The South Asia High （SAH） is the dominant feature of the circulation in the upper troposphere and lower stratosphere （UTLS） during the boreal summer, and the upper tropospheric anticyclonic circulation extends int...The South Asia High （SAH） is the dominant feature of the circulation in the upper troposphere and lower stratosphere （UTLS） during the boreal summer, and the upper tropospheric anticyclonic circulation extends into the lower stratosphere. The preferred locations of the center of the SAH occur in two different regions, and the center can be located over the Iranian Plateau or over the Tibetan Plateau. This bimodality has an impact on the distribution of chemical constituents in the UTLS region. We analyzed water vapor （H20）, carbon monoxide （CO）, and ozone （03） data derived from the Aura Microwave Limb Sounder （MLS） and total column ozone data from the Ozone Monitoring Instrument （OMI）. For the Iranian Plateau mode of the SAH, the tropospheric tracers exhibited a positive anomaly over the Iranian Plateau and a negative anomaly over the Tibetan Plateau, whereas the stratospheric tracer exhibited a negative and a positive anomaly over the Iranian Plateau and the Tibetan Plateau, respectively. For the Tibetan Plateau mode, however, the distribution of the anomaly was the reverse of that found for the chemical species in the UTLS region. Furthermore, the locations of the extrema within the anomaly seemed to differ across chemical species. The anomaly extrema for H20 occurred in the vicinity of the SAH ridgeline, whereas CO and O3 exhibited a northward shift of 4-8 degrees. These impacts of the variation in the SAH on the chemical constitutes in the UTLS region can be attributed in part to the dynamical structure delineated by the tropopause field and the temperature field at 100 hPa.展开更多
The observed South Asia High （SAH） center is characterized by two distinctive equilibrium modes during boreal midsummer, namely the center of SAH is located between 82.5°-92.5°E for the Tibetan Plateau mod...The observed South Asia High （SAH） center is characterized by two distinctive equilibrium modes during boreal midsummer, namely the center of SAH is located between 82.5°-92.5°E for the Tibetan Plateau mode and between 55°-65°E for the Iranian Plateau mode respectively. The present study describes the ability of 15 coupled general circulation models （CGCM） used in the Intergovernmental Panel on Climate Change＇s （IPCC） 4th Assessment Report to reproduce the observed bimodality of the SAH. These models reveal a wide range of skill in simulating this bimodality. Nearly half of the models reproduced the bimodality, while the other half of the models did not simulate well these two modes whereas usually preferring one mode, The models that reproduced the bimodality of the SAH present similar horizontal and vertical circulations as those features from the NCEP reanalysis data. The results from these models identify the warm characteristics of the SAH and indicate that these two modes have different dynamic and thermodynamic properties. Different characteristics of the simulated sensible heat and latent heat related to precipitation partly contribute to the difference in the simulations of the SAH bimodality. The majority of these models that prefer to simulate the Tibetan Plateau mode produce a small sensible heat flux difference between the Iranian Plateau and the Tibetan Plateau, and also generally simulate a very strong false precipitation center over the east of the Tibetan Plateau, which indicates strong latent release and thereby contributes to the preference of the SAH center on the Tibetan Plateau. Whereas, the models that reproduce the bimodality of the SAH tend to simulate large precipitation over the southern Himalayas and no obviously false precipitation is produced over the east of the Tibetan Plateau. In addition, the model＇s resolution may also have important impacts on the simulations of precipitation.展开更多
In recent years,metal matrix syntactic foams(MMSFs)have become highly attractive owing to their unique physical,microstructural and mechanical features.Due to their promising potential for different industrial areas l...In recent years,metal matrix syntactic foams(MMSFs)have become highly attractive owing to their unique physical,microstructural and mechanical features.Due to their promising potential for different industrial areas like automotive,aviation,and defense,these advanced engineering materials can also be evaluated as serious alternatives to particle reinforced metallic composites and conventional metallic foams.Differently from previously reported laboratory scaled techniques in the literature,this experimental effort focuses on the feasibility of MMSF manufacturing via a fully automated and industrial-based cold chamber die casting technique.Accordingly,1-2 mm,2-4 mm,and bimodal(50vol.%)natural-based pumice filled aluminum syntactic foams were manufactured utilizing a purpose-made casting machine.Physical,macroscopic,and microscopic examinations show that all of the fabricated samples display perfect matrix/filler harmony.Average density levels of fabricated syntactic foams range between 1.50 and 1.80 g·cm^(-3) depending upon the pumice particles size interval.To assess mechanical responses,quasi-static compression tests were performed.Furthermore,half of the foam samples were subjected to heat treatment to explore possible influences of aging on the compressive features and damage modes.Results indicate that although the heat treatment enhances the compressive strength,plateau stress,and energy absorption properties of the fabricated foams,it changes damage mode of the samples by causing brittle dominant deformation.展开更多
Combined conductivity-temperature-depth （CTD） casts and Argo profiles, 3 086 historical hydrocasts were used to quantify the water column characteristics in the northern South China Sea （SCS） and its adjacent wate...Combined conductivity-temperature-depth （CTD） casts and Argo profiles, 3 086 historical hydrocasts were used to quantify the water column characteristics in the northern South China Sea （SCS） and its adjacent waters. Based on a two-dimensional ＂gravest empirical mode＂ （GEM）, a gravitational potential （4, a vertically integrated variable） was used as proxy for the vertical temperature profiles TG（P, φ）. φ integrated from 8 MPa to the surface shows a close relationship with the temperature, except in the deep layer greater than 15 MPa, which was caused by the bimodal deep water in the region. The GEM temperature profiles successfully revealed the bimodality of the Luzon Strait deep water, that disparate hydrophic vertical profiles can produce distinct specific volume anomaly （δ） in the SCS and the western Philippine Sea （WPS）, but failed in the Luzon Strait, where different temperature profiles may produce a same 6. A significant temperature divergence between the SCS water and the WPS water confirmed that the bimodal structure is strong. The deepwater bifurcation starts at about 15 MPa, and gets stronger with increasing depth. As the only deep channel connecting the bimodal-structure waters, water column characteristics in the Luzon Strait is in between, but much closer to the SCS water because of its better connectivity with the SCS. A bimodal temperature structure below 15 MPa reveals that there was a persistent baroclinic pressure gradient driving flow through the Luzon Strait. A volume flux predicted through the Bashi Channel with the hydraulic theory yields a value of 5.62×10^6 m^3/s using all available profiles upstream and downstream of the overflow region, and 4.03×10^6 and 2.70×10^6 m^3/s by exclusively using the profiles collected during spring and summer, respectively. No volume flux was calculated during autumn and winter because profiles are only available for the upstream of the Bashi Channel during the corresponding period.展开更多
