In order to solve the problem of poor formability caused by different materials and properties in the process of tailor-welded sheets forming,a forming method was proposed to change the stress state of tailor-welded s...In order to solve the problem of poor formability caused by different materials and properties in the process of tailor-welded sheets forming,a forming method was proposed to change the stress state of tailor-welded sheets by covering the tailor-welded sheets with better plastic properties overlapping sheets.At the same time,the interface friction effect between the overlapping and tailor-welded sheets was utilized to control the stress magnitude and further improve the formability and quality of the tailor-welded sheets.In this work,the bulging process of the tailor-welded overlapping sheets was taken as the research object.Aluminum alloy tailor-welded overlapping sheets bulging specimens were studied by a combination of finite element analysis and experimental verification.The results show that the appropriate use of interface friction between tailor-welded and overlapping sheets can improve the formability of tailor-welded sheets and control the flow of weld seam to improve the forming quality.When increasing the interface friction coefficient on the side of tailor-welded sheets with higher strength and decreasing that on the side of tailor-welded sheets with lower strength,the deformation of the tailor-welded sheets are more uniform,the offset of the weld seam is minimal,the limit bulging height is maximal,and the forming quality is optimal.展开更多
EuB_(6),a magnetic topological semimetal,has attracted considerable attention in recent years due to its rich intriguing physical properties,including a colossal negative magnetoresistance(CNMR)ratio exceeding-80%,a t...EuB_(6),a magnetic topological semimetal,has attracted considerable attention in recent years due to its rich intriguing physical properties,including a colossal negative magnetoresistance(CNMR)ratio exceeding-80%,a topological phase transition and a predicted quantum anomalous Hall effect(QAHE)approaching the two-dimensional(2D)limit.Yet,studies of the influence of the dimensionality approaching 2D on the electronic transport properties of EuB_(6) are still scarce.In this work,EuB_(6) thin sheets with thicknesses ranging from 35μm to 180μm were successfully fabricated through careful mechanical polishing of high-quality EuB_(6) single crystals.The reduced thickness,temperature and magnetic field have a strong influence on the electronic transport properties,including the CNMR and carrier concentration of EuB_(6) thin sheets.As the thickness of EuB_(6) thin sheets decreases from 180μm to 35μm,the magnetization transition temperature and the corresponding suppressing temperature of the Kondo effect decrease from 15.2 K to 10.9 K,while the CNMR ratio increases from-87.2%to-90.8%.Furthermore,the weak antilocalization effect transits to a weak localization effect and the carrier concentration increases by 9.4%at 30 K in a 35μm EuB_(6) thin sheet compared to the value reported for a 180μm thin sheet.Our findings demonstrate an obvious tunable effect of the reduced dimensionality on the transport properties of EuB_(6) along with the temperature and magnetic field,which could provide a route to exploring the QAHE near the 2D limit in EuB_(6) and other topological semimetals.展开更多
In this work,AZ31B extruded sheets with mixed-grain microstructures were prepared through extrusion.Samples of mixed-grain microstructure with different morphologies were selected from the AZ31B extruded sheets(referr...In this work,AZ31B extruded sheets with mixed-grain microstructures were prepared through extrusion.Samples of mixed-grain microstructure with different morphologies were selected from the AZ31B extruded sheets(referred to as M1 and M2 samples,respectively).The creep tests were performed on these samples at the temperature range of 150-200℃,and the stress level range of 50-100 MPa.The creep properties and fracture behavior of AZ31 extruded sheets with mixed-grain microstructures were studied.Results showed that the creep properties of the M2 sample always outperformed that of the M1 sample and M1 and M2 samples’creep was dominated by dislocation movement.The creep rate of M2 samples(1.5×10^(-7)±1.1×10^(-10) s^(-1))is an order of magnitude lower than that of M1 samples(4.8×10^(-6)±8.1×10^(-10) s^(-1))at 200℃under 50 MPa The high activity of basal slip and softening mechanism in the M1 sample significantly accelerated creep,resulting in a relatively high creep rate.Moreover,the stress concentration within the M1 sample caused by deformation incompatibility,increased the initiation and propagation of voids,ultimately leading to fracture and poorer creep performance.However,the numerous<10µm fine grains surrounding deformed coarse grains in the M2 sample facilitated better coordination of deformation through dislocation slip,effectively slowing down the initiation of voids during the creep process.Meanwhile,the strain was uniformly distributed within each grain,mitigating stress concentration,inhibiting voids propagation,and contributing to the superior creep resistance of the M2 sample.展开更多
Experimental validation of laser intensity is particularly important for the study of fundamental physics at extremely high intensities.However,reliable diagnosis of the focal spot and peak intensity faces huge challe...Experimental validation of laser intensity is particularly important for the study of fundamental physics at extremely high intensities.However,reliable diagnosis of the focal spot and peak intensity faces huge challenges.In this work,we demonstrate for the firs time that the coherent radiation farfiel patterns from laser–foil interactions can serve as an in situ,real-time,and easy-to-implement diagnostic for an ultraintense laser focus.The laser-driven electron sheets,curved by the spatially varying laser fiel and leaving the targets at nearly the speed of light,produce doughnut-shaped patterns depending on the shapes of the focal spot and the absolute laser intensities.Assisted by particle-in-cell simulations,we can achieve measurements of the intensity and the focal spot,and provide immediate feedback to optimize the focal spots for extremely high intensity.展开更多
