AZ31-4.6% Mg2Si （mass fraction） composite was prepared by conventional casting method. Repetitive upsetting （RU） was applied to severely deforming the as-cast composite at 400 ℃ for 1, 3, and 5 passes. Finite ele...AZ31-4.6% Mg2Si （mass fraction） composite was prepared by conventional casting method. Repetitive upsetting （RU） was applied to severely deforming the as-cast composite at 400 ℃ for 1, 3, and 5 passes. Finite element analysis of the material flow indicates that deformation concentrates in the bottom region of the sample after 1 pass, and much more uniform deformation is obtained after 5 passes. During multi-pass RU process, both dendritic and Chinese script type Mg2Si phases are broken up into smaller particles owing to the shear stress forced by the matrix. With the increasing number of RU passes, finer grain size and more homogeneous distribution of Mg2Si particles are obtained along with significant enhancement in both strength and ductility. AZ31-4.6%Mg2Si composite exhibits tensile strength of 284 MPa and elongation of 9.8%after 5 RU passes at 400 ℃ compared with the initial 128 MPa and 5.4%of original AZ31-4.6%Mg2Si composite.展开更多
A newly developed severe plastic deformation （SPD） technique, i.e. repetitive upsetting （RU）, is employed to improve the strength and ductility of a Mg-Gd-Y-Zr alloy. During the RU processing, dynamic recrystalliz...A newly developed severe plastic deformation （SPD） technique, i.e. repetitive upsetting （RU）, is employed to improve the strength and ductility of a Mg-Gd-Y-Zr alloy. During the RU processing, dynamic recrystallization occurs in the Mg alloy, which leads to a significant grain refinement from 11.2 p.m to 2.8 μm. The yield strength （YS）, ultimate tensile strength （UTS） and elongation increase simultaneously with increasing RU passes. The microstructural evolution is affected by processing temperatures. Dynamic recrystallization prevails at low temperatures, while dynamic recovery is the main effect factor at high temperatures. Texture characteristics gradually become random during multiple passes of RU processing, which reduces the tension-compression asymmetry of the Mg-Gd-Y-Zr alloy. 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.展开更多
The breakage mechanism of W-Ni-Fe alloy in the process of electro-heat upsetting studied both theoretically and experimetnally, and also the behaviors of crack formation and propagation were analysed. Alloy suffers fr...The breakage mechanism of W-Ni-Fe alloy in the process of electro-heat upsetting studied both theoretically and experimetnally, and also the behaviors of crack formation and propagation were analysed. Alloy suffers from corrosion and thermal-mechanical fatigue mutual function. Simultaneously, the practical ways to improve the anvil life was discussed.展开更多
The microstructure and hardness of a 2024 aluminum alloy subjected tomulti-pass upsetting extrusion at ambient temperature were studied. Experimental results indicatedthat with the number of upsetting extrusion passes...The microstructure and hardness of a 2024 aluminum alloy subjected tomulti-pass upsetting extrusion at ambient temperature were studied. Experimental results indicatedthat with the number of upsetting extrusion passes increasing, the grains of the alloy are graduallyrefined and the hardness increases correspondingly. After ten passes of upsetting extrusionprocessing, the grain size decreases to less than 200 nm in diameter and the sample maintains itsoriginal shape, while the hardness is double owing to equal-axial ultrafine grains and workhardening effect caused by large plastic deformation.展开更多
A meshless approach, called the rigid-plastic reproducing kernel particle method （RKPM）, is presented for three-dimensional （3D） bulk metal forming simulation. The approach is a combination of RKPM with the flow t...A meshless approach, called the rigid-plastic reproducing kernel particle method （RKPM）, is presented for three-dimensional （3D） bulk metal forming simulation. The approach is a combination of RKPM with the flow theory of 3D rigid-plastic mechanics. For the treatments of essential boundary conditions and incompressibility constraint, the boundary singular kernel method and the modified penalty method are utilized, respectively. The arc-tangential friction model is employed to treat the contact conditions. The compression of rectangular blocks, a typical 3D upsetting operation, is analyzed for different friction conditions and the numerical results are compared with those obtained using commercial rigid-plastic FEM （finite element method） software Deform^3D. As results show, when handling 3D plastic deformations, the proposed approach eliminates the need of expensive meshing and remeshing procedures which are unavoidable in conventional FEM and can provide results that are in good agreement with finite element predictions.展开更多
