The mechanical properties of solid oxide fuel cells(SOFCs)can limit their mechanical stability and lifespan.Understanding the correlation between the microstructure and mechanical properties of porous electrode is ess...The mechanical properties of solid oxide fuel cells(SOFCs)can limit their mechanical stability and lifespan.Understanding the correlation between the microstructure and mechanical properties of porous electrode is essential for enhancing the performance and durability of SOFCs.Accurate prediction of mechanical properties of porous electrode can be achieved by microscale finite element modeling based on three-dimensional(3D)microstructures,which requires expensive 3D tomography techniques and massive computational resources.In this study,we proposed a cost-effective alternative approach to access the mechanical properties of porous electrodes,with the elastic properties of La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δc)athode serving as a case study.Firstly,a stochastic modeling was used to reconstruct 3D microstructures from two-dimensional(2D)cross-sections as an alternative to expensive tomography.Then,the discrete element method(DEM)was used to predict the elastic properties of porous ceramics based on the discretized 3D microstructures reconstructed by stochastic modeling.Based on 2D microstructure and the elastic properties calculated by the DEM modeling of the 3D reconstructed porous microstructures,a convolutional neural network(CNN)based deep learning model was built to predict the elastic properties rapidly from 2D microstructures.The proposed combined framework can be implemented with limited computational resources and provide a basis for rapid prediction of mechanical properties and parameter estimation for multiscale modeling of SOFCs.展开更多
Silicon is the most extensively studied semiconductor mainly owing to its wide applicability in the photovoltaic solar cell industry.However the qualily of Si photovoltaic cells depends on the purity of the material a...Silicon is the most extensively studied semiconductor mainly owing to its wide applicability in the photovoltaic solar cell industry.However the qualily of Si photovoltaic cells depends on the purity of the material and on the grain structure of the ingot from which the wafers are cutting.The electrical performance of such materials,i.e. mainly their minority carrier lifetime,is closely related to metal impurities present in the feedstock or introduced during crystal growth.These impurities strongly interact with existing crystal defects to form complexes,accumulate at dislocations or grain boundaries in different forms,or even form silieide precipitates,which simultaneously contain several metal impurities.In such a context,it is necessary to control the segregation of impurities especially metallic in the grown ingot in order to optimize the cell properties as a function of the raw material purity.A new Bridgman set-up is developed in order to study the crystallization of photovoltaic Si under independently controlled solidification parameters growth rate,thermal gradient,purity and convection.Convection,either natural or forced,plays a very important role during the crystallization.Its intensity and flow pattern affect heat and mass transfer and,consequently,macrostructure and segregation in a solidified ingot.Here the convection can be controlled by a travelling magnetic field in order to homogenize or segregate the rejected impurities such as metallic elements.The effects of the magnetic field intensity and frequency on the segregation and crystalline structure will be presented.展开更多
In the present study,a novel method of surface finish improvement is proposed using shot blasting of soda lime(SBSL)beads on the Mg-AZ31 alloy.The effect of the soda blasting process parameters,such as blast pressure,...In the present study,a novel method of surface finish improvement is proposed using shot blasting of soda lime(SBSL)beads on the Mg-AZ31 alloy.The effect of the soda blasting process parameters,such as blast pressure,stand-off distance,and blast duration,have been studied in-response of material removal rate(MRR)and surface roughness(SR)and corresponding statistical models have been obtained.The multi-objective optimization has also been performed to obtain parameters for maximum MRR and minimum SR.The corrosion behavior of the treated specimens has been performed to study their in-vitro biodegradability in simulated body fluid(SBF)for 1,3,7,10,15,and 21 days.The wettability study of the SBSL treated samples has been investigated using sessile drop methodology.Further,cell adhesion test has also been performed to study the biocompatibility characteristics of the SBSL treated samples using Huh7 liver cell lines.Based on obtained quantitative data as well as scanning electron microscopy analysis of treated samples,the SBSL treatment of the AZ31 alloy has been found highly useful in producing biocompatibility surfaces along with desirable morphological features.展开更多
This paper proposes an estimate of the stirring intensity needed to maintain an efficient segregation of impurities towards the liquid when crystallizing semiconductors such as silicon,with rapid solidification rates(...This paper proposes an estimate of the stirring intensity needed to maintain an efficient segregation of impurities towards the liquid when crystallizing semiconductors such as silicon,with rapid solidification rates(several cm/h).The method,valid far from stagnation points or detachments,is based on the properties of turbulent boundary layers,with a normal velocity of the liquid towards the solid/liquid interface due to solidification,that has the same effect as boundary layer suction in aeronautics.The transition between the diffusive regime(no segregation),and the convective regime(efficient segregation)occurs if the friction at the wall is greater than a threshold depending on the solidification rate.A chart is given to estimate the convecto-diffusive parameter from the ratio between stirring and solidification velocity,and the Reynolds number.展开更多