This article examines the influence of annealing temperature on fracture toughness and forming limit curves of dissimilar aluminum/silver sheets.In the cold roll bonding process,after brushing and acid washing,the pre...This article examines the influence of annealing temperature on fracture toughness and forming limit curves of dissimilar aluminum/silver sheets.In the cold roll bonding process,after brushing and acid washing,the prepared surfaces are placed on top of each other and by rolling with reduction more than 50%,the bonding between layers is established.In this research,the roll bonding process was done at room temperature,without the use of lubricants and with a 70%thickness reduction.Then,the final thickness of the Ag/Al bilayer sheet reached 350μm by several stages of cold rolling.Before cold rolling,it should be noted that to decrease the hardness created due to plastic deformation,the roll-bonded samples were subjected to annealing heat treatment at 400℃for 90 min.Thus,the final samples were annealed at 200,300 and 400℃for 90 min and cooled in a furnace to examine the annealing temperature effects.The uniaxial tensile and microhardness tests measured mechanical properties.Also,to investigate the fracture mechanism,the fractography of the cross-section was examined by scanning electron microscope(SEM).To evaluate the formability of Ag/Al bilayer sheets,forming limit curves were obtained experimentally through the Nakazima test.The resistance of composites to failure due to cracking was also investigated by fracture toughness.The results showed that annealing increases the elongation and formability of the Ag/Al bilayer sheet while reduces the ultimate tensile strength and fracture toughness.However,the changing trend is not the same at different temperatures,and according to the results,the most significant effect is obtained at 300℃and aluminum layers.It was also determined that by increasing annealing temperature,the fracture mechanism from shear ductile with small and shallow dimples becomes ductile with deep cavities.展开更多
The mechanical properties and texture of AM60（Mg-6.0Al-0.3Mn,mass fraction %） and ZXM200（Mg-1.6Zn-0.5Ca-0.2Mn） Mg alloys subjected to multi-pass hot rolling were investigated.The finer recrystallized grains usuall...The mechanical properties and texture of AM60（Mg-6.0Al-0.3Mn,mass fraction %） and ZXM200（Mg-1.6Zn-0.5Ca-0.2Mn） Mg alloys subjected to multi-pass hot rolling were investigated.The finer recrystallized grains usually exhibit particular preferred orientations and then alter the total texture feature of rolled sheets.Ca solid solution into Mg matrix serves to the formation of texture component with c-axis rotated away from normal direction towards transverse direction and then weakens the overall texture intensity,resulting in a similar anisotropic characteristic to RE-containing Mg alloys.展开更多
The formability of AA5052/polyethylene/AA5052 sandwich sheets was experimentally studied. Three kinds of AA5052/polyethylene/AA5052 sandwich specimens with different thicknesses of core materials were prepared by the ...The formability of AA5052/polyethylene/AA5052 sandwich sheets was experimentally studied. Three kinds of AA5052/polyethylene/AA5052 sandwich specimens with different thicknesses of core materials were prepared by the hot pressing adhesive method. Then, the uniaxial tensile tests were conducted to investigate the mechanical properties of AA5052/polyethylene/ AA5052 sandwich sheets, and the stretching tests were carried out to investigate the influences of polymer core thickness on the limit dome height of the sandwich sheet. The forming limit curves for three kinds of sandwich sheets were obtained. The experimental results show that the forming limit of the AA5052/polyethylene/AA5052 sandwich sheet is higher than that of the monolithic AA5052 sheet, and it increases with increasing the thickness of polyethylene core.展开更多
Edge cracking is one of the most serious problems in the rolling process of magnesium alloy sheets,which limits its application.In this work,the edge cracking behavior of different initial AZ31 alloy sheets,including ...Edge cracking is one of the most serious problems in the rolling process of magnesium alloy sheets,which limits its application.In this work,the edge cracking behavior of different initial AZ31 alloy sheets,including as-cast(AC),as-rolled(AR)and as-extruded(AE),was systematically investigated and compared under the online heating rolling(O-LHR)process with a single-pass reduction of 50% at 250℃.The results show that both AC and AR sheets exhibit severe edge cracking behavior after the O-LHR.Among them,the AR sheet exhibits the severest edge cracking behavior on the rolling plane(RD-TD)and longitudinal section(RD-ND),which is attributed to the strong basal texture and extremely uneven microstructure with shear bands.While no visible edge crack appears in the AE rolled sheet,which is mainly related to the tilted texture and the more dynamic recrystallization during rolling process.Moreover,it is also found that the micro-cracks of the AC rolled sheet are mainly generated in the local fine-grained area and the twins where recrystallization occurs.In the AR rolled sheet,micro-cracks mainly develop inside the shear bands.Meanwhile,the micro-crack initiation mechanism of AC and AR rolled sheets was also discussed.展开更多
The deformation behavior of hot-rolled AZ31 magnesium(Mg)alloy sheet was analyzed when subjected to uniaxial tension along its normal direction at temperatures ranging from 100 to 400℃and strain rates ranging from 0....The deformation behavior of hot-rolled AZ31 magnesium(Mg)alloy sheet was analyzed when subjected to uniaxial tension along its normal direction at temperatures ranging from 100 to 400℃and strain rates ranging from 0.5 to 100 mm/min.Based on the stress−strain curves and the dynamic material model,the hot processing map was established,which demonstrates that the power dissipation factor(η)is the most sensitive to strain rate at 400℃via absorption of dislocations.At 400℃,sample at 0.5 mm/min possessesηof 0.89 because of its lower kernel average misorientation(KAM)value of 0.51,while sample at 100 mm/min possessesηof 0.46 with a higher KAM value of 1.147.In addition,the flow stress presents a slight decrease of 25.94 MPa at 10 mm/min compared to that at 100 mm/min and 100℃.The reasons are twofold:a special~34°texture component during 100℃-100 mm/min favoring the activation of basal slip,and dynamic recrystallization(DRX)also providing softening effect to some extent by absorbing dislocations.Difference in activation of basal slip among twin laminas during 100℃-100 mm/min results in deformation inhomogeneity within the grains,which generates stress that helps matrix grains tilt to a direction favorable to basal slip,forming the special~34°texture component.展开更多
Presetting tensile twins(TTs)can enhance the mechanical properties of magnesium(Mg)alloys.Two as-received(AR)sheets,as-received state-A(AR-A)with fiber texture and nonuniform grains and as-received state-B with basal ...Presetting tensile twins(TTs)can enhance the mechanical properties of magnesium(Mg)alloys.Two as-received(AR)sheets,as-received state-A(AR-A)with fiber texture and nonuniform grains and as-received state-B with basal texture and uniform equiaxial grains are selected to induce TTs via a novel method called corrugated wide limit alignment(CWLA),and the corresponding CWLA-processed sheets are denoted as CWLA-processed state-A(C-A)and CWLA-processed state-B(C-B).The results demonstrate that a larger initial average grain size correlates with a higher fraction of TTs induced in Mg sheets,thereby refining the grains and forming a new rolling direction(RD)tilted texture during CWLA.The ultimate tensile strength increases by 32%from AR-A to C-A,primarily due to refinement strengthening and twinning-induced strain hardening.The recrystallization mechanism of C-A is dominated by twinning-induced dynamic recrystallization(DRX),where DRX grains prefer to inherit the orientation of TTs,resulting in an enhanced RD-tilted texture and the formation of multi-modal texture.The recrystallization mechanism of C-B is mainly discontinuous DRX and continuous DRX,and the DRX grains prefer to inherit the orientation of matrix grains,ultimately forming a basal texture.In summary,the tensile mechanical behavior of pre-twinned Mg sheets significantly depends on the grain size and texture of the AR sheets,so they present similar changing trends during tensile deformation.展开更多
