In the background of carbon neutrality,monolithic ceramic catalysts are universally used in energy conversion and chemical catalysis due to the high heat and mass transfer efficiencies,low bed pressures,and scalabilit...In the background of carbon neutrality,monolithic ceramic catalysts are universally used in energy conversion and chemical catalysis due to the high heat and mass transfer efficiencies,low bed pressures,and scalability through modular design.However,traditional manufacturing processes are limited by mold dependence,organic solvent toxicity,and insufficient molding capability for complex structures,resulting in difficulty achieving precise regulation of cross-scale pores.Additive manufacturing(AM)technology employs a digital layered molding strategy to achieve the cross-scale structural regulation of catalysts from macroscopic flow channels to mesopores and micropores.This paper summarizes recent advances in the structural design of monolithic catalysts enabled by AM technologies and highlights their emerging applications in catalytic processes.Structurally,AM-fabricated monoliths have been effectively employed in key chemical reactions such as fuel reforming,CO_(2)conversion,biofuel synthesis.Strategies such as geometrical topology optimization,multi-scale pore synergy,biomimetic structural design,and functional gradient integration have been utilized to enhance heat and mass transport,reduce pressure drops,and improve overall catalytic performance.By overcoming the limitations of traditional catalysts,AM technologies create a new paradigm for addressing the longstanding challenge of coupling mass transfer with reaction kinetics.This approach provides a feasible pathway for driving both theoretical innovation and practical implementation of high-efficiency catalytic systems.展开更多
In current research,many researchers propose analytical expressions for calculating the packing structure of spherical particles such as DN Model,Compact Model and NLS criterion et al.However,there is still a question...In current research,many researchers propose analytical expressions for calculating the packing structure of spherical particles such as DN Model,Compact Model and NLS criterion et al.However,there is still a question that has not been well explained yet.That is:What is the core factors affecting the thermal conductivity of particles?In this paper,based on the coupled discrete element-finite difference(DE-FD)method and spherical aluminum powder,the relationship between the parameters and the thermal conductivity of the powder(ETC_(p))is studied.It is found that the key factor that can described the change trend of ETC_(p) more accurately is not the materials of the powder but the average contact area between particles(a_(ave))which also have a close nonlinear relationship with the average particle size d_(50).Based on this results,the expression for calculating the ETC_(p) of the sphere metal powder is successfully reduced to only one main parameter d_(50)and an efficient calculation model is proposed which can applicate both in room and high temperature and the corresponding error is less than 20.9%in room temperature.Therefore,in this study,based on the core factors analyzation,a fast calculation model of ETC_(p) is proposed,which has a certain guiding significance in the field of thermal field simulation.展开更多
Considering the fracture problem of the silica-based ceramic core in the integrated casting of hollow turbine blades during directional solidification,the influence of various whiskers,including silicon carbide whiske...Considering the fracture problem of the silica-based ceramic core in the integrated casting of hollow turbine blades during directional solidification,the influence of various whiskers,including silicon carbide whiskers,silicon nitride whiskers,and mullite whiskers,on the high-temperature strength of the silica-based ceramic core was investigated.Additionally,the formation of microstructure morphology and phase structure was analyzed.Research results show that silicon carbide whiskers can reduce the microcracks caused by the shrinkage of cristobalite.During the sintering process,some of the silicon carbide whiskers oxidize and react with aluminum powder to form mullite,which can improve the high-temperature strength of the ceramic cores.When the content of silicon carbide whiskers is 3wt.%,the high-temperature bending strength of the cores reaches the maximum value of 21 MPa.Silicon nitride whiskers decompose in a high-temperature environment and react with aluminum powder in the matrix material to form mullite whiskers.When the content of silicon nitride whiskers is 5wt.%,the high-temperature bending strength of the cores reaches 20 MPa.By adding mullite whiskers,a structure of cristobalite wrapped mullite whiskers can be formed to achieve toughening.When the content of mullite whiskers is 4wt.%,the high-temperature bending strength can reach 17.2 MPa.By comparing the performance of silicon carbide whiskers,silicon nitride whiskers,and mullite whiskers,along with conducting slurry viscosity tests and casting experiments,it is determined that a ceramic slurry containing 4wt.%mullite whiskers is the most suitable for making the cores used in the integrated casting of hollow turbine blades.展开更多