Lightweight,high-strength,and heat-resistant protective structures have consistently been crucial for applications in extreme environments,such as aerospace,semiconductors,and nuclear power industries.Multilayered TC4...Lightweight,high-strength,and heat-resistant protective structures have consistently been crucial for applications in extreme environments,such as aerospace,semiconductors,and nuclear power industries.Multilayered TC4/TB8 titanium(Ti)laminates,inspired by theheterostructures of natural biological shells,were fabricated using a hybrid diffusion bonding-hot rolling process followed by an aging treatment,resulting in an architected micro structure.The laminate achieves an ultra-high yield stress of 1020 MPa and proper uniform elongation of 4.2%at 500℃.The TB8 layers with high-density nano-precipitates and dislocations act as hard zone,contributing to high strength.The TC4 layers,with their bimodal structure consisting of coarse and fine grains characterized by equiaxed and lamellar structures,experience more plastic strain than the TB8 layers.The hetero deformation associated with the detwinning ofαgrains in the TC4 layer induces toughening at high temperatures.展开更多
The trade-offbetween strength and ductility remains a persistent obstacle in the development of advanced structural materials.In the present study,a novel dual-heterogeneous structure with a bimodal grain distribution...The trade-offbetween strength and ductility remains a persistent obstacle in the development of advanced structural materials.In the present study,a novel dual-heterogeneous structure with a bimodal grain distribution in both ferrite and austenite phases was fabricated via cold rolling and partial recrystallization annealing on solution-treated 2205 duplex stainless steel(DSS).The processed steel exhibited superior mechanical properties,with the yield strength increasing from 586 MPa to 903 MPa,and the ultimate tensile strength from 796 MPa to 1082 MPa,while maintaining a high total elongation of 35.3%.Based on in-situ electron backscatter diffraction(EBSD)and scanning electron microscope(SEM)analyses,the microstructural deformation behavior and strengthening mechanisms of the dual-heterostructured 2205 DSS were elucidated.The outstanding combination of strength and ductility was ascribed to the synergistic effects of grain refinement,dislocation strengthening,and hetero-deformation induced(HDI)strengthening.Moreover,the high ductility in DSS was attributed to the coactivation of cross-slip systems in ferrite{110}and{112}along with the single-slip systems in austenite{111}.These findings provide a new strategy for the design and development of high-strength and ultra-high-strength DSSs.展开更多
In this work,a heterogeneous structure(HS)with an alternating distribution of coarse and fineαlamella is fabricated in bimodal Ti6242 alloy via insufficient diffusion of alloying elements induced by fast heat-ing tre...In this work,a heterogeneous structure(HS)with an alternating distribution of coarse and fineαlamella is fabricated in bimodal Ti6242 alloy via insufficient diffusion of alloying elements induced by fast heat-ing treatment.Instead of a distinct interface between the primaryα_(p)hase(α_(p))andβ_(t)ransformation microstructure(β_(t))in the equiaxed microstructure(EM),allα_(p)/β_(t)interfaces are eliminated in the HS,and the largeα_(p)phases are replaced by coarseαlamella.Compared to the EM alloy,the heterostruc-tured alloy exhibits a superior strength-ductility combination.The enhanced strength is predominantly attributed to the increased interfaces ofα/βplates and hetero-deformation induced(HDI)strengthening caused by back stress.Meanwhile,good ductility is ascribed to its uniform distribution of coarse and fineαlamella,which effectively inhibits strain localization and generates an extra HDI hardening.This can be evidenced by the accumulated geometrically necessary dislocations(GNDs)induced by strain partitioning of the heterostructure.Significantly,the HDI causes extra<c+a>dislocations piling up in the coarseαlamella,which generates an extra strain hardening to further improve the ductility.Such hetero-interface coordinated deformation mechanism sheds light on a new perspective for tailoring bimodal titanium al-loys with excellent mechanical properties.展开更多
A new unified constitutive model was developed to predict the two-stage creep-aging(TSCA)behavior of Al-Zn-Mg-Cu alloys.The particular bimodal precipitation feature was analyzed and modeled by considering the primary ...A new unified constitutive model was developed to predict the two-stage creep-aging(TSCA)behavior of Al-Zn-Mg-Cu alloys.The particular bimodal precipitation feature was analyzed and modeled by considering the primary micro-variables evolution at different temperatures and their interaction.The dislocation density was incorporated into the model to capture the effect of creep deformation on precipitation.Quantitative transmission electron microscopy and experimental data obtained from a previous study were used to calibrate the model.Subsequently,the developed constitutive model was implemented in the finite element(FE)software ABAQUS via the user subroutines for TSCA process simulation and the springback prediction of an integral panel.A TSCA test was performed.The result shows that the maximum radius deviation between the formed plate and the simulation results is less than 0.4 mm,thus validating the effectiveness of the developed constitutive model and FE model.展开更多
AZ31 magnesium alloy was used as the object of study to fabricate an alloy with the bimodal grain structure using singlepass hot rolling,and to explore how this structure enhances the strength and plasticity of the al...AZ31 magnesium alloy was used as the object of study to fabricate an alloy with the bimodal grain structure using singlepass hot rolling,and to explore how this structure enhances the strength and plasticity of the alloy.The results show that the formation of the bimodal grain structure is more pronounced at rolling temperatures ranging from 350°C to 450°C,especially under conditions of large reduction(≥40%).The optimized proportion and distribution of the bimodal grain structure play a pivotal role in simultaneously enhancing the strength and ductility of the alloy,significantly impacting the mechanical properties.The rolled sheet with the bimodal grain structure achieves an ultimate tensile strength of 258.3 MPa and an elongation of 17.1%under a rolling reduction of 40%with the rolling rate of 75 m/min and rolling temperature of 400°C.Adjusting rolling parameters,including temperature,reduction ratio and rolling rate,is crucial for optimizing the bimodal grain structure,thereby achieving a balance between plasticity improvement and high strength maintenance.展开更多