The mechanical properties, microstructures, and fractographs of TA15 sheets vacuum-annealed under different patterns were investigated. The results indicate that vacuum annealing significantly improves the mechanical ...The mechanical properties, microstructures, and fractographs of TA15 sheets vacuum-annealed under different patterns were investigated. The results indicate that vacuum annealing significantly improves the mechanical properties of the sheets in comparison with those after ambient annealing. With increasing the annealing temperature, the phase boundaries and secondary a-phase increase, whereas the volume fraction of primary a-phase decreases, resulting in increased strength and decreased elongation A relatively fine secondary a-phase is obtained after double annealing. The desirable mechanical properties （i.e., ultimate tensile strength, yield strength, and elongation are 1070 MPa, 958 MPa, and 15%, respectively） are obtained through double annealing （（950 ℃/2 h, AC）＋（600 ℃/2 h, AC））. The fractographs obtained after tensile tests show that the deepest and largest dimples are formed in the specimen annealed at 850 ℃, which indicates that the best plasticity is obtained at this annealing temperature.展开更多
Shougang Group has carried out a strategic structure adjustment in order to realize the promise of Chinese people to the Olympic Games.Automotive sheets are chosen as a type of strategic product and an engine to upgra...Shougang Group has carried out a strategic structure adjustment in order to realize the promise of Chinese people to the Olympic Games.Automotive sheets are chosen as a type of strategic product and an engine to upgrade enterprise management,technology and operation to reach the top international level during the transition from long products to steel sheets in Shougang Group.Since 2006,Shougang Group has made an elaborate preparation on steel sheet culture,production line construction,technology import,pilot plant and talent reserve.It lays the foundation for the development of automotive sheets.The developing history of cold rolled automotive sheets is reviewed and the research and development of cold rolled automotive sheets, tackling key problem of defect on surface and the latest progress of automotive sheets construction are described in this paper.The main contents were given as follows:①The products of automotive sheets realize zero breakthrough in Shougang Group.Monthly output was 300 ton in January,2009 and it increased to 48 000 ton in June,2010.The ratio of IF steel sheets increases to 70%from 40%.The proportion of outside panel in automotive sheets occupys more than 15%.②A high emulational pilot plant is used as a product developing platform to develop successfully automotive sheets with 1 000 MPa and below.It guarantees that the industrial development of DP and TRIP sheets gets success at a time.It covers continuous annealing sheets with tensile strength≤780 MPa and galvanizing sheets with tensile strength≤590 MPa.③Individual design is used to meet special requirement of customer.Shougang owns 23 inner brands of LCAK and IF steels.It insures that the grades of yield strength cover whole range from 120 to 270 MPa.It keeps the stabilization of steel performance by means of chemical composition control and high accuracy rolling technology.For example,the strength of soft steel fluctuates within±15 MPa.④The steel sheets with surface grade O5 are produced steadily by solving forming striation of IF steel,grain coarse on surface,edge curling skin and mountains - and - waters painting defects.⑤The safeguard mechanism on quality of products is improved steadily and the output of automotive sheets and outside panel increases greatly by building consistency quality management system、information - system and customer service system.展开更多
The effect of the repeated unidirectional bending （RUB） process and annealing on the formability of magnesium alloy sheets was investigated. The RUB process and annealing treatments produce two effects on microstruc...The effect of the repeated unidirectional bending （RUB） process and annealing on the formability of magnesium alloy sheets was investigated. The RUB process and annealing treatments produce two effects on microstructure： grain coarsening and weakening of the texture. The sheet that underwent RUB and was annealed at 300 ℃exhibits the best formability owing to the reduction of the （0002） basal texture intensity, which results in low yield strength, large fracture elongation, small Lankford value （r-value） and large strain hardening exponent （n-value）. Compared with the as-received sheet, the coarse-grain sheet produced by RUB and annealing at 400 ℃ exhibits lower tensile properties but higher formability. The phenomenon is because the deformation twin enhanced by grain coarsening can accommodate the strain of thickness.展开更多
Titanium dioxide sheet photocatalysts composed of interwoven microstrips were successfully synthesized using filter paper as templates. The synthesized samples were characterized by means of Fourier transform infrared...Titanium dioxide sheet photocatalysts composed of interwoven microstrips were successfully synthesized using filter paper as templates. The synthesized samples were characterized by means of Fourier transform infrared spectroscopy, surface area analyzer, thermogravimetric analysis, powder X-ray diffraction, and scanning electron microscopy. The photocatalytic activities of the samples were evaluated by the degradation of methyl orange in an aqueous solution under UV-illumination. The results demonstrated that the paper-like TiO2 sheets with the optimum proportion of anatase/rutile （10/1） had the highest photoactivity. And the presence of the filter paper fiber can improve the crystallinity, raise the anatase-rutile transformation temperature and contribute to the formation of being paper-like. A detailed formation mechanism for TiO2 sheets is proposed.展开更多
In order to study the fatigue failure mode and fatigue life laws of basalt-aramid and basalt-carbon hybrid fiber reinforced polymer （ FRP ） sheets, fatigue experiments are carried out, considering two hybrid ratios ...In order to study the fatigue failure mode and fatigue life laws of basalt-aramid and basalt-carbon hybrid fiber reinforced polymer （ FRP ） sheets, fatigue experiments are carried out, considering two hybrid ratios of 1 ： 1 and 2：1 under different stress levels from 0.6 to 0.95. The results show that fractures occur first in carbon fibers or aramid fibers for the specimens with hybrid ratio of 1： 1, namely B1A1 and B1C1, while a fracture occurs first in basalt fibers for the specimens with a hybrid ratio of 2： 1, namely B2A1 and B2C1. The fatigue lives of the hybrid FRP sheets increase with the improvement of the content of carbon fibers or aramid fibers, and the influence of the carbon fibers content improvement to fatigue life is more significant. The fatigue performance of B2A1 is relatively worse, while the fatigue performance of B1C1 and B2C1 is relatively better. Finally, a new fatigue stiffness degradation model with dual variables and double inflection points is presented, which is applicable to both hybrid and normal FRP sheets.展开更多