Conventional powder/pellet-based systems used for mitigating the environmental challenges posed by CO_(2)emissions present inefficiencies in mass/heat transfer,pressure drop,and clogging.Monolithic adsorption material...Conventional powder/pellet-based systems used for mitigating the environmental challenges posed by CO_(2)emissions present inefficiencies in mass/heat transfer,pressure drop,and clogging.Monolithic adsorption materials have emerged as a promising alternative to such systems.Additive manufacturing(AM)enables precise structural optimization and active component control in monolithic adsorbents,enhancing the adsorption kinetics while minimizing mechanical wear.This review examines the progress in AM-driven CO_(2)adsorbent development,covering the following aspects:(1)fabrication techniques for monolithic adsorbents and key metrics for evaluating their mechanical and adsorption properties,(2)applications of AM methods(extrusion,coating,gel spinning,and 3D printing)under fixed-source and direct-air capture scenarios,and(3)integrated systems combining CO_(2)adsorption and conversion.However,balancing adsorption performance with mechanical strength is a critical challenge.The trade-off can be addressed through advanced AM strategies such as hybrid material architectures and computational design.Future advancements will hinge on hybrid AM techniques to decouple structural and functional demands,AI/ML-driven multi-objective optimization for pore structure refinement and stress distribution,and lifecycle sustainability analytics to reduce energy use and material waste.By synergizing these approaches,next-generation monolithic adsorbents can achieve high capacity,mechanical robustness,and cost-effectiveness,positioning AM as a scalable and sustainable platform for carbon capture technologies.展开更多
A novel metal matrix composite freeform fabrication approach,fiber traction printing(FTP),is demonstrated through controlling the wetting behavior between fibers and the matrix.This process utilizes the fiber bundle t...A novel metal matrix composite freeform fabrication approach,fiber traction printing(FTP),is demonstrated through controlling the wetting behavior between fibers and the matrix.This process utilizes the fiber bundle to control the cross-sectional shape of the liquid metal,shaping it from circular to rectangular which is more precise.The FTP process could resolve manufacturing difficulties in the complex structure of continuous fiber reinforced metal matrix composites.The printing of the first layer monofilament is discussed in detail,and the effects of the fibrous coating thickness on the mechanical properties and microstructures of the composite are also investigated in this paper.The composite material prepared by the FTP process has a tensile strength of 235.2 MPa,which is close to that of composites fabricated by conventional processes.The complex structures are printed to demonstrate the advantages and innovations of this approach.Moreover,the FTP method is suited to other material systems with good wettability,such as modified carbon fiber,surfactants,and aluminum alloys.展开更多
High-quality repair of damaged Inconel 718(IN718)superalloy components can achieve great economic benefits.However,the directly double aging(DA)treatment by industrial standards,yields an inferior ductility on the rep...High-quality repair of damaged Inconel 718(IN718)superalloy components can achieve great economic benefits.However,the directly double aging(DA)treatment by industrial standards,yields an inferior ductility on the repaired component than that of the wrought base metal.In this work,wrought IN718 components were repaired by laser-directed energy deposition(LDED),a novel tailored heat treatment(THT)schedule consisting of a short-term low-temperature homogenization,and subsequent DA was sub-sequently conducted to strengthen the repaired IN718 alloys.The microstructure evolution and mechan-ical properties of the DA and THT-treated repaired alloys were comparatively investigated.The results indicated that the THT effectively dissolved most of the hard brittle Laves precipitates in the deposition region with only slight coarsening of the grains in the substrate.As compared to the DA sample,the elon-gation of the THT sample increased remarkably by 88%with only a slight reduction of 19.2 MPa in yield stress.Moreover,the strain distribution of the THT sample was overall more even but then destabilized in a narrow abnormal coarsened grain region caused by the static recrystallization.In general,this study breaks through the limitation of the low ductility of the DA-treated repaired IN718 alloys and provides a promising way to further improve the mechanical properties.展开更多
Improvement of fabrication efficiency and part performance was the main challenge for the large-scale powder bed fusion(PBF)process.In this study,a dynamic monitoring and feedback system of powder bed temperature fiel...Improvement of fabrication efficiency and part performance was the main challenge for the large-scale powder bed fusion(PBF)process.In this study,a dynamic monitoring and feedback system of powder bed temperature field using an infrared thermal imager has been established and integrated into a four-laser PBF equipment with a working area of 2000 mm×2000 mm.The heat-affected zone(HAZ)temperature field has been controlled by adjusting the scanning speed dynamically.Simultaneously,the relationship among spot size,HAZ temperature,and part performance has been established.The fluctuation of the HAZ temperature in four-laser scanning areas was decreased from 30.85℃to 17.41℃.Thus,the consistency of the sintering performance of the produced large component has been improved.Based on the controllable temperature field,a dynamically adjusting strategy for laser spot size was proposed,by which the fabrication efficiency was improved up to 65.38%.The current research results were of great significance to the further industrial applications of large-scale PBF equipment.展开更多
