields as electronic skin,healthcare,and intelligent robotics.Traditional capacitive pressure sensors,however,face the problem of low sensitivity,which limits their wider application.In this paper,a flexible capacitive pressure sensor with microstructured ionization layer is fabricated by a sandwich-type process,with a low-cost and simple process of inverted molding with sandpapers being used to form a thermoplastic polyurethane elastomer ionic film with double-sided microstructure as the dielectric layer of the sensor,with silver nanowires as electrodes.The operating mechanism of this iontronic pressure sensor is analyzed using a graphical method,and the sensor is tested on a pressure platform.The test results show that the sensor has ultrahigh pressure sensitivities of 3.744 and 1.689 kPa^(−1) at low(0-20 kPa)and high(20-800 kPa)pressures,respectively,as well as a rapid response time(100 ms),and it exhibits good stability and repeatability.The sensor can be used for sensitive monitoring of activities such as finger bending,and for facial expression(smile,frown)recognition,as well as speech recognition.展开更多
Nano-lamellar Ti_(3)Al/TiAl(α2/γ)alloy with significantly improved nanohardness was prepared using dual-wire-fed electron beam-directed energy deposition(EB-DED)in this study.This investigation focused on the evolut...Nano-lamellar Ti_(3)Al/TiAl(α2/γ)alloy with significantly improved nanohardness was prepared using dual-wire-fed electron beam-directed energy deposition(EB-DED)in this study.This investigation focused on the evolution of the colony shape and lamellar thickness of the Ti-43Al lamellar alloy at different heights.Nanoindentation tests were employed to evaluate deformation resistance,and numerical simulations provided deeper insights into the deposition process.The results indicate that the colonies are mostly columnar,except for a few equiaxed colonies at the top.Rapid cooling significantly refines theα2 lamellae,resulting in an average spacing of 218 nm and thickness of 41 nm.Additionally,substantial microstrain and a nonequilibrium Al distribution lead to a significant generation ofγvariants,refining theγlamellae to 57 nm.Abundantγ/γ’andα2/γinterfaces,along with fineα2 phases,contribute to improved deformation resistance.Consequently,the nano-lamellar TiAl alloy exhibited a notable 32%increase in nanohardness(8.3 GPa)while maintaining a similar modulus(197 GPa)to conventionally prepared alloys.This study holds significant promise for advancing high-performance TiAl alloys through the dual-wire-fed EB-DED process.展开更多
For a long time,the large loss of the strength and toughness of fusion welded joints for thick nearβtitanium alloys has largely hindered their engineering application,which results from the few precipitations of the ...For a long time,the large loss of the strength and toughness of fusion welded joints for thick nearβtitanium alloys has largely hindered their engineering application,which results from the few precipitations of the strengtheningαphase during welding cooling.In this study,double annealing treatment was designed for electron beam welded joints of 30-mm-thick nearβTi-5Al-5Mo-5V-1Cr-1Fe alloy,with the aim of regulating the proportion of multi-level lamellar microstructures and enhancing the joint properties.Among various annealing temperatures(first annealing at 750–880 ℃+second annealing at 580 ℃),the 750 ℃+580 ℃ annealed joint exhibited simultaneously enhanced strength and toughness,with the increase in tensile strength and impact energy from 844 MPa and 8.8 J for the as-welded joint to 1129 MPa and 14.5 J for annealed joint,respectively,which were superior to those of the joints of Ti5Al-5Mo-5V-1Cr-1Fe alloy as reported.The great increases in the strength and toughness were mainly attributed to the excellent proportion matching of formed multi-level lamellar microstructures(76.1%of primaryα(αp)lamellae and 7.9%of secondaryα(αs)lamellae),among which theαp phase andαs phase mainly affected the joint toughness and strength,respectively.The good coupling ofαp phase andαs phase improved the precipitation strengthening and the resistance to crack propagation.The modified strengthening mechanism models were proposed by introducing the thickness and proportion parameters of the precipitated phase.It was indicated that the theoretical calculation values were in good agreement with the experimental ones,and the solution strengthening and precipitation strengthening provided a large contribution(a sum of about 75%)to the yield strength of the annealed joints.This study provides a novel method via designing proper multi-level lamellar microstructures to simultaneously improve the strength and toughness of nearβtitanium alloy joints.展开更多
Electron beam powder bed fusion(EB-PBF)offers a promising route for producing Ti_(6)Al_(4)V alloys with tailored microstructures and superior mechanical properties.Herein,EB-PBF produced nearly fully dense Ti 6Al 4V a...Electron beam powder bed fusion(EB-PBF)offers a promising route for producing Ti_(6)Al_(4)V alloys with tailored microstructures and superior mechanical properties.Herein,EB-PBF produced nearly fully dense Ti 6Al 4V alloys(≥98.5%)with basketweave microstructures containing fine equilibriumαlamellae,different from typicalα′acicular observed in materials produced via laser-PBF.The as-printed horizontal material has a yield strength(YS)of 992 MPa,an ultimate tensile strength(UTS)of 1053 MPa,and a fracture strain(ε)of 10.9%.Meanwhile,the as-printed longitudinal material shows inferior mechanical properties(YS of 934 MPa,UTS of 979 MPa,andεof 2.4%).The horizontal and longitudinal samples show notable hysteresis loops in the loading unloading reloading curves,indicating substantial heterogeneous-induced strengthening.Flow stress,back stress,and effective stress increase with increasing strain,where back stress is comparable to effective stress during the overall deformation.Furthermore,a monotonically decreased strain hardening rate with increasing strain can be attributed to dislocation activities,whose failure is related to the strain localization at theαlamellae boundary.展开更多