The relationship among microstructure,mechanical properties and texture of TA32 titanium alloy sheets during hot tensile deformation at 800℃was investigated.In the test,the original sheet exhibited relatively low flo...The relationship among microstructure,mechanical properties and texture of TA32 titanium alloy sheets during hot tensile deformation at 800℃was investigated.In the test,the original sheet exhibited relatively low flow stress and sound plasticity,and increasing the heat treatment temperature resulted in an increased ultimate tensile strength(UTS)and a decreased elongation(EL).The deformation mechanism of TA32 alloy was dominated by high angle grain boundaries sliding and coordinated by dislocation motion.The coarsening of grains and the annihilation of dislocations in heat-treated specimens weakened the deformation ability of material,which led to the increase in flow stress.Based on the high-temperature creep equation,the quantitative relationship between microstructure and flow stress was established.The grain size exponent andαphase strength constant of TA32 alloy were calculated to be 1.57 and 549.58 MPa,respectively.The flow stress was accurately predicted by combining with the corresponding phase volume fraction and grain size.Besides,the deformation behavior of TA32 alloy was also dependent on the orientation of predominantαphase,and the main slip mode was the activation of prismaticslip system.The decrease of near prism-oriented texture in heat-treated specimens resulted in the enhancement of strength of the material.展开更多
The performance of a lubricant largely depends on the additives it involves.However,currently used additives cause severe pollution if they are burned and exhausted.Therefore,it is necessary to develop a new generatio...The performance of a lubricant largely depends on the additives it involves.However,currently used additives cause severe pollution if they are burned and exhausted.Therefore,it is necessary to develop a new generation of green additives.Graphene oxide(GO)consists of only C,H and O and thus is considered to be environmentally friendly.So the tribological properties of the few-layer GO sheet as an additive in hydrocarbon base oil are investigated systematically.It is found that,with the addition of GO sheets,both the coefficient of friction(COF)and wear are decreased and the working temperature range of the lubricant is expanded in the positive direction.Moreover,GO sheets has better performance under higher sliding speed and the optimized concentration of GO sheets is determined to be 0.5wt%.After rubbing,GO is detected on the wear scars through Raman spectroscopy.And it is believed that,during the rubbing,GO sheets adhere to the sliding surfaces,behaving like protective films and preventing the sliding surfaces from contacting with each other directly.This paper proves that the GO sheet is an effective lubricant additive,illuminates the lubrication mechanism,and provides some critical parameters for the practical application of GO sheets in lubrication.展开更多
The refining effect of Al3Ti1B1RE master alloy on Al sheets used for pressure can manufacture and the behavior of mixed rare earths in master alloy were investigated with XRD, OM, SEM and EDAX. It is found that the r...The refining effect of Al3Ti1B1RE master alloy on Al sheets used for pressure can manufacture and the behavior of mixed rare earths in master alloy were investigated with XRD, OM, SEM and EDAX. It is found that the refining effect of the refiner on the material has superiority over foreign or domestic Al5Ti1B refiner, and the refiner still retains its refining ability for 6 h after adding it to molten Al, thus improving the strength and plasticity of the material remarkably. The excellent refining effect and stability of AlTiBRE refiner result from that RE can lower the surface energy of molten Al and improve the wetting characteristics of molten Al on refinement nuclei such as TiAl 3, TiB 2, etc., thus giving full play to the effect of heterogeneous nucleation and impeding the congregating tendency of TiB 2 phase in molten Al. At the same time, RE gathering in front of solid/liquid interface are also easy to cause composition supercooling in molten Al, thus impeding the growth of α Al grains and promoting α Al nucleation on refinement nuclei. In addition, RE also play certain role in purification and grain refinement, or modification, especially their effect of purification can improve the metallurgical quality of AlTiBRE master alloy.展开更多
In this paper, repeated unidirectional bending （RUB）, was applied to improve the texture of AZ31B magnesium alloy sheets so as to enhance their stamping properties. The samples undergoing RUB were annealed at differ...In this paper, repeated unidirectional bending （RUB）, was applied to improve the texture of AZ31B magnesium alloy sheets so as to enhance their stamping properties. The samples undergoing RUB were annealed at different temperatures. The mechanical properties, formability, textural components and microstructure of the samples before and after RUB were characterized and compared. It was found that the basal textural component was reduced dramatically by RUB, and that （1212） and （1211） textural components appeared. Annealing has a great effect on the mechanical properties of samples undergoing RUB. The plasticity and stamping formability of samples were greatly improved by RUB and annealing at 260℃ for 1 h, and elongation to fracture and Erichsen value were increased to 38% and 67%, respectively.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.52075347,51575364)and the Natural Science Foundation of Liaoning Provincial(No.2022-MS-295)。
文摘In order to solve the problem of poor formability caused by different materials and properties in the process of tailor-welded sheets forming,a forming method was proposed to change the stress state of tailor-welded sheets by covering the tailor-welded sheets with better plastic properties overlapping sheets.At the same time,the interface friction effect between the overlapping and tailor-welded sheets was utilized to control the stress magnitude and further improve the formability and quality of the tailor-welded sheets.In this work,the bulging process of the tailor-welded overlapping sheets was taken as the research object.Aluminum alloy tailor-welded overlapping sheets bulging specimens were studied by a combination of finite element analysis and experimental verification.The results show that the appropriate use of interface friction between tailor-welded and overlapping sheets can improve the formability of tailor-welded sheets and control the flow of weld seam to improve the forming quality.When increasing the interface friction coefficient on the side of tailor-welded sheets with higher strength and decreasing that on the side of tailor-welded sheets with lower strength,the deformation of the tailor-welded sheets are more uniform,the offset of the weld seam is minimal,the limit bulging height is maximal,and the forming quality is optimal.
