On the Broadband World Forum Europe 2010 held in Paris, ZTE Corporation launched a European FTTx Business Model which is developed to give operators the right balance of products and solutions for the requirements of ...On the Broadband World Forum Europe 2010 held in Paris, ZTE Corporation launched a European FTTx Business Model which is developed to give operators the right balance of products and solutions for the requirements of the European optical network markets. At the same time, ZTE unveiled its Uni-FAN broadband acceleration solution to help operators rapidly deploy broadband networks.展开更多
Shanghai Power Station Auxiliary Equipment Works (referred to as SDF) was established in April, 1980 on the base of the urban area previously owned by Shanghai Boiler Works so as to facilitate
China’s cultural dxchanges with foreign countries have advanced from separate and shortterm prog5rams inta conprehensive and largescale alal activities the 2000 ferlin asia-pacific week highlighting chinese culture h...China’s cultural dxchanges with foreign countries have advanced from separate and shortterm prog5rams inta conprehensive and largescale alal activities the 2000 ferlin asia-pacific week highlighting chinese culture has just wuond up successfully china culture year will be heid in france in展开更多
Since its founding in 1949, the CAS has been in duty bound to settle key S&T problems posed during national economic and defense construction,and has devoted itself to the renewal of China’s traditional industry ...Since its founding in 1949, the CAS has been in duty bound to settle key S&T problems posed during national economic and defense construction,and has devoted itself to the renewal of China’s traditional industry and the development of new technology.In June 1950, the State authorities stipulated that the main tasks for the CAS were "to cultivate versatile S&T workers and a competent work force for national construction, striving to draw close the ties between academic research and actual demands so that science can really serve the country’s industry, agriculture, national defense,展开更多
The microstructures and mechanical properties of Al-8.3Zn-3.3Cu-2.2Mg alloys prepared via hot extrusion and liquid forging methods were investigated.Results show that based on DEFORM simulation analysis,the optimal ho...The microstructures and mechanical properties of Al-8.3Zn-3.3Cu-2.2Mg alloys prepared via hot extrusion and liquid forging methods were investigated.Results show that based on DEFORM simulation analysis,the optimal hot extrusion parameters are determined as ingot initial temperature of 380°C and extrusion speed of 3 mm/s.The hot-extruded aluminum alloy after T6 heat treatment presents superior mechanical properties with yield strength of 519.6 MPa,ultimate tensile strength of 582.1 MPa,and elongation of 11.0%.Compared with the properties of gravity-cast and liquid-forged alloys,the yield strength of hot-extruded alloy increases by 30.8%and 4.9%,and the ultimate tensile strength improves by 43.5%and 10.2%,respectively.The significant improvement in tensile strength of the hot-extruded alloys is attributed to the elimination of casting defects and the refinement of matrix grain and eutectic phases.In addition,the hot-extruded alloy demonstrates superior plasticity compared with the liquid-forged alloy.This is because severe plastic deformation occurs during hot extrusion,which effectively breaks and disperses the eutectic phases,facilitating the dissolution and precipitation of the second phases and inhibiting the microcrack initiation.展开更多
The differences in damage values,residual stresses,microstructure and mechanical properties of Ti–6Al–4V alloy under hammer forging and press forging were explored through physical experiments and numerical simulati...The differences in damage values,residual stresses,microstructure and mechanical properties of Ti–6Al–4V alloy under hammer forging and press forging were explored through physical experiments and numerical simulations.The results showed that the temperature field and equivalent strain field of forgings under the hammer forging process were more uniformly distributed,resulting in smaller surface cracks and better residual stress distribution.The impact dynamic loading of hammer forging leads to forgings with higher dislocation densities,while the stabilized strain rate of press forging results in forgings exhibiting finer grain sizes.In this context,the yield strength enhancement of forgings by both processes was nearly identical,while the forgings demonstrated more excellent elongation under the hammer forging process.Additionally,increasing the number of blows in the hammer forging process or enhancing the loading rate in the press forging process can optimize the residual stress distribution of the forgings while simultaneously promoting dislocation multiplication and grain refinement.展开更多
This study systematically investigated the microstructure,mechanical properties,and corrosion behavior of an extruded Zn-0.2Mg alloy processed by multi-directional forging(MDF)at 100℃.The mean grain size was remarkab...This study systematically investigated the microstructure,mechanical properties,and corrosion behavior of an extruded Zn-0.2Mg alloy processed by multi-directional forging(MDF)at 100℃.The mean grain size was remarkably decreased from 17.2±0.5µm to 1.9±0.3µm,and 84.4%of the microstructure was occupied by grains of below 1µm in size after applying three MDF passes.Electron backscattered difraction examinations revealed that continuous dynamic recrystallization,progressive lattice rotation,and particle-stimulated nucleation mechanisms were recognized as contributing to microstructural evolution.Furthermore,transmission electron microscopy results showed that nanoparticles of Mg/Zn dynamically formed under high strain MDF,while the initial extrusion fber texture was altered to be<0001>parallel to the fnal forging axis.A synergistic efect of grain refnement,texture evolution,second-phase precipitates,and dislocation strengthening resulted in an increased ultimate tensile strength of 232±5 MPa after three MDF passes.However,this was accompanied by a reduction in the elongation(8±2.1%).Additionally,a high corrosion rate of 0.59 mm/year was measured for the experimental alloy fabricated by 3 MDF passes.In agreement with the latter,electrochemical impedance spectroscopy results indicated that the grain refnement improved the passivation kinetics of the oxide layer.展开更多