The present study focuses on the relationship of hardness with grain size for commercially pure titanium （CpTi） and ultra fine grained titanium （UFG-Ti） produced by equal channel angular process （ECAP） of Cp-Ti...The present study focuses on the relationship of hardness with grain size for commercially pure titanium （CpTi） and ultra fine grained titanium （UFG-Ti） produced by equal channel angular process （ECAP） of Cp-Ti）.Vickers and Knoop indentations of UFG-Ti at different loads was ～2.5 times harder than those of Cp-Ti.Xray diffraction （XRD） analysis showed peak broadening in UFG-Ti due to reduced grain size and micro-lattice strains.Scanning electron microscopy （SEM） revealed that ECAP had reduced the grain size of Cp-Ti by ～10 times.Weibull statistics showed UFG-Ti with lower dispersion in hardness values compare to Cp-Ti indicating a more uniform microstructure.展开更多
The solution-treated Mg-4Y-4Sm-0.5Zr alloy was extruded at temperatures from 325℃ to 500℃.Dynamic recrystallization(DRX) completely occurs when the alloy is extruded at 350℃and above.The grains of the extruded allo...The solution-treated Mg-4Y-4Sm-0.5Zr alloy was extruded at temperatures from 325℃ to 500℃.Dynamic recrystallization(DRX) completely occurs when the alloy is extruded at 350℃and above.The grains of the extruded alloy are obviously refined by the occurrence of DRX.The average grain size of the extruded alloy increases with increasing the extrusion temperature,leading to a slight decrease of the ultimate tensile strength(UTS) and the yield strength(YS) .On the contrary,the UTS and YS of the extruded and aged alloy increase with increasing the extrusion temperature.Values of UTS of 400 MPa,YS larger than 300 MPa and elongation(EL) of 7%are achieved after extrusion at 400℃ and ageing at 200℃ for 16 h.Both grain refinement and precipitation are efficient strengthening mechanisms for the Mg-4Y-4Sm-0.5Zr alloy.展开更多
Ti6Al4V powders with three different particle size distributions(0–20, 20–45, and 45–75 μm) were used to evaluate the effect of the particle size distribution on the solid-state sintering and their mechanical prop...Ti6Al4V powders with three different particle size distributions(0–20, 20–45, and 45–75 μm) were used to evaluate the effect of the particle size distribution on the solid-state sintering and their mechanical properties. The sintering kinetics was determined by dilatometry at temperatures from 900 to 1260°C. The mechanical properties of the sintered samples were evaluated by microhardness and compression tests. The sintering kinetics indicated that the predominant mechanism depends on the relative density irrespective of the particle size used. The mechanical properties of the sintered samples are adversely affected by increasing pore volume fraction. The elastic Young's modulus and yield stress follow a power law function of the relative density. The fracture behavior after compression is linked to the neck size developed during sintering, exhibiting two different mechanisms of failure: interparticle neck breaking and intergranular cracking in samples with relative densities below and above of 90%, respectively. The main conclusion is that relative density is responsible for the kinetics, mechanical properties, and failure behavior of Ti6 Al4 V powders.展开更多
The paper studies specific pumping characteristics of the annular linear pumps with travelling field(ALIP)for liquid sodium.This research represents a preliminary step in the study and development of very large electr...The paper studies specific pumping characteristics of the annular linear pumps with travelling field(ALIP)for liquid sodium.This research represents a preliminary step in the study and development of very large electromagnetic pumps able to provide high flow rates.Since in such cases the magnetic Reynolds number are quite large,it is necessary to take into account the full magnetohydrodynamic interaction between the electromagnetic field and the liquid metal flow inside the pumping channel.The case where the velocity field is uniform in the channel cross section is firstly considered. Then,the coupling between the electromagnetic aspects with the hydrodynamic ones in a 2D axisyrnmetric fmite element model is studied,in order to compare the magnetic convection and the magnetic diffusion.展开更多
A volume averaged columnar solidification model,which couples the flow,temperature and solute concentration fields,is applied to simulate experimental continuous casting cases with and without vertical electromagnetic...A volume averaged columnar solidification model,which couples the flow,temperature and solute concentration fields,is applied to simulate experimental continuous casting cases with and without vertical electromagnetic stirring(V-EMS).The calculated distribution of magnetic induction intensity and final macrosegregation maps are consistent with the experimental results.Calculation results reveal that the V-EMS promotes longitudinal melt flow,accelerates heat dissipation and solidification and finally reduces the central segregation of carbon.However,when V-EMS is applied,the solute distribution becomes asymmetric because the melt flow shows opposite directions between the near and far sides from stirrer.An obvious positive segregation band is observed at about 1/4 width of the billet near the stirrer in both calculated and experimental results.The position and degree of such positive segregation could be affected by installation height of stirrer,as demonstrated by additional simulation cases.展开更多