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1204100)the National Natural Science Foundation of China(Grant No.62488201)+1 种基金the Chinese Academy of Sciences(Grant Nos.XDB33030000 and YSBR-053)Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700)。
文摘EuB_(6),a magnetic topological semimetal,has attracted considerable attention in recent years due to its rich intriguing physical properties,including a colossal negative magnetoresistance(CNMR)ratio exceeding-80%,a topological phase transition and a predicted quantum anomalous Hall effect(QAHE)approaching the two-dimensional(2D)limit.Yet,studies of the influence of the dimensionality approaching 2D on the electronic transport properties of EuB_(6) are still scarce.In this work,EuB_(6) thin sheets with thicknesses ranging from 35μm to 180μm were successfully fabricated through careful mechanical polishing of high-quality EuB_(6) single crystals.The reduced thickness,temperature and magnetic field have a strong influence on the electronic transport properties,including the CNMR and carrier concentration of EuB_(6) thin sheets.As the thickness of EuB_(6) thin sheets decreases from 180μm to 35μm,the magnetization transition temperature and the corresponding suppressing temperature of the Kondo effect decrease from 15.2 K to 10.9 K,while the CNMR ratio increases from-87.2%to-90.8%.Furthermore,the weak antilocalization effect transits to a weak localization effect and the carrier concentration increases by 9.4%at 30 K in a 35μm EuB_(6) thin sheet compared to the value reported for a 180μm thin sheet.Our findings demonstrate an obvious tunable effect of the reduced dimensionality on the transport properties of EuB_(6) along with the temperature and magnetic field,which could provide a route to exploring the QAHE near the 2D limit in EuB_(6) and other topological semimetals.
基金supported by the National Natural Science Foundation of China(52474419,52374395)Natural Science Foundation of Shanxi Province(20210302123135,202303021221143)+3 种基金Scientific and Technological Achievements Transformation Guidance Special Project of Shanxi Province(202104021301022,202204021301009)Central Government Guided Local Science and Technology development projects(YDZJSX20231B003,YDZJSX2021A010)The Ministry of Science and Higher Education of the Russian Federation for financial support under the Megagrant(No.075-15-2022-1133)the National Research Foundation(NRF)grant funded by the Ministry of Science and ICT(2015R1A2A1A01006795)of Korea through the Research Institute of Advanced.
文摘In this work,AZ31B extruded sheets with mixed-grain microstructures were prepared through extrusion.Samples of mixed-grain microstructure with different morphologies were selected from the AZ31B extruded sheets(referred to as M1 and M2 samples,respectively).The creep tests were performed on these samples at the temperature range of 150-200℃,and the stress level range of 50-100 MPa.The creep properties and fracture behavior of AZ31 extruded sheets with mixed-grain microstructures were studied.Results showed that the creep properties of the M2 sample always outperformed that of the M1 sample and M1 and M2 samples’creep was dominated by dislocation movement.The creep rate of M2 samples(1.5×10^(-7)±1.1×10^(-10) s^(-1))is an order of magnitude lower than that of M1 samples(4.8×10^(-6)±8.1×10^(-10) s^(-1))at 200℃under 50 MPa The high activity of basal slip and softening mechanism in the M1 sample significantly accelerated creep,resulting in a relatively high creep rate.Moreover,the stress concentration within the M1 sample caused by deformation incompatibility,increased the initiation and propagation of voids,ultimately leading to fracture and poorer creep performance.However,the numerous<10µm fine grains surrounding deformed coarse grains in the M2 sample facilitated better coordination of deformation through dislocation slip,effectively slowing down the initiation of voids during the creep process.Meanwhile,the strain was uniformly distributed within each grain,mitigating stress concentration,inhibiting voids propagation,and contributing to the superior creep resistance of the M2 sample.
基金supported by the Guangdong High Level Innovation Research Institute(Grant No.2021B0909050006)the National Grand Instrument Project(Grant No.2019YFF01014402)+1 种基金the National Natural Science Foundation of China(Grant No.12205008)support from the National Science Fund for Distinguished Young Scholars(Grant No.12225501)。
文摘Experimental validation of laser intensity is particularly important for the study of fundamental physics at extremely high intensities.However,reliable diagnosis of the focal spot and peak intensity faces huge challenges.In this work,we demonstrate for the firs time that the coherent radiation farfiel patterns from laser–foil interactions can serve as an in situ,real-time,and easy-to-implement diagnostic for an ultraintense laser focus.The laser-driven electron sheets,curved by the spatially varying laser fiel and leaving the targets at nearly the speed of light,produce doughnut-shaped patterns depending on the shapes of the focal spot and the absolute laser intensities.Assisted by particle-in-cell simulations,we can achieve measurements of the intensity and the focal spot,and provide immediate feedback to optimize the focal spots for extremely high intensity.