Stray grains,the most serious casting defect,mainly occur in the platform because of the abrupt transition of the cross-section in the directional solidification of superalloy single-crystal blades.A new mould baffle ...Stray grains,the most serious casting defect,mainly occur in the platform because of the abrupt transition of the cross-section in the directional solidification of superalloy single-crystal blades.A new mould baffle technology based on 3D printing and gelcasting is proposed herein to reduce the formation of stray grains in the platform.The influence of the proposed mould baffle technology on the temperature field in the platform during solidification was investigated by simulation and experiment.The numerical simulation results indicate that the proposed mould baffle technology can effectively hinder the radiation and heat dissipation at the platform extremities,and therefore,reduce undercooling in the platform and the formation of stray grains during directional solidification.Casting trials of a hollow turbine blade were conducted using CMSX-4 superalloy.The trial results demonstrate the potential of the proposed approach for manufacturing single-crystal superalloy blades.展开更多
Cast molding process has provided a reliable, simple and cost-effective way to fabricate micro structures since decades ago. In order to obtain structures with fine, dense and deep nano-size features by cast molding, ...Cast molding process has provided a reliable, simple and cost-effective way to fabricate micro structures since decades ago. In order to obtain structures with fine, dense and deep nano-size features by cast molding, it is necessary to study the forming mechanism in the process. In this paper, based on major steps of cast molding, filling models of liquid are established and solved; and the forming mechanism of liquid is revealed. Moreover, the scale effect between the liquid and the cavity on the filling velocity of liquid is studied.It is also interesting to find out that the wettability of liquid on the cavity may be changed from wetting to dewetting depends on the pressure difference. Finally, we experimentally verify some of our modeling results on the flowing and filling state of the liquid during the cast molding process.展开更多
In this study,an AlCu/AlMgSc bimetallic alloy is prepared using a dual-wire arc direct energy deposition method and a triple heterogeneous microstructure(fine/coarse equiaxed grains/columnar grains)is constructed.Addi...In this study,an AlCu/AlMgSc bimetallic alloy is prepared using a dual-wire arc direct energy deposition method and a triple heterogeneous microstructure(fine/coarse equiaxed grains/columnar grains)is constructed.Additionally,a quantitative comparative analysis of the deformation behavior of triple and dual heterogeneous microstructures during interrupted tensile testing is conducted,with emphasis on the effects of grain morphology and size on the tensile deformation mechanisms in the heterogeneous microstructure.Compared with the AlCu alloy with a double heterogeneous microstructure(equiaxed/columnar grain),the AlCu/AlMgSc bimetallic alloy exhibits a higher ultimate tensile strength of 301.4±7.9 MPa,a yield strength of 181.3±1.4 MPa,and an elongation of 9.7%±1.3%,which correspond to increases by 19.4%,21.2%,and 24.4%,respectively.Interrupted tensile testing is performed and a quasi-in-situ approach is employed to investigate the plastic deformation mechanisms of the triple heterogeneous microstructure during tensile deformation.The density of geometrically necessary dislocations(GNDs)in the fine equiaxed grains and the rate of GND accumulation during deformation,surpassed those observed in coarse equiaxed and columnar grains.Furthermore,in micrometer-sized equiaxed grains,the ability to accumulate GNDs decreases as the equiaxed grain size increases,and the equiaxed grains exhibit a higher capacity to accumulate GNDs compared with columnar grains.The triple heterogeneous microstructure provides a more favorable environment for trapping GNDs,thus resulting in enhanced strength and plastic deformation capabilities.This study offers guidance for the formulation and engineering application of heterogeneous microstructure alloys with diverse grain morphologies and multiple length scales.Additionally,novel approaches are introduced to enhance the strength and ductility of Al alloys.展开更多
A technique in which a polydimethylsiloxane(PDMS) template is used to assemble silicon oxide nanoparticles is proposed herein. The PDMS substrate was first constructed in a series of casting steps and a copper mask wa...A technique in which a polydimethylsiloxane(PDMS) template is used to assemble silicon oxide nanoparticles is proposed herein. The PDMS substrate was first constructed in a series of casting steps and a copper mask was then made with a laser marking system. Silicon oxide nanoparticles were generated by a modified Stober method. A PDMS substrate covered by the copper mask was then coated with a metal Au layer via sputtering to form the PDMS template. Finally, the silicon oxide nanoparticles were spin-coated on the PDMS template. Because the PDMS template consists of highly hydrophobic PDMS and less hydrophilic Au patterns, the nanoparticles undergo a dual dewetting process on the PDMS template to form an annular distribution around the borders of the Au patterns.展开更多
