The mechanical properties of metal yttrium such as strength, plasticity, hardness and elasticity were introduced . The purifying techniques of yttrium were discussed in detail. The processing methods for metal yttrium...The mechanical properties of metal yttrium such as strength, plasticity, hardness and elasticity were introduced . The purifying techniques of yttrium were discussed in detail. The processing methods for metal yttrium including extruding, forging, rolling, wiredrawing and welding were also introduced. Finally, the potential use of yttrium and its alloys were prospected.展开更多
The friction and wear properties of plasma-sprayed nanostructured FeS coating were investigated on an MHK- 500 friction and wear tester under both oil lubrication and dry friction condition. The microstructure, worn s...The friction and wear properties of plasma-sprayed nanostructured FeS coating were investigated on an MHK- 500 friction and wear tester under both oil lubrication and dry friction condition. The microstructure, worn surface morphology and phase composition of the coating were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. It was found that the coating was mainly composed of FeS. a small quantity of Fe1-xS and oxide were also found. The coating was formed by small particles of 50～100 nm in size The thickness of the coating is approximately 150 μm. The friction-reduction and wear-resistance properties of plasma-sprayed nanostructured FeS coating were superior to that of GCr15 steel substrate. Especially under oil lubrication condition, the friction coefficient of nanostructured FeS coating was 50% of that of GCr15 steel, the wear scar widths of the coating were also reduced to nearly 50% of that of GCr15 steel under high load. The failure of the coating was mainly attributed to plastic deformation under both oil lubrication and dry friction condition.展开更多
An experiment procedure was presented for the synthesis of γ-AIOOH nanoparticles by a dehydration process which employed the solution of H202 as dehydrator. The phase and morphology of the product were investigated b...An experiment procedure was presented for the synthesis of γ-AIOOH nanoparticles by a dehydration process which employed the solution of H202 as dehydrator. The phase and morphology of the product were investigated by XRD and TEM. The tribological properties of γ-AIOOH nanoparticles with the average diameter of 15 nm as additives in liquid paraffin were investigated by a four-ball tester, and the worn surfaces were analyzed by SEM and EDS. Results show that the average size of synthesized γ-AIOOH nanoparticles increases with the increase of the pH value and temperature of the reactant. The γ-AIOOH nanoparticles as additives could exhibit good tribological properties due to their covering effect, which prevents the direct contact of asperities and reduces the adhesion. As the real area of contact decreases with the decrease of applied load, the optimum concentration varies from 0.4 % to 0.1% when the applied load decreases from 294 N to 200 N.展开更多
Static recrystallization(SRX)characteristics of a powder metallurgy superalloy were investigated by isothermal compression at 1080–1170°C under strain rates of 0.01–0.1 s−1,strains of 0.1,0.22,or 0.5,and holdin...Static recrystallization(SRX)characteristics of a powder metallurgy superalloy were investigated by isothermal compression at 1080–1170°C under strain rates of 0.01–0.1 s−1,strains of 0.1,0.22,or 0.5,and holding time of 0–300 s.The impacts of temperature,strain rate,holding time,and strain on the SRXed grain size,volume fraction,and microtexture were explored by electron backscatter diffraction technique.It was found that temperature played a key role in these processes.As SRX progressed,the<110>fiber parallel to the axis compression direction gradually weakened and was replaced by the<001>fiber because<001>was the preferred recrystallization orientation and grain growth direction for the Ni-based superalloy.Moreover,high temperatures and low strain rates promoted the formation of the<001>fiber.Three nucleation mechanisms during SRX process were found:grain boundary bulging,primary twin assistance,and subgrain coalescence.Grain boundary bulging occurred under all process conditions;however,at low temperatures and high strain rates,the latter two mechanisms could provide additional nucleation modes.In addition,SRX size and volume fraction models were established.展开更多
A flexible technique of hot working of bars by axial feed rolling was introduced. The process deformation, strain field, stress field, and temperature fie M of the parts are analyzed by finite element method （ FEM）-...A flexible technique of hot working of bars by axial feed rolling was introduced. The process deformation, strain field, stress field, and temperature fie M of the parts are analyzed by finite element method （ FEM）-simulation software DEFORM-3D. The material flow rule and tool load have been investigated.展开更多