PurposeThe purpose of the study was to investigate the effect of bimodal beamforming on speech recognition and comfort for cochlear implant (CI) users with the bimodal hearing solution made up by linking a hearing aid...PurposeThe purpose of the study was to investigate the effect of bimodal beamforming on speech recognition and comfort for cochlear implant (CI) users with the bimodal hearing solution made up by linking a hearing aid to the CI sound processor.Methods19 subjects participated in this study. Speech tests were conducted in quiet and in noisy environments, with the target speech presented from 0° and the noise signal from 45°. Speech recognition thresholds (SRTs) were compared among the previously used bimodal hearing configuration (baseline, any CI sound processor plus any hearing aid), the Naída Bimodal Hearing Solution with omnidirectional microphone, and with directional microphone (so called StereoZoom) switched on. In addition, the study participants provided subjective feedback on their hearing impressions.ResultsThe SRT results showed no significant difference among the three hearing conditions in the quiet environment. No significant improvement was reported when using Naída bimodal system with omnidirectional microphone in noise compared to the baseline (p=0.27). When applying StereoZoom, SRT in noise showed significant improvements compared to omnidirectional settings (p<0.05). Subjective feedback showed that 13 participants were satisfied with Naída Bimodal Hearing Solution, and wanted to continue using it after the trial.ConclusionThe Naída Bimodal Hearing Solution with the same pre-processing algorithm can provide satisfying hearing performance. Beamforming technology can further improve speech perception in noisy environments.展开更多
The tectonic setting of the Himalaya during the Early Paleozoic has been a subject of enduring debate within the scientific community.Newly discovered bimodal intrusive rocks from comprehensive field geological invest...The tectonic setting of the Himalaya during the Early Paleozoic has been a subject of enduring debate within the scientific community.Newly discovered bimodal intrusive rocks from comprehensive field geological investigation in the central mountain range were subjected to petrology,zircon U-Pb geochronology,zircon Hf isotopes and whole-rock geochemistry analyses.The Palie bimodal intrusive rocks,comprising amphibolite and granitic gneiss,were formed at~489 Ma.The amphibolite exhibits geochemical characteristics consistent with N-MORB,while the granitic gneiss is classified as high potassium calc-alkaline peraluminous S-type granite.Both igneous rocks exhibit negative zirconε_(Hf)(t)values and display ancient T_(DM)^(C)ages.In conjunction with regional geological survey findings,it can be inferred that the formation of the Palie bimodal intrusive rocks occurred within a post-collision extensional tectonic setting.The amphibolite genesis involved partial melting of an enriched lithospheric mantle with some crustal assimilation,whereas the origin of the granitic gneiss can be attributed to partial melting of pre-existing felsic crust.Our data indicate that during the Early Paleozoic,the Himalaya underwent a transition from a pan-African collisional setting to post-collisional extensional tectonics.展开更多
For a long time,the conventional superplastic forming temperature for Ti alloys is generally too high(~900-920℃),which leads to too long production cycles,heavy surface oxidation,and property reduction.In this study,...For a long time,the conventional superplastic forming temperature for Ti alloys is generally too high(~900-920℃),which leads to too long production cycles,heavy surface oxidation,and property reduction.In this study,an ultrafine bimodal microstructure,consisting of ultrafine equiaxed microstructure(0.66μm)and 43.3%lamellar microstructure,was achieved in the Ti-6Al-4V alloy by friction stir processing(FSP).The low-temperature superplastic behavior and deformation mechanism of the FSP Ti-6Al-4V alloy were investigated at temperatures of 550-675℃and strain rates ranging from 1×10^(−4)to 3×10^(−3)s^(−1).The FSP alloy exhibited superplastic elongations of>200%at the temperature range from 550 to 650℃,and an optimal superplastic elongation of 611%was achieved at 625℃and 1×10^(−4)s^(−1).This is the first time to report the low-temperature superplasticity of the bimodal microstructure in Ti alloys.Grain boundary sliding was identified as the dominant deformation mechanism,which was effectively accommodated by the comprehensive effect of dislocation-inducedβphase precipitation and dynamic spheroidization of the lamellar structure.This study provides a novel insight into the low-temperature superplastic deformation behavior of the bimodal microstructure.展开更多
The strength improvement in the heat-treatable Al-Zn-Mg-Cu alloys is generally achieved by increasing the volume fraction of nanoprecipitates and reducing the grain size.However,utilizing one of them usu-ally leads to...The strength improvement in the heat-treatable Al-Zn-Mg-Cu alloys is generally achieved by increasing the volume fraction of nanoprecipitates and reducing the grain size.However,utilizing one of them usu-ally leads to a drastic decrease in ductility.Herein,we architect a hierarchical microstructure integrating bimodal grain structures,nanoprecipitates,and hard-brittle coarse particles wrapped by ductility coarse grain(CG)bands via conventional cold rolling(CR)deformation and heat treatment methods to break the strength-ductility dilemma in the Al-8.89Zn-1.98Mg-2.06Cu-0.12Zr-0.05Sc-0.05Hf(wt.%)alloy.The results reveal that the coupling of high-volume fraction(∼1.2%)nanoprecipitates,∼52%narrow CG bands,and most coarse particles encapsulated by CG bands contribute to the 45%CR sample with outstanding over-all mechanical properties(a tensile strength of 655 MPa,a yield strength of 620 MPa,and an elongation of 15.5%).Microstructure-based strength analysis confirms that the high strength relates to a trade-offbetween the hierarchical features,namely high-volume fraction nanoprecipitates to counterbalance the strength loss caused by grain coarsening.The excellent ductility is due to the introduction of medium CG content with a narrow width that can trigger a cross-scale strain distribution during plastic deforma-tion,suppressing the catastrophic failure in the fine grain(FG)regions and facilitating the dimple fracture along the CG bands.This study proposes a feasible approach for tailoring hierarchical microstructures in Al-Zn-Mg-Cu alloys to achieve a superior strength-ductility combination.展开更多
