The process parameters of laser additive manufacturing have an important influence on the forming quality of the produced items or parts.In the present work,a finite element model for simulating transient heat transfe...The process parameters of laser additive manufacturing have an important influence on the forming quality of the produced items or parts.In the present work,a finite element model for simulating transient heat transfer in such processes has been implemented using the ANSYS software,and the temperature and stress distributions related to 316L stainless steel thin-walled ring parts have been simulated and analyzed.The effect of the laser power,scanning speed,and scanning mode on temperature distribution,molten pool structure,deformation,and stress field has been studied.The simulation results show that the peak temperature,weld pool size,deformation,and residual stress increase with an increase in laser power and a decrease in the scanning speed.The scanning mode has no obvious effect on temperature distribution,deformation,and residual stress.In addition,a forming experiment was carried out.The experimental results show that the samples prepared by laser power P=800 W,V=6 mm/s,and the normal scanning method display good quality,whereas the samples prepared under other parameters have obvious defects.The experimental findings are consistent with the simulation results.展开更多
The refractory metal rhenium(Re),with content of 0−2 at.%,was introduced into a typicalγ-TiAl alloy of Ti−48Al−2Cr−2Nb(at.%)through vacuum arc melting.The effect of Re content on the microstructure and mechanical pro...The refractory metal rhenium(Re),with content of 0−2 at.%,was introduced into a typicalγ-TiAl alloy of Ti−48Al−2Cr−2Nb(at.%)through vacuum arc melting.The effect of Re content on the microstructure and mechanical properties of theγ-TiAl alloy was investigated.The results show that theγ-TiAl−xRe alloy is composed ofγ,α2,andβphases.As the Re content increases,the proportion ofβphase increases,while the content and size ofα2+γlamellar structure decrease gradually.Furthermore,the compressive strength increases with increasing Re content.A maximum compressive strength of 2282 MPa is achieved for theγ-TiAl−2Re alloy.Theγ-TiAl−2Re alloy exhibits a fracture strain of 36.7%,considerably higher than that of theγ-TiAl alloy(31.0%).Moreover,compared with theγ-TiAl alloy,the hardness and compressive strength of theγ-TiAl−2Re alloy considerably increase by 17.5%and 34.2%,respectively.展开更多
Although the seemingly negative effect of deformation-induced martensite(DIM)volume fraction on the impact toughness of austenitic steels has been well documented,it relies mostly on analyzing crack propagation withou...Although the seemingly negative effect of deformation-induced martensite(DIM)volume fraction on the impact toughness of austenitic steels has been well documented,it relies mostly on analyzing crack propagation without explicitly considering the crack initiation process which,however,plays a crucial role in these ductile alloys.The dependence of crack initiation energy(Ei)on martensitic transformation mechanisms is still ambiguous,inhibiting the precise design of damage-tolerant and ductile alloys.Here,we explore the temperature-dependent crack initiation energy of a SUS321 stainless steel at various temperatures(25,-50,and-196℃).Contrary to the crack propagation energy(Ep),the Ei has a weak correlation with the volume fraction ofα′-martensite but a strong correlation with the martensitic transformation rate.Also contrary to the traditional viewpoint of Ep consideringε-martensite as a detrimental phase,a high volume fraction ofε-martensite turns out to be beneficial to the increase of Ei,thereby enhancing impact toughness.As such,an optimal value(15 mJ/m^(2))for the stacking fault energy(SFE),which dictates theγ→ε→α′transformation sequence,is given as a new design guideline for enhancing the Ei and consequently the impact toughness of ductile steels.The generality of this guideline is further validated in multiple austenitic steels with different compositions and grain sizes.展开更多