Digital modeling and autonomous control of the die forging process are significant challenges in realizing high-quality intelli-gent forging of components.Using the die forging of AA2014 aluminum alloy as a case study...Digital modeling and autonomous control of the die forging process are significant challenges in realizing high-quality intelli-gent forging of components.Using the die forging of AA2014 aluminum alloy as a case study,a machine-learning-assisted method for di-gital modeling of the forging force and autonomous control in response to forging parameter disturbances was proposed.First,finite ele-ment simulations of the forging processes were conducted under varying friction factors,die temperatures,billet temperatures,and for-ging velocities,and the sample data,including process parameters and forging force under different forging strokes,were gathered.Pre-diction models for the forging force were established using the support vector regression algorithm.The prediction error of F_(f),that is,the forging force required to fill the die cavity fully,was as low as 4.1%.To further improve the prediction accuracy of the model for the ac-tual F_(f),two rounds of iterative forging experiments were conducted using the Bayesian optimization algorithm,and the prediction error of F_(f) in the forging experiments was reduced from 6.0%to 1.5%.Finally,the prediction model of F_(f) combined with a genetic algorithm was used to establish an autonomous optimization strategy for the forging velocity at each stage of the forging stroke,when the billet and die temperatures were disturbed,which realized the autonomous control in response to disturbances.In cases of−20 or−40℃ reductions in the die and billet temperatures,forging experiments conducted with the autonomous optimization strategy maintained the measured F_(f) around the target value of 180 t,with the relative error ranging from−1.3%to+3.1%.This work provides a reference for the study of di-gital modeling and autonomous optimization control of quality factors in the forging process.展开更多
Magnesium alloy thin-walled cylindrical components with the advantages of high specific stiffness and strength present broad prospect for the lightweight of aerospace components.However,poor formability resulting from...Magnesium alloy thin-walled cylindrical components with the advantages of high specific stiffness and strength present broad prospect for the lightweight of aerospace components.However,poor formability resulting from the hexagonal close-packed crystal structure in magnesium alloy puts forwards a great challenge for thin-walled cylindrical components fabrication,especially for extreme structure with the thicknesschanging web and the high thin-wall.In this research,an ZK61 magnesium alloy thin-walled cylindrical component was successfully fabricated by two-step forging,i.e.,the pre-forging and final-forging is mainly used for wed and thin-wall formation,respectively.Microstructure and mechanical properties at the core,middle and margin of the web and the thin-wall of the pre-forged and final-forged components are studied in detail.Due to the large strain-effectiveness and metal flow along the radial direction(RD),the grains of the web are all elongated along RD for the pre-forged component,where an increasingly elongated trend is found from the core to the margin of the wed.A relatively low recrystallized degree occurs during pre-forging,and the web at different positions are all with prismatic and pyramid textures.During finalforging,the microstructures of the web and the thin-wall are almost equiaxed due to the remarkable occurrence of dynamic recrystallization.Similarity,except for few basal texture of the thin-wall,only prismatic and pyramid textures are found for the final-forged component.Compared with the initial billet,an obviously improved mechanical isotropy is achieved during pre-forging,which is well-maintained during final-forging.展开更多
The mechanical properties,microstructure and second phase precipitation behavior of flange forgings for high-pressure hydrogen storage vessels at different tempering temperatures(620–700℃)were studied.The results sh...The mechanical properties,microstructure and second phase precipitation behavior of flange forgings for high-pressure hydrogen storage vessels at different tempering temperatures(620–700℃)were studied.The results showed that when tempered at 620–680°C,the main microstructure of the test steel was tempered sorbite,and the main microstructure of tempered steel changed to martensite at 700℃.At 700℃,the dislocation density increased and some retained austenite existed.With the tempering temperature increasing,the yield strength showed a decreasing trend,the formation of fresh martensite made the tensile strength first decrease and then increase slightly,the impact energy at−40℃increased first and then decreased,and the impact energy at 660℃had the maximum value.The precipitates of MC type were mainly(Mo,V,Ti)C.The test steel had excellent strength and toughness matching at 660℃tempering,the tensile strength at different cross section locations was above 750 MPa,the impact energy was above 200 J at−40℃,and the relative percentage reduction of area(ZH2/ZN2)was above 75%at hydrogen environment of 6.3 MPa.展开更多
Today,I want to share how international standards can forge trust and fuel innovation,laying the foundation for a future where AI benefits everyone,everywhere.First,AI standards,developed jointly by ISO and IEC-the In...Today,I want to share how international standards can forge trust and fuel innovation,laying the foundation for a future where AI benefits everyone,everywhere.First,AI standards,developed jointly by ISO and IEC-the International Electrotechnical Commission-help build global trust and enable responsible innovation by bringing clarity and coherence to an ever-changing AI landscape.As developments in AI continue to emerge at speed,regulation is struggling to keep up and the proliferation of competing standards has created confusion rather than clarity.ISO and our partner IEC are addressing this challenge through the work of our expert committee on AI,SC 42,which takes a holistic,cohesive approach to AI standardization.展开更多