High-entropy alloys(HEAs)are considered alternatives to traditional structural materials because of their superior mechanical,physical,and chemical properties.However,alloy composition combinations are too numerous to...High-entropy alloys(HEAs)are considered alternatives to traditional structural materials because of their superior mechanical,physical,and chemical properties.However,alloy composition combinations are too numerous to explore.Finding a rapid synthesis method to accelerate the development of HEA bulks is imperative.Existing in situ synthesis methods based on additive manufacturing are insufficient for efficiently controlling the uniformity and accuracy of components.In this work,laser powder bed fusion(L-PBF)is adopted for the in situ synthesis of equiatomic CoCrFeMnNi HEA from elemental powder mixtures.High composition accuracy is achieved in parallel with ensuring internal density.The L-PBF-based process parameters are optimized;and two different methods,namely,a multi-melting process and homogenization heat treatment,are adopted to address the problem of incompletely melted Cr particles in the single-melted samples.X-ray diffraction indicates that HEA microstructure can be obtained from elemental powders via L-PBF.In the triple-melted samples,a strong crystallographic texture can be observed through electron backscatter diffraction,with a maximum polar density of 9.92 and a high ultimate tensile strength(UTS)of(735.3±14.1)MPa.The homogenization heat-treated samples appear more like coarse equiaxed grains,with a UTS of(650.8±16.1)MPa and an elongation of(40.2%±1.3%).Cellular substructures are also observed in the triple-melted samples,but not in the homogenization heat-treated samples.The differences in mechanical properties primarily originate from the changes in strengthening mechanism.The even and flat fractographic morphologies of the homogenization heat-treated samples represent a more uniform internal microstructure that is different from the complex morphologies of the triple-melted samples.Relative to the multi-melted samples,the homogenization heat-treated samples exhibit better processability,with a smaller composition deviation,i.e.,≤0.32 at.%.The two methods presented in this study are expected to have considerable potential for developing HEAs with high composition accuracy and composition flexibility.展开更多
A square-grid triboelectric nanogenerator （SG-TENG） is demonstrated for harvesting vibrational energy and sensing impulsive forces. Each square of the three-dimensional （3D）-printed square grid is filled with an a...A square-grid triboelectric nanogenerator （SG-TENG） is demonstrated for harvesting vibrational energy and sensing impulsive forces. Each square of the three-dimensional （3D）-printed square grid is filled with an aluminum （A1） ball. The grid structure allows the SG-TENG to harvest vibrational energy over a broad bandwidth and operate at different vibrational angles. The most striking feature of the SG-TENG is its ability of being scaled and integrated. After connecting two SG-TENGs in parallel, the open-circuit voltage and short-circuit current are significantly increased over the full vibrational frequency range. Being integrated with a table tennis racket, the SG-TENG can harvest the vibrational energy from hitting a ping pong ball using the racket, where a direct hit by the racket generates an average output voltage of 10,9 ~ 0.6 V and an average output current of 0.09 ± 0.02 boA. Moreover, the SG-TENG integrated into a focus mitt can be used in various combat sports, such as boxing and taekwondo, to monitor the frequency and magnitude of the punches or kicks from boxers and other practitioners. The collected data allow athletes to monitor their status and improve their performance skills. This work demonstrates the enormous potential of the SG-TENG in energy harvesting and sensing applications.展开更多
The changes of the wettability of the solid surfaces have attracted massive attention due to their important practical implications in numerous fields. As a new subject, the research on the wettability under the diffe...The changes of the wettability of the solid surfaces have attracted massive attention due to their important practical implications in numerous fields. As a new subject, the research on the wettability under the different environments is still in its early stage. So the fundamental research must be performed for the practical applications under different environments. However, it is seldom that the comprehensive wettability of a surface in air, in water and in oil has been reported. In this paper, the authors investigated the wettability of the stainless steel mesh coated with polyurethane in the above three different environments. The surface of the uncoated mesh was found to be hydrophobic in air, but the surface of the coated mesh was superhydrophilic in air. More interestingly, the surfaces of the coated meshes were superoleophilic in water and superhydrophobic in oil. Due to the coated meshes with these wettabilities were fabricated via a facile two-step method, the presented method may be adopted for large-scale industrial production, in various fields, such as icing prevention or the oil-field industry.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52405414)the China Postdoctoral Science Foundation(Grant No.2024M762580)+1 种基金Young Talent Fund of Xi'an Association for Science and Technology(Grant No.0959202513033)the Youth Innovation Team of Shaanxi Universities,and the Fundamental Research Funds for Central Universities.The authors gratefully acknowledge the support by the Instrumental Analysis Center of Xi’an Jiaotong University for sample characterization.