The use of low electrically conducting liquids is more and more widespread.This is the case for molten glass,salt or slag processing,ionic liquids used in biotechnology,batteries in energy storage and metallurgy.The p...The use of low electrically conducting liquids is more and more widespread.This is the case for molten glass,salt or slag processing,ionic liquids used in biotechnology,batteries in energy storage and metallurgy.The present paper deals with the design of a new electromagnetic induction device that can heat and stir low electricallyconducting liquids.It consists of a resistance-capacity-inductance circuit coupled with a low-conducting liquid load.The device is supplied by a unique electric power source delivering a single-phase high frequency electric current.The main working principle of the circuit is based on a double oscillating circuit inductor connected to the solid-state transistor generator.This technique,which yields a set of coupled oscillating circuits,consists of coupling a forced phase and an induced phase,neglecting the influence of the electric parameters of the loading part(i.e.,the low-conductivity liquid).It is shown that such an inductor is capable to provide a two-phase AC traveling magnetic field at high frequency.To better understand the working principle,the present work improves a previous existing simplified theory by taking into account a complex electrical equivalent diagram due to the different mutual couplings between the two inductors and the two corresponding induced current sets.A more detailed theoretical model is provided,and the key and sensitive elements are elaborated.Based on this theory,equipment is designed to provide a stirring effect on sodium chloride-salted water at 40 S/m.It is shown that such a device fed by several hundred kiloHertz electric currents is able to mimic a linear motor.A set of optimized operating parameters are proposed to guide the experiment.A pure electromagnetic numerical model is presented.Numerical modelling of the load is performed in order to assess the efficiency of the stirrer with a salt water load.Such a device can generate a significant liquid motion with both controlled flow patterns and adjustable amplitude.Based on the magnetohydrodynamic theory,numerical modeling of the salt water flow generated by the stirrer confirms its feasibility.展开更多
Coatings of metal matrix composites(Cu?WC)were fabricated by solid-state sintering.WC reinforcing particles indifferent quantities from5%up to30%(volume fraction)were mixed with Cu particles.After mixing,the powders w...Coatings of metal matrix composites(Cu?WC)were fabricated by solid-state sintering.WC reinforcing particles indifferent quantities from5%up to30%(volume fraction)were mixed with Cu particles.After mixing,the powders were poured ontothe surface of copper substrates.Sintering was carried out at1000°C under a reducing atmosphere in a vertical dilatometer.Sinteringkinetics was affected by both rigid substrates and WC particles which retarded the radial and axial densification of powders.However,the coatings were strongly attached to the substrate,and WC particles were randomly distributed within the matrix.The addition ofthe reinforcing particles enhanced the microhardness and reduced the volume loss in wear tests to1/17compared to the unreinforcedsample.The predominant wear mechanism was identified as abrasion at a load of5N.20%WC(volume fraction)reinforcingparticles led to the maximum values of properties for the composite coating.展开更多
The serrated plastic flow,microstructure and residual stress of a Zr_（55）Cu_（30）Ni_5Al_（10） bulk metallic glass（BMG）undergone surface mechanical attrition treatment（SMAT）have been investigated by a combinati...The serrated plastic flow,microstructure and residual stress of a Zr_（55）Cu_（30）Ni_5Al_（10） bulk metallic glass（BMG）undergone surface mechanical attrition treatment（SMAT）have been investigated by a combination of compression tests with scanning electron microscopy（SEM）,high resolution transmission electron microscopy（HRTEM）and the incremental hole-drilling strain-gage method.It is found that SMAT leads to various microstructural modifications and residual stress distribution in the surface layers of the Zrbased BMG due to the mechanically-induced nanocrystallization and generation of shear bands.As a result,the BMG alloy exhibits a remarkable work-hardening like behavior and significant increase of plastic strain from less than 1%to 15%,and its plastic deformation dynamics yields a power-law distribution of shear avalanches.Based upon the analysis of the experimental results,it is indicated that this can be connected to the SMAT-induced microstructural modifications and the resulting residual compressive stress in the Zr-based BMG.展开更多
A physical simulation was carried out to investigate the realistic experiment of bulk solidifying the Zn-Bi hyper-monotectic alloy under various compound electric-magnetic fields(CEMF).For this experiment,two crucial ...A physical simulation was carried out to investigate the realistic experiment of bulk solidifying the Zn-Bi hyper-monotectic alloy under various compound electric-magnetic fields(CEMF).For this experiment,two crucial parameters determinate the cast microstructure,the one is electric-magnetic force(EMF)and the other is the frequency of AC current.Results show that the minor phase could be mixed in the other phase from the initial layered structure when the EMF above a specific value under fixed frequency,and the average diameter of minor phase droplet decreases with increasing EMF.The evolution of the liquid phases structure is reasonable agree with the realistic experiment of Zn-Bi hyper-monotectic alloy,which suggests that the mechanism revealed by the physical simulation could represent the one in the realistic experiment.展开更多
After the cold rolling sequence of the production line,stainless steels strips present highly disordered structure and have to be annealed to recover their crystalline structure.This operation takes place by passing t...After the cold rolling sequence of the production line,stainless steels strips present highly disordered structure and have to be annealed to recover their crystalline structure.This operation takes place by passing the moving strip through a furnace heated by combustion of natural gas with little air excess.Although the time at high temperature is short(<1 min),the formed surface oxide is thick enough to modify the surface aspect of the steel,making necessary subsequent chemical pickling.The present work explores the oxidation step of various stainless steels during final annealing in order to better understand the mechanisms involved and make further improvements in the pickling sequence.展开更多