Bimodal pressure sensors capable of simultaneously detecting static and dynamic forces are essential to medical detection and bio-robotics.However,conventional pressure sensors typically integrate multiple operating m...Bimodal pressure sensors capable of simultaneously detecting static and dynamic forces are essential to medical detection and bio-robotics.However,conventional pressure sensors typically integrate multiple operating mechanisms to achieve bimodal detection,leading to complex device architectures and challenges in signal decoupling.In this work,we address these limitations by leveraging the unique piezotronic effect of Y-ion-doped ZnO to develop a bimodal piezotronic sensor(BPS)with a simplified structure and enhanced sensitivity.Through a combination of finite element simulations and experimental validation,we demonstrate that the BPS can effectively monitor both dynamic and static forces,achieving an on/off ratio of 1029,a gauge factor of 23,439 and a static force response duration of up to 600 s,significantly outperforming the performance of conventional piezoelectric sensors.As a proof-of-concept,the BPS demonstrates the continuous monitoring of Achilles tendon behavior under mixed dynamic and static loading conditions.Aided by deep learning algorithms,the system achieves 96%accuracy in identifying Achilles tendon movement patterns,thus enabling warnings for dangerous movements.This work provides a viable strategy for bimodal force monitoring,highlighting its potential in wearable electronics.展开更多
AZ31 Mg alloy plates with bimodal grain structures were fabricated via conventional extrusion under varying temperatures and speeds to investigate the mechanisms governing dynamic recrystallization(DRX)and texture evo...AZ31 Mg alloy plates with bimodal grain structures were fabricated via conventional extrusion under varying temperatures and speeds to investigate the mechanisms governing dynamic recrystallization(DRX)and texture evolution.Although all samples exhibited similar DRXed grain sizes(5.0–6.5μm)and fractions(76%–80%),they developed distinct c-axis orientations and mechanical properties.The P1 sample(350℃,0.1 mm/min)exhibited the lowest yield strength(∼192 MPa)but the highest elongation(∼18.2%),whereas the P3 sample(400℃,0.6 mm/min)showed the highest yield strength(∼241 MPa)and the lowest elongation(∼14.2%).The P2 sample(400℃,0.1 mm/min)demonstrated intermediate behavior(∼226 MPa,∼17.7%).These variations were primarily attributed to differences in c-axis orientations,particularly their alignment with respect to the normal direction(ND)and their slight deviation from the extrusion direction(ED).Microstructural analysis revealed that distinct DRX mechanisms were activated under different extrusion conditions.P1 predominantly exhibited twinning-induced dynamic recrystallization(TDRX)and continuous dynamic recrystallization(CDRX),whereas P3 primarily showed CDRX and discontinuous dynamic recrystallization(DDRX).These DRX mechanisms,in combination with the activated slip systems governed by the evolving local stress state,collectively contributed to orientation rotation and texture development.During the early stage of extrusion,tensile strain along the ED promoted basalslip,rotating the c-axes toward the ND.As deformation progressed,compressive strain along the ND became dominant.In P1,basalslip remained active,aligning the c-axes along the ND and forming a smaller angle with the ED.In contrast,P3 exhibited predominant pyramidal<c+a>slip,resulting in a pronounced deviation of the c-axes from the ND and a slightly larger angle relative to the ED.The P2 sample exhibited a transitional texture state between those of P1 and P3.展开更多
In this study,the power generation difference between the east-west and the north-south orientation of the vertically installed heterojunction solar cell(HJT)modules was deeply discussed.East-west oriented HJT module ...In this study,the power generation difference between the east-west and the north-south orientation of the vertically installed heterojunction solar cell(HJT)modules was deeply discussed.East-west oriented HJT module has 30%higher power generation,especially in desert photovoltaic(PV)with a bimodal distribution.While the south-north one has a single peak,the same as normal PV modules.Vertical power generation technology of HJT also has less land occupation,which is of great significance for optimizing the design of photovoltaic systems.展开更多
Magnesium(Mg)alloys typically suffer from cold brittleness at cryogenic temperatures(CT),where strength significantly increases and ductility decreases with decreasing temperature.This study investigates the improveme...Magnesium(Mg)alloys typically suffer from cold brittleness at cryogenic temperatures(CT),where strength significantly increases and ductility decreases with decreasing temperature.This study investigates the improvement of the strength-ductility balance at CT in Mg-3.6Y(wt.%)alloys with a bimodal grain structure,consisting of fine dynamically recrystallized(DRXed)grains and elongated unDRXed grains.The results demonstrate that the sample with∼50%DRXed region fraction achieves a remarkable strength-ductility synergy at CT.Dislocation strengthening in the unDRXed regions and grain boundary strengthening in the DRXed regions increase the tensile yield strength(TYS)by 1.6 times at CT compared to room temperature(RT).Concurrently,activation of{10¯12}tensile twinning and non-basal slip systems in DRXed regions,including prismatic a and pyramidal I c+a slips,along with abnormal pyramidal slip within unDRXed grains,reduces fracture elongation by only 1%relative to RT.Furthermore,the bimodal grain structure effectively alleviates strain localization through strain partitioning between DRXed and unDRXed grains,leading to the formation of interface-affected zones(IAZs)that promote the accumulation of geometrically necessary dislocations(GNDs)and enhance hetero-deformation-induced(HDI)hardening.At CT,the IAZs become wider and more pronounced,indicating enhanced GND accumulation that promotes stronger strain partitioning and more effective HDI strengthening.This work demonstrates that the bimodal grain structure is an effective approach to overcoming the low-temperature brittleness of Mg alloys,providing valuable insights for the design of high-performance materials for cryogenic applications.展开更多
Through the innovative integration of semi-solid rheo-casting with extrusion shear process,the short-process fabrication of low-alloyed wrought Mg-2Zn-1Mn alloy is achieved in this study.Uniaxial tensile testing of lo...Through the innovative integration of semi-solid rheo-casting with extrusion shear process,the short-process fabrication of low-alloyed wrought Mg-2Zn-1Mn alloy is achieved in this study.Uniaxial tensile testing of low-temperature extrusion shear specimens(200℃)demonstrates the exceptional strength-ductility synergy,yield strength of 277 MPa,yield strength ratio of 0.95,and elongation of 24%.Microstructural observations reveal the mechanisms underlying its high strength-plasticity synergy at room temperature.This study investigates the effects of different temperature gradients on the microstructure by analyzing experiments conducted at three temperatures:300℃,250℃,and 200◦C.Ultimately,the formation mechanism of the bimodal microstructure obtained at 200℃ is elucidated.The distinctive crystallographic texture oriented at 34°relative to the loading axis direction effectively mitigates stress concentration by inducing the synergistic activation of multiple slip systems.Furthermore,the transition trends of different slip systems and texture evolution during tensile deformation are validated through Visco-Plastic Self-Consistent(VPSC)simulations and corroborated by microstructural analysis.With geometrically necessary dislocation(GND)density(4.28×10^(15)m^(-2))and pyramidal slip activation(~45%).This study has successfully broken through the bottleneck of strength-ductility trade-off in magnesium alloys,providing theoretical support for the development of high-reliability magnesium alloys.展开更多