The isothermal repetitive upsetting extrusion(RUE)was implemented to process ZK60 magnesium alloy at 380℃.Then,the relationship between the microstructural characters,including grain refinement and texture evolution,...The isothermal repetitive upsetting extrusion(RUE)was implemented to process ZK60 magnesium alloy at 380℃.Then,the relationship between the microstructural characters,including grain refinement and texture evolution,and the mechanical performance of the alloy was investigated.Results showed that after 3 passes of RUE,the average grain size was refined from 115.0 to 26.5μm,which was mainly caused by the continuous dynamic recrystallization and discontinuous dynamic recrystallization.Meanwhile,the elongation of the alloy increased from 13.8 to 21.6%,and the superplasticity(142%)of the alloy has been achieved in the following high temperature tensile test,which is very beneficial for the further processing of the alloy into components.In particular,the alloy formed a distinctive texture distributed between<2-1-11>and<2-1-14>,which was greatly related to the Schmid factor of extrusion direction(ED)and transverse direction(TD).This texture changed the initiation ability of basal and prismatic slip in both directions and inhibited the initiation of partial tensile twinning in TD;thus,the anisotropy in both directions was weakened.As expected,the tensile yield strength difference decreased from25.9 to 3.4 MPa,but it was used as the cost of tensile yield strength in ED.展开更多
Cold upsetting experiments were carried out on sintered Fe 0.8%C1.0%Si-0. 4%Cu steel preforms in order to evaluate their deformation characteristics. Powder preforms of 86 % of theoretical density, with two different ...Cold upsetting experiments were carried out on sintered Fe 0.8%C1.0%Si-0. 4%Cu steel preforms in order to evaluate their deformation characteristics. Powder preforms of 86 % of theoretical density, with two different ratios of height to diameter, were prepared using a suitable die set assembly on a 1.0 MN capacity hydraulic testing machine. Sintering was carried out in an electric muffle furnace for 1.5 h at 1 150 ℃. Each sintered compact was subjected to incremental loading of 0.04 MN under dry friction condition till a crack appeared at the free surfaces. The experimental results were critically analysed, the stress as a function of strain and densification was obtained, then the work hardening behaviour was analyzed. It has been found that in the process of enhancing densification, strength and strain hardening is also induced during upsetting, but the work hardening behaviour is not homogenously enhanced against strain and densification.展开更多
A kind of surface instability,basin-like depression defect companied by mixed grain structure at the bottom of large-scale valve during electric upsetting process,would significantly influence the microstructures and ...A kind of surface instability,basin-like depression defect companied by mixed grain structure at the bottom of large-scale valve during electric upsetting process,would significantly influence the microstructures and mechanical properties of components.In order to analyze the forming process of the basin-like depression defect,a finite element model for the electric upsetting process of Ni80A superalloy was developed using multi-field and multi-scale coupling analysis method.Subsequently,a series of parameters loading path schemes for force and current were designed by varying the initial value,peak value and value level,and their effects on basin-like depression and mixed grain structure were simulated and uncovered.It is concluded that the changes of heating speed and pressurization speed result in the different flow velocities between the inner and outer layers of billet,thus exerting the basin-like depression.Simulation results also indicate that these defects can be optimized through the parameter coordination between force and current.Finally,the validity and reliability of the finite element model were verified by physical experiments in electric upsetting process.展开更多
Theoretical analyses show that the variation of wall thickness is in direct proportion to outer-diameter, inter-diameter, and (1+R_s)^(1/2) (Rs is sectional increase ratio of tube), the theoretical calculated results ...Theoretical analyses show that the variation of wall thickness is in direct proportion to outer-diameter, inter-diameter, and (1+R_s)^(1/2) (Rs is sectional increase ratio of tube), the theoretical calculated results of wall thickness during tube dieless upsetting are very approximate to the experimental one. As the width of deformation field increases, both the variation of wall thickness and the derivative of wall thickness variation to width of deformation field (to/tf) reduce.展开更多
The current research investigates the effect of homogenization on the microstructure and mechanical properties of the AZ91 D alloy processed by repetitive upsetting（RU）. Results show that during RU processing, the i...The current research investigates the effect of homogenization on the microstructure and mechanical properties of the AZ91 D alloy processed by repetitive upsetting（RU）. Results show that during RU processing, the initial large Mg;Al;particles in the as-cast specimen accelerate the dynamic recrystallization（DRX） due to the particle stimulating nucleation（PSN） mechanism. With the progress of RU,the inherent large strain breaks the large second phases into small fragments, which indicates the PSN gradually disappears, while the pinning effect becomes obvious. As for the homogenized specimen, a pre-heat treatment leads to the absence of Mg;Al;particles but a uniform distribution of Al atoms in the Mg alloy. Though the subsequent RU promotes the precipitation of Mg;Al;particles, the relatively small particle size and the uniform distribution are more favorable to act as obstacles for grain growth than contributors to PSN. Finally, a more homogeneous and refined microstructure is obtained in the specimen with prior homogenization than the as-cast one.展开更多