This study investigates the differences in microstructural control between cryogenic forging combined with pre-deformation(PCF)and traditional thermal forging(TTF)for 7050 aluminum forgings intended for aerospace appl...This study investigates the differences in microstructural control between cryogenic forging combined with pre-deformation(PCF)and traditional thermal forging(TTF)for 7050 aluminum forgings intended for aerospace applications.The PCF process,utilizing cryogenic deformation,significantly refines the coarse grains at the surface of the forgings,resulting in a finer and more uniform microstructure,thereby effectively addressing the issue of surface coarse grains associated with traditional methods.The findings indicate that the PCF process can accumulate higher stored energy,facilitating static recrystallization(SRX)during subsequent heat treatment and enhancing the microstructural uniformity.Utilizing various analytical techniques,including optical microscopy(OM),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM).This study reveals the superiority of the PCF process in terms of strain accumulation,dislocation density,and grain refinement.In conclusion,this method offers advantages in enhancing the performance and microstructural uniformity of 7050 aluminum forgings,presenting new opportunities for applications in the aluminum forging industry.展开更多
To explore ambient strengthening and high temperature ductility,a combined forming approach of multidirectional forging and asymmetric rolling was proposed.A novel multicomponent ultralight Mg-3.11Li-2.31Al-1.95Sn-0.9...To explore ambient strengthening and high temperature ductility,a combined forming approach of multidirectional forging and asymmetric rolling was proposed.A novel multicomponent ultralight Mg-3.11Li-2.31Al-1.95Sn-0.94Y-0.45Er alloy was fabricated.The microstructural evolution and mechanical properties were investigated by microstructural characterization and tensile test.The combined forming results in remarkable grain refinement.The ultimate tensile strength and elongation of(255±7)MPa and 24.9%,respectively,were obtained at room temperature.The contribution of various strengthening mechanisms of the rolled alloy was obtained.Microstructural examination revealed the occurrence of dynamic recrystallization at 473-573 K and dynamic grain growth at 573-623 K.The maximum elongation of 293.9%was demonstrated at 623 K and 5×10^(-4)s^(-1).The dominate deformation mechanism at elevated temperatures is dislocation viscous glide.展开更多
The homogenized Mg−5.6Gd−0.8Zn(wt.%)alloys were treated with water cooling and furnace cooling to obtain specimens without and with the 14H long-period stacking ordered(LPSO)phase.Subsequently,multi-directional forgin...The homogenized Mg−5.6Gd−0.8Zn(wt.%)alloys were treated with water cooling and furnace cooling to obtain specimens without and with the 14H long-period stacking ordered(LPSO)phase.Subsequently,multi-directional forging(MDF)experiments were carried out.The microstructure and mechanical properties of different regions(the center,middle and edge regions)in the MDFed alloys were systematically investigated,and the effect of LPSO phase on them was discussed.The results show that the alloys in different regions undergo significant grain refinement during the MDF process.Inhomogeneous microstructures with different degrees of dynamic recrystallization(DRX)are formed,resulting in microhardness heterogeneity.The alloy with the LPSO phase has higher microstructure homogeneity,a higher degree of recrystallization,and better comprehensive mechanical properties than the alloy without the LPSO phase.The furnace-cooled alloy after 18 passes of MDF has the best comprehensive mechanical properties,with an ultimate compressive strength of 488 MPa,yield strength of 258 MPa,and fracture strain of 21.2%.DRX behavior is closely related to the LPSO phase and deformation temperature.The kinked LPSO phase can act as a potential nucleation site for DRX grains,while the fragmented LPSO phase promotes DRX nucleation through the particle-stimulated nucleation mechanism.展开更多
In-situ TiB_(2)/Al–Cu composite was processed by multidirectional forging(MDF)for six passes.The microstructure evolution of the forged workpiece was examined across various regions.The mechanical properties of the a...In-situ TiB_(2)/Al–Cu composite was processed by multidirectional forging(MDF)for six passes.The microstructure evolution of the forged workpiece was examined across various regions.The mechanical properties of the as-cast and MDFed composites were compared,and their strengthening mechanisms were analyzed.Results indicate that the grain refinement achieved through the MDF process is mainly due to the subdivision of the original grains through mechanical geometric fragmentation and the occurrence of dynamic recrystallization(DRX).DRX grains are formed through discontinuous DRX,continuous DRX,and recrystallization induced by particle-stimulated nucleation.A rise in accumulated equivalent strain(Σ?ε)results in finerα-Al grains and a more uniform distribution of TiB_(2)particles,which enhance the Vickers hardness of the composite.In addition,the tensile properties of the MDFed composite significantly improve compared with those of the as-cast composites,with ultimate tensile strength and yield strength increasing by 51.2%and 54%,respectively.This enhancement is primarily due to grain refinement strengthening and dislocation strengthening achieved by the MDF process.展开更多
The superplasticity of the Mg−8.59Gd−3.85Y−1.14Zn−0.49Zr alloy was investigated before and after multi-directional forging(MDF)and the mechanisms affecting superplastic deformation were analyzed.The results indicate t...The superplasticity of the Mg−8.59Gd−3.85Y−1.14Zn−0.49Zr alloy was investigated before and after multi-directional forging(MDF)and the mechanisms affecting superplastic deformation were analyzed.The results indicate that after MDF at a temperature of 350℃and strain rates of 0.1 and 0.01 s^(−1)(1-MDFed and 2-MDFed),the superplasticity of the alloy can be significantly improved.The elongations of the MDFed alloys exceed 400%under the strain rate of 6.06×10^(−4)s^(−1)and temperatures of 350,375,and 400℃,and reach the maximum values of 766%(1-MDFed)and 693%(2-MDFed)at 375℃.The grain boundary sliding of the MDFed alloy is sufficient,and the energy barrier of deformation decreases.Theβphase limits the grain growth and promotes dynamic recrystallization,maintaining the stability of the fine-grained structure during superplastic deformation.Several Y-rich phases nucleate in the high-strain region(i.e.,the final fracture region)at high temperatures,accelerating the fracture of the specimen.展开更多