Fe-Mo functionally graded materials(FGMs)with different composition-change rates from 100%304 stainless steel to 100%Mo along the composition gradient direction were prepared by electron beam-directed energy depositio...Fe-Mo functionally graded materials(FGMs)with different composition-change rates from 100%304 stainless steel to 100%Mo along the composition gradient direction were prepared by electron beam-directed energy deposition(EB-DED)technique,including three samples with composition mutation of 100%,composition change rate of 10%and 30%.Results show that the composition-change rate significantly affects the microstructure and mechanical properties of the samples.In the sample with abrupt change of composition,the sharp shift in composition between 304 stainless steel and Mo leads to a great difference in the microstructure and hardness near the interface between the two materials.With the increase in the number of gradient layers,the composition changes continuously along the direction of deposition height,and the microstructure morphology shows a smooth transition from 304 stainless steel to Mo,which is gradually transformed from columnar crystal to dendritic crystal.Elements Fe,Mo,and other major elements transform linearly along the gradient direction,with sufficient interlayer diffusion between the deposited layers,leading to good metallurgical bonding.The smaller the change in composition gradient,the greater the microhardness value along the deposition direction.When the composition gradient is 10%,the gradient layer exhibits higher hardness(940 HV)and excellent resistance to surface abrasion,and the overall compressive properties of the samples are better,with the compressive fracture stress in the top region reaching 750.05±14 MPa.展开更多
TiAl alloys fabricated by electron beam powder bed fusion(EB-PBF)usually exhibit special microstructures with alternating fine-grained(FG)regions and coarse-grained(CG)bands.In previous studies,the CG microstructures ...TiAl alloys fabricated by electron beam powder bed fusion(EB-PBF)usually exhibit special microstructures with alternating fine-grained(FG)regions and coarse-grained(CG)bands.In previous studies,the CG microstructures were equiaxed γ phases,and the FG microstructures presented three types:near gamma,duplex,and nearly lamellar.However,the rule for controlling FG microstructures has not been found.Hence,a method needs to be built to find the rule for controlling FG microstructures.Here,we established a normalized process diagram by combining Al-equivalent and dimensionless process parameters.Based on the normalized process diagram,we successfully control the FG microstructures and customize three FG microstructures of the Ti-48Al-2Cr-2Nb alloy.Meanwhile,the average tensile yield strength reaches 756 MPa when the FG microstructure is near gamma.The yield strength is higher than the previous data for the Ti-48Al-2Cr-2Nb alloy.This is attributed to the strong interface-strengthening effect between FG near γ microstructures and CG γ bands.These findings can help shorten the research time of the other TiAl alloys fabricated by EB-PBF,improving the mechanical properties of the other EBPBF-built TiAl alloys in the future.展开更多
It is rather difficult for titanium alloy ultra-thick plates to achieve superior weld formation and excellent mechanical properties along the weld penetration direction due to the large fluctuations of the molten pool...It is rather difficult for titanium alloy ultra-thick plates to achieve superior weld formation and excellent mechanical properties along the weld penetration direction due to the large fluctuations of the molten pool,largely limiting their engineering application.In this study,106-mm-thick Ti-6Al-4V ELI alloy plates were successfully butt welded via electron beam welding(EBW).The defect-free EBW joint with full penetration was obtained.The precipitated secondary α(α_(s))in heat affected zone(HAZ),αlamellae in fusion line(FL)and α′martensite in fusion zone(FZ)increased the α_(s)/β,α/β and α′/β interfaces,respectively,resulting in the higher microhardness and impact energy values(57 J in the HAZ,62 J in the FL and 51.9 J in the FZ)than those in the base material(BM).The impact energy of the joint in this study was higher than that for Ti-6Al-4V ELI alloy joints as reported,which was mainly attributed to the formation of the relatively thickerαphase and finer interlamellar spacing in this study,enhancing the resistance to crack propagation.Furthermore,the average fracture toughness(90.2 MPa m^(1/2))of the FZ was higher than that of the BM(74.2 MPa m^(1/2)).This study provides references for the welding application of titanium alloy ultra-thick plates in the manufacture of large-sized components.展开更多
Nearly undamaged joints of electron beam welded(EBW)dual-phase Mg-8Li-3Al-2Zn-0.5Y alloy were achieved with joint coefficients exceeding 95%.All specimens were fractured at the base metal(BM),implying a significant de...Nearly undamaged joints of electron beam welded(EBW)dual-phase Mg-8Li-3Al-2Zn-0.5Y alloy were achieved with joint coefficients exceeding 95%.All specimens were fractured at the base metal(BM),implying a significant departure from conventional fracture modes of welded joints.The fusion zone(FZ)consists of ultrafine acicular α-Mg and equiaxed β-Li,with grain sizes reduced by approximately 90% and 80%,respectively,compared to the base metal.This results in a significant increase in microhardness of about 40%.A unique multiphase mixture was observed in the heat-affected zone(HAZ),which mainly consists of lamellar eutectoid structures,fine precipitates zone,and numerous fine Mg_(3)(Al,Zn)particles.This mixture was transformed from typical Li(Al,Zn)(a common softening phase)undergoing atomic diffusion and solid-state phase transformation during welding.It introduces a synergistic strengthening effect,making the heat-affected zone no longer the weakest part of the joint.This study provides valuable insights into the electron beam welding technology for Mg-Li alloys and offers theoretical support for manufacturing high-quality joints.展开更多
The influence of homogenization parameters on element segregation,dendritic structure,and the precipitate evolution in the GH3535-0.08wt%Y alloy was investigated.Additionally,some specific homogenization parameters we...The influence of homogenization parameters on element segregation,dendritic structure,and the precipitate evolution in the GH3535-0.08wt%Y alloy was investigated.Additionally,some specific homogenization parameters were maintained constant throughout the experiments.Results indicate that the heat treatment at 1150℃for 10 h is the optimal homogenization condition.Following this optimal treatment,dendrite structures and element segregation are eliminated.Furthermore,both SiC and Y_(5)Si_(3)precipitates in the as-cast alloy decrease significantly.Conversely,the homogenization at 1188℃induces overheating defects within the alloy.Although SiC and Y_(5)Si_(3)phases also decrease,some large M6C phases can still be observed,adversely affecting subsequent forging processes.展开更多