文摘In the background of carbon neutrality,monolithic ceramic catalysts are universally used in energy conversion and chemical catalysis due to the high heat and mass transfer efficiencies,low bed pressures,and scalability through modular design.However,traditional manufacturing processes are limited by mold dependence,organic solvent toxicity,and insufficient molding capability for complex structures,resulting in difficulty achieving precise regulation of cross-scale pores.Additive manufacturing(AM)technology employs a digital layered molding strategy to achieve the cross-scale structural regulation of catalysts from macroscopic flow channels to mesopores and micropores.This paper summarizes recent advances in the structural design of monolithic catalysts enabled by AM technologies and highlights their emerging applications in catalytic processes.Structurally,AM-fabricated monoliths have been effectively employed in key chemical reactions such as fuel reforming,CO_(2)conversion,biofuel synthesis.Strategies such as geometrical topology optimization,multi-scale pore synergy,biomimetic structural design,and functional gradient integration have been utilized to enhance heat and mass transport,reduce pressure drops,and improve overall catalytic performance.By overcoming the limitations of traditional catalysts,AM technologies create a new paradigm for addressing the longstanding challenge of coupling mass transfer with reaction kinetics.This approach provides a feasible pathway for driving both theoretical innovation and practical implementation of high-efficiency catalytic systems.
基金Supported by National Natural Science Foundation of China (Grant No.51975459)Shaanxi Provincial Natural Science Foundation of China (Grant No.2017JM5046)。
文摘In current research,many researchers propose analytical expressions for calculating the packing structure of spherical particles such as DN Model,Compact Model and NLS criterion et al.However,there is still a question that has not been well explained yet.That is:What is the core factors affecting the thermal conductivity of particles?In this paper,based on the coupled discrete element-finite difference(DE-FD)method and spherical aluminum powder,the relationship between the parameters and the thermal conductivity of the powder(ETC_(p))is studied.It is found that the key factor that can described the change trend of ETC_(p) more accurately is not the materials of the powder but the average contact area between particles(a_(ave))which also have a close nonlinear relationship with the average particle size d_(50).Based on this results,the expression for calculating the ETC_(p) of the sphere metal powder is successfully reduced to only one main parameter d_(50)and an efficient calculation model is proposed which can applicate both in room and high temperature and the corresponding error is less than 20.9%in room temperature.Therefore,in this study,based on the core factors analyzation,a fast calculation model of ETC_(p) is proposed,which has a certain guiding significance in the field of thermal field simulation.
文摘Considering the fracture problem of the silica-based ceramic core in the integrated casting of hollow turbine blades during directional solidification,the influence of various whiskers,including silicon carbide whiskers,silicon nitride whiskers,and mullite whiskers,on the high-temperature strength of the silica-based ceramic core was investigated.Additionally,the formation of microstructure morphology and phase structure was analyzed.Research results show that silicon carbide whiskers can reduce the microcracks caused by the shrinkage of cristobalite.During the sintering process,some of the silicon carbide whiskers oxidize and react with aluminum powder to form mullite,which can improve the high-temperature strength of the ceramic cores.When the content of silicon carbide whiskers is 3wt.%,the high-temperature bending strength of the cores reaches the maximum value of 21 MPa.Silicon nitride whiskers decompose in a high-temperature environment and react with aluminum powder in the matrix material to form mullite whiskers.When the content of silicon nitride whiskers is 5wt.%,the high-temperature bending strength of the cores reaches 20 MPa.By adding mullite whiskers,a structure of cristobalite wrapped mullite whiskers can be formed to achieve toughening.When the content of mullite whiskers is 4wt.%,the high-temperature bending strength can reach 17.2 MPa.By comparing the performance of silicon carbide whiskers,silicon nitride whiskers,and mullite whiskers,along with conducting slurry viscosity tests and casting experiments,it is determined that a ceramic slurry containing 4wt.%mullite whiskers is the most suitable for making the cores used in the integrated casting of hollow turbine blades.
基金supported by National Natural Science Foundation of China(Grant Nos.52476223,22038011)the Programme of Introducing Talents of Discipline to Universities(Grant No.B23025)+1 种基金K.C.Wong Education Foundation,Fundamental Research Funds for the Central Universities(Grant No.xzy012023074)the Innovation Capability Support Program of Shaanxi(Grant Nos.2023KJKXX-004,2022KXJ-126).