In order to obtain homogenous Zn-Bi hyper-monotectic alloys and investigate what mechanism the magnetic field functions,we carried out the solidification experiments of Zn-4wt%Bi,5wt%Bi,6wt%Bi,7wt%Bi, 15wt%Bi and 30wt...In order to obtain homogenous Zn-Bi hyper-monotectic alloys and investigate what mechanism the magnetic field functions,we carried out the solidification experiments of Zn-4wt%Bi,5wt%Bi,6wt%Bi,7wt%Bi, 15wt%Bi and 30wt%Bi alloys under a 18T static magnetic field which was set up in LNCMI.Water quenching was also chosen to further damp the segregation caused by Stokes convection and Marangoni movement.The results indicated that when the content of Bismuth is 5-7wt%,the superimposition of 18Tesla magnetic field can damp the segregation remarkably,and the size of the second phase particles also is decreased.Furthermore,to Zn-4wt%Bi alloy solidified in 18T magnetic field,no spherical bismuth particles are found even magnifying 1000 times by microscope, which hints that the 18T magnetic field may change its solidifying character.To Zn-15wt%Bi and Zn-30wt%Bi alloy, due to their strong segregation trend,the 18T magnetic field still cannot damp the Stokes settlement thoroughly even by quenching way,however,no layered bismuth and zinc appears when compared to 0T,large Bismuth block are formed in the lower half part of the sample.展开更多
ntergranular slow crack growth in zirconia polycrystal is described with a cohesive zone model that simulate mechanically the reaction-rupture mechanism underlying stress and environ- mentally assisted failure. A 2D p...ntergranular slow crack growth in zirconia polycrystal is described with a cohesive zone model that simulate mechanically the reaction-rupture mechanism underlying stress and environ- mentally assisted failure. A 2D polycrystal is considered with cohesive surfaces inserted along the grain boundaries. The anisotropic elastic modulus and grain-to-grain misorientation are accounted for together with an initial stress state related to the processing. A minimum load threshold is shown to originate from the onset of the reaction-rupture mechanism to proceed where a minimum traction is reached locally and from the magnitude of the initial compression stresses. This work aims at providing reliable predictions in long lasting applications of ceramics.展开更多
Sn-3wt%Pb alloy was directionally solidified without and with a 0.08T transverse magnetic field(TMF),and real-time recorded by in-situ synchrotron X-ray imaging.Results indicate that TMF shortened the distance from th...Sn-3wt%Pb alloy was directionally solidified without and with a 0.08T transverse magnetic field(TMF),and real-time recorded by in-situ synchrotron X-ray imaging.Results indicate that TMF shortened the distance from the location of nucleation to the advancing interface,and accelerated the growth rate of the equiaxed crystal,which caused the columnar-to-equiaxed transition(CET)finally.The thermoelectromagnetic convection(TEMC)in front of the interface and around the crystal’s dendritic branch should respond to changes of the distance and the growth rate.展开更多
Lightening structure is one of the goals of many fields of research. As a result, magnesium alloys are studied due to their low density. However, one drawback of these alloys is their low formability at room temperatu...Lightening structure is one of the goals of many fields of research. As a result, magnesium alloys are studied due to their low density. However, one drawback of these alloys is their low formability at room temperature due to their hexagonal closed-packed structure. In the present work, the forming capacity of an AZ31 Mg alloys has been studied using a mini deep-drawing device, image correlation techniques and tests (tension and expansion) at temperatures contained between 20°C and 200°C. To investigate formability limits of Mg alloys in expansion, major and minor strains data were generated using hemispherical punch tests and analyzed with 3D digital images correlation techniques. Thanks to images correlation, strains on the surface of the samples were observed by means of a double digitization of the sample in three dimensions before and after deformation by using stereoscopic vision and triangulation. Image correlations have also been used in 2D to measure strains on the surface of the tensile test samples. These tests gave interesting information on the evolution of various parameters such as hardening coefficient, strain rate sensitivity parameter, and Lankford coefficient, which may affect the behavior of the alloys. Finally, the forming limits in both configurations (tension and expansion) were compared and discussed.展开更多
The Energy Climate Package is the EU response to the Global Warming Challenge.Induction heating processes can contribute to the energy saving goal:20%saving within 2020.European induction manufacturer already propose ...The Energy Climate Package is the EU response to the Global Warming Challenge.Induction heating processes can contribute to the energy saving goal:20%saving within 2020.European induction manufacturer already propose many efficient solutions at industrial scale.To improve induction devices for an always better energy efficiency, EDF R&D set up a French cooperative project called ISIS with a financial support of the French National Research Agency.Its objective is to promote induction heating as Best Available Technology(BAT)and to develop innovative solutions to increase its efficiency.The ISIS innovations concern the electroheat conversion of induction devices(auto-adaptive multi-coil power supply,low losses coils)and the recovering of fatally lost energy.This paper shows the mid-term results of this project.Firsts control algorithms were successfully tested on a 100 kW 3-coil power supply.A homogenization technique is proposed to model a multi-strand coil.A heat recovery test bench is build and equipped with a PFC control loop to fit with the production fluctuations.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12172104 and 11932005)the Talent Recruitment Project of Guangdong(2021QN02L892)+3 种基金the Stable Supporting Fund of Shenzhen(GXWD20231130153335002)the Shccig-Qinling Program(SMYJY202300140C)the program of Innovation Team in Universities and Colleges in Guangdong(2021KCXTD006)Development and Reform Commission of Shenzhen(XMHT20220103004).