A whole analysis model including forging and flat platens is built,which is used to analyse the process of upsetting a cylinder between flat platens.The influence of surface friction and transient temperature are comp...A whole analysis model including forging and flat platens is built,which is used to analyse the process of upsetting a cylinder between flat platens.The influence of surface friction and transient temperature are comprehensively considered.By means of ANSYS software,the elasto plastic FEM analysis of the whole upsetting process is carried out.From the point of view of numerical calculation,the correctness of the centre region tension stress theory about upsetting a cylinder between flat platens is tested and verified.The concept of plasto nucleus is presented to explain the forming of double dumps.The efffect of temperature is inspected.The relation curves between the radial stress of the symmetry centre point and the relative pression ratio are given.展开更多
FEM is used to analyze the influence of interface friction on the material flow and the cause of forming defect in the cold upsetting of tube flange. Based on the FEM simulation results, the relationships between flan...FEM is used to analyze the influence of interface friction on the material flow and the cause of forming defect in the cold upsetting of tube flange. Based on the FEM simulation results, the relationships between flange width and the extreme friction factors are established. The concept of forming limit diagram for cold upsetting of tube flange is presented.展开更多
It is of great significance to study the corrosion process of aluminum(Al)alloys fasteners in order to mitigate corrosion for their widespread applications.In this paper,a method for enhancing the corrosion resistance...It is of great significance to study the corrosion process of aluminum(Al)alloys fasteners in order to mitigate corrosion for their widespread applications.In this paper,a method for enhancing the corrosion resistance of Al alloy fasteners is proposed.7075 Al alloy parts with a fine-grained microstructure were prepared by pre-heat treatment(PHT),combined subsequent equal channel angular pressing(ECAP)and cold upsetting(CU).The corrosion behavior of the specimens was investigated by intergranular corrosion and electrochemical test.Microstructure investigations were carried out by field emission scanning electron microscopy,energy dispersive spectrometer and transmission electron microscopy.The relationship between microstructural evolution and corrosion resistance changes was also explored.The results show that both PHT and ECAP-CU significantly improved the corrosion resistance of the samples and modified the corrosion process.The open circuit potential,corrosion current density and corrosion rate of the alloy on electrochemical test were(-0.812±8.854)×10^(-5) V(vs.SCE),(6.379±0.025)×10^(-6) A/cm^(2) and 0.066 mm/year,respectively,and the intergranular corrosion depth was(557±8)μm.The main factor controlling the corrosion behavior was the microstructure evolution.After PHT,the disappearance of the dendritic structure and the dissolution of the nonequilibrium second phase eliminated the potential difference between the phases,reducing the free energy in the as cast state.When ECAP-CU was used after PHT,the grain refinement was accompanied by a high density of grain boundaries and dislocations,which led to the formation of a denser passivation film on the alloy surface,improving the corrosion resistance in an aggressive environment.展开更多
In the paper a self-adjusting hydraulic machine for combination forming of upsetting and extruding is systematacially presented in terms of mechanical principle, design principle, machine construction, design of the k...In the paper a self-adjusting hydraulic machine for combination forming of upsetting and extruding is systematacially presented in terms of mechanical principle, design principle, machine construction, design of the key components and working routine. The machine is designed with the following features: The lower movable beam is adjusted by the ejecting cylinder, the upper upsetting beam is reset by the backstroke slide rods, and the upsetting cylinders communicate with the gas-liquid accumulators. These features make the machine conformation compact, save both the backstroke cylinder of the upper upsetting beam and the upsetting cylinder of the lower movable beam, and simplify the hydraulic system. Furthermore, the machine can resolve such problems as incomplete filling at the addendum position, microcracks at the dedendum position, greater force and lower die life during precision forging of spur gears.展开更多