The microstructure and mechanical properties of the Ti-5Al-5Mo-5V-1Cr-1Fe(Ti-55511)alloy under different strains were investigated through the design of step-shaped die forging.The results indicate that continuous dyn...The microstructure and mechanical properties of the Ti-5Al-5Mo-5V-1Cr-1Fe(Ti-55511)alloy under different strains were investigated through the design of step-shaped die forging.The results indicate that continuous dynamic recrystallization(CDRX)and discontinuous dynamic recrystallization(DDRX)occur in the high strain region.The orientation of the grains produced by CDRX is random and does not weaken the fiber texture.<100>-oriented grains expand gradually with increasing strain,thereby enhancing the strength of{100}texture.Significant anisotropic mechanical properties are observed in the large strain region and analyzed through in-situ tensile experiments.When the loading direction is parallel to the longitudinal(L)direction,strain concentration is observed near the dynamically recrystallized(DRXed)grains and inside grains oriented along<100>,leading to crack initiation.Furthermore,the small angle between the loading direction and the c-axis hinders the activation of prismatic and basal slip,thereby enhancing the strength.When the loading direction is parallel to the short transverse(ST)direction,cracks are initiated not only within grains oriented along<100>,but also at the grain boundaries.Regarding impact toughness,the elongatedβgrains in the L direction enhance the resistance to crack propagation.展开更多
The deformation mechanism,microstructure evolution,and precipitation behavior of a Mg-8.9Gd-1.8Y-0.5Zr-0.2Ag(wt.%)alloy multi-directionally forged at three different temperatures were investigated.As the forging tempe...The deformation mechanism,microstructure evolution,and precipitation behavior of a Mg-8.9Gd-1.8Y-0.5Zr-0.2Ag(wt.%)alloy multi-directionally forged at three different temperatures were investigated.As the forging temperature increases,the particle-stimulated nucleation(PSN)effect diminishes as the num-ber of dynamic precipitates decreases,pyramidal slip is activated,grain boundary migration accelerates,and continuous dynamic recrystallization(CDRX)dominates.The microstructures varied greatly,although fine-grained structures were formed at all different forging temperatures.Competitive precipitation be-tween dynamic precipitate growth,dislocation-induced precipitation,and homogeneous precipitation was observed after aging treatment.Among them,the medium temperature(748 K)forged and aged alloy ex-hibits the best mechanical performance,with an ultimate tensile strength of 436 MPa,and elongation of 16.3%.The calculation indicates that the mixed precipitation structure containing theβprecipitate band provides a 35%higher strengthening contribution than the typical homogeneously distributed precipi-tates.The formation of precipitation-free zones(PFZs)ensures that aging will not cause a dramatic de-crease in ductility,which provides a reference for the industrial preparation of high-performance wrought Mg-Gd series alloys.展开更多
The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co...The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co-design method of the forming process chain is put forward towards the objective of precision forming,which not only proposes a standard process route composed of multiple processes of upsetting,punching,rectangular ring rolling,loose tooling forging and profiled ring rolling,but also presents co-design methods of dies and blanks for all the processes.For profiled ring rolling,a design method of preformed blank that makes the blank and the target conical-section ring have the same axial volume distribution is proposed.By the method,the axial metal redistribution during the process can be alleviated greatly thus improving the forming stability and precision of the ring.Based on the geometric features of designed preformed blank,design methods of blanks and dies for loose tolling forging,rectangular ring rolling,punching and upsetting are proposed sequentially.In view of the key roles of loose tooling forging(manufacturing the preformed blank)and profiled ring rolling on the final quality of the conical ring parts,inherited FE simulations for these two processes are performed to verify the proposed design methods and determine appropriate design parameter.It is demonstrated that the proposed design method has significant advantages in improving forming precision.Besides,a suggestive value 1.5 of the rolling ratio for profiled ring rolling(a key design parameter)is given based on comprehensive consideration of multiple indicators such as ring roundness,deformation uniformity and forming load.The corresponding industrial experiments performed illustrate that a high forming precision of the conical-section aeroengine casing ring is achieved.展开更多
The effect of die forging on the microstructure evolution and deformation behavior of metastable β-titanium alloy Ti55511 was investigated by electron backscatter diffraction.Before die forging,the alloy Ti55511 was ...The effect of die forging on the microstructure evolution and deformation behavior of metastable β-titanium alloy Ti55511 was investigated by electron backscatter diffraction.Before die forging,the alloy Ti55511 was subjected to multi-pass forging to optimize the microstructural heterogeneity(texture)which can cause mechanical behavior anisotropy of titanium alloys.Results show that after die forging,Ti55511 components exhibit different microstructures and textures in different local areas.No<100>fiber texture is found in all areas with different degrees of deformation.Dynamic recrystallization occurs in the area where large strain occurs during the early stage of die forging.Basket-weave microstructure forms in most local areas.展开更多
文摘On the Broadband World Forum Europe 2010 held in Paris, ZTE Corporation launched a European FTTx Business Model which is developed to give operators the right balance of products and solutions for the requirements of the European optical network markets. At the same time, ZTE unveiled its Uni-FAN broadband acceleration solution to help operators rapidly deploy broadband networks.