Overcoming the strength and ductility trade-off is conducive to expanding the application prospects of the Mg matrix composites.A new approach of using the master alloy containing particulate reinforcements to achieve...Overcoming the strength and ductility trade-off is conducive to expanding the application prospects of the Mg matrix composites.A new approach of using the master alloy containing particulate reinforcements to achieve the strength and ductility synergy in the Mg matrix composites was proposed,which can induce the grain size bimodal structure by regulating the dynamic recrystallization(DRX).Specifically,a novel AlN-Al master alloy was prepared via powder metallurgy to fabricate the AlN/ZK60 composite,and the effects of adding the AlN-Al master alloy on microstructure evolution related to the strength and ductility synergy in the composite were thoughtfully investigated,involving precipitation,grain size,and DRX behavior.The reaction between the Al in the master alloy and the Zr in the ZK60 Mg alloy suppressed the grain refinement,and the coarse grains were further formed after the solution treatment on the as-cast composite.Subsequently,deformation heterogeneity between the AlN and Mg matrix during the hot extrusion induced discontinuous dynamic recrystallization(DDRX)and promoted fine grain fraction.The combination formed the bimodal structure in the AlN/ZK60 composite,and coarse and fine grains acted as hard and soft zones,respectively,during the room temperature deformation.The hard zone was enhanced by the basal texture strengthening,and the ductility was improved due to the promotion of the basalslipping in the soft zone,jointly leading to the strength and ductility synergy in the AlN/ZK60 composite for the ultimate tensile strength increased by ~7.4%while maintaining the same elongation compared with the ZK60 Mg alloy.展开更多
The ordered bimodal mesoporous silica MCM-48 spheres were facile synthesized by mild- temperature post-synthesis H2O2 hydrothermal treatment of as-synthesized MCM-48. The results showed that H2O2 is indispensable for ...The ordered bimodal mesoporous silica MCM-48 spheres were facile synthesized by mild- temperature post-synthesis H2O2 hydrothermal treatment of as-synthesized MCM-48. The results showed that H2O2 is indispensable for simultaneously removing organic templates and forming ordered bimodal mesoporous silica MCM-48 spheres. The bimodal mesoporous MCM-48 was characterized by X-ray diffraction, transmission electron micrographs, FT-IR, and N2 adsorption-desorption, and a possible mechanism was proposed for the formation of bimodal mesoporous MCM-48.展开更多
基金supported by the National Basic Research Program of China (Grant No.2010CB428602)the National Natural Science Foundation of China (Grant No.40830102)
文摘The South Asia High （SAH） is the dominant feature of the circulation in the upper troposphere and lower stratosphere （UTLS） during the boreal summer, and the upper tropospheric anticyclonic circulation extends into the lower stratosphere. The preferred locations of the center of the SAH occur in two different regions, and the center can be located over the Iranian Plateau or over the Tibetan Plateau. This bimodality has an impact on the distribution of chemical constituents in the UTLS region. We analyzed water vapor （H20）, carbon monoxide （CO）, and ozone （03） data derived from the Aura Microwave Limb Sounder （MLS） and total column ozone data from the Ozone Monitoring Instrument （OMI）. For the Iranian Plateau mode of the SAH, the tropospheric tracers exhibited a positive anomaly over the Iranian Plateau and a negative anomaly over the Tibetan Plateau, whereas the stratospheric tracer exhibited a negative and a positive anomaly over the Iranian Plateau and the Tibetan Plateau, respectively. For the Tibetan Plateau mode, however, the distribution of the anomaly was the reverse of that found for the chemical species in the UTLS region. Furthermore, the locations of the extrema within the anomaly seemed to differ across chemical species. The anomaly extrema for H20 occurred in the vicinity of the SAH ridgeline, whereas CO and O3 exhibited a northward shift of 4-8 degrees. These impacts of the variation in the SAH on the chemical constitutes in the UTLS region can be attributed in part to the dynamical structure delineated by the tropopause field and the temperature field at 100 hPa.
基金jointly supported by the National Basic Research Program of China(973 Program)Grant 2007CB411806the National Natural Science Foundation of China(NSFC)Grant Nos.40675049 and 40821092
文摘The observed South Asia High （SAH） center is characterized by two distinctive equilibrium modes during boreal midsummer, namely the center of SAH is located between 82.5°-92.5°E for the Tibetan Plateau mode and between 55°-65°E for the Iranian Plateau mode respectively. The present study describes the ability of 15 coupled general circulation models （CGCM） used in the Intergovernmental Panel on Climate Change＇s （IPCC） 4th Assessment Report to reproduce the observed bimodality of the SAH. These models reveal a wide range of skill in simulating this bimodality. Nearly half of the models reproduced the bimodality, while the other half of the models did not simulate well these two modes whereas usually preferring one mode, The models that reproduced the bimodality of the SAH present similar horizontal and vertical circulations as those features from the NCEP reanalysis data. The results from these models identify the warm characteristics of the SAH and indicate that these two modes have different dynamic and thermodynamic properties. Different characteristics of the simulated sensible heat and latent heat related to precipitation partly contribute to the difference in the simulations of the SAH bimodality. The majority of these models that prefer to simulate the Tibetan Plateau mode produce a small sensible heat flux difference between the Iranian Plateau and the Tibetan Plateau, and also generally simulate a very strong false precipitation center over the east of the Tibetan Plateau, which indicates strong latent release and thereby contributes to the preference of the SAH center on the Tibetan Plateau. Whereas, the models that reproduce the bimodality of the SAH tend to simulate large precipitation over the southern Himalayas and no obviously false precipitation is produced over the east of the Tibetan Plateau. In addition, the model＇s resolution may also have important impacts on the simulations of precipitation.