文摘Conventional powder/pellet-based systems used for mitigating the environmental challenges posed by CO_(2)emissions present inefficiencies in mass/heat transfer,pressure drop,and clogging.Monolithic adsorption materials have emerged as a promising alternative to such systems.Additive manufacturing(AM)enables precise structural optimization and active component control in monolithic adsorbents,enhancing the adsorption kinetics while minimizing mechanical wear.This review examines the progress in AM-driven CO_(2)adsorbent development,covering the following aspects:(1)fabrication techniques for monolithic adsorbents and key metrics for evaluating their mechanical and adsorption properties,(2)applications of AM methods(extrusion,coating,gel spinning,and 3D printing)under fixed-source and direct-air capture scenarios,and(3)integrated systems combining CO_(2)adsorption and conversion.However,balancing adsorption performance with mechanical strength is a critical challenge.The trade-off can be addressed through advanced AM strategies such as hybrid material architectures and computational design.Future advancements will hinge on hybrid AM techniques to decouple structural and functional demands,AI/ML-driven multi-objective optimization for pore structure refinement and stress distribution,and lifecycle sustainability analytics to reduce energy use and material waste.By synergizing these approaches,next-generation monolithic adsorbents can achieve high capacity,mechanical robustness,and cost-effectiveness,positioning AM as a scalable and sustainable platform for carbon capture technologies.
基金Supported by National Key R&D Program of China(Grant Nos.2017YFB1103400,2016YFB1100902)National Natural Science Foundation of China(Grant No.51575430,51811530107)The Youth Innovation Team of Shaanxi Universities.
文摘A novel metal matrix composite freeform fabrication approach,fiber traction printing(FTP),is demonstrated through controlling the wetting behavior between fibers and the matrix.This process utilizes the fiber bundle to control the cross-sectional shape of the liquid metal,shaping it from circular to rectangular which is more precise.The FTP process could resolve manufacturing difficulties in the complex structure of continuous fiber reinforced metal matrix composites.The printing of the first layer monofilament is discussed in detail,and the effects of the fibrous coating thickness on the mechanical properties and microstructures of the composite are also investigated in this paper.The composite material prepared by the FTP process has a tensile strength of 235.2 MPa,which is close to that of composites fabricated by conventional processes.The complex structures are printed to demonstrate the advantages and innovations of this approach.Moreover,the FTP method is suited to other material systems with good wettability,such as modified carbon fiber,surfactants,and aluminum alloys.
基金support from the National Natural Science Foundation of China(Nos.52275374 and 52205414)the Xiaomi Foundation through the Xi-aomi Young Scholar Program,the Key Research and Develop-ment Projects of Shaanxi Province(No.2023-YBGY-361)as well as the Young Elite Scientists Sponsorship Program by CAST(No.2021QNRC001).
文摘High-quality repair of damaged Inconel 718(IN718)superalloy components can achieve great economic benefits.However,the directly double aging(DA)treatment by industrial standards,yields an inferior ductility on the repaired component than that of the wrought base metal.In this work,wrought IN718 components were repaired by laser-directed energy deposition(LDED),a novel tailored heat treatment(THT)schedule consisting of a short-term low-temperature homogenization,and subsequent DA was sub-sequently conducted to strengthen the repaired IN718 alloys.The microstructure evolution and mechan-ical properties of the DA and THT-treated repaired alloys were comparatively investigated.The results indicated that the THT effectively dissolved most of the hard brittle Laves precipitates in the deposition region with only slight coarsening of the grains in the substrate.As compared to the DA sample,the elon-gation of the THT sample increased remarkably by 88%with only a slight reduction of 19.2 MPa in yield stress.Moreover,the strain distribution of the THT sample was overall more even but then destabilized in a narrow abnormal coarsened grain region caused by the static recrystallization.In general,this study breaks through the limitation of the low ductility of the DA-treated repaired IN718 alloys and provides a promising way to further improve the mechanical properties.
基金Supported by National High Technology Research and Development Program of China(863 Program,Grant No.2015AA042503)K.C.Wong Education Foundation.
文摘Improvement of fabrication efficiency and part performance was the main challenge for the large-scale powder bed fusion(PBF)process.In this study,a dynamic monitoring and feedback system of powder bed temperature field using an infrared thermal imager has been established and integrated into a four-laser PBF equipment with a working area of 2000 mm×2000 mm.The heat-affected zone(HAZ)temperature field has been controlled by adjusting the scanning speed dynamically.Simultaneously,the relationship among spot size,HAZ temperature,and part performance has been established.The fluctuation of the HAZ temperature in four-laser scanning areas was decreased from 30.85℃to 17.41℃.Thus,the consistency of the sintering performance of the produced large component has been improved.Based on the controllable temperature field,a dynamically adjusting strategy for laser spot size was proposed,by which the fabrication efficiency was improved up to 65.38%.The current research results were of great significance to the further industrial applications of large-scale PBF equipment.