文摘Shanghai Power Station Auxiliary Equipment Works (referred to as SDF) was established in April, 1980 on the base of the urban area previously owned by Shanghai Boiler Works so as to facilitate
文摘China’s cultural dxchanges with foreign countries have advanced from separate and shortterm prog5rams inta conprehensive and largescale alal activities the 2000 ferlin asia-pacific week highlighting chinese culture has just wuond up successfully china culture year will be heid in france in
文摘Since its founding in 1949, the CAS has been in duty bound to settle key S&T problems posed during national economic and defense construction,and has devoted itself to the renewal of China’s traditional industry and the development of new technology.In June 1950, the State authorities stipulated that the main tasks for the CAS were "to cultivate versatile S&T workers and a competent work force for national construction, striving to draw close the ties between academic research and actual demands so that science can really serve the country’s industry, agriculture, national defense,
基金Natural Science Foundation of Shandong Province of China(ZR2023QE193)。
文摘The microstructures and mechanical properties of Al-8.3Zn-3.3Cu-2.2Mg alloys prepared via hot extrusion and liquid forging methods were investigated.Results show that based on DEFORM simulation analysis,the optimal hot extrusion parameters are determined as ingot initial temperature of 380°C and extrusion speed of 3 mm/s.The hot-extruded aluminum alloy after T6 heat treatment presents superior mechanical properties with yield strength of 519.6 MPa,ultimate tensile strength of 582.1 MPa,and elongation of 11.0%.Compared with the properties of gravity-cast and liquid-forged alloys,the yield strength of hot-extruded alloy increases by 30.8%and 4.9%,and the ultimate tensile strength improves by 43.5%and 10.2%,respectively.The significant improvement in tensile strength of the hot-extruded alloys is attributed to the elimination of casting defects and the refinement of matrix grain and eutectic phases.In addition,the hot-extruded alloy demonstrates superior plasticity compared with the liquid-forged alloy.This is because severe plastic deformation occurs during hot extrusion,which effectively breaks and disperses the eutectic phases,facilitating the dissolution and precipitation of the second phases and inhibiting the microcrack initiation.
基金supported by the National Natural Science Foundation of China(Nos.52175145 and 51775427)the Key Research and Development Projects of Shaanxi Province(Grant No.2023-YBGY-335).
文摘The differences in damage values,residual stresses,microstructure and mechanical properties of Ti–6Al–4V alloy under hammer forging and press forging were explored through physical experiments and numerical simulations.The results showed that the temperature field and equivalent strain field of forgings under the hammer forging process were more uniformly distributed,resulting in smaller surface cracks and better residual stress distribution.The impact dynamic loading of hammer forging leads to forgings with higher dislocation densities,while the stabilized strain rate of press forging results in forgings exhibiting finer grain sizes.In this context,the yield strength enhancement of forgings by both processes was nearly identical,while the forgings demonstrated more excellent elongation under the hammer forging process.Additionally,increasing the number of blows in the hammer forging process or enhancing the loading rate in the press forging process can optimize the residual stress distribution of the forgings while simultaneously promoting dislocation multiplication and grain refinement.
文摘This study systematically investigated the microstructure,mechanical properties,and corrosion behavior of an extruded Zn-0.2Mg alloy processed by multi-directional forging(MDF)at 100℃.The mean grain size was remarkably decreased from 17.2±0.5µm to 1.9±0.3µm,and 84.4%of the microstructure was occupied by grains of below 1µm in size after applying three MDF passes.Electron backscattered difraction examinations revealed that continuous dynamic recrystallization,progressive lattice rotation,and particle-stimulated nucleation mechanisms were recognized as contributing to microstructural evolution.Furthermore,transmission electron microscopy results showed that nanoparticles of Mg/Zn dynamically formed under high strain MDF,while the initial extrusion fber texture was altered to be<0001>parallel to the fnal forging axis.A synergistic efect of grain refnement,texture evolution,second-phase precipitates,and dislocation strengthening resulted in an increased ultimate tensile strength of 232±5 MPa after three MDF passes.However,this was accompanied by a reduction in the elongation(8±2.1%).Additionally,a high corrosion rate of 0.59 mm/year was measured for the experimental alloy fabricated by 3 MDF passes.In agreement with the latter,electrochemical impedance spectroscopy results indicated that the grain refnement improved the passivation kinetics of the oxide layer.