This paper explores the impact of back-gate bias (V_(soi)) and supply voltage (V_(DD)) on the single-event upset (SEU) cross section of 0.18μm configurable silicon-on-insulator static random-access memory (SRAM) unde...This paper explores the impact of back-gate bias (V_(soi)) and supply voltage (V_(DD)) on the single-event upset (SEU) cross section of 0.18μm configurable silicon-on-insulator static random-access memory (SRAM) under high linear energy transfer heavyion experimentation.The experimental findings demonstrate that applying a negative back-gate bias to NMOS and a positive back-gate bias to PMOS enhances the SEU resistance of SRAM.Specifically,as the back-gate bias for N-type transistors(V_(nsoi)) decreases from 0 to-10 V,the SEU cross section decreases by 93.23%,whereas an increase in the back-gate bias for P-type transistors (V_(psoi)) from 0 to 10 V correlates with an 83.7%reduction in SEU cross section.Furthermore,a significant increase in the SEU cross section was observed with increase in supply voltage,as evidenced by a 159%surge at V_(DD)=1.98 V compared with the nominal voltage of 1.8 V.To explore the physical mechanisms underlying these experimental data,we analyzed the dependence of the critical charge of the circuit and the collected charge on the bias voltage by simulating SEUs using technology computer-aided design.展开更多
The 28 nm process has a high cost-performance ratio and has gradually become the standard for the field of radiation-hardened devices.However,owing to the minimum physical gate length of only 35 nm,the physical area o...The 28 nm process has a high cost-performance ratio and has gradually become the standard for the field of radiation-hardened devices.However,owing to the minimum physical gate length of only 35 nm,the physical area of a standard 6T SRAM unit is approximately 0.16μm^(2),resulting in a significant enhancement of multi-cell charge-sharing effects.Multiple-cell upsets(MCUs)have become the primary physical mechanism behind single-event upsets(SEUs)in advanced nanometer node devices.The range of ionization track effects increases with higher ion energies,and spacecraft in orbit primarily experience SEUs caused by high-energy ions.However,ground accelerator experiments have mainly obtained low-energy ion irradiation data.Therefore,the impact of ion energy on the SEU cross section,charge collection mechanisms,and MCU patterns and quantities in advanced nanometer devices remains unclear.In this study,based on the experimental platform of the Heavy Ion Research Facility in Lanzhou,low-and high-energy heavy-ion beams were used to study the SEUs of 28 nm SRAM devices.The influence of ion energy on the charge collection processes of small-sensitive-volume devices,MCU patterns,and upset cross sections was obtained,and the applicable range of the inverse cosine law was clarified.The findings of this study are an important guide for the accurate evaluation of SEUs in advanced nanometer devices and for the development of radiation-hardening techniques.展开更多
We study the problem of multiple node upset （MNU） using three-dimensional device simulation. The results show the transient floating node and charge lateral diffusion are the key reasons for MNU. We compare the MNU ...We study the problem of multiple node upset （MNU） using three-dimensional device simulation. The results show the transient floating node and charge lateral diffusion are the key reasons for MNU. We compare the MNU with multiple bit upset （MBU）,and find that their characteristics are different. Methods to avoid MNU are also discussed.展开更多
The effect of predeformation manner, predeformation ratio and isothermal heat-treat parameter on the non-dendrite structure of AZ61 magnesium alloy in SIMA process was studied. Under coequal heat-treat condition, the ...The effect of predeformation manner, predeformation ratio and isothermal heat-treat parameter on the non-dendrite structure of AZ61 magnesium alloy in SIMA process was studied. Under coequal heat-treat condition, the impact of the hot upsetting pre- deformation on semi-solid microstructure in SIMA process was compared with that of the cold compressive predeformation. The results indicate that non-dendrite microstructure in AZ61 magnesium alloy billets can be obtained by hot or cold upsetting predeformation in SIMA process, although their mechanisms of evolution are different. Increasing hot or cold upsetting predeformation ratio can enhance the effect and quality of the non-dendrite microstructure formed before storage energy up to saturation, but the proper isothermal temperature and holding time should be selected.展开更多
The paper concisely introduced the hoopment of photoplastic simulation and the principle of its appli- cation.Deformations of combine extrusion and strain distributin in the process of upsetting the cylinder with vo...The paper concisely introduced the hoopment of photoplastic simulation and the principle of its appli- cation.Deformations of combine extrusion and strain distributin in the process of upsetting the cylinder with void were studied by this physical photoplasic simulation method. Some important informations obtained from the simulation experiment are helpful to understand the deformation law and the charac- teristics of material flowing.The validity of the physical simulation method and the importance of com- bining the physical simulation method with numerical simulation method together were proposed in the paper.展开更多