The age-hardening response,mechanical,and corrosion-resistant properties of AA7085 alloys with and without the addition of 0.3 wt.%scandium(Sc)were compared.Using advanced techniques such as aberration-corrected trans...The age-hardening response,mechanical,and corrosion-resistant properties of AA7085 alloys with and without the addition of 0.3 wt.%scandium(Sc)were compared.Using advanced techniques such as aberration-corrected transmission electron microscopy and first-principles calculations,the underlying micromechanisms of Sc microalloying were revealed.Results show that the increase in strength of the AA7085-Sc alloy is mainly attributed to the decreased Al grain size and increased number density of both Al_(3)Sc@Al_(3)(Sc,Zr)core−shell nanoparticles and Sc-containingη_(p) and GP−η_(p) nanoprecipitates.Strong strain fields and evident electron transfer from Zr to the neighboring matrix Al atoms exist at the Al_(3)Sc@Al_(3)(Sc,Zr)/Al interface.The Sc doping in GP−η_(p) andη_(p) suppresses the GP−η_(p)→η_(p) transformation.Modified corrosion resistance of the AA7085-Sc alloy compared with AA7085 alloy is associated with the fine grain boundary precipitates ofη_(p)hases and narrow precipitation free zone.The reasons of property changes of AA7085 alloy after Sc microalloying are explored based on the multiscale microstructural characterization.展开更多
Vacancy defects,as fundamental disruptions in metallic lattices,play an important role in shaping the mechanical and electronic properties of aluminum crystals.However,the influence of vacancy position under coupled t...Vacancy defects,as fundamental disruptions in metallic lattices,play an important role in shaping the mechanical and electronic properties of aluminum crystals.However,the influence of vacancy position under coupled thermomechanical fields remains insufficiently understood.In this study,transmission and scanning electron microscopy were employed to observe dislocation structures and grain boundary heterogeneities in processed aluminum alloys,suggesting stress concentrations and microstructural inhomogeneities associated with vacancy accumulation.To complement these observations,first-principles calculations and molecular dynamics simulations were conducted for seven single-vacancy configurations in face-centered cubic aluminum.The stress response,total energy,density of states(DOS),and differential charge density were examined under varying compressive strain(ε=0–0.1)and temperature(0–600 K).The results indicate that face-centered vacancies tend to reduce mechanical strength and perturb electronic states near the Fermi level,whereas corner and edge vacancies appear to have weaker effects.Elevated temperatures may partially restore electronic uniformity through thermal excitation.Overall,these findings suggest that vacancy position exerts a critical but position-dependent influence on coupled structure-property relationships,offering theoretical insights and preliminary experimental support for defect-engineered aluminum alloy design.展开更多
Cu_(2)ZnSnSSe_(4)(CZTSSe)thin film solar cells,with adjustable bandgap and rich elemental content,hold promise in next-gen photovoltaics.Crystalline quality is pivotal for efficient light absorption and carrier transp...Cu_(2)ZnSnSSe_(4)(CZTSSe)thin film solar cells,with adjustable bandgap and rich elemental content,hold promise in next-gen photovoltaics.Crystalline quality is pivotal for efficient light absorption and carrier transport.During the post-selenization process,understanding crystal growth mechanisms,and improving layer quality are essential.We explored the effects of ramp rate and annealing temperature on CZTSSe films,using X-ray diffraction(XRD),Raman spectroscopy,scanning electron microscope(SEM),and ultraviolet-visual spectrophotometry(UV-Vis).The optimal performance occurred at 25.25°C/min ramp rate and 530°C annealing.This led to smoother surfaces,higher density,and larger grains.This condition produced a single-layer structure with large grains,no secondary phases,and a 1.14 eV bandgap,making it promising for photovoltaic applications.The study has highlighted the effect of selenization conditions on the characteristics of the CZTSSe absorber layer and has provided valuable information for developing CZTSSe thin film solar cells.展开更多
High-density interconnect(HDI)soft electronics that can integrate multiple individual functions into one miniaturized monolithic system is promising for applications related to smart healthcare,soft robotics,and human...High-density interconnect(HDI)soft electronics that can integrate multiple individual functions into one miniaturized monolithic system is promising for applications related to smart healthcare,soft robotics,and human-machine interactions.However,despite the recent advances,the development of three-dimensional(3D)soft electronics with both high resolution and high integration is still challenging because of the lack of efficient manufacturing methods to guarantee interlayer alignment of the high-density vias and reliable interlayer electrical conductivity.Here,an advanced 3D laser printing pathway,based on femtosecond laser direct writing(FLDW),is demonstrated for preparing liquid metal(LM)-based any layer HDI soft electronics.FLDW technology,with the characteristics of high spatial resolution and high precision,allows the maskless fabrication of high-resolution embedded LM microchannels and high-density vertical interconnect accesses for 3D integrated circuits.High-aspect-ratio blind/through LM microstructures are formed inside the elastomer due to the supermetalphobicity induced during laser ablation.The LM-based HDI circuit featuring high resolution(~1.5μm)and high integration(10-layer electrical interconnection)is achieved for customized soft electronics,including various customized multilayer passive electric components,soft multilayer circuit,and cross-scale multimode sensors.The 3D laser printing method provides a versatile approach for developing chip-level soft electronics.展开更多
To investigate the influence of Al-Zn-Mg-Cu alloy with as-homogenized and as-rolled initial microstructures on the tensile flow behavior,isothermal tensile tests were conducted on a GLEEBLE-3500 isothermal simulator a...To investigate the influence of Al-Zn-Mg-Cu alloy with as-homogenized and as-rolled initial microstructures on the tensile flow behavior,isothermal tensile tests were conducted on a GLEEBLE-3500 isothermal simulator at temperatures of 380-440℃and strain rates of 0.05-1 s^(−1).The Johnson-Cook model,Hensel-Spittel model,strain-compensated Arrhenius model,and critical fracture strain model were established.Results show that through the evaluation of the models using the correlation coefficient(R)and the average absolute relative error,the strain-compensated Arrhenius model can represent the flow behavior of the alloy more accurately.Shear bands are more pronounced in the as-homogenized specimens,whereas dynamic recrystallization is predominantly observed in as-rolled specimens.Fracture morphology analysis reveals that a mixed fracture mechanism is prevalent in the as-homogenized specimen,whereas a ductile fracture mechanism is predominant in the as-rolled specimen.The processing maps indicate that the unstable region is reduced in the as-rolled specimens compared with that in the as-homogenized specimens.The optimal hot working windows for the as-homogenized and as-rolled specimens are determined as 410-440℃/0.14-1 s^(−1)and 380-400℃/0.05-0.29 s^(−1),respectively.展开更多