基金financially supported by the National Key Research and Development Program of China(No.2022YFB3706901)the National Natural Science Foundation of China(No.52090041)the Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC 001).
文摘Digital modeling and autonomous control of the die forging process are significant challenges in realizing high-quality intelli-gent forging of components.Using the die forging of AA2014 aluminum alloy as a case study,a machine-learning-assisted method for di-gital modeling of the forging force and autonomous control in response to forging parameter disturbances was proposed.First,finite ele-ment simulations of the forging processes were conducted under varying friction factors,die temperatures,billet temperatures,and for-ging velocities,and the sample data,including process parameters and forging force under different forging strokes,were gathered.Pre-diction models for the forging force were established using the support vector regression algorithm.The prediction error of F_(f),that is,the forging force required to fill the die cavity fully,was as low as 4.1%.To further improve the prediction accuracy of the model for the ac-tual F_(f),two rounds of iterative forging experiments were conducted using the Bayesian optimization algorithm,and the prediction error of F_(f) in the forging experiments was reduced from 6.0%to 1.5%.Finally,the prediction model of F_(f) combined with a genetic algorithm was used to establish an autonomous optimization strategy for the forging velocity at each stage of the forging stroke,when the billet and die temperatures were disturbed,which realized the autonomous control in response to disturbances.In cases of−20 or−40℃ reductions in the die and billet temperatures,forging experiments conducted with the autonomous optimization strategy maintained the measured F_(f) around the target value of 180 t,with the relative error ranging from−1.3%to+3.1%.This work provides a reference for the study of di-gital modeling and autonomous optimization control of quality factors in the forging process.
基金supported by the National Natural Science Foundation of China(No.52405408,No.U21A20131,No.U2037204,No.52422510)the Natural Science Foundation of Hubei Province(No.2023AFB116)+1 种基金the State Key Laboratory of Materials Processing and Die&Mould TechnologyHuazhong University of Science and Technology(No.P2022-005)。
文摘Magnesium alloy thin-walled cylindrical components with the advantages of high specific stiffness and strength present broad prospect for the lightweight of aerospace components.However,poor formability resulting from the hexagonal close-packed crystal structure in magnesium alloy puts forwards a great challenge for thin-walled cylindrical components fabrication,especially for extreme structure with the thicknesschanging web and the high thin-wall.In this research,an ZK61 magnesium alloy thin-walled cylindrical component was successfully fabricated by two-step forging,i.e.,the pre-forging and final-forging is mainly used for wed and thin-wall formation,respectively.Microstructure and mechanical properties at the core,middle and margin of the web and the thin-wall of the pre-forged and final-forged components are studied in detail.Due to the large strain-effectiveness and metal flow along the radial direction(RD),the grains of the web are all elongated along RD for the pre-forged component,where an increasingly elongated trend is found from the core to the margin of the wed.A relatively low recrystallized degree occurs during pre-forging,and the web at different positions are all with prismatic and pyramid textures.During finalforging,the microstructures of the web and the thin-wall are almost equiaxed due to the remarkable occurrence of dynamic recrystallization.Similarity,except for few basal texture of the thin-wall,only prismatic and pyramid textures are found for the final-forged component.Compared with the initial billet,an obviously improved mechanical isotropy is achieved during pre-forging,which is well-maintained during final-forging.
基金supported by the National Key research and Development Program of China(No.2022YFB4003001).
文摘The mechanical properties,microstructure and second phase precipitation behavior of flange forgings for high-pressure hydrogen storage vessels at different tempering temperatures(620–700℃)were studied.The results showed that when tempered at 620–680°C,the main microstructure of the test steel was tempered sorbite,and the main microstructure of tempered steel changed to martensite at 700℃.At 700℃,the dislocation density increased and some retained austenite existed.With the tempering temperature increasing,the yield strength showed a decreasing trend,the formation of fresh martensite made the tensile strength first decrease and then increase slightly,the impact energy at−40℃increased first and then decreased,and the impact energy at 660℃had the maximum value.The precipitates of MC type were mainly(Mo,V,Ti)C.The test steel had excellent strength and toughness matching at 660℃tempering,the tensile strength at different cross section locations was above 750 MPa,the impact energy was above 200 J at−40℃,and the relative percentage reduction of area(ZH2/ZN2)was above 75%at hydrogen environment of 6.3 MPa.
文摘Today,I want to share how international standards can forge trust and fuel innovation,laying the foundation for a future where AI benefits everyone,everywhere.First,AI standards,developed jointly by ISO and IEC-the International Electrotechnical Commission-help build global trust and enable responsible innovation by bringing clarity and coherence to an ever-changing AI landscape.As developments in AI continue to emerge at speed,regulation is struggling to keep up and the proliferation of competing standards has created confusion rather than clarity.ISO and our partner IEC are addressing this challenge through the work of our expert committee on AI,SC 42,which takes a holistic,cohesive approach to AI standardization.