文摘The mechanical properties of solid oxide fuel cells(SOFCs)can limit their mechanical stability and lifespan.Understanding the correlation between the microstructure and mechanical properties of porous electrode is essential for enhancing the performance and durability of SOFCs.Accurate prediction of mechanical properties of porous electrode can be achieved by microscale finite element modeling based on three-dimensional(3D)microstructures,which requires expensive 3D tomography techniques and massive computational resources.In this study,we proposed a cost-effective alternative approach to access the mechanical properties of porous electrodes,with the elastic properties of La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δc)athode serving as a case study.Firstly,a stochastic modeling was used to reconstruct 3D microstructures from two-dimensional(2D)cross-sections as an alternative to expensive tomography.Then,the discrete element method(DEM)was used to predict the elastic properties of porous ceramics based on the discretized 3D microstructures reconstructed by stochastic modeling.Based on 2D microstructure and the elastic properties calculated by the DEM modeling of the 3D reconstructed porous microstructures,a convolutional neural network(CNN)based deep learning model was built to predict the elastic properties rapidly from 2D microstructures.The proposed combined framework can be implemented with limited computational resources and provide a basis for rapid prediction of mechanical properties and parameter estimation for multiscale modeling of SOFCs.
文摘Silicon is the most extensively studied semiconductor mainly owing to its wide applicability in the photovoltaic solar cell industry.However the qualily of Si photovoltaic cells depends on the purity of the material and on the grain structure of the ingot from which the wafers are cutting.The electrical performance of such materials,i.e. mainly their minority carrier lifetime,is closely related to metal impurities present in the feedstock or introduced during crystal growth.These impurities strongly interact with existing crystal defects to form complexes,accumulate at dislocations or grain boundaries in different forms,or even form silieide precipitates,which simultaneously contain several metal impurities.In such a context,it is necessary to control the segregation of impurities especially metallic in the grown ingot in order to optimize the cell properties as a function of the raw material purity.A new Bridgman set-up is developed in order to study the crystallization of photovoltaic Si under independently controlled solidification parameters growth rate,thermal gradient,purity and convection.Convection,either natural or forced,plays a very important role during the crystallization.Its intensity and flow pattern affect heat and mass transfer and,consequently,macrostructure and segregation in a solidified ingot.Here the convection can be controlled by a travelling magnetic field in order to homogenize or segregate the rejected impurities such as metallic elements.The effects of the magnetic field intensity and frequency on the segregation and crystalline structure will be presented.
文摘In the present study,a novel method of surface finish improvement is proposed using shot blasting of soda lime(SBSL)beads on the Mg-AZ31 alloy.The effect of the soda blasting process parameters,such as blast pressure,stand-off distance,and blast duration,have been studied in-response of material removal rate(MRR)and surface roughness(SR)and corresponding statistical models have been obtained.The multi-objective optimization has also been performed to obtain parameters for maximum MRR and minimum SR.The corrosion behavior of the treated specimens has been performed to study their in-vitro biodegradability in simulated body fluid(SBF)for 1,3,7,10,15,and 21 days.The wettability study of the SBSL treated samples has been investigated using sessile drop methodology.Further,cell adhesion test has also been performed to study the biocompatibility characteristics of the SBSL treated samples using Huh7 liver cell lines.Based on obtained quantitative data as well as scanning electron microscopy analysis of treated samples,the SBSL treatment of the AZ31 alloy has been found highly useful in producing biocompatibility surfaces along with desirable morphological features.
基金Item Sponsored by the French Agency for Environment and Energy (ADEME) as Part of the ISOPEM Project and labelled by TENERRDIS (Rhone-Alpes Energy Cluster)
文摘This paper proposes an estimate of the stirring intensity needed to maintain an efficient segregation of impurities towards the liquid when crystallizing semiconductors such as silicon,with rapid solidification rates(several cm/h).The method,valid far from stagnation points or detachments,is based on the properties of turbulent boundary layers,with a normal velocity of the liquid towards the solid/liquid interface due to solidification,that has the same effect as boundary layer suction in aeronautics.The transition between the diffusive regime(no segregation),and the convective regime(efficient segregation)occurs if the friction at the wall is greater than a threshold depending on the solidification rate.A chart is given to estimate the convecto-diffusive parameter from the ratio between stirring and solidification velocity,and the Reynolds number.