Recently,the intelligent strategies for adapting to multiple challengeable surfaces of electroactive programmable materials integrated with bio-inspired architectures offer expanded directions beyond traditional limit...Recently,the intelligent strategies for adapting to multiple challengeable surfaces of electroactive programmable materials integrated with bio-inspired architectures offer expanded directions beyond traditional limitations in soft grippers,medical mobile robots,and XR(Extended Reality)interfaces.These electroactive programmable adhesive materials are adaptively designed for a variety of complex surfaces,including soft,wet,non-flat,or contamination-susceptible feature such as bio-surfaces and vulnerable objects.They can be produced via solution-based methods of replica coating or 3/4-dimensional printing.The integration of electroactive programmable materials and intelligent adhesive architecture enables super-adaptive switchable adhesion to a variety of complex surfaces through control of physical deformation and mechanical properties at the adhesive interface,presenting a breakthrough in soft electro-robotics and extended reality(XR)Haptic interfaces technology.These surface-adaptive platform can provide multiple functionalities that can efficiently control physical deformations of soft bioinspired architectures or transfer physical energy(heat,vibration,pressure)into the engaged surfaces in a lightweight and human-friendly form.This review focuses on intelligent strategies,principles,design,and fabrication methods of super-adaptive electroactive programmable materials intelligently combined with bioinspired switchable adhesives for next-generation human–robot interaction devices,along with current challenges and prospects.展开更多
Titanium alloys find extensive use in the aerospace and biomedical industries due to a unique combination of strength,density,and corrosion resistance.Decades of mostly experimental research has led to a large body of...Titanium alloys find extensive use in the aerospace and biomedical industries due to a unique combination of strength,density,and corrosion resistance.Decades of mostly experimental research has led to a large body of knowledge of the processingmicrostructure-properties linkages.But much of the existing understanding of point defects that play a significant role in the mechanical properties of titanium is based on semi-empirical rules.In this work,we present the results of a detailed self-consistent first-principles study that was developed to determine formation energies of intrinsic point defects including vacancies,selfinterstitials,and extrinsic point defects,such as,interstitial and substitutional impurities/dopants.We find that most elements,regardless of size,prefer substitutional positions,but highly electronegative elements,such as C,N,O,F,S,and Cl,some of which are common impurities in Ti,occupy interstitial positions.展开更多
基金funded by the National Natural Science Foundation of China(Grant Nos.51975339,51605262)China Postdoctoral Science Foundation(Grant Nos.2019T120602,2017M610439)Youth Innovation and Technology Support Program for University in Shandong Province(Grant No.2019KJB003).
文摘The process parameters of laser additive manufacturing have an important influence on the forming quality of the produced items or parts.In the present work,a finite element model for simulating transient heat transfer in such processes has been implemented using the ANSYS software,and the temperature and stress distributions related to 316L stainless steel thin-walled ring parts have been simulated and analyzed.The effect of the laser power,scanning speed,and scanning mode on temperature distribution,molten pool structure,deformation,and stress field has been studied.The simulation results show that the peak temperature,weld pool size,deformation,and residual stress increase with an increase in laser power and a decrease in the scanning speed.The scanning mode has no obvious effect on temperature distribution,deformation,and residual stress.In addition,a forming experiment was carried out.The experimental results show that the samples prepared by laser power P=800 W,V=6 mm/s,and the normal scanning method display good quality,whereas the samples prepared under other parameters have obvious defects.The experimental findings are consistent with the simulation results.
基金Natural Science Foundation of Zhejiang Province,China(No.LQ21E040004)National Natural Science Foundation of China(No.52271040)+1 种基金State Key Lab of Advanced Metals and Materials,China(No.2021-Z03)State Key Laboratory of Powder Metallurgy,Central South University,China。
文摘The refractory metal rhenium(Re),with content of 0−2 at.%,was introduced into a typicalγ-TiAl alloy of Ti−48Al−2Cr−2Nb(at.%)through vacuum arc melting.The effect of Re content on the microstructure and mechanical properties of theγ-TiAl alloy was investigated.The results show that theγ-TiAl−xRe alloy is composed ofγ,α2,andβphases.As the Re content increases,the proportion ofβphase increases,while the content and size ofα2+γlamellar structure decrease gradually.Furthermore,the compressive strength increases with increasing Re content.A maximum compressive strength of 2282 MPa is achieved for theγ-TiAl−2Re alloy.Theγ-TiAl−2Re alloy exhibits a fracture strain of 36.7%,considerably higher than that of theγ-TiAl alloy(31.0%).Moreover,compared with theγ-TiAl alloy,the hardness and compressive strength of theγ-TiAl−2Re alloy considerably increase by 17.5%and 34.2%,respectively.