文摘In recent years,metal matrix syntactic foams(MMSFs)have become highly attractive owing to their unique physical,microstructural and mechanical features.Due to their promising potential for different industrial areas like automotive,aviation,and defense,these advanced engineering materials can also be evaluated as serious alternatives to particle reinforced metallic composites and conventional metallic foams.Differently from previously reported laboratory scaled techniques in the literature,this experimental effort focuses on the feasibility of MMSF manufacturing via a fully automated and industrial-based cold chamber die casting technique.Accordingly,1-2 mm,2-4 mm,and bimodal(50vol.%)natural-based pumice filled aluminum syntactic foams were manufactured utilizing a purpose-made casting machine.Physical,macroscopic,and microscopic examinations show that all of the fabricated samples display perfect matrix/filler harmony.Average density levels of fabricated syntactic foams range between 1.50 and 1.80 g·cm^(-3) depending upon the pumice particles size interval.To assess mechanical responses,quasi-static compression tests were performed.Furthermore,half of the foam samples were subjected to heat treatment to explore possible influences of aging on the compressive features and damage modes.Results indicate that although the heat treatment enhances the compressive strength,plateau stress,and energy absorption properties of the fabricated foams,it changes damage mode of the samples by causing brittle dominant deformation.
基金The Zhejiang Provincial Natural Science Foundation of China under contract No.Y5110187the Scientific Research Fund of the Second Institute of Oceanography,State Oceanic Administration(SOA)of China under contract No.JG1204+1 种基金the Youth Ocean Science Foundation of SOA under contract No.2012724the Public Science and Technology Research Funds Projects of Ocean from SOA of China under contract No.201105009
文摘Combined conductivity-temperature-depth （CTD） casts and Argo profiles, 3 086 historical hydrocasts were used to quantify the water column characteristics in the northern South China Sea （SCS） and its adjacent waters. Based on a two-dimensional ＂gravest empirical mode＂ （GEM）, a gravitational potential （4, a vertically integrated variable） was used as proxy for the vertical temperature profiles TG（P, φ）. φ integrated from 8 MPa to the surface shows a close relationship with the temperature, except in the deep layer greater than 15 MPa, which was caused by the bimodal deep water in the region. The GEM temperature profiles successfully revealed the bimodality of the Luzon Strait deep water, that disparate hydrophic vertical profiles can produce distinct specific volume anomaly （δ） in the SCS and the western Philippine Sea （WPS）, but failed in the Luzon Strait, where different temperature profiles may produce a same 6. A significant temperature divergence between the SCS water and the WPS water confirmed that the bimodal structure is strong. The deepwater bifurcation starts at about 15 MPa, and gets stronger with increasing depth. As the only deep channel connecting the bimodal-structure waters, water column characteristics in the Luzon Strait is in between, but much closer to the SCS water because of its better connectivity with the SCS. A bimodal temperature structure below 15 MPa reveals that there was a persistent baroclinic pressure gradient driving flow through the Luzon Strait. A volume flux predicted through the Bashi Channel with the hydraulic theory yields a value of 5.62×10^6 m^3/s using all available profiles upstream and downstream of the overflow region, and 4.03×10^6 and 2.70×10^6 m^3/s by exclusively using the profiles collected during spring and summer, respectively. No volume flux was calculated during autumn and winter because profiles are only available for the upstream of the Bashi Channel during the corresponding period.
基金financially supported by the Natural Science Foundation of Changsha,China(No.kq2402015)the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIP)(Nos.NRF-2021R1A2C3006662 and NRF-2022R1A5A1030054)supported by Brain Pool Program through the NRF of Korea,funded by the Ministry of Science and ICT(No.NRF-RS_(2)02300263999)
文摘Lightweight,high-strength,and heat-resistant protective structures have consistently been crucial for applications in extreme environments,such as aerospace,semiconductors,and nuclear power industries.Multilayered TC4/TB8 titanium(Ti)laminates,inspired by theheterostructures of natural biological shells,were fabricated using a hybrid diffusion bonding-hot rolling process followed by an aging treatment,resulting in an architected micro structure.The laminate achieves an ultra-high yield stress of 1020 MPa and proper uniform elongation of 4.2%at 500℃.The TB8 layers with high-density nano-precipitates and dislocations act as hard zone,contributing to high strength.The TC4 layers,with their bimodal structure consisting of coarse and fine grains characterized by equiaxed and lamellar structures,experience more plastic strain than the TB8 layers.The hetero deformation associated with the detwinning ofαgrains in the TC4 layer induces toughening at high temperatures.
基金supported by the National Natural Science Foundation of China(Nos.U1960115 and U21A20116)the Fundamental Research Funds for the Central Universities(No.N232405-10)Special thanks are due to the instrumental and data analysis from Analytical and Testing Center,Northeastern University.
文摘The trade-offbetween strength and ductility remains a persistent obstacle in the development of advanced structural materials.In the present study,a novel dual-heterogeneous structure with a bimodal grain distribution in both ferrite and austenite phases was fabricated via cold rolling and partial recrystallization annealing on solution-treated 2205 duplex stainless steel(DSS).The processed steel exhibited superior mechanical properties,with the yield strength increasing from 586 MPa to 903 MPa,and the ultimate tensile strength from 796 MPa to 1082 MPa,while maintaining a high total elongation of 35.3%.Based on in-situ electron backscatter diffraction(EBSD)and scanning electron microscope(SEM)analyses,the microstructural deformation behavior and strengthening mechanisms of the dual-heterostructured 2205 DSS were elucidated.The outstanding combination of strength and ductility was ascribed to the synergistic effects of grain refinement,dislocation strengthening,and hetero-deformation induced(HDI)strengthening.Moreover,the high ductility in DSS was attributed to the coactivation of cross-slip systems in ferrite{110}and{112}along with the single-slip systems in austenite{111}.These findings provide a new strategy for the design and development of high-strength and ultra-high-strength DSSs.