基金Project(2021GK1040) supported by the Major Projects of Scientific and Technology Innovation of Hunan Province,ChinaProjects(52375398,52171018) supported by the National Natural Science Foundation of China+1 种基金Project(Kfkt2023-09) supported by the Open Research Fund of State Key Laboratory of Precision Manufacturing for Extreme Service Performance,Central South University,ChinaProject(E2021203059) supported by the Natural Science Foundation of Hebei Province,China。
文摘This study investigates the differences in microstructural control between cryogenic forging combined with pre-deformation(PCF)and traditional thermal forging(TTF)for 7050 aluminum forgings intended for aerospace applications.The PCF process,utilizing cryogenic deformation,significantly refines the coarse grains at the surface of the forgings,resulting in a finer and more uniform microstructure,thereby effectively addressing the issue of surface coarse grains associated with traditional methods.The findings indicate that the PCF process can accumulate higher stored energy,facilitating static recrystallization(SRX)during subsequent heat treatment and enhancing the microstructural uniformity.Utilizing various analytical techniques,including optical microscopy(OM),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM).This study reveals the superiority of the PCF process in terms of strain accumulation,dislocation density,and grain refinement.In conclusion,this method offers advantages in enhancing the performance and microstructural uniformity of 7050 aluminum forgings,presenting new opportunities for applications in the aluminum forging industry.
基金supported by the National Natural Science Foundation of China(No.51334006)。
文摘To explore ambient strengthening and high temperature ductility,a combined forming approach of multidirectional forging and asymmetric rolling was proposed.A novel multicomponent ultralight Mg-3.11Li-2.31Al-1.95Sn-0.94Y-0.45Er alloy was fabricated.The microstructural evolution and mechanical properties were investigated by microstructural characterization and tensile test.The combined forming results in remarkable grain refinement.The ultimate tensile strength and elongation of(255±7)MPa and 24.9%,respectively,were obtained at room temperature.The contribution of various strengthening mechanisms of the rolled alloy was obtained.Microstructural examination revealed the occurrence of dynamic recrystallization at 473-573 K and dynamic grain growth at 573-623 K.The maximum elongation of 293.9%was demonstrated at 623 K and 5×10^(-4)s^(-1).The dominate deformation mechanism at elevated temperatures is dislocation viscous glide.
基金the financial supports from the Key Research and Development Program of Hunan Province,China(No.2023GK2020)。
文摘The homogenized Mg−5.6Gd−0.8Zn(wt.%)alloys were treated with water cooling and furnace cooling to obtain specimens without and with the 14H long-period stacking ordered(LPSO)phase.Subsequently,multi-directional forging(MDF)experiments were carried out.The microstructure and mechanical properties of different regions(the center,middle and edge regions)in the MDFed alloys were systematically investigated,and the effect of LPSO phase on them was discussed.The results show that the alloys in different regions undergo significant grain refinement during the MDF process.Inhomogeneous microstructures with different degrees of dynamic recrystallization(DRX)are formed,resulting in microhardness heterogeneity.The alloy with the LPSO phase has higher microstructure homogeneity,a higher degree of recrystallization,and better comprehensive mechanical properties than the alloy without the LPSO phase.The furnace-cooled alloy after 18 passes of MDF has the best comprehensive mechanical properties,with an ultimate compressive strength of 488 MPa,yield strength of 258 MPa,and fracture strain of 21.2%.DRX behavior is closely related to the LPSO phase and deformation temperature.The kinked LPSO phase can act as a potential nucleation site for DRX grains,while the fragmented LPSO phase promotes DRX nucleation through the particle-stimulated nucleation mechanism.
基金supported by the Key Program for International Cooperation of the Ministry of Science and Technology,China(No.ZCGX2022001L)。
文摘In-situ TiB_(2)/Al–Cu composite was processed by multidirectional forging(MDF)for six passes.The microstructure evolution of the forged workpiece was examined across various regions.The mechanical properties of the as-cast and MDFed composites were compared,and their strengthening mechanisms were analyzed.Results indicate that the grain refinement achieved through the MDF process is mainly due to the subdivision of the original grains through mechanical geometric fragmentation and the occurrence of dynamic recrystallization(DRX).DRX grains are formed through discontinuous DRX,continuous DRX,and recrystallization induced by particle-stimulated nucleation.A rise in accumulated equivalent strain(Σ?ε)results in finerα-Al grains and a more uniform distribution of TiB_(2)particles,which enhance the Vickers hardness of the composite.In addition,the tensile properties of the MDFed composite significantly improve compared with those of the as-cast composites,with ultimate tensile strength and yield strength increasing by 51.2%and 54%,respectively.This enhancement is primarily due to grain refinement strengthening and dislocation strengthening achieved by the MDF process.