The effects of accumulative hot rolling followed by solution treatment on the microstructural evolution and fracture behavior of 30CrMo/316L multilayered composites have been investigated.A scanning electron microscop...The effects of accumulative hot rolling followed by solution treatment on the microstructural evolution and fracture behavior of 30CrMo/316L multilayered composites have been investigated.A scanning electron microscope equipped with an electron backscatter diffraction probe,a laser confocal microscope,an electron probe microanalysis,and a universal testing machine were employed to characterize the microstructures and mechanical properties.The results indicate that solution treatment transformed the microstructure of the 30CrMo layer from ferrite to martensite,while the 316L layer remained austenitic but transitioned from the rolled to the recrystallized state.Additionally,solution treatment significantly enhanced the mechanical properties of the composite,leading to an increase in yield strength and ultimate tensile strength to 744 and 1106 MPa,respectively—258 and 276 MPa higher than those of the hot-rolled plate.The enhancement in strength is primarily attributed to the formation of high-strength martensite in the 30CrMo layer.During deformation,the composite interface effectively impeded crack propagation and induced step-like deflection.However,the formation of cross-layer grains facilitated crack nucleation at grain boundaries,leading to rapid crack propagation and instantaneous fracture.Therefore,preventing the formation of cross-layer grains during the heat treatment process is crucial,as their presence weakens the interfacial strengthening effect of the composite plate.This study provides valuable insights for the design and development of multi-layered steels.展开更多
Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively invest...Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively investigated.Macroscopic morphology,microstructure,and interfacial structure of the joints were analyzed using scanning electron microscope,energy dispersive spectrometer,and X-ray diffractometer(XRD).The results show that magnetic pulse welding of dissimilar Mg/Fe metals is achieved using an Al interlayer,which acts as a bridge for deformation and diffusion.Specifically,the AZ31B/AA1060 interface exhibits a typical wavy morphology,and a transition zone exists at the joint interface,which may result in an extremely complex microstructure.The microstructure of this transition zone differs from that of AZ31B magnesium and 1060 Al alloys,and it is identified as brittle intermetallic compounds(IMCs)Al_(3)Mg_(2) and Al_(12)Mg_(17).The transition zone is mainly distributed on the Al side,with the maximum thickness of Al-side transition layer reaching approximately 13.53μm.Incomplete melting layers with varying thicknesses are observed at the primary weld interface,while micron-sized hole defects appear in the transition zone of the secondary weld interface.The AA1060/DC56D interface is mainly straight,with only a small number of discontinuous transition zones distributed intermittently along the interface.These transition zones are characterized by the presence of the brittle IMC FeAl_(3),with a maximum thickness of about 4μm.展开更多
Stretchable electronics have been recognized as intriguing next-generation electronics that possess huge market value,and stretchable electronic conductors(SECs)are essential for stretchable electronics,which not only...Stretchable electronics have been recognized as intriguing next-generation electronics that possess huge market value,and stretchable electronic conductors(SECs)are essential for stretchable electronics,which not only can serve as critical functional components but also are the indispensable electronic connections bridging various electronic components within stretchable electronic systems.Herein,we offer a comprehensive review of recent progress in SECs including the material categories,structure designs,fabrication techniques,and applications.The characteristics,performance enhancement strategies,and application requirements are emphasized.Based on the recent advances,the existing challenges and future prospects are outlined and discussed.展开更多
Permeable electronics promise improved physiological comfort,but remain constrained by limited functional integration and poor mechanical robustness.Here,we report a three-dimensional(3D)permeable electronic system th...Permeable electronics promise improved physiological comfort,but remain constrained by limited functional integration and poor mechanical robustness.Here,we report a three-dimensional(3D)permeable electronic system that overcomes these challenges by combining electrospun SEBS nanofiber mats,high-resolution liquid metal conductors patterned via thermal imprinting(50μm),and a strain isolators(SIL)that protects vertical interconnects(VIAs)from stress concentration.This architecture achieves ultrahigh air permeability(>5.09 m L cm^(-2)min^(-1)),exceptional stretchability(750%fracture strain),and reliable conductivity maintained through more than 32,500 strain cycles.Leveraging these advances,we have integrated multilayer circuits,strain sensors,and a three-axis accelerometer to achieve a fully integrated,stretchable,permeable wireless real-time gesture recognition glove.The system enables accurate sign language interpretation(98%)and seamless robotic hand control,demonstrating its potential for assistive technologies.By uniting comfort,durability,and high-density integration,this work establishes a versatile platform for nextgeneration wearable electronics and interactive human-robot interfaces.展开更多
基金supported by the Youth Project of the National Natural Science Foundation of China(Grant No.52105594)the Youth Project of the Applied Basic Research Program of Shanxi Province(Grant No.20210302124274)+4 种基金the Key Research and Development Program of Shanxi Province(Grant No.202102030201005)the Natural Youth Science Foundation of Shanxi Province(Grant Nos.202103021223005 and 202203021212015)the Fund for Shanxi 1331 Project,the Science and Technology Innovation Plan for Colleges and Universities in Shanxi Province(Grant No.2022L575)the Science and Technology Innovation Project in Higher Schools in Shanxi(Grant No.J2020383)Teaching Reform and Innovation Project of the Education Department of Shanxi Province(Grant No.J20221195).