A ductile fracture criterion of 316LN stainless steel, combined with the plastic deformation capacity of ma- terial and the stress state dependent damages, was proposed to predict ductile fracture during hot deformati...A ductile fracture criterion of 316LN stainless steel, combined with the plastic deformation capacity of ma- terial and the stress state dependent damages, was proposed to predict ductile fracture during hot deformation. To the end, tensile tests at high temperatures were first performed to investigate the fracture behavior of 316LN stain- less steel. The experimental results show the variation of the critical fracture strain as a function of temperature and strain rate. Second, the criterion was calibrated by using the upsetting tests and the corresponding numerical simula- tions. Finally, the proposed fracture criterion was validated by the designed tests and the corresponding finite ele- ment （FE） simulation. The results show that the criterion can successfully predict the onset of ductile fracture at ele- vated temperatures.展开更多
基金Projects(51074106,51374145)supported by the National Natural Science Foundation of ChinaProject(09JC1408200)supported by the Science and Technology Commission of Shanghai Municipality,China+1 种基金Project(2014M561466)supported by China Postdoctoral Science FoundationProject(14R21411000)supported by Shanghai Postdoctoral Scientific Program,China
文摘AZ31-4.6% Mg2Si （mass fraction） composite was prepared by conventional casting method. Repetitive upsetting （RU） was applied to severely deforming the as-cast composite at 400 ℃ for 1, 3, and 5 passes. Finite element analysis of the material flow indicates that deformation concentrates in the bottom region of the sample after 1 pass, and much more uniform deformation is obtained after 5 passes. During multi-pass RU process, both dendritic and Chinese script type Mg2Si phases are broken up into smaller particles owing to the shear stress forced by the matrix. With the increasing number of RU passes, finer grain size and more homogeneous distribution of Mg2Si particles are obtained along with significant enhancement in both strength and ductility. AZ31-4.6%Mg2Si composite exhibits tensile strength of 284 MPa and elongation of 9.8%after 5 RU passes at 400 ℃ compared with the initial 128 MPa and 5.4%of original AZ31-4.6%Mg2Si composite.
基金supported by the National Key R&D Program of China (grant number 2017YFA0204403)the National Natural Science Foundation of China (NSFC) under Grant Nos. 51601003, 51301092, 51404151, 51401172+1 种基金Project supported by Beijing Postdoctoral Research Foundation under Grant No. 2016ZZ-02Project of Science & Technology Department of Sichuan Province (No. 2015HH0012)
文摘A newly developed severe plastic deformation （SPD） technique, i.e. repetitive upsetting （RU）, is employed to improve the strength and ductility of a Mg-Gd-Y-Zr alloy. During the RU processing, dynamic recrystallization occurs in the Mg alloy, which leads to a significant grain refinement from 11.2 p.m to 2.8 μm. The yield strength （YS）, ultimate tensile strength （UTS） and elongation increase simultaneously with increasing RU passes. The microstructural evolution is affected by processing temperatures. Dynamic recrystallization prevails at low temperatures, while dynamic recovery is the main effect factor at high temperatures. Texture characteristics gradually become random during multiple passes of RU processing, which reduces the tension-compression asymmetry of the Mg-Gd-Y-Zr alloy. 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.
文摘The breakage mechanism of W-Ni-Fe alloy in the process of electro-heat upsetting studied both theoretically and experimetnally, and also the behaviors of crack formation and propagation were analysed. Alloy suffers from corrosion and thermal-mechanical fatigue mutual function. Simultaneously, the practical ways to improve the anvil life was discussed.
基金This project is financially supported by the Natural Science Foundation (No. E5305293) of South China University of Technology.
文摘The microstructure and hardness of a 2024 aluminum alloy subjected tomulti-pass upsetting extrusion at ambient temperature were studied. Experimental results indicatedthat with the number of upsetting extrusion passes increasing, the grains of the alloy are graduallyrefined and the hardness increases correspondingly. After ten passes of upsetting extrusionprocessing, the grain size decreases to less than 200 nm in diameter and the sample maintains itsoriginal shape, while the hardness is double owing to equal-axial ultrafine grains and workhardening effect caused by large plastic deformation.
基金This work was supported by the National Natural Science Foundation of China （No. 50275094）.
文摘A meshless approach, called the rigid-plastic reproducing kernel particle method （RKPM）, is presented for three-dimensional （3D） bulk metal forming simulation. The approach is a combination of RKPM with the flow theory of 3D rigid-plastic mechanics. For the treatments of essential boundary conditions and incompressibility constraint, the boundary singular kernel method and the modified penalty method are utilized, respectively. The arc-tangential friction model is employed to treat the contact conditions. The compression of rectangular blocks, a typical 3D upsetting operation, is analyzed for different friction conditions and the numerical results are compared with those obtained using commercial rigid-plastic FEM （finite element method） software Deform^3D. As results show, when handling 3D plastic deformations, the proposed approach eliminates the need of expensive meshing and remeshing procedures which are unavoidable in conventional FEM and can provide results that are in good agreement with finite element predictions.