基金supported by the National Natural Science Foundation of China(No.52127808)。
文摘The superplasticity of the Mg−8.59Gd−3.85Y−1.14Zn−0.49Zr alloy was investigated before and after multi-directional forging(MDF)and the mechanisms affecting superplastic deformation were analyzed.The results indicate that after MDF at a temperature of 350℃and strain rates of 0.1 and 0.01 s^(−1)(1-MDFed and 2-MDFed),the superplasticity of the alloy can be significantly improved.The elongations of the MDFed alloys exceed 400%under the strain rate of 6.06×10^(−4)s^(−1)and temperatures of 350,375,and 400℃,and reach the maximum values of 766%(1-MDFed)and 693%(2-MDFed)at 375℃.The grain boundary sliding of the MDFed alloy is sufficient,and the energy barrier of deformation decreases.Theβphase limits the grain growth and promotes dynamic recrystallization,maintaining the stability of the fine-grained structure during superplastic deformation.Several Y-rich phases nucleate in the high-strain region(i.e.,the final fracture region)at high temperatures,accelerating the fracture of the specimen.
基金funded by Department of Science and Technology of Sichuan Province,China(No.2022YFG0102)the China Postdoctoral Science Foundation(No.2023M733314).
文摘The microstructure and mechanical properties of the Ti-5Al-5Mo-5V-1Cr-1Fe(Ti-55511)alloy under different strains were investigated through the design of step-shaped die forging.The results indicate that continuous dynamic recrystallization(CDRX)and discontinuous dynamic recrystallization(DDRX)occur in the high strain region.The orientation of the grains produced by CDRX is random and does not weaken the fiber texture.<100>-oriented grains expand gradually with increasing strain,thereby enhancing the strength of{100}texture.Significant anisotropic mechanical properties are observed in the large strain region and analyzed through in-situ tensile experiments.When the loading direction is parallel to the longitudinal(L)direction,strain concentration is observed near the dynamically recrystallized(DRXed)grains and inside grains oriented along<100>,leading to crack initiation.Furthermore,the small angle between the loading direction and the c-axis hinders the activation of prismatic and basal slip,thereby enhancing the strength.When the loading direction is parallel to the short transverse(ST)direction,cracks are initiated not only within grains oriented along<100>,but also at the grain boundaries.Regarding impact toughness,the elongatedβgrains in the L direction enhance the resistance to crack propagation.
基金supported by the National Key R&D Program of China(No.2021YFB3701100).
文摘The deformation mechanism,microstructure evolution,and precipitation behavior of a Mg-8.9Gd-1.8Y-0.5Zr-0.2Ag(wt.%)alloy multi-directionally forged at three different temperatures were investigated.As the forging temperature increases,the particle-stimulated nucleation(PSN)effect diminishes as the num-ber of dynamic precipitates decreases,pyramidal slip is activated,grain boundary migration accelerates,and continuous dynamic recrystallization(CDRX)dominates.The microstructures varied greatly,although fine-grained structures were formed at all different forging temperatures.Competitive precipitation be-tween dynamic precipitate growth,dislocation-induced precipitation,and homogeneous precipitation was observed after aging treatment.Among them,the medium temperature(748 K)forged and aged alloy ex-hibits the best mechanical performance,with an ultimate tensile strength of 436 MPa,and elongation of 16.3%.The calculation indicates that the mixed precipitation structure containing theβprecipitate band provides a 35%higher strengthening contribution than the typical homogeneously distributed precipi-tates.The formation of precipitation-free zones(PFZs)ensures that aging will not cause a dramatic de-crease in ductility,which provides a reference for the industrial preparation of high-performance wrought Mg-Gd series alloys.
基金the National Natural Science Foundation of China(52275378).
文摘The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co-design method of the forming process chain is put forward towards the objective of precision forming,which not only proposes a standard process route composed of multiple processes of upsetting,punching,rectangular ring rolling,loose tooling forging and profiled ring rolling,but also presents co-design methods of dies and blanks for all the processes.For profiled ring rolling,a design method of preformed blank that makes the blank and the target conical-section ring have the same axial volume distribution is proposed.By the method,the axial metal redistribution during the process can be alleviated greatly thus improving the forming stability and precision of the ring.Based on the geometric features of designed preformed blank,design methods of blanks and dies for loose tolling forging,rectangular ring rolling,punching and upsetting are proposed sequentially.In view of the key roles of loose tooling forging(manufacturing the preformed blank)and profiled ring rolling on the final quality of the conical ring parts,inherited FE simulations for these two processes are performed to verify the proposed design methods and determine appropriate design parameter.It is demonstrated that the proposed design method has significant advantages in improving forming precision.Besides,a suggestive value 1.5 of the rolling ratio for profiled ring rolling(a key design parameter)is given based on comprehensive consideration of multiple indicators such as ring roundness,deformation uniformity and forming load.The corresponding industrial experiments performed illustrate that a high forming precision of the conical-section aeroengine casing ring is achieved.
基金National Science and Technology Project of China(JPPT-135-GH-2-017)Fellowship of China Postdoctoral Science Foundation(2022M720399)。
文摘The effect of die forging on the microstructure evolution and deformation behavior of metastable β-titanium alloy Ti55511 was investigated by electron backscatter diffraction.Before die forging,the alloy Ti55511 was subjected to multi-pass forging to optimize the microstructural heterogeneity(texture)which can cause mechanical behavior anisotropy of titanium alloys.Results show that after die forging,Ti55511 components exhibit different microstructures and textures in different local areas.No<100>fiber texture is found in all areas with different degrees of deformation.Dynamic recrystallization occurs in the area where large strain occurs during the early stage of die forging.Basket-weave microstructure forms in most local areas.