基金Project(4013311)supported by the National Science Foundation of Iran(INSF)。
文摘This article examines the influence of annealing temperature on fracture toughness and forming limit curves of dissimilar aluminum/silver sheets.In the cold roll bonding process,after brushing and acid washing,the prepared surfaces are placed on top of each other and by rolling with reduction more than 50%,the bonding between layers is established.In this research,the roll bonding process was done at room temperature,without the use of lubricants and with a 70%thickness reduction.Then,the final thickness of the Ag/Al bilayer sheet reached 350μm by several stages of cold rolling.Before cold rolling,it should be noted that to decrease the hardness created due to plastic deformation,the roll-bonded samples were subjected to annealing heat treatment at 400℃for 90 min.Thus,the final samples were annealed at 200,300 and 400℃for 90 min and cooled in a furnace to examine the annealing temperature effects.The uniaxial tensile and microhardness tests measured mechanical properties.Also,to investigate the fracture mechanism,the fractography of the cross-section was examined by scanning electron microscope(SEM).To evaluate the formability of Ag/Al bilayer sheets,forming limit curves were obtained experimentally through the Nakazima test.The resistance of composites to failure due to cracking was also investigated by fracture toughness.The results showed that annealing increases the elongation and formability of the Ag/Al bilayer sheet while reduces the ultimate tensile strength and fracture toughness.However,the changing trend is not the same at different temperatures,and according to the results,the most significant effect is obtained at 300℃and aluminum layers.It was also determined that by increasing annealing temperature,the fracture mechanism from shear ductile with small and shallow dimples becomes ductile with deep cavities.
基金Project(51204003)supported by the National Natural Science Foundation of ChinaProject(KJ2011A051)supported by the Scientific Research Foundation of Education Department of Anhui Province,China
文摘The mechanical properties and texture of AM60（Mg-6.0Al-0.3Mn,mass fraction %） and ZXM200（Mg-1.6Zn-0.5Ca-0.2Mn） Mg alloys subjected to multi-pass hot rolling were investigated.The finer recrystallized grains usually exhibit particular preferred orientations and then alter the total texture feature of rolled sheets.Ca solid solution into Mg matrix serves to the formation of texture component with c-axis rotated away from normal direction towards transverse direction and then weakens the overall texture intensity,resulting in a similar anisotropic characteristic to RE-containing Mg alloys.
基金Project(HIT.NSRIF.2009033) supported by the Scientific Research Foundation of Harbin Institute of Technology,China
文摘The formability of AA5052/polyethylene/AA5052 sandwich sheets was experimentally studied. Three kinds of AA5052/polyethylene/AA5052 sandwich specimens with different thicknesses of core materials were prepared by the hot pressing adhesive method. Then, the uniaxial tensile tests were conducted to investigate the mechanical properties of AA5052/polyethylene/ AA5052 sandwich sheets, and the stretching tests were carried out to investigate the influences of polymer core thickness on the limit dome height of the sandwich sheet. The forming limit curves for three kinds of sandwich sheets were obtained. The experimental results show that the forming limit of the AA5052/polyethylene/AA5052 sandwich sheet is higher than that of the monolithic AA5052 sheet, and it increases with increasing the thickness of polyethylene core.
基金financially supported by the National Natural Science Foundation of China(Nos.52071036,U2037601)the Guangdong Major Project of Basic and Applied Basic Research,China(No.2020B0301030006)+1 种基金the Independent Research Project of State Key Laboratory of Mechanical Transmissions,China(Nos.SKLMT-ZZKT-2022Z01,SKLMT-ZZKT-2022M12)the Chongqing Science and Technology Commission,China(No.CSTB2022TIAD-KPX0021)。
文摘Edge cracking is one of the most serious problems in the rolling process of magnesium alloy sheets,which limits its application.In this work,the edge cracking behavior of different initial AZ31 alloy sheets,including as-cast(AC),as-rolled(AR)and as-extruded(AE),was systematically investigated and compared under the online heating rolling(O-LHR)process with a single-pass reduction of 50% at 250℃.The results show that both AC and AR sheets exhibit severe edge cracking behavior after the O-LHR.Among them,the AR sheet exhibits the severest edge cracking behavior on the rolling plane(RD-TD)and longitudinal section(RD-ND),which is attributed to the strong basal texture and extremely uneven microstructure with shear bands.While no visible edge crack appears in the AE rolled sheet,which is mainly related to the tilted texture and the more dynamic recrystallization during rolling process.Moreover,it is also found that the micro-cracks of the AC rolled sheet are mainly generated in the local fine-grained area and the twins where recrystallization occurs.In the AR rolled sheet,micro-cracks mainly develop inside the shear bands.Meanwhile,the micro-crack initiation mechanism of AC and AR rolled sheets was also discussed.
基金Project(52005362) supported by the National Natural Science Foundation of ChinaProjects(202303021221005,202303021211045) supported by the Natural Science Foundation of Shanxi Province,China+1 种基金Project(202402003) supported by the Patent Commercialization Program of Shanxi Province,ChinaProject supported by the Key Research and Development Plan of Xinzhou City,China。
文摘The deformation behavior of hot-rolled AZ31 magnesium(Mg)alloy sheet was analyzed when subjected to uniaxial tension along its normal direction at temperatures ranging from 100 to 400℃and strain rates ranging from 0.5 to 100 mm/min.Based on the stress−strain curves and the dynamic material model,the hot processing map was established,which demonstrates that the power dissipation factor(η)is the most sensitive to strain rate at 400℃via absorption of dislocations.At 400℃,sample at 0.5 mm/min possessesηof 0.89 because of its lower kernel average misorientation(KAM)value of 0.51,while sample at 100 mm/min possessesηof 0.46 with a higher KAM value of 1.147.In addition,the flow stress presents a slight decrease of 25.94 MPa at 10 mm/min compared to that at 100 mm/min and 100℃.The reasons are twofold:a special~34°texture component during 100℃-100 mm/min favoring the activation of basal slip,and dynamic recrystallization(DRX)also providing softening effect to some extent by absorbing dislocations.Difference in activation of basal slip among twin laminas during 100℃-100 mm/min results in deformation inhomogeneity within the grains,which generates stress that helps matrix grains tilt to a direction favorable to basal slip,forming the special~34°texture component.