Temperature field numerical simulation about he heat treatment process curve of large turbine rotor is presented. With simulation software Deform3D in according to the heat treatment processing of China First Heavy Ma...Temperature field numerical simulation about he heat treatment process curve of large turbine rotor is presented. With simulation software Deform3D in according to the heat treatment processing of China First Heavy Machinery, the details of temperature change at the different location of the rotor is to be found. Once knowing the temperature field change, the duplex grain defect long time existed in large forgings can be solved with a quantitative analysis instead of only the qualitative one. Precondition for small metal samples is brought to simulate microstructare and grain size change of large rotor according to the numerical simulation result. Also, consistent feature with real manufacture is showed from the physical experiment, so that the simulation can be used to not only improve the products process but also prevent wasting unnecessary energy and shorten process periods. The rotor quality is controlled thoroughly with plenty of experiments data.展开更多
Some improvements in Jin's thermal visco-plastic constitutive model considering dy- namic recrysytallization is presented in this paper.By introducing the influence of the strain rate on the mobility of dynamic re...Some improvements in Jin's thermal visco-plastic constitutive model considering dy- namic recrysytallization is presented in this paper.By introducing the influence of the strain rate on the mobility of dynamic recovery,the improved model can be more smoothly applied to numeri- cal simulation of material flow behaviour and microstructure prediction during hot working.Another improvement is to consider the accumulated dislocation energy in the newly recrystallized grains as a resistance to the driving force of dynamic recrystallization volume.This improvement makes the predicted results of dynamic recrystallization progress agree better with the actual physical process. Finally,some numerical examples are given to show the advantages of the improved model and the ability to predict the dynamic recrystallization.展开更多
Background Horizontal collimators in the storage ring of high energy photon source(HEPS)are used to localize the majority of the particle loss,making it possible to set local shields.Moreover,movable jaws of the colli...Background Horizontal collimators in the storage ring of high energy photon source(HEPS)are used to localize the majority of the particle loss,making it possible to set local shields.Moreover,movable jaws of the collimators are also designed as beam dumps for the machine protection,to absorb and scatter the mis-steered beam.Because of the compact lattice,each collimator should be installed between the limited space of 240 mm in the beam direction.It is necessary for the collimators to have good thermal dissipation ability to endure the synchrotron radiation and HOM load,as well as good resistance to thermal-shock from sudden beam loss simultaneously,which brings great challenges to the design.Purpose The purpose of this paper is to introduce the designing scheme of the collimators in HEPS,including the structure design and the analyses of the key components.Method Thermal and mechanical calculation has been done,based on which the jaw structure has been optimized.Besides,the modal analysis of the whole magnet-collimator-support assembly has been studied to optimize the shields structure.Result Graphite will be used as the tip for movable jaws in the collimators,which is attached to copper by vacuum brazing.The maximum temperature of the jaw during normal operation is 131°C,while maximum stress of the graphite–copper weld joint is 15.6 MPa.Graphite tip can resist thermal shock caused by whole mis-steered beam.Eigen frequency of the standard assembly is acceptable for HEPS.Conclusion The results of calculations indicate that the present structure can work well for considered operating modes.展开更多
This study analyzed the deformation law of rear axles with variable wall thickness under bidirectional horizontal extrusion and found that necking was accompanied by upsetting deformation through theoretical calculati...This study analyzed the deformation law of rear axles with variable wall thickness under bidirectional horizontal extrusion and found that necking was accompanied by upsetting deformation through theoretical calculation, numerical simulation, and experimental research. The sequence and occurrence of necking and upsetting deformations were obtained. A theory of deformation was proposed by controlling the distribution of temperature field. Effective processes to control the wall thickness of rear axle at different positions were also proposed. The ultimate limit deformation with a necking coefficient of 0.68 could be achieved using the temperature gradient coefficient. A new technology of two-step heating and two-step extrusion for a 13 t rear axle was developed, qualified test samples were obtained, and suggestions for further industrial application were put forward.展开更多
文摘The mechanical properties of metal yttrium such as strength, plasticity, hardness and elasticity were introduced . The purifying techniques of yttrium were discussed in detail. The processing methods for metal yttrium including extruding, forging, rolling, wiredrawing and welding were also introduced. Finally, the potential use of yttrium and its alloys were prospected.