基金the Industry-University Research Cooperation Project of Aero Engine Corporation of China(Grant No.HFZL2019CXY023)the National Science and Technology Major Project(Grant No.2017-Ⅶ-0008-0101)。
文摘Stray grains,the most serious casting defect,mainly occur in the platform because of the abrupt transition of the cross-section in the directional solidification of superalloy single-crystal blades.A new mould baffle technology based on 3D printing and gelcasting is proposed herein to reduce the formation of stray grains in the platform.The influence of the proposed mould baffle technology on the temperature field in the platform during solidification was investigated by simulation and experiment.The numerical simulation results indicate that the proposed mould baffle technology can effectively hinder the radiation and heat dissipation at the platform extremities,and therefore,reduce undercooling in the platform and the formation of stray grains during directional solidification.Casting trials of a hollow turbine blade were conducted using CMSX-4 superalloy.The trial results demonstrate the potential of the proposed approach for manufacturing single-crystal superalloy blades.
基金financially supported by NSFC under Grant No. 90923040China’s National "973" Program under Grant No. 2009CB724202
文摘Cast molding process has provided a reliable, simple and cost-effective way to fabricate micro structures since decades ago. In order to obtain structures with fine, dense and deep nano-size features by cast molding, it is necessary to study the forming mechanism in the process. In this paper, based on major steps of cast molding, filling models of liquid are established and solved; and the forming mechanism of liquid is revealed. Moreover, the scale effect between the liquid and the cavity on the filling velocity of liquid is studied.It is also interesting to find out that the wettability of liquid on the cavity may be changed from wetting to dewetting depends on the pressure difference. Finally, we experimentally verify some of our modeling results on the flowing and filling state of the liquid during the cast molding process.
基金supported by the National Natu-ral Science Foundation of China(No.52205414)the Young Elite Scientists Sponsorship Program by CAST(No.2021QNRC001)+3 种基金the Advance Research Projects in the Field of Manned Spaceflight,China Manned Space Agency,China(No.040302)the Shang-hai Aerospace Science and Technology Innovation Fund Project,the Shanghai Academy of Spaceflight Technology,China(No.SAST2018-066)the 73rd batch of China Postdoctoral Science Foun-dation General Financial Support(No.2023MD734199)the Shaanxi Provincial Natural Science Basic Research Program(No.2023-JC-QN-0551).
文摘In this study,an AlCu/AlMgSc bimetallic alloy is prepared using a dual-wire arc direct energy deposition method and a triple heterogeneous microstructure(fine/coarse equiaxed grains/columnar grains)is constructed.Additionally,a quantitative comparative analysis of the deformation behavior of triple and dual heterogeneous microstructures during interrupted tensile testing is conducted,with emphasis on the effects of grain morphology and size on the tensile deformation mechanisms in the heterogeneous microstructure.Compared with the AlCu alloy with a double heterogeneous microstructure(equiaxed/columnar grain),the AlCu/AlMgSc bimetallic alloy exhibits a higher ultimate tensile strength of 301.4±7.9 MPa,a yield strength of 181.3±1.4 MPa,and an elongation of 9.7%±1.3%,which correspond to increases by 19.4%,21.2%,and 24.4%,respectively.Interrupted tensile testing is performed and a quasi-in-situ approach is employed to investigate the plastic deformation mechanisms of the triple heterogeneous microstructure during tensile deformation.The density of geometrically necessary dislocations(GNDs)in the fine equiaxed grains and the rate of GND accumulation during deformation,surpassed those observed in coarse equiaxed and columnar grains.Furthermore,in micrometer-sized equiaxed grains,the ability to accumulate GNDs decreases as the equiaxed grain size increases,and the equiaxed grains exhibit a higher capacity to accumulate GNDs compared with columnar grains.The triple heterogeneous microstructure provides a more favorable environment for trapping GNDs,thus resulting in enhanced strength and plastic deformation capabilities.This study offers guidance for the formulation and engineering application of heterogeneous microstructure alloys with diverse grain morphologies and multiple length scales.Additionally,novel approaches are introduced to enhance the strength and ductility of Al alloys.