基金Project(LQ21E040004) supported by the Natural Science Foundation of Zhejiang Province,ChinaProject(2021-Z03) supported by the State Key Laboratory of Advanced Metals and Materials,China。
基金supported by the National Natural Science Foundation of China(No.52201112,U22A20106,and 52071066)the China Postdoctoral Science Foundation(2022M710627)+1 种基金the support from the Innovation and Technology Fund(MHP-064-20)the support from the National Natural Science Foundation of China(No.52101133).
文摘Although the seemingly negative effect of deformation-induced martensite(DIM)volume fraction on the impact toughness of austenitic steels has been well documented,it relies mostly on analyzing crack propagation without explicitly considering the crack initiation process which,however,plays a crucial role in these ductile alloys.The dependence of crack initiation energy(Ei)on martensitic transformation mechanisms is still ambiguous,inhibiting the precise design of damage-tolerant and ductile alloys.Here,we explore the temperature-dependent crack initiation energy of a SUS321 stainless steel at various temperatures(25,-50,and-196℃).Contrary to the crack propagation energy(Ep),the Ei has a weak correlation with the volume fraction ofα′-martensite but a strong correlation with the martensitic transformation rate.Also contrary to the traditional viewpoint of Ep consideringε-martensite as a detrimental phase,a high volume fraction ofε-martensite turns out to be beneficial to the increase of Ei,thereby enhancing impact toughness.As such,an optimal value(15 mJ/m^(2))for the stacking fault energy(SFE),which dictates theγ→ε→α′transformation sequence,is given as a new design guideline for enhancing the Ei and consequently the impact toughness of ductile steels.The generality of this guideline is further validated in multiple austenitic steels with different compositions and grain sizes.
基金National Research Foundation of Korea,Grant/Award Numbers:NRF-2022R1A4A3032923,RS-2023-00214236,RS-2024-00352352South Korean Ministry of Trade,Industry and Energy,Grant/Award Number:RS-2022-00154781National Research Council of Science and Technology,Grant/Award Number:CRC230231-000。
文摘Recently,the intelligent strategies for adapting to multiple challengeable surfaces of electroactive programmable materials integrated with bio-inspired architectures offer expanded directions beyond traditional limitations in soft grippers,medical mobile robots,and XR(Extended Reality)interfaces.These electroactive programmable adhesive materials are adaptively designed for a variety of complex surfaces,including soft,wet,non-flat,or contamination-susceptible feature such as bio-surfaces and vulnerable objects.They can be produced via solution-based methods of replica coating or 3/4-dimensional printing.The integration of electroactive programmable materials and intelligent adhesive architecture enables super-adaptive switchable adhesion to a variety of complex surfaces through control of physical deformation and mechanical properties at the adhesive interface,presenting a breakthrough in soft electro-robotics and extended reality(XR)Haptic interfaces technology.These surface-adaptive platform can provide multiple functionalities that can efficiently control physical deformations of soft bioinspired architectures or transfer physical energy(heat,vibration,pressure)into the engaged surfaces in a lightweight and human-friendly form.This review focuses on intelligent strategies,principles,design,and fabrication methods of super-adaptive electroactive programmable materials intelligently combined with bioinspired switchable adhesives for next-generation human–robot interaction devices,along with current challenges and prospects.
文摘Titanium alloys find extensive use in the aerospace and biomedical industries due to a unique combination of strength,density,and corrosion resistance.Decades of mostly experimental research has led to a large body of knowledge of the processingmicrostructure-properties linkages.But much of the existing understanding of point defects that play a significant role in the mechanical properties of titanium is based on semi-empirical rules.In this work,we present the results of a detailed self-consistent first-principles study that was developed to determine formation energies of intrinsic point defects including vacancies,selfinterstitials,and extrinsic point defects,such as,interstitial and substitutional impurities/dopants.We find that most elements,regardless of size,prefer substitutional positions,but highly electronegative elements,such as C,N,O,F,S,and Cl,some of which are common impurities in Ti,occupy interstitial positions.