基金financially supported by the Program for the Supported by Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxithe‘HIGH-GRADE CNC machine tools and basic manufacturing equipment’Major National Science and Technology Projects(No.2019ZX04022001-004)。
文摘The isothermal repetitive upsetting extrusion(RUE)was implemented to process ZK60 magnesium alloy at 380℃.Then,the relationship between the microstructural characters,including grain refinement and texture evolution,and the mechanical performance of the alloy was investigated.Results showed that after 3 passes of RUE,the average grain size was refined from 115.0 to 26.5μm,which was mainly caused by the continuous dynamic recrystallization and discontinuous dynamic recrystallization.Meanwhile,the elongation of the alloy increased from 13.8 to 21.6%,and the superplasticity(142%)of the alloy has been achieved in the following high temperature tensile test,which is very beneficial for the further processing of the alloy into components.In particular,the alloy formed a distinctive texture distributed between<2-1-11>and<2-1-14>,which was greatly related to the Schmid factor of extrusion direction(ED)and transverse direction(TD).This texture changed the initiation ability of basal and prismatic slip in both directions and inhibited the initiation of partial tensile twinning in TD;thus,the anisotropy in both directions was weakened.As expected,the tensile yield strength difference decreased from25.9 to 3.4 MPa,but it was used as the cost of tensile yield strength in ED.
文摘Cold upsetting experiments were carried out on sintered Fe 0.8%C1.0%Si-0. 4%Cu steel preforms in order to evaluate their deformation characteristics. Powder preforms of 86 % of theoretical density, with two different ratios of height to diameter, were prepared using a suitable die set assembly on a 1.0 MN capacity hydraulic testing machine. Sintering was carried out in an electric muffle furnace for 1.5 h at 1 150 ℃. Each sintered compact was subjected to incremental loading of 0.04 MN under dry friction condition till a crack appeared at the free surfaces. The experimental results were critically analysed, the stress as a function of strain and densification was obtained, then the work hardening behaviour was analyzed. It has been found that in the process of enhancing densification, strength and strain hardening is also induced during upsetting, but the work hardening behaviour is not homogenously enhanced against strain and densification.
基金support from the National Natural Science Foundation of China(No.52175287)Open Fund of State Key Laboratory of Materials Processing and Die&Mould Technology,China(No.P2020-001).
文摘A kind of surface instability,basin-like depression defect companied by mixed grain structure at the bottom of large-scale valve during electric upsetting process,would significantly influence the microstructures and mechanical properties of components.In order to analyze the forming process of the basin-like depression defect,a finite element model for the electric upsetting process of Ni80A superalloy was developed using multi-field and multi-scale coupling analysis method.Subsequently,a series of parameters loading path schemes for force and current were designed by varying the initial value,peak value and value level,and their effects on basin-like depression and mixed grain structure were simulated and uncovered.It is concluded that the changes of heating speed and pressurization speed result in the different flow velocities between the inner and outer layers of billet,thus exerting the basin-like depression.Simulation results also indicate that these defects can be optimized through the parameter coordination between force and current.Finally,the validity and reliability of the finite element model were verified by physical experiments in electric upsetting process.
基金Sponsored by Ministry of Education of China and Natural Science Foundation of Liaoning Province
文摘Theoretical analyses show that the variation of wall thickness is in direct proportion to outer-diameter, inter-diameter, and (1+R_s)^(1/2) (Rs is sectional increase ratio of tube), the theoretical calculated results of wall thickness during tube dieless upsetting are very approximate to the experimental one. As the width of deformation field increases, both the variation of wall thickness and the derivative of wall thickness variation to width of deformation field (to/tf) reduce.
基金sponsored by the National Natural Science Foundation of China (NSFC) under Grant No. 51374145the Science and Technology Commission of Shanghai Municipality under Grant No. 09JC1408200
文摘The current research investigates the effect of homogenization on the microstructure and mechanical properties of the AZ91 D alloy processed by repetitive upsetting（RU）. Results show that during RU processing, the initial large Mg;Al;particles in the as-cast specimen accelerate the dynamic recrystallization（DRX） due to the particle stimulating nucleation（PSN） mechanism. With the progress of RU,the inherent large strain breaks the large second phases into small fragments, which indicates the PSN gradually disappears, while the pinning effect becomes obvious. As for the homogenized specimen, a pre-heat treatment leads to the absence of Mg;Al;particles but a uniform distribution of Al atoms in the Mg alloy. Though the subsequent RU promotes the precipitation of Mg;Al;particles, the relatively small particle size and the uniform distribution are more favorable to act as obstacles for grain growth than contributors to PSN. Finally, a more homogeneous and refined microstructure is obtained in the specimen with prior homogenization than the as-cast one.