文摘Flexible pressure sensors show great promise for applications in such fields as electronic skin,healthcare,and intelligent robotics.Traditional capacitive pressure sensors,however,face the problem of low sensitivity,which limits their wider application.In this paper,a flexible capacitive pressure sensor with microstructured ionization layer is fabricated by a sandwich-type process,with a low-cost and simple process of inverted molding with sandpapers being used to form a thermoplastic polyurethane elastomer ionic film with double-sided microstructure as the dielectric layer of the sensor,with silver nanowires as electrodes.The operating mechanism of this iontronic pressure sensor is analyzed using a graphical method,and the sensor is tested on a pressure platform.The test results show that the sensor has ultrahigh pressure sensitivities of 3.744 and 1.689 kPa^(−1) at low(0-20 kPa)and high(20-800 kPa)pressures,respectively,as well as a rapid response time(100 ms),and it exhibits good stability and repeatability.The sensor can be used for sensitive monitoring of activities such as finger bending,and for facial expression(smile,frown)recognition,as well as speech recognition.
基金supported by the National Key Research and Development Program of China(No.2022YFF0609000)the National Natural Science Foundation of China(Nos.51871075,52171034 and 52101037).
文摘Nano-lamellar Ti_(3)Al/TiAl(α2/γ)alloy with significantly improved nanohardness was prepared using dual-wire-fed electron beam-directed energy deposition(EB-DED)in this study.This investigation focused on the evolution of the colony shape and lamellar thickness of the Ti-43Al lamellar alloy at different heights.Nanoindentation tests were employed to evaluate deformation resistance,and numerical simulations provided deeper insights into the deposition process.The results indicate that the colonies are mostly columnar,except for a few equiaxed colonies at the top.Rapid cooling significantly refines theα2 lamellae,resulting in an average spacing of 218 nm and thickness of 41 nm.Additionally,substantial microstrain and a nonequilibrium Al distribution lead to a significant generation ofγvariants,refining theγlamellae to 57 nm.Abundantγ/γ’andα2/γinterfaces,along with fineα2 phases,contribute to improved deformation resistance.Consequently,the nano-lamellar TiAl alloy exhibited a notable 32%increase in nanohardness(8.3 GPa)while maintaining a similar modulus(197 GPa)to conventionally prepared alloys.This study holds significant promise for advancing high-performance TiAl alloys through the dual-wire-fed EB-DED process.
基金supported by the National Key Re-search and Development Program of China(No.2023YFC2810700)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2021193)+2 种基金Liaoning Province Excellent Youth Foundation(No.2024JH3/10200021)the Liaoning Revital-ization Talents Program(No.XLYC2403094)the Scientific In-strument Developing Project of the Chinese Academy of Sciences(No.PTYQ2024YZ0009).
文摘For a long time,the large loss of the strength and toughness of fusion welded joints for thick nearβtitanium alloys has largely hindered their engineering application,which results from the few precipitations of the strengtheningαphase during welding cooling.In this study,double annealing treatment was designed for electron beam welded joints of 30-mm-thick nearβTi-5Al-5Mo-5V-1Cr-1Fe alloy,with the aim of regulating the proportion of multi-level lamellar microstructures and enhancing the joint properties.Among various annealing temperatures(first annealing at 750–880 ℃+second annealing at 580 ℃),the 750 ℃+580 ℃ annealed joint exhibited simultaneously enhanced strength and toughness,with the increase in tensile strength and impact energy from 844 MPa and 8.8 J for the as-welded joint to 1129 MPa and 14.5 J for annealed joint,respectively,which were superior to those of the joints of Ti5Al-5Mo-5V-1Cr-1Fe alloy as reported.The great increases in the strength and toughness were mainly attributed to the excellent proportion matching of formed multi-level lamellar microstructures(76.1%of primaryα(αp)lamellae and 7.9%of secondaryα(αs)lamellae),among which theαp phase andαs phase mainly affected the joint toughness and strength,respectively.The good coupling ofαp phase andαs phase improved the precipitation strengthening and the resistance to crack propagation.The modified strengthening mechanism models were proposed by introducing the thickness and proportion parameters of the precipitated phase.It was indicated that the theoretical calculation values were in good agreement with the experimental ones,and the solution strengthening and precipitation strengthening provided a large contribution(a sum of about 75%)to the yield strength of the annealed joints.This study provides a novel method via designing proper multi-level lamellar microstructures to simultaneously improve the strength and toughness of nearβtitanium alloy joints.
基金support from the National Key Research and Development Program of China(No.2022YFB3705600)the Shanghai Science and Technology Innovation Action Plan(No.22SQBS00600).
文摘Electron beam powder bed fusion(EB-PBF)offers a promising route for producing Ti_(6)Al_(4)V alloys with tailored microstructures and superior mechanical properties.Herein,EB-PBF produced nearly fully dense Ti 6Al 4V alloys(≥98.5%)with basketweave microstructures containing fine equilibriumαlamellae,different from typicalα′acicular observed in materials produced via laser-PBF.The as-printed horizontal material has a yield strength(YS)of 992 MPa,an ultimate tensile strength(UTS)of 1053 MPa,and a fracture strain(ε)of 10.9%.Meanwhile,the as-printed longitudinal material shows inferior mechanical properties(YS of 934 MPa,UTS of 979 MPa,andεof 2.4%).The horizontal and longitudinal samples show notable hysteresis loops in the loading unloading reloading curves,indicating substantial heterogeneous-induced strengthening.Flow stress,back stress,and effective stress increase with increasing strain,where back stress is comparable to effective stress during the overall deformation.Furthermore,a monotonically decreased strain hardening rate with increasing strain can be attributed to dislocation activities,whose failure is related to the strain localization at theαlamellae boundary.