基金supported by the National Natural Science Foundation of China(No.52005362)the Fundamental Research Program of Shanxi Province(Nos.202303021221005 and 202303021211045)+1 种基金the Patent Commercialization Program of Shanxi Province(No.202402003)the Key Research and Development Plan of Xinzhou City.
文摘Presetting tensile twins(TTs)can enhance the mechanical properties of magnesium(Mg)alloys.Two as-received(AR)sheets,as-received state-A(AR-A)with fiber texture and nonuniform grains and as-received state-B with basal texture and uniform equiaxial grains are selected to induce TTs via a novel method called corrugated wide limit alignment(CWLA),and the corresponding CWLA-processed sheets are denoted as CWLA-processed state-A(C-A)and CWLA-processed state-B(C-B).The results demonstrate that a larger initial average grain size correlates with a higher fraction of TTs induced in Mg sheets,thereby refining the grains and forming a new rolling direction(RD)tilted texture during CWLA.The ultimate tensile strength increases by 32%from AR-A to C-A,primarily due to refinement strengthening and twinning-induced strain hardening.The recrystallization mechanism of C-A is dominated by twinning-induced dynamic recrystallization(DRX),where DRX grains prefer to inherit the orientation of TTs,resulting in an enhanced RD-tilted texture and the formation of multi-modal texture.The recrystallization mechanism of C-B is mainly discontinuous DRX and continuous DRX,and the DRX grains prefer to inherit the orientation of matrix grains,ultimately forming a basal texture.In summary,the tensile mechanical behavior of pre-twinned Mg sheets significantly depends on the grain size and texture of the AR sheets,so they present similar changing trends during tensile deformation.
基金Project supported by Beijing Laboratory of Metallic Materials and Processing for Modern Transportation
文摘The mechanical properties, microstructures, and fractographs of TA15 sheets vacuum-annealed under different patterns were investigated. The results indicate that vacuum annealing significantly improves the mechanical properties of the sheets in comparison with those after ambient annealing. With increasing the annealing temperature, the phase boundaries and secondary a-phase increase, whereas the volume fraction of primary a-phase decreases, resulting in increased strength and decreased elongation A relatively fine secondary a-phase is obtained after double annealing. The desirable mechanical properties （i.e., ultimate tensile strength, yield strength, and elongation are 1070 MPa, 958 MPa, and 15%, respectively） are obtained through double annealing （（950 ℃/2 h, AC）＋（600 ℃/2 h, AC））. The fractographs obtained after tensile tests show that the deepest and largest dimples are formed in the specimen annealed at 850 ℃, which indicates that the best plasticity is obtained at this annealing temperature.
文摘Shougang Group has carried out a strategic structure adjustment in order to realize the promise of Chinese people to the Olympic Games.Automotive sheets are chosen as a type of strategic product and an engine to upgrade enterprise management,technology and operation to reach the top international level during the transition from long products to steel sheets in Shougang Group.Since 2006,Shougang Group has made an elaborate preparation on steel sheet culture,production line construction,technology import,pilot plant and talent reserve.It lays the foundation for the development of automotive sheets.The developing history of cold rolled automotive sheets is reviewed and the research and development of cold rolled automotive sheets, tackling key problem of defect on surface and the latest progress of automotive sheets construction are described in this paper.The main contents were given as follows:①The products of automotive sheets realize zero breakthrough in Shougang Group.Monthly output was 300 ton in January,2009 and it increased to 48 000 ton in June,2010.The ratio of IF steel sheets increases to 70%from 40%.The proportion of outside panel in automotive sheets occupys more than 15%.②A high emulational pilot plant is used as a product developing platform to develop successfully automotive sheets with 1 000 MPa and below.It guarantees that the industrial development of DP and TRIP sheets gets success at a time.It covers continuous annealing sheets with tensile strength≤780 MPa and galvanizing sheets with tensile strength≤590 MPa.③Individual design is used to meet special requirement of customer.Shougang owns 23 inner brands of LCAK and IF steels.It insures that the grades of yield strength cover whole range from 120 to 270 MPa.It keeps the stabilization of steel performance by means of chemical composition control and high accuracy rolling technology.For example,the strength of soft steel fluctuates within±15 MPa.④The steel sheets with surface grade O5 are produced steadily by solving forming striation of IF steel,grain coarse on surface,edge curling skin and mountains - and - waters painting defects.⑤The safeguard mechanism on quality of products is improved steadily and the output of automotive sheets and outside panel increases greatly by building consistency quality management system、information - system and customer service system.
基金Project(CSTC2010AA4035)supported by Scientific and Technological Project of Chongqing Science and Technology Commission,ChinaProject(50504019)supported by the National Natural Science Foundation of China+1 种基金Project(CDJZR11130008)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(CDJXS10130001)supported by the Chongqing University Postgraduates'Science and Innovation Fund,China
文摘The effect of the repeated unidirectional bending （RUB） process and annealing on the formability of magnesium alloy sheets was investigated. The RUB process and annealing treatments produce two effects on microstructure： grain coarsening and weakening of the texture. The sheet that underwent RUB and was annealed at 300 ℃exhibits the best formability owing to the reduction of the （0002） basal texture intensity, which results in low yield strength, large fracture elongation, small Lankford value （r-value） and large strain hardening exponent （n-value）. Compared with the as-received sheet, the coarse-grain sheet produced by RUB and annealing at 400 ℃ exhibits lower tensile properties but higher formability. The phenomenon is because the deformation twin enhanced by grain coarsening can accommodate the strain of thickness.
基金This work was supported by the Natural Science Foundation of Shanxi Province （No.2009011099）, the Program for the Top Science and Technology Innovation Team of Higher Learning Institutions of Shanxi, and the Program for the Top Young Academic Leaders of Higher Learning Institutions of Shanxi.