文摘The present study focuses on the relationship of hardness with grain size for commercially pure titanium （CpTi） and ultra fine grained titanium （UFG-Ti） produced by equal channel angular process （ECAP） of Cp-Ti）.Vickers and Knoop indentations of UFG-Ti at different loads was ～2.5 times harder than those of Cp-Ti.Xray diffraction （XRD） analysis showed peak broadening in UFG-Ti due to reduced grain size and micro-lattice strains.Scanning electron microscopy （SEM） revealed that ECAP had reduced the grain size of Cp-Ti by ～10 times.Weibull statistics showed UFG-Ti with lower dispersion in hardness values compare to Cp-Ti indicating a more uniform microstructure.
基金Project(2009AA033501)supported by the National Hi-tech Research and Development Program of ChinaProject(2006BAE04B01-2)supported by the National Key Technology Research&Development Program of ChinaProject(06SR07104)supported by theInternational Cooperation Fund of Shanghai Science and Technology Committee,Shanghai/Rhone-Alpes Science and Technology
文摘The solution-treated Mg-4Y-4Sm-0.5Zr alloy was extruded at temperatures from 325℃ to 500℃.Dynamic recrystallization(DRX) completely occurs when the alloy is extruded at 350℃and above.The grains of the extruded alloy are obviously refined by the occurrence of DRX.The average grain size of the extruded alloy increases with increasing the extrusion temperature,leading to a slight decrease of the ultimate tensile strength(UTS) and the yield strength(YS) .On the contrary,the UTS and YS of the extruded and aged alloy increase with increasing the extrusion temperature.Values of UTS of 400 MPa,YS larger than 300 MPa and elongation(EL) of 7%are achieved after extrusion at 400℃ and ageing at 200℃ for 16 h.Both grain refinement and precipitation are efficient strengthening mechanisms for the Mg-4Y-4Sm-0.5Zr alloy.
基金the National Laboratory SEDEAM-National Council for Science and Technology (CONACYT)ECOS M15P01 for the financial support and the facilities to develop this study
文摘Ti6Al4V powders with three different particle size distributions(0–20, 20–45, and 45–75 μm) were used to evaluate the effect of the particle size distribution on the solid-state sintering and their mechanical properties. The sintering kinetics was determined by dilatometry at temperatures from 900 to 1260°C. The mechanical properties of the sintered samples were evaluated by microhardness and compression tests. The sintering kinetics indicated that the predominant mechanism depends on the relative density irrespective of the particle size used. The mechanical properties of the sintered samples are adversely affected by increasing pore volume fraction. The elastic Young's modulus and yield stress follow a power law function of the relative density. The fracture behavior after compression is linked to the neck size developed during sintering, exhibiting two different mechanisms of failure: interparticle neck breaking and intergranular cracking in samples with relative densities below and above of 90%, respectively. The main conclusion is that relative density is responsible for the kinetics, mechanical properties, and failure behavior of Ti6 Al4 V powders.
文摘The paper studies specific pumping characteristics of the annular linear pumps with travelling field(ALIP)for liquid sodium.This research represents a preliminary step in the study and development of very large electromagnetic pumps able to provide high flow rates.Since in such cases the magnetic Reynolds number are quite large,it is necessary to take into account the full magnetohydrodynamic interaction between the electromagnetic field and the liquid metal flow inside the pumping channel.The case where the velocity field is uniform in the channel cross section is firstly considered. Then,the coupling between the electromagnetic aspects with the hydrodynamic ones in a 2D axisyrnmetric fmite element model is studied,in order to compare the magnetic convection and the magnetic diffusion.
基金financial support from the National Natural Science Foundation of China(Grant No.U1760206)the National Key R&D Program of China(Grant No.2017YFE0107900)+1 种基金the 111 Project 2.0 of China(Grant No.BP0719037)the financial support provided by the ESA-MAP MICAST project contract 14347/01/NL/SH.
文摘A volume averaged columnar solidification model,which couples the flow,temperature and solute concentration fields,is applied to simulate experimental continuous casting cases with and without vertical electromagnetic stirring(V-EMS).The calculated distribution of magnetic induction intensity and final macrosegregation maps are consistent with the experimental results.Calculation results reveal that the V-EMS promotes longitudinal melt flow,accelerates heat dissipation and solidification and finally reduces the central segregation of carbon.However,when V-EMS is applied,the solute distribution becomes asymmetric because the melt flow shows opposite directions between the near and far sides from stirrer.An obvious positive segregation band is observed at about 1/4 width of the billet near the stirrer in both calculated and experimental results.The position and degree of such positive segregation could be affected by installation height of stirrer,as demonstrated by additional simulation cases.
基金This study was supported by the Instrument and Equipment Development Project of the Chinese Academy of Sciences(YJKYYQ20200053)the“Double First-Class”Construction Fund(111800XX62)the Mechanical Engineering Discipline Construction Fund(111800M000).