基金The authors would like to thank the National Natural Science Foundation of China（No.50375015） for its financial support.
文摘The friction and wear properties of plasma-sprayed nanostructured FeS coating were investigated on an MHK- 500 friction and wear tester under both oil lubrication and dry friction condition. The microstructure, worn surface morphology and phase composition of the coating were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. It was found that the coating was mainly composed of FeS. a small quantity of Fe1-xS and oxide were also found. The coating was formed by small particles of 50～100 nm in size The thickness of the coating is approximately 150 μm. The friction-reduction and wear-resistance properties of plasma-sprayed nanostructured FeS coating were superior to that of GCr15 steel substrate. Especially under oil lubrication condition, the friction coefficient of nanostructured FeS coating was 50% of that of GCr15 steel, the wear scar widths of the coating were also reduced to nearly 50% of that of GCr15 steel under high load. The failure of the coating was mainly attributed to plastic deformation under both oil lubrication and dry friction condition.
基金Sponsored by the Excellent Young Scholars Research Fund of Beijing Institute of Technology(2006Y0411)
文摘An experiment procedure was presented for the synthesis of γ-AIOOH nanoparticles by a dehydration process which employed the solution of H202 as dehydrator. The phase and morphology of the product were investigated by XRD and TEM. The tribological properties of γ-AIOOH nanoparticles with the average diameter of 15 nm as additives in liquid paraffin were investigated by a four-ball tester, and the worn surfaces were analyzed by SEM and EDS. Results show that the average size of synthesized γ-AIOOH nanoparticles increases with the increase of the pH value and temperature of the reactant. The γ-AIOOH nanoparticles as additives could exhibit good tribological properties due to their covering effect, which prevents the direct contact of asperities and reduces the adhesion. As the real area of contact decreases with the decrease of applied load, the optimum concentration varies from 0.4 % to 0.1% when the applied load decreases from 294 N to 200 N.
基金supported by the technology development fund of Beijing Research Institute of Mechanical&Electrical Technology Co.,Ltd.,CAM,Construction of Innovation Leading Talents and Innovation Team of China Academy of Machinery Science and Technology Group:Vacuum forming technology and equipment innovation team.
文摘Static recrystallization(SRX)characteristics of a powder metallurgy superalloy were investigated by isothermal compression at 1080–1170°C under strain rates of 0.01–0.1 s−1,strains of 0.1,0.22,or 0.5,and holding time of 0–300 s.The impacts of temperature,strain rate,holding time,and strain on the SRXed grain size,volume fraction,and microtexture were explored by electron backscatter diffraction technique.It was found that temperature played a key role in these processes.As SRX progressed,the<110>fiber parallel to the axis compression direction gradually weakened and was replaced by the<001>fiber because<001>was the preferred recrystallization orientation and grain growth direction for the Ni-based superalloy.Moreover,high temperatures and low strain rates promoted the formation of the<001>fiber.Three nucleation mechanisms during SRX process were found:grain boundary bulging,primary twin assistance,and subgrain coalescence.Grain boundary bulging occurred under all process conditions;however,at low temperatures and high strain rates,the latter two mechanisms could provide additional nucleation modes.In addition,SRX size and volume fraction models were established.
基金the National Natural Science Foundation of China （Nos. 50205003 ,50675014）.