文摘Titanium dioxide sheet photocatalysts composed of interwoven microstrips were successfully synthesized using filter paper as templates. The synthesized samples were characterized by means of Fourier transform infrared spectroscopy, surface area analyzer, thermogravimetric analysis, powder X-ray diffraction, and scanning electron microscopy. The photocatalytic activities of the samples were evaluated by the degradation of methyl orange in an aqueous solution under UV-illumination. The results demonstrated that the paper-like TiO2 sheets with the optimum proportion of anatase/rutile （10/1） had the highest photoactivity. And the presence of the filter paper fiber can improve the crystallinity, raise the anatase-rutile transformation temperature and contribute to the formation of being paper-like. A detailed formation mechanism for TiO2 sheets is proposed.
基金The National Natural Science Foundation of China(No.51108238)
文摘In order to study the fatigue failure mode and fatigue life laws of basalt-aramid and basalt-carbon hybrid fiber reinforced polymer （ FRP ） sheets, fatigue experiments are carried out, considering two hybrid ratios of 1 ： 1 and 2：1 under different stress levels from 0.6 to 0.95. The results show that fractures occur first in carbon fibers or aramid fibers for the specimens with hybrid ratio of 1： 1, namely B1A1 and B1C1, while a fracture occurs first in basalt fibers for the specimens with a hybrid ratio of 2： 1, namely B2A1 and B2C1. The fatigue lives of the hybrid FRP sheets increase with the improvement of the content of carbon fibers or aramid fibers, and the influence of the carbon fibers content improvement to fatigue life is more significant. The fatigue performance of B2A1 is relatively worse, while the fatigue performance of B1C1 and B2C1 is relatively better. Finally, a new fatigue stiffness degradation model with dual variables and double inflection points is presented, which is applicable to both hybrid and normal FRP sheets.
基金Project(51805256)supported by the National Natural Science Foundation of China。
文摘The relationship among microstructure,mechanical properties and texture of TA32 titanium alloy sheets during hot tensile deformation at 800℃was investigated.In the test,the original sheet exhibited relatively low flow stress and sound plasticity,and increasing the heat treatment temperature resulted in an increased ultimate tensile strength(UTS)and a decreased elongation(EL).The deformation mechanism of TA32 alloy was dominated by high angle grain boundaries sliding and coordinated by dislocation motion.The coarsening of grains and the annihilation of dislocations in heat-treated specimens weakened the deformation ability of material,which led to the increase in flow stress.Based on the high-temperature creep equation,the quantitative relationship between microstructure and flow stress was established.The grain size exponent andαphase strength constant of TA32 alloy were calculated to be 1.57 and 549.58 MPa,respectively.The flow stress was accurately predicted by combining with the corresponding phase volume fraction and grain size.Besides,the deformation behavior of TA32 alloy was also dependent on the orientation of predominantαphase,and the main slip mode was the activation of prismaticslip system.The decrease of near prism-oriented texture in heat-treated specimens resulted in the enhancement of strength of the material.
基金Supported by National Natural Science Foundation of China(Grant Nos.51335005,51321092)National Key Basic Research Program of China(973 Program,Grant No.2013CB934200)the Foundation for the Supervisor of Beijing Excellent Doctoral Dissertation(Grant No.20111000305)
文摘The performance of a lubricant largely depends on the additives it involves.However,currently used additives cause severe pollution if they are burned and exhausted.Therefore,it is necessary to develop a new generation of green additives.Graphene oxide(GO)consists of only C,H and O and thus is considered to be environmentally friendly.So the tribological properties of the few-layer GO sheet as an additive in hydrocarbon base oil are investigated systematically.It is found that,with the addition of GO sheets,both the coefficient of friction(COF)and wear are decreased and the working temperature range of the lubricant is expanded in the positive direction.Moreover,GO sheets has better performance under higher sliding speed and the optimized concentration of GO sheets is determined to be 0.5wt%.After rubbing,GO is detected on the wear scars through Raman spectroscopy.And it is believed that,during the rubbing,GO sheets adhere to the sliding surfaces,behaving like protective films and preventing the sliding surfaces from contacting with each other directly.This paper proves that the GO sheet is an effective lubricant additive,illuminates the lubrication mechanism,and provides some critical parameters for the practical application of GO sheets in lubrication.
文摘The refining effect of Al3Ti1B1RE master alloy on Al sheets used for pressure can manufacture and the behavior of mixed rare earths in master alloy were investigated with XRD, OM, SEM and EDAX. It is found that the refining effect of the refiner on the material has superiority over foreign or domestic Al5Ti1B refiner, and the refiner still retains its refining ability for 6 h after adding it to molten Al, thus improving the strength and plasticity of the material remarkably. The excellent refining effect and stability of AlTiBRE refiner result from that RE can lower the surface energy of molten Al and improve the wetting characteristics of molten Al on refinement nuclei such as TiAl 3, TiB 2, etc., thus giving full play to the effect of heterogeneous nucleation and impeding the congregating tendency of TiB 2 phase in molten Al. At the same time, RE gathering in front of solid/liquid interface are also easy to cause composition supercooling in molten Al, thus impeding the growth of α Al grains and promoting α Al nucleation on refinement nuclei. In addition, RE also play certain role in purification and grain refinement, or modification, especially their effect of purification can improve the metallurgical quality of AlTiBRE master alloy.
基金supported by the National Natural Science Foundation of China under Grant No. 50504019Natural Science Foundation Project of CQ CSTC under Grant No. 2008BB4040
文摘In this paper, repeated unidirectional bending （RUB）, was applied to improve the texture of AZ31B magnesium alloy sheets so as to enhance their stamping properties. The samples undergoing RUB were annealed at different temperatures. The mechanical properties, formability, textural components and microstructure of the samples before and after RUB were characterized and compared. It was found that the basal textural component was reduced dramatically by RUB, and that （1212） and （1211） textural components appeared. Annealing has a great effect on the mechanical properties of samples undergoing RUB. The plasticity and stamping formability of samples were greatly improved by RUB and annealing at 260℃ for 1 h, and elongation to fracture and Erichsen value were increased to 38% and 67%, respectively.