基金supported by the National Natural Science Foundation of China (51475353, 51475352 and 51375361)the Tribology Science Fund of the State Key Laboratory of Tribology of China (SKLTKF14A02)
文摘A technique in which a polydimethylsiloxane(PDMS) template is used to assemble silicon oxide nanoparticles is proposed herein. The PDMS substrate was first constructed in a series of casting steps and a copper mask was then made with a laser marking system. Silicon oxide nanoparticles were generated by a modified Stober method. A PDMS substrate covered by the copper mask was then coated with a metal Au layer via sputtering to form the PDMS template. Finally, the silicon oxide nanoparticles were spin-coated on the PDMS template. Because the PDMS template consists of highly hydrophobic PDMS and less hydrophilic Au patterns, the nanoparticles undergo a dual dewetting process on the PDMS template to form an annular distribution around the borders of the Au patterns.
文摘High-entropy alloys(HEAs)are considered alternatives to traditional structural materials because of their superior mechanical,physical,and chemical properties.However,alloy composition combinations are too numerous to explore.Finding a rapid synthesis method to accelerate the development of HEA bulks is imperative.Existing in situ synthesis methods based on additive manufacturing are insufficient for efficiently controlling the uniformity and accuracy of components.In this work,laser powder bed fusion(L-PBF)is adopted for the in situ synthesis of equiatomic CoCrFeMnNi HEA from elemental powder mixtures.High composition accuracy is achieved in parallel with ensuring internal density.The L-PBF-based process parameters are optimized;and two different methods,namely,a multi-melting process and homogenization heat treatment,are adopted to address the problem of incompletely melted Cr particles in the single-melted samples.X-ray diffraction indicates that HEA microstructure can be obtained from elemental powders via L-PBF.In the triple-melted samples,a strong crystallographic texture can be observed through electron backscatter diffraction,with a maximum polar density of 9.92 and a high ultimate tensile strength(UTS)of(735.3±14.1)MPa.The homogenization heat-treated samples appear more like coarse equiaxed grains,with a UTS of(650.8±16.1)MPa and an elongation of(40.2%±1.3%).Cellular substructures are also observed in the triple-melted samples,but not in the homogenization heat-treated samples.The differences in mechanical properties primarily originate from the changes in strengthening mechanism.The even and flat fractographic morphologies of the homogenization heat-treated samples represent a more uniform internal microstructure that is different from the complex morphologies of the triple-melted samples.Relative to the multi-melted samples,the homogenization heat-treated samples exhibit better processability,with a smaller composition deviation,i.e.,≤0.32 at.%.The two methods presented in this study are expected to have considerable potential for developing HEAs with high composition accuracy and composition flexibility.
文摘A square-grid triboelectric nanogenerator （SG-TENG） is demonstrated for harvesting vibrational energy and sensing impulsive forces. Each square of the three-dimensional （3D）-printed square grid is filled with an aluminum （A1） ball. The grid structure allows the SG-TENG to harvest vibrational energy over a broad bandwidth and operate at different vibrational angles. The most striking feature of the SG-TENG is its ability of being scaled and integrated. After connecting two SG-TENGs in parallel, the open-circuit voltage and short-circuit current are significantly increased over the full vibrational frequency range. Being integrated with a table tennis racket, the SG-TENG can harvest the vibrational energy from hitting a ping pong ball using the racket, where a direct hit by the racket generates an average output voltage of 10,9 ~ 0.6 V and an average output current of 0.09 ± 0.02 boA. Moreover, the SG-TENG integrated into a focus mitt can be used in various combat sports, such as boxing and taekwondo, to monitor the frequency and magnitude of the punches or kicks from boxers and other practitioners. The collected data allow athletes to monitor their status and improve their performance skills. This work demonstrates the enormous potential of the SG-TENG in energy harvesting and sensing applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.51475353,51375361&51475352)the Tribology Science Fund of the State Key Laboratory of Tribology(Grant No.SKLTKF14A02)+1 种基金the Natural Science Basic Research Program of Shaanxi Province(Grant No.2016JM5004)the Key Laboratory of the Shaanxi Provincial Department of Education(Grant No.16JS057)
文摘The changes of the wettability of the solid surfaces have attracted massive attention due to their important practical implications in numerous fields. As a new subject, the research on the wettability under the different environments is still in its early stage. So the fundamental research must be performed for the practical applications under different environments. However, it is seldom that the comprehensive wettability of a surface in air, in water and in oil has been reported. In this paper, the authors investigated the wettability of the stainless steel mesh coated with polyurethane in the above three different environments. The surface of the uncoated mesh was found to be hydrophobic in air, but the surface of the coated mesh was superhydrophilic in air. More interestingly, the surfaces of the coated meshes were superoleophilic in water and superhydrophobic in oil. Due to the coated meshes with these wettabilities were fabricated via a facile two-step method, the presented method may be adopted for large-scale industrial production, in various fields, such as icing prevention or the oil-field industry.