基金National Natural Science Foundation of China(51975286)。
文摘Fe-Mo functionally graded materials(FGMs)with different composition-change rates from 100%304 stainless steel to 100%Mo along the composition gradient direction were prepared by electron beam-directed energy deposition(EB-DED)technique,including three samples with composition mutation of 100%,composition change rate of 10%and 30%.Results show that the composition-change rate significantly affects the microstructure and mechanical properties of the samples.In the sample with abrupt change of composition,the sharp shift in composition between 304 stainless steel and Mo leads to a great difference in the microstructure and hardness near the interface between the two materials.With the increase in the number of gradient layers,the composition changes continuously along the direction of deposition height,and the microstructure morphology shows a smooth transition from 304 stainless steel to Mo,which is gradually transformed from columnar crystal to dendritic crystal.Elements Fe,Mo,and other major elements transform linearly along the gradient direction,with sufficient interlayer diffusion between the deposited layers,leading to good metallurgical bonding.The smaller the change in composition gradient,the greater the microhardness value along the deposition direction.When the composition gradient is 10%,the gradient layer exhibits higher hardness(940 HV)and excellent resistance to surface abrasion,and the overall compressive properties of the samples are better,with the compressive fracture stress in the top region reaching 750.05±14 MPa.
基金financially supported by the National Science Foundation of China(Nos.92163215,52305379,52322101,52174364,52101143,51771093,and 12202201)the Fundamental Research Funds for the Central Universities(Nos.30922010202,and 30922010711)+4 种基金the Key Laboratory Funds for the Science and Technology of National Defense(No.6142212210103)the Natural Science Foundation of Jiangsu Province Major Project(No.BK20212009)the Xi’an Qinchuangyuan Construction of Two-Chain Integration Major Special Projects(No.23LLRHZDZX0015)the Aviation Science Foundation of AVIC(No.2024M0530S8002)the Natural Science Basic Research Program of Shaanxi Province(No.2024JC-YBQN-0579).
文摘TiAl alloys fabricated by electron beam powder bed fusion(EB-PBF)usually exhibit special microstructures with alternating fine-grained(FG)regions and coarse-grained(CG)bands.In previous studies,the CG microstructures were equiaxed γ phases,and the FG microstructures presented three types:near gamma,duplex,and nearly lamellar.However,the rule for controlling FG microstructures has not been found.Hence,a method needs to be built to find the rule for controlling FG microstructures.Here,we established a normalized process diagram by combining Al-equivalent and dimensionless process parameters.Based on the normalized process diagram,we successfully control the FG microstructures and customize three FG microstructures of the Ti-48Al-2Cr-2Nb alloy.Meanwhile,the average tensile yield strength reaches 756 MPa when the FG microstructure is near gamma.The yield strength is higher than the previous data for the Ti-48Al-2Cr-2Nb alloy.This is attributed to the strong interface-strengthening effect between FG near γ microstructures and CG γ bands.These findings can help shorten the research time of the other TiAl alloys fabricated by EB-PBF,improving the mechanical properties of the other EBPBF-built TiAl alloys in the future.
基金supported by the National Key Research and Development Program of China(No.2023YFC2810700)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2021193)+2 种基金the Liaoning Province Excellent Youth Foundation(No.2024JH3/10200021)the Liaoning Revitalization Talents Program(No.XLYC2403094)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(No.PTYQ2024YZ0009).
文摘It is rather difficult for titanium alloy ultra-thick plates to achieve superior weld formation and excellent mechanical properties along the weld penetration direction due to the large fluctuations of the molten pool,largely limiting their engineering application.In this study,106-mm-thick Ti-6Al-4V ELI alloy plates were successfully butt welded via electron beam welding(EBW).The defect-free EBW joint with full penetration was obtained.The precipitated secondary α(α_(s))in heat affected zone(HAZ),αlamellae in fusion line(FL)and α′martensite in fusion zone(FZ)increased the α_(s)/β,α/β and α′/β interfaces,respectively,resulting in the higher microhardness and impact energy values(57 J in the HAZ,62 J in the FL and 51.9 J in the FZ)than those in the base material(BM).The impact energy of the joint in this study was higher than that for Ti-6Al-4V ELI alloy joints as reported,which was mainly attributed to the formation of the relatively thickerαphase and finer interlamellar spacing in this study,enhancing the resistance to crack propagation.Furthermore,the average fracture toughness(90.2 MPa m^(1/2))of the FZ was higher than that of the BM(74.2 MPa m^(1/2)).This study provides references for the welding application of titanium alloy ultra-thick plates in the manufacture of large-sized components.
基金financially supported by the National Defense Basic Research Program(No.JCKY2023204A005)Project of High Modulus Magnesium Alloy Forgings(JXXT-2023-014hbza)+1 种基金Research Program of Joint Research Center of Advanced Spaceflight Technologies(No.USCAST2023-3)Major Scientific and Technological Innovation Project of Luoyang(No.2201029A).
文摘Nearly undamaged joints of electron beam welded(EBW)dual-phase Mg-8Li-3Al-2Zn-0.5Y alloy were achieved with joint coefficients exceeding 95%.All specimens were fractured at the base metal(BM),implying a significant departure from conventional fracture modes of welded joints.The fusion zone(FZ)consists of ultrafine acicular α-Mg and equiaxed β-Li,with grain sizes reduced by approximately 90% and 80%,respectively,compared to the base metal.This results in a significant increase in microhardness of about 40%.A unique multiphase mixture was observed in the heat-affected zone(HAZ),which mainly consists of lamellar eutectoid structures,fine precipitates zone,and numerous fine Mg_(3)(Al,Zn)particles.This mixture was transformed from typical Li(Al,Zn)(a common softening phase)undergoing atomic diffusion and solid-state phase transformation during welding.It introduces a synergistic strengthening effect,making the heat-affected zone no longer the weakest part of the joint.This study provides valuable insights into the electron beam welding technology for Mg-Li alloys and offers theoretical support for manufacturing high-quality joints.