文摘A whole analysis model including forging and flat platens is built,which is used to analyse the process of upsetting a cylinder between flat platens.The influence of surface friction and transient temperature are comprehensively considered.By means of ANSYS software,the elasto plastic FEM analysis of the whole upsetting process is carried out.From the point of view of numerical calculation,the correctness of the centre region tension stress theory about upsetting a cylinder between flat platens is tested and verified.The concept of plasto nucleus is presented to explain the forming of double dumps.The efffect of temperature is inspected.The relation curves between the radial stress of the symmetry centre point and the relative pression ratio are given.
基金This bark wu suPPorted w suPPorted by the Nabnonal Key Laboratory of Precision HOt Processing of Metals Foundation of China
文摘FEM is used to analyze the influence of interface friction on the material flow and the cause of forming defect in the cold upsetting of tube flange. Based on the FEM simulation results, the relationships between flange width and the extreme friction factors are established. The concept of forming limit diagram for cold upsetting of tube flange is presented.
基金Project(52275350)supported by the National Natural Science Foundation of ChinaProject(0301006)supported by International Cooperative Scientific Research Platform of SUES,China。
文摘It is of great significance to study the corrosion process of aluminum(Al)alloys fasteners in order to mitigate corrosion for their widespread applications.In this paper,a method for enhancing the corrosion resistance of Al alloy fasteners is proposed.7075 Al alloy parts with a fine-grained microstructure were prepared by pre-heat treatment(PHT),combined subsequent equal channel angular pressing(ECAP)and cold upsetting(CU).The corrosion behavior of the specimens was investigated by intergranular corrosion and electrochemical test.Microstructure investigations were carried out by field emission scanning electron microscopy,energy dispersive spectrometer and transmission electron microscopy.The relationship between microstructural evolution and corrosion resistance changes was also explored.The results show that both PHT and ECAP-CU significantly improved the corrosion resistance of the samples and modified the corrosion process.The open circuit potential,corrosion current density and corrosion rate of the alloy on electrochemical test were(-0.812±8.854)×10^(-5) V(vs.SCE),(6.379±0.025)×10^(-6) A/cm^(2) and 0.066 mm/year,respectively,and the intergranular corrosion depth was(557±8)μm.The main factor controlling the corrosion behavior was the microstructure evolution.After PHT,the disappearance of the dendritic structure and the dissolution of the nonequilibrium second phase eliminated the potential difference between the phases,reducing the free energy in the as cast state.When ECAP-CU was used after PHT,the grain refinement was accompanied by a high density of grain boundaries and dislocations,which led to the formation of a denser passivation film on the alloy surface,improving the corrosion resistance in an aggressive environment.
基金Supported by the Key Project of Jilin Province Science & Technology Department (Grant No. 20030311)the "985 Project" of Jilin University
文摘In the paper a self-adjusting hydraulic machine for combination forming of upsetting and extruding is systematacially presented in terms of mechanical principle, design principle, machine construction, design of the key components and working routine. The machine is designed with the following features: The lower movable beam is adjusted by the ejecting cylinder, the upper upsetting beam is reset by the backstroke slide rods, and the upsetting cylinders communicate with the gas-liquid accumulators. These features make the machine conformation compact, save both the backstroke cylinder of the upper upsetting beam and the upsetting cylinder of the lower movable beam, and simplify the hydraulic system. Furthermore, the machine can resolve such problems as incomplete filling at the addendum position, microcracks at the dedendum position, greater force and lower die life during precision forging of spur gears.
基金supported by the National Key Laboratory of Materials Behavior and Evaluation Technology in Space Environment(No.6142910220208)National Natural Science Foundation of China(Nos.12105341 and 12035019)the opening fund of Key Laboratory of Silicon Device and Technology,Chinese Academy of Sciences(No.KLSDTJJ2022-3).