文摘A flexible technique of hot working of bars by axial feed rolling was introduced. The process deformation, strain field, stress field, and temperature fie M of the parts are analyzed by finite element method （ FEM）-simulation software DEFORM-3D. The material flow rule and tool load have been investigated.
基金supported by the National Key Basic Research and Development Programme of China(No.G2000067208)
文摘Temperature field numerical simulation about he heat treatment process curve of large turbine rotor is presented. With simulation software Deform3D in according to the heat treatment processing of China First Heavy Machinery, the details of temperature change at the different location of the rotor is to be found. Once knowing the temperature field change, the duplex grain defect long time existed in large forgings can be solved with a quantitative analysis instead of only the qualitative one. Precondition for small metal samples is brought to simulate microstructare and grain size change of large rotor according to the numerical simulation result. Also, consistent feature with real manufacture is showed from the physical experiment, so that the simulation can be used to not only improve the products process but also prevent wasting unnecessary energy and shorten process periods. The rotor quality is controlled thoroughly with plenty of experiments data.
基金The project supported by the National Key Basic Research Development Plan (973 Planning) of Ministry of Science and Technology of China (G2000067200)
文摘Some improvements in Jin's thermal visco-plastic constitutive model considering dy- namic recrysytallization is presented in this paper.By introducing the influence of the strain rate on the mobility of dynamic recovery,the improved model can be more smoothly applied to numeri- cal simulation of material flow behaviour and microstructure prediction during hot working.Another improvement is to consider the accumulated dislocation energy in the newly recrystallized grains as a resistance to the driving force of dynamic recrystallization volume.This improvement makes the predicted results of dynamic recrystallization progress agree better with the actual physical process. Finally,some numerical examples are given to show the advantages of the improved model and the ability to predict the dynamic recrystallization.
基金supported by Key Laboratory of Particle Acceleration Physics&Technology,Institute of High Energy Physics,Chinese Academy of Sciences[JSQ2020ZZ05].
文摘Background Horizontal collimators in the storage ring of high energy photon source(HEPS)are used to localize the majority of the particle loss,making it possible to set local shields.Moreover,movable jaws of the collimators are also designed as beam dumps for the machine protection,to absorb and scatter the mis-steered beam.Because of the compact lattice,each collimator should be installed between the limited space of 240 mm in the beam direction.It is necessary for the collimators to have good thermal dissipation ability to endure the synchrotron radiation and HOM load,as well as good resistance to thermal-shock from sudden beam loss simultaneously,which brings great challenges to the design.Purpose The purpose of this paper is to introduce the designing scheme of the collimators in HEPS,including the structure design and the analyses of the key components.Method Thermal and mechanical calculation has been done,based on which the jaw structure has been optimized.Besides,the modal analysis of the whole magnet-collimator-support assembly has been studied to optimize the shields structure.Result Graphite will be used as the tip for movable jaws in the collimators,which is attached to copper by vacuum brazing.The maximum temperature of the jaw during normal operation is 131°C,while maximum stress of the graphite–copper weld joint is 15.6 MPa.Graphite tip can resist thermal shock caused by whole mis-steered beam.Eigen frequency of the standard assembly is acceptable for HEPS.Conclusion The results of calculations indicate that the present structure can work well for considered operating modes.
基金This work was supported by the National High-tech R&D Programof China (Grant No. 2012AA040202).
文摘This study analyzed the deformation law of rear axles with variable wall thickness under bidirectional horizontal extrusion and found that necking was accompanied by upsetting deformation through theoretical calculation, numerical simulation, and experimental research. The sequence and occurrence of necking and upsetting deformations were obtained. A theory of deformation was proposed by controlling the distribution of temperature field. Effective processes to control the wall thickness of rear axle at different positions were also proposed. The ultimate limit deformation with a necking coefficient of 0.68 could be achieved using the temperature gradient coefficient. A new technology of two-step heating and two-step extrusion for a 13 t rear axle was developed, qualified test samples were obtained, and suggestions for further industrial application were put forward.