基金National Natural Science Foundation of China(51801227,52071331)。
文摘The influence of homogenization parameters on element segregation,dendritic structure,and the precipitate evolution in the GH3535-0.08wt%Y alloy was investigated.Additionally,some specific homogenization parameters were maintained constant throughout the experiments.Results indicate that the heat treatment at 1150℃for 10 h is the optimal homogenization condition.Following this optimal treatment,dendrite structures and element segregation are eliminated.Furthermore,both SiC and Y_(5)Si_(3)precipitates in the as-cast alloy decrease significantly.Conversely,the homogenization at 1188℃induces overheating defects within the alloy.Although SiC and Y_(5)Si_(3)phases also decrease,some large M6C phases can still be observed,adversely affecting subsequent forging processes.
基金the support from the National Natural Science Foundation of China (Nos. U20A20274, 52061003)the Natural Science Foundation of Yunnan Province, China (No. 202301AT070209)the Science and Technology Major Project of Yunnan Province, China (No. 202102AG050017)。
文摘The age-hardening response,mechanical,and corrosion-resistant properties of AA7085 alloys with and without the addition of 0.3 wt.%scandium(Sc)were compared.Using advanced techniques such as aberration-corrected transmission electron microscopy and first-principles calculations,the underlying micromechanisms of Sc microalloying were revealed.Results show that the increase in strength of the AA7085-Sc alloy is mainly attributed to the decreased Al grain size and increased number density of both Al_(3)Sc@Al_(3)(Sc,Zr)core−shell nanoparticles and Sc-containingη_(p) and GP−η_(p) nanoprecipitates.Strong strain fields and evident electron transfer from Zr to the neighboring matrix Al atoms exist at the Al_(3)Sc@Al_(3)(Sc,Zr)/Al interface.The Sc doping in GP−η_(p) andη_(p) suppresses the GP−η_(p)→η_(p) transformation.Modified corrosion resistance of the AA7085-Sc alloy compared with AA7085 alloy is associated with the fine grain boundary precipitates ofη_(p)hases and narrow precipitation free zone.The reasons of property changes of AA7085 alloy after Sc microalloying are explored based on the multiscale microstructural characterization.
基金supported by the Research Project on Strengthening the Construction of an Important Ecological Security Barrier in Northern China by Higher Education Institutions in the Inner Mongolia Autonomous Region(STAQZX202313)the Inner Mongolia Autonomous Region Education Science‘14th Five-Year Plan’2024 Annual Research Project(NGJGH2024635).
文摘Vacancy defects,as fundamental disruptions in metallic lattices,play an important role in shaping the mechanical and electronic properties of aluminum crystals.However,the influence of vacancy position under coupled thermomechanical fields remains insufficiently understood.In this study,transmission and scanning electron microscopy were employed to observe dislocation structures and grain boundary heterogeneities in processed aluminum alloys,suggesting stress concentrations and microstructural inhomogeneities associated with vacancy accumulation.To complement these observations,first-principles calculations and molecular dynamics simulations were conducted for seven single-vacancy configurations in face-centered cubic aluminum.The stress response,total energy,density of states(DOS),and differential charge density were examined under varying compressive strain(ε=0–0.1)and temperature(0–600 K).The results indicate that face-centered vacancies tend to reduce mechanical strength and perturb electronic states near the Fermi level,whereas corner and edge vacancies appear to have weaker effects.Elevated temperatures may partially restore electronic uniformity through thermal excitation.Overall,these findings suggest that vacancy position exerts a critical but position-dependent influence on coupled structure-property relationships,offering theoretical insights and preliminary experimental support for defect-engineered aluminum alloy design.
基金supported by the Science and Technology Innovation Development Program(No.70304901).
文摘Cu_(2)ZnSnSSe_(4)(CZTSSe)thin film solar cells,with adjustable bandgap and rich elemental content,hold promise in next-gen photovoltaics.Crystalline quality is pivotal for efficient light absorption and carrier transport.During the post-selenization process,understanding crystal growth mechanisms,and improving layer quality are essential.We explored the effects of ramp rate and annealing temperature on CZTSSe films,using X-ray diffraction(XRD),Raman spectroscopy,scanning electron microscope(SEM),and ultraviolet-visual spectrophotometry(UV-Vis).The optimal performance occurred at 25.25°C/min ramp rate and 530°C annealing.This led to smoother surfaces,higher density,and larger grains.This condition produced a single-layer structure with large grains,no secondary phases,and a 1.14 eV bandgap,making it promising for photovoltaic applications.The study has highlighted the effect of selenization conditions on the characteristics of the CZTSSe absorber layer and has provided valuable information for developing CZTSSe thin film solar cells.
基金supported by the National Science Foundation of China under the Grant Nos.12127806 and 62175195the International Joint Research Laboratory for Micro/Nano Manufacturing and Measurement Technologies。
文摘High-density interconnect(HDI)soft electronics that can integrate multiple individual functions into one miniaturized monolithic system is promising for applications related to smart healthcare,soft robotics,and human-machine interactions.However,despite the recent advances,the development of three-dimensional(3D)soft electronics with both high resolution and high integration is still challenging because of the lack of efficient manufacturing methods to guarantee interlayer alignment of the high-density vias and reliable interlayer electrical conductivity.Here,an advanced 3D laser printing pathway,based on femtosecond laser direct writing(FLDW),is demonstrated for preparing liquid metal(LM)-based any layer HDI soft electronics.FLDW technology,with the characteristics of high spatial resolution and high precision,allows the maskless fabrication of high-resolution embedded LM microchannels and high-density vertical interconnect accesses for 3D integrated circuits.High-aspect-ratio blind/through LM microstructures are formed inside the elastomer due to the supermetalphobicity induced during laser ablation.The LM-based HDI circuit featuring high resolution(~1.5μm)and high integration(10-layer electrical interconnection)is achieved for customized soft electronics,including various customized multilayer passive electric components,soft multilayer circuit,and cross-scale multimode sensors.The 3D laser printing method provides a versatile approach for developing chip-level soft electronics.