文摘This paper explores the impact of back-gate bias (V_(soi)) and supply voltage (V_(DD)) on the single-event upset (SEU) cross section of 0.18μm configurable silicon-on-insulator static random-access memory (SRAM) under high linear energy transfer heavyion experimentation.The experimental findings demonstrate that applying a negative back-gate bias to NMOS and a positive back-gate bias to PMOS enhances the SEU resistance of SRAM.Specifically,as the back-gate bias for N-type transistors(V_(nsoi)) decreases from 0 to-10 V,the SEU cross section decreases by 93.23%,whereas an increase in the back-gate bias for P-type transistors (V_(psoi)) from 0 to 10 V correlates with an 83.7%reduction in SEU cross section.Furthermore,a significant increase in the SEU cross section was observed with increase in supply voltage,as evidenced by a 159%surge at V_(DD)=1.98 V compared with the nominal voltage of 1.8 V.To explore the physical mechanisms underlying these experimental data,we analyzed the dependence of the critical charge of the circuit and the collected charge on the bias voltage by simulating SEUs using technology computer-aided design.
基金supported by the National Natural Science Foundation of China(Nos.12105341 and 12035019)the opening fund of Key Laboratory of Silicon Device and Technology,Chinese Academy of Sciences(No.KLSDTJJ2022-3).
文摘The 28 nm process has a high cost-performance ratio and has gradually become the standard for the field of radiation-hardened devices.However,owing to the minimum physical gate length of only 35 nm,the physical area of a standard 6T SRAM unit is approximately 0.16μm^(2),resulting in a significant enhancement of multi-cell charge-sharing effects.Multiple-cell upsets(MCUs)have become the primary physical mechanism behind single-event upsets(SEUs)in advanced nanometer node devices.The range of ionization track effects increases with higher ion energies,and spacecraft in orbit primarily experience SEUs caused by high-energy ions.However,ground accelerator experiments have mainly obtained low-energy ion irradiation data.Therefore,the impact of ion energy on the SEU cross section,charge collection mechanisms,and MCU patterns and quantities in advanced nanometer devices remains unclear.In this study,based on the experimental platform of the Heavy Ion Research Facility in Lanzhou,low-and high-energy heavy-ion beams were used to study the SEUs of 28 nm SRAM devices.The influence of ion energy on the charge collection processes of small-sensitive-volume devices,MCU patterns,and upset cross sections was obtained,and the applicable range of the inverse cosine law was clarified.The findings of this study are an important guide for the accurate evaluation of SEUs in advanced nanometer devices and for the development of radiation-hardening techniques.
文摘We study the problem of multiple node upset （MNU） using three-dimensional device simulation. The results show the transient floating node and charge lateral diffusion are the key reasons for MNU. We compare the MNU with multiple bit upset （MBU）,and find that their characteristics are different. Methods to avoid MNU are also discussed.
基金This work was financially supported by the National Natural Science Foundation of China （No.50465003）.
文摘The effect of predeformation manner, predeformation ratio and isothermal heat-treat parameter on the non-dendrite structure of AZ61 magnesium alloy in SIMA process was studied. Under coequal heat-treat condition, the impact of the hot upsetting pre- deformation on semi-solid microstructure in SIMA process was compared with that of the cold compressive predeformation. The results indicate that non-dendrite microstructure in AZ61 magnesium alloy billets can be obtained by hot or cold upsetting predeformation in SIMA process, although their mechanisms of evolution are different. Increasing hot or cold upsetting predeformation ratio can enhance the effect and quality of the non-dendrite microstructure formed before storage energy up to saturation, but the proper isothermal temperature and holding time should be selected.
文摘The paper concisely introduced the hoopment of photoplastic simulation and the principle of its appli- cation.Deformations of combine extrusion and strain distributin in the process of upsetting the cylinder with void were studied by this physical photoplasic simulation method. Some important informations obtained from the simulation experiment are helpful to understand the deformation law and the charac- teristics of material flowing.The validity of the physical simulation method and the importance of com- bining the physical simulation method with numerical simulation method together were proposed in the paper.
基金Item Sponsored by National Science and Technology Major Project of China(2011ZX04014-051)National Basic Research Program of China(2011CB012903)085 Project of Shanghai Univercity of Engineering Science of China(nhky-2013-05)
文摘A ductile fracture criterion of 316LN stainless steel, combined with the plastic deformation capacity of ma- terial and the stress state dependent damages, was proposed to predict ductile fracture during hot deformation. To the end, tensile tests at high temperatures were first performed to investigate the fracture behavior of 316LN stain- less steel. The experimental results show the variation of the critical fracture strain as a function of temperature and strain rate. Second, the criterion was calibrated by using the upsetting tests and the corresponding numerical simula- tions. Finally, the proposed fracture criterion was validated by the designed tests and the corresponding finite ele- ment （FE） simulation. The results show that the criterion can successfully predict the onset of ductile fracture at ele- vated temperatures.