基金financially supported by the National Natural Science Foundation of China(Nos.52161019 and 52271054)the Science and Technology Project of Guizhou Province,China(No.[2023]047)+1 种基金the GuiZhou DIIT Innovation Project(No.[2023]153)the One Hundred Person Project of Guizhou Province,China(No.[2020]6006).
文摘In this work,a heterogeneous structure(HS)with an alternating distribution of coarse and fineαlamella is fabricated in bimodal Ti6242 alloy via insufficient diffusion of alloying elements induced by fast heat-ing treatment.Instead of a distinct interface between the primaryα_(p)hase(α_(p))andβ_(t)ransformation microstructure(β_(t))in the equiaxed microstructure(EM),allα_(p)/β_(t)interfaces are eliminated in the HS,and the largeα_(p)phases are replaced by coarseαlamella.Compared to the EM alloy,the heterostruc-tured alloy exhibits a superior strength-ductility combination.The enhanced strength is predominantly attributed to the increased interfaces ofα/βplates and hetero-deformation induced(HDI)strengthening caused by back stress.Meanwhile,good ductility is ascribed to its uniform distribution of coarse and fineαlamella,which effectively inhibits strain localization and generates an extra HDI hardening.This can be evidenced by the accumulated geometrically necessary dislocations(GNDs)induced by strain partitioning of the heterostructure.Significantly,the HDI causes extra<c+a>dislocations piling up in the coarseαlamella,which generates an extra strain hardening to further improve the ductility.Such hetero-interface coordinated deformation mechanism sheds light on a new perspective for tailoring bimodal titanium al-loys with excellent mechanical properties.
基金supported by the National Key R&D Program of China(No.2021YFB3400900)the National Natural Science Foundation of China(Nos.52175373,52205435)+1 种基金Natural Science Foundation of Hunan Province,China(No.2022JJ40621)the Innovation Fund of National Commercial Aircraft Manufacturing Engineering Technology Center,China(No.COMACSFGS-2022-1875)。
文摘A new unified constitutive model was developed to predict the two-stage creep-aging(TSCA)behavior of Al-Zn-Mg-Cu alloys.The particular bimodal precipitation feature was analyzed and modeled by considering the primary micro-variables evolution at different temperatures and their interaction.The dislocation density was incorporated into the model to capture the effect of creep deformation on precipitation.Quantitative transmission electron microscopy and experimental data obtained from a previous study were used to calibrate the model.Subsequently,the developed constitutive model was implemented in the finite element(FE)software ABAQUS via the user subroutines for TSCA process simulation and the springback prediction of an integral panel.A TSCA test was performed.The result shows that the maximum radius deviation between the formed plate and the simulation results is less than 0.4 mm,thus validating the effectiveness of the developed constitutive model and FE model.
基金Corresponding author:Jiang Haitao,Ph.D.,Professor,Institute of Engineering Technology,University of Science and Technology Beijing,Beijing 102206,P.R.China,Tel:0086-10-62332598,E-mail:jianght@ustb.edu.cn。
文摘AZ31 magnesium alloy was used as the object of study to fabricate an alloy with the bimodal grain structure using singlepass hot rolling,and to explore how this structure enhances the strength and plasticity of the alloy.The results show that the formation of the bimodal grain structure is more pronounced at rolling temperatures ranging from 350°C to 450°C,especially under conditions of large reduction(≥40%).The optimized proportion and distribution of the bimodal grain structure play a pivotal role in simultaneously enhancing the strength and ductility of the alloy,significantly impacting the mechanical properties.The rolled sheet with the bimodal grain structure achieves an ultimate tensile strength of 258.3 MPa and an elongation of 17.1%under a rolling reduction of 40%with the rolling rate of 75 m/min and rolling temperature of 400°C.Adjusting rolling parameters,including temperature,reduction ratio and rolling rate,is crucial for optimizing the bimodal grain structure,thereby achieving a balance between plasticity improvement and high strength maintenance.
基金supported by grants from Capital’s Funds for Health Improvement and Research(No.2022-1-2023)the National Natural Science Foundation of China(No.82371148)Open project National Clinical Research Center for Otolaryngologic Diseases(202200010).
文摘PurposeThe purpose of the study was to investigate the effect of bimodal beamforming on speech recognition and comfort for cochlear implant (CI) users with the bimodal hearing solution made up by linking a hearing aid to the CI sound processor.Methods19 subjects participated in this study. Speech tests were conducted in quiet and in noisy environments, with the target speech presented from 0° and the noise signal from 45°. Speech recognition thresholds (SRTs) were compared among the previously used bimodal hearing configuration (baseline, any CI sound processor plus any hearing aid), the Naída Bimodal Hearing Solution with omnidirectional microphone, and with directional microphone (so called StereoZoom) switched on. In addition, the study participants provided subjective feedback on their hearing impressions.ResultsThe SRT results showed no significant difference among the three hearing conditions in the quiet environment. No significant improvement was reported when using Naída bimodal system with omnidirectional microphone in noise compared to the baseline (p=0.27). When applying StereoZoom, SRT in noise showed significant improvements compared to omnidirectional settings (p<0.05). Subjective feedback showed that 13 participants were satisfied with Naída Bimodal Hearing Solution, and wanted to continue using it after the trial.ConclusionThe Naída Bimodal Hearing Solution with the same pre-processing algorithm can provide satisfying hearing performance. Beamforming technology can further improve speech perception in noisy environments.