文摘The use of low electrically conducting liquids is more and more widespread.This is the case for molten glass,salt or slag processing,ionic liquids used in biotechnology,batteries in energy storage and metallurgy.The present paper deals with the design of a new electromagnetic induction device that can heat and stir low electricallyconducting liquids.It consists of a resistance-capacity-inductance circuit coupled with a low-conducting liquid load.The device is supplied by a unique electric power source delivering a single-phase high frequency electric current.The main working principle of the circuit is based on a double oscillating circuit inductor connected to the solid-state transistor generator.This technique,which yields a set of coupled oscillating circuits,consists of coupling a forced phase and an induced phase,neglecting the influence of the electric parameters of the loading part(i.e.,the low-conductivity liquid).It is shown that such an inductor is capable to provide a two-phase AC traveling magnetic field at high frequency.To better understand the working principle,the present work improves a previous existing simplified theory by taking into account a complex electrical equivalent diagram due to the different mutual couplings between the two inductors and the two corresponding induced current sets.A more detailed theoretical model is provided,and the key and sensitive elements are elaborated.Based on this theory,equipment is designed to provide a stirring effect on sodium chloride-salted water at 40 S/m.It is shown that such a device fed by several hundred kiloHertz electric currents is able to mimic a linear motor.A set of optimized operating parameters are proposed to guide the experiment.A pure electromagnetic numerical model is presented.Numerical modelling of the load is performed in order to assess the efficiency of the stirrer with a salt water load.Such a device can generate a significant liquid motion with both controlled flow patterns and adjustable amplitude.Based on the magnetohydrodynamic theory,numerical modeling of the salt water flow generated by the stirrer confirms its feasibility.
基金CONACy T through the project CB-167111the Scientific Research Department of the UMSNH and the Guadalajara University for the financial support and the facilities to develop this study
文摘Coatings of metal matrix composites(Cu?WC)were fabricated by solid-state sintering.WC reinforcing particles indifferent quantities from5%up to30%(volume fraction)were mixed with Cu particles.After mixing,the powders were poured ontothe surface of copper substrates.Sintering was carried out at1000°C under a reducing atmosphere in a vertical dilatometer.Sinteringkinetics was affected by both rigid substrates and WC particles which retarded the radial and axial densification of powders.However,the coatings were strongly attached to the substrate,and WC particles were randomly distributed within the matrix.The addition ofthe reinforcing particles enhanced the microhardness and reduced the volume loss in wear tests to1/17compared to the unreinforcedsample.The predominant wear mechanism was identified as abrasion at a load of5N.20%WC(volume fraction)reinforcingparticles led to the maximum values of properties for the composite coating.
基金the financial supports provided by National Natural Science Foundation of China(Grant Nos.51171099,50871063)the MOST 973 Program of China(Grant Nos.2015CB856800 and 2012CB932203)
文摘The serrated plastic flow,microstructure and residual stress of a Zr_（55）Cu_（30）Ni_5Al_（10） bulk metallic glass（BMG）undergone surface mechanical attrition treatment（SMAT）have been investigated by a combination of compression tests with scanning electron microscopy（SEM）,high resolution transmission electron microscopy（HRTEM）and the incremental hole-drilling strain-gage method.It is found that SMAT leads to various microstructural modifications and residual stress distribution in the surface layers of the Zrbased BMG due to the mechanically-induced nanocrystallization and generation of shear bands.As a result,the BMG alloy exhibits a remarkable work-hardening like behavior and significant increase of plastic strain from less than 1%to 15%,and its plastic deformation dynamics yields a power-law distribution of shear avalanches.Based upon the analysis of the experimental results,it is indicated that this can be connected to the SMAT-induced microstructural modifications and the resulting residual compressive stress in the Zr-based BMG.
基金Item Sponsored by National Science Foundation of China (No.50974085) National High-tech R&D Program of China (No.2009AA03Z109) +3 种基金Key Project from Science and Technology Commission of Shanghai Municipality (No.09dz1206401No.08dj 1400404 and No.08DZ1130100) Development Foundation for Talents in Shanghai (No.2009046) Specialized Research Fund for Doctoral Program of Higher Education (No.20093108110012)
文摘A physical simulation was carried out to investigate the realistic experiment of bulk solidifying the Zn-Bi hyper-monotectic alloy under various compound electric-magnetic fields(CEMF).For this experiment,two crucial parameters determinate the cast microstructure,the one is electric-magnetic force(EMF)and the other is the frequency of AC current.Results show that the minor phase could be mixed in the other phase from the initial layered structure when the EMF above a specific value under fixed frequency,and the average diameter of minor phase droplet decreases with increasing EMF.The evolution of the liquid phases structure is reasonable agree with the realistic experiment of Zn-Bi hyper-monotectic alloy,which suggests that the mechanism revealed by the physical simulation could represent the one in the realistic experiment.
文摘After the cold rolling sequence of the production line,stainless steels strips present highly disordered structure and have to be annealed to recover their crystalline structure.This operation takes place by passing the moving strip through a furnace heated by combustion of natural gas with little air excess.Although the time at high temperature is short(<1 min),the formed surface oxide is thick enough to modify the surface aspect of the steel,making necessary subsequent chemical pickling.The present work explores the oxidation step of various stainless steels during final annealing in order to better understand the mechanisms involved and make further improvements in the pickling sequence.