文摘To investigate the influence of Al-Zn-Mg-Cu alloy with as-homogenized and as-rolled initial microstructures on the tensile flow behavior,isothermal tensile tests were conducted on a GLEEBLE-3500 isothermal simulator at temperatures of 380-440℃and strain rates of 0.05-1 s^(−1).The Johnson-Cook model,Hensel-Spittel model,strain-compensated Arrhenius model,and critical fracture strain model were established.Results show that through the evaluation of the models using the correlation coefficient(R)and the average absolute relative error,the strain-compensated Arrhenius model can represent the flow behavior of the alloy more accurately.Shear bands are more pronounced in the as-homogenized specimens,whereas dynamic recrystallization is predominantly observed in as-rolled specimens.Fracture morphology analysis reveals that a mixed fracture mechanism is prevalent in the as-homogenized specimen,whereas a ductile fracture mechanism is predominant in the as-rolled specimen.The processing maps indicate that the unstable region is reduced in the as-rolled specimens compared with that in the as-homogenized specimens.The optimal hot working windows for the as-homogenized and as-rolled specimens are determined as 410-440℃/0.14-1 s^(−1)and 380-400℃/0.05-0.29 s^(−1),respectively.
基金supported by the National Key Research and Development Program of China(No.2018YFA0707304).
文摘The effects of accumulative hot rolling followed by solution treatment on the microstructural evolution and fracture behavior of 30CrMo/316L multilayered composites have been investigated.A scanning electron microscope equipped with an electron backscatter diffraction probe,a laser confocal microscope,an electron probe microanalysis,and a universal testing machine were employed to characterize the microstructures and mechanical properties.The results indicate that solution treatment transformed the microstructure of the 30CrMo layer from ferrite to martensite,while the 316L layer remained austenitic but transitioned from the rolled to the recrystallized state.Additionally,solution treatment significantly enhanced the mechanical properties of the composite,leading to an increase in yield strength and ultimate tensile strength to 744 and 1106 MPa,respectively—258 and 276 MPa higher than those of the hot-rolled plate.The enhancement in strength is primarily attributed to the formation of high-strength martensite in the 30CrMo layer.During deformation,the composite interface effectively impeded crack propagation and induced step-like deflection.However,the formation of cross-layer grains facilitated crack nucleation at grain boundaries,leading to rapid crack propagation and instantaneous fracture.Therefore,preventing the formation of cross-layer grains during the heat treatment process is crucial,as their presence weakens the interfacial strengthening effect of the composite plate.This study provides valuable insights for the design and development of multi-layered steels.
文摘Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively investigated.Macroscopic morphology,microstructure,and interfacial structure of the joints were analyzed using scanning electron microscope,energy dispersive spectrometer,and X-ray diffractometer(XRD).The results show that magnetic pulse welding of dissimilar Mg/Fe metals is achieved using an Al interlayer,which acts as a bridge for deformation and diffusion.Specifically,the AZ31B/AA1060 interface exhibits a typical wavy morphology,and a transition zone exists at the joint interface,which may result in an extremely complex microstructure.The microstructure of this transition zone differs from that of AZ31B magnesium and 1060 Al alloys,and it is identified as brittle intermetallic compounds(IMCs)Al_(3)Mg_(2) and Al_(12)Mg_(17).The transition zone is mainly distributed on the Al side,with the maximum thickness of Al-side transition layer reaching approximately 13.53μm.Incomplete melting layers with varying thicknesses are observed at the primary weld interface,while micron-sized hole defects appear in the transition zone of the secondary weld interface.The AA1060/DC56D interface is mainly straight,with only a small number of discontinuous transition zones distributed intermittently along the interface.These transition zones are characterized by the presence of the brittle IMC FeAl_(3),with a maximum thickness of about 4μm.
基金supported by the National Natural Science Foundation of China(52172170)Guangdong Natural Science Foundation for Distinguished Young Scholars(2023B1515020114)+2 种基金Fundamental Research Funds for the Central Universities(24lgqb003)Guangdong University Innovation and Enhancement Program(2024KTSCX003)Science and Technology Projects of Guangzhou(2025A04J4230).
文摘Stretchable electronics have been recognized as intriguing next-generation electronics that possess huge market value,and stretchable electronic conductors(SECs)are essential for stretchable electronics,which not only can serve as critical functional components but also are the indispensable electronic connections bridging various electronic components within stretchable electronic systems.Herein,we offer a comprehensive review of recent progress in SECs including the material categories,structure designs,fabrication techniques,and applications.The characteristics,performance enhancement strategies,and application requirements are emphasized.Based on the recent advances,the existing challenges and future prospects are outlined and discussed.
基金supported in part by the National Key R&D Program of China under Grant 2024YFB4405300 and 2022YFA1204300the Natural Science Foundation of Hunan Province under Grant 2023JJ20016+2 种基金the National Natural Science Foundation of China under Grants of 52221001 and 62090035the Key Research and Development Plan of Hunan Province under grants of 2022GK3002 and 2023GK2012the Key Program of Science and Technology Department of Hunan Province under grant of 2020XK2001。
文摘Permeable electronics promise improved physiological comfort,but remain constrained by limited functional integration and poor mechanical robustness.Here,we report a three-dimensional(3D)permeable electronic system that overcomes these challenges by combining electrospun SEBS nanofiber mats,high-resolution liquid metal conductors patterned via thermal imprinting(50μm),and a strain isolators(SIL)that protects vertical interconnects(VIAs)from stress concentration.This architecture achieves ultrahigh air permeability(>5.09 m L cm^(-2)min^(-1)),exceptional stretchability(750%fracture strain),and reliable conductivity maintained through more than 32,500 strain cycles.Leveraging these advances,we have integrated multilayer circuits,strain sensors,and a three-axis accelerometer to achieve a fully integrated,stretchable,permeable wireless real-time gesture recognition glove.The system enables accurate sign language interpretation(98%)and seamless robotic hand control,demonstrating its potential for assistive technologies.By uniting comfort,durability,and high-density integration,this work establishes a versatile platform for nextgeneration wearable electronics and interactive human-robot interfaces.