基金Item Sponsored by National Science Foundation of China (No.50974085No.51034010) +5 种基金Development Foundation for Talents in Shanghai (No.2009046) National High-tech R&D Program of China (No.2009AA03Z109) Key Research and Innovation Program from Shanghai Municipal Education Commission (No.09zz98) Key Project from Science and Technology Commission of Shanghai Municipality (No:09dz120640109dz1206402) EuroMagNET under the EU contract n 228043
文摘In order to obtain homogenous Zn-Bi hyper-monotectic alloys and investigate what mechanism the magnetic field functions,we carried out the solidification experiments of Zn-4wt%Bi,5wt%Bi,6wt%Bi,7wt%Bi, 15wt%Bi and 30wt%Bi alloys under a 18T static magnetic field which was set up in LNCMI.Water quenching was also chosen to further damp the segregation caused by Stokes convection and Marangoni movement.The results indicated that when the content of Bismuth is 5-7wt%,the superimposition of 18Tesla magnetic field can damp the segregation remarkably,and the size of the second phase particles also is decreased.Furthermore,to Zn-4wt%Bi alloy solidified in 18T magnetic field,no spherical bismuth particles are found even magnifying 1000 times by microscope, which hints that the 18T magnetic field may change its solidifying character.To Zn-15wt%Bi and Zn-30wt%Bi alloy, due to their strong segregation trend,the 18T magnetic field still cannot damp the Stokes settlement thoroughly even by quenching way,however,no layered bismuth and zinc appears when compared to 0T,large Bismuth block are formed in the lower half part of the sample.
文摘ntergranular slow crack growth in zirconia polycrystal is described with a cohesive zone model that simulate mechanically the reaction-rupture mechanism underlying stress and environ- mentally assisted failure. A 2D polycrystal is considered with cohesive surfaces inserted along the grain boundaries. The anisotropic elastic modulus and grain-to-grain misorientation are accounted for together with an initial stress state related to the processing. A minimum load threshold is shown to originate from the onset of the reaction-rupture mechanism to proceed where a minimum traction is reached locally and from the magnitude of the initial compression stresses. This work aims at providing reliable predictions in long lasting applications of ceramics.
基金Item Sponsored by the CNRS/ANR OPTIMAG projectthe Natural Science Foundation of China (No.50911130365) the National 973 Project (No.2011CB610404)
文摘Sn-3wt%Pb alloy was directionally solidified without and with a 0.08T transverse magnetic field(TMF),and real-time recorded by in-situ synchrotron X-ray imaging.Results indicate that TMF shortened the distance from the location of nucleation to the advancing interface,and accelerated the growth rate of the equiaxed crystal,which caused the columnar-to-equiaxed transition(CET)finally.The thermoelectromagnetic convection(TEMC)in front of the interface and around the crystal’s dendritic branch should respond to changes of the distance and the growth rate.
文摘Lightening structure is one of the goals of many fields of research. As a result, magnesium alloys are studied due to their low density. However, one drawback of these alloys is their low formability at room temperature due to their hexagonal closed-packed structure. In the present work, the forming capacity of an AZ31 Mg alloys has been studied using a mini deep-drawing device, image correlation techniques and tests (tension and expansion) at temperatures contained between 20°C and 200°C. To investigate formability limits of Mg alloys in expansion, major and minor strains data were generated using hemispherical punch tests and analyzed with 3D digital images correlation techniques. Thanks to images correlation, strains on the surface of the samples were observed by means of a double digitization of the sample in three dimensions before and after deformation by using stereoscopic vision and triangulation. Image correlations have also been used in 2D to measure strains on the surface of the tensile test samples. These tests gave interesting information on the evolution of various parameters such as hardening coefficient, strain rate sensitivity parameter, and Lankford coefficient, which may affect the behavior of the alloys. Finally, the forming limits in both configurations (tension and expansion) were compared and discussed.
基金Item Sponsored by French Research National Agency (ANR) Through "Efficacite Energetique et Reduction des Emissions de CO_2 Dans les Systemes Industriels" Program(Project ISIS n°ANR-09-EESI-004)
文摘The Energy Climate Package is the EU response to the Global Warming Challenge.Induction heating processes can contribute to the energy saving goal:20%saving within 2020.European induction manufacturer already propose many efficient solutions at industrial scale.To improve induction devices for an always better energy efficiency, EDF R&D set up a French cooperative project called ISIS with a financial support of the French National Research Agency.Its objective is to promote induction heating as Best Available Technology(BAT)and to develop innovative solutions to increase its efficiency.The ISIS innovations concern the electroheat conversion of induction devices(auto-adaptive multi-coil power supply,low losses coils)and the recovering of fatally lost energy.This paper shows the mid-term results of this project.Firsts control algorithms were successfully tested on a 100 kW 3-coil power supply.A homogenization technique is proposed to model a multi-strand coil.A heat recovery test bench is build and equipped with a PFC control loop to fit with the production fluctuations.