基金supported by the China Geological Survey Program(Grant No.DD20220989)the National Natural Science Foundation of China(Grant No.41972118)。
文摘The tectonic setting of the Himalaya during the Early Paleozoic has been a subject of enduring debate within the scientific community.Newly discovered bimodal intrusive rocks from comprehensive field geological investigation in the central mountain range were subjected to petrology,zircon U-Pb geochronology,zircon Hf isotopes and whole-rock geochemistry analyses.The Palie bimodal intrusive rocks,comprising amphibolite and granitic gneiss,were formed at~489 Ma.The amphibolite exhibits geochemical characteristics consistent with N-MORB,while the granitic gneiss is classified as high potassium calc-alkaline peraluminous S-type granite.Both igneous rocks exhibit negative zirconε_(Hf)(t)values and display ancient T_(DM)^(C)ages.In conjunction with regional geological survey findings,it can be inferred that the formation of the Palie bimodal intrusive rocks occurred within a post-collision extensional tectonic setting.The amphibolite genesis involved partial melting of an enriched lithospheric mantle with some crustal assimilation,whereas the origin of the granitic gneiss can be attributed to partial melting of pre-existing felsic crust.Our data indicate that during the Early Paleozoic,the Himalaya underwent a transition from a pan-African collisional setting to post-collisional extensional tectonics.
基金supported by the funding from the Shi Changxu Innovation Center for Advanced Materials(No.SCXKFJJ202210)the National Natural Science Foundation of China(No.52271043)+2 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2021193)the Liaoning Province Excellent Youth Foundation(No.2024JH3/10200021)the Liaoning Revitalization Talents Program(No.XLYC2403094).
文摘For a long time,the conventional superplastic forming temperature for Ti alloys is generally too high(~900-920℃),which leads to too long production cycles,heavy surface oxidation,and property reduction.In this study,an ultrafine bimodal microstructure,consisting of ultrafine equiaxed microstructure(0.66μm)and 43.3%lamellar microstructure,was achieved in the Ti-6Al-4V alloy by friction stir processing(FSP).The low-temperature superplastic behavior and deformation mechanism of the FSP Ti-6Al-4V alloy were investigated at temperatures of 550-675℃and strain rates ranging from 1×10^(−4)to 3×10^(−3)s^(−1).The FSP alloy exhibited superplastic elongations of>200%at the temperature range from 550 to 650℃,and an optimal superplastic elongation of 611%was achieved at 625℃and 1×10^(−4)s^(−1).This is the first time to report the low-temperature superplasticity of the bimodal microstructure in Ti alloys.Grain boundary sliding was identified as the dominant deformation mechanism,which was effectively accommodated by the comprehensive effect of dislocation-inducedβphase precipitation and dynamic spheroidization of the lamellar structure.This study provides a novel insight into the low-temperature superplastic deformation behavior of the bimodal microstructure.
基金supported by the Key Laboratory Fund of National Key Laboratory of Science and Technology on High-strength Structural Materials(Nos.412130024,623020031)the Pre-research Fund(No.412130024).
文摘The strength improvement in the heat-treatable Al-Zn-Mg-Cu alloys is generally achieved by increasing the volume fraction of nanoprecipitates and reducing the grain size.However,utilizing one of them usu-ally leads to a drastic decrease in ductility.Herein,we architect a hierarchical microstructure integrating bimodal grain structures,nanoprecipitates,and hard-brittle coarse particles wrapped by ductility coarse grain(CG)bands via conventional cold rolling(CR)deformation and heat treatment methods to break the strength-ductility dilemma in the Al-8.89Zn-1.98Mg-2.06Cu-0.12Zr-0.05Sc-0.05Hf(wt.%)alloy.The results reveal that the coupling of high-volume fraction(∼1.2%)nanoprecipitates,∼52%narrow CG bands,and most coarse particles encapsulated by CG bands contribute to the 45%CR sample with outstanding over-all mechanical properties(a tensile strength of 655 MPa,a yield strength of 620 MPa,and an elongation of 15.5%).Microstructure-based strength analysis confirms that the high strength relates to a trade-offbetween the hierarchical features,namely high-volume fraction nanoprecipitates to counterbalance the strength loss caused by grain coarsening.The excellent ductility is due to the introduction of medium CG content with a narrow width that can trigger a cross-scale strain distribution during plastic deforma-tion,suppressing the catastrophic failure in the fine grain(FG)regions and facilitating the dimple fracture along the CG bands.This study proposes a feasible approach for tailoring hierarchical microstructures in Al-Zn-Mg-Cu alloys to achieve a superior strength-ductility combination.
基金financially supported by the National Natural Science Foundation of China(No.U2330120)the Natural Science Foundation of Sichuan Province of China(No.2023NSFSC0313)the Basic Research Cultivation Project of Southwest Jiaotong University(No.2682023KJ024)。
文摘Bimodal pressure sensors capable of simultaneously detecting static and dynamic forces are essential to medical detection and bio-robotics.However,conventional pressure sensors typically integrate multiple operating mechanisms to achieve bimodal detection,leading to complex device architectures and challenges in signal decoupling.In this work,we address these limitations by leveraging the unique piezotronic effect of Y-ion-doped ZnO to develop a bimodal piezotronic sensor(BPS)with a simplified structure and enhanced sensitivity.Through a combination of finite element simulations and experimental validation,we demonstrate that the BPS can effectively monitor both dynamic and static forces,achieving an on/off ratio of 1029,a gauge factor of 23,439 and a static force response duration of up to 600 s,significantly outperforming the performance of conventional piezoelectric sensors.As a proof-of-concept,the BPS demonstrates the continuous monitoring of Achilles tendon behavior under mixed dynamic and static loading conditions.Aided by deep learning algorithms,the system achieves 96%accuracy in identifying Achilles tendon movement patterns,thus enabling warnings for dangerous movements.This work provides a viable strategy for bimodal force monitoring,highlighting its potential in wearable electronics.
基金supported by National Key Research&Development Program of China(Grant no.2022YFE0110600)National Natural Science Foundation(Grant no.52220105003)+3 种基金the State Key Laboratory of Advanced Welding and Joining,Harbin Institute of Technology(Grant no.XNDCQQ2910201124)the National Natural Science Foundation for Young Scientists of China(Grant nos.51801042 and 51704088)Natural Science Foundation of Heilongjiang Province-Outstanding Youth Fund(Grant no.YQ2020E006)JSPS KAKENHI(Grant no.JP21H01669).
文摘AZ31 Mg alloy plates with bimodal grain structures were fabricated via conventional extrusion under varying temperatures and speeds to investigate the mechanisms governing dynamic recrystallization(DRX)and texture evolution.Although all samples exhibited similar DRXed grain sizes(5.0–6.5μm)and fractions(76%–80%),they developed distinct c-axis orientations and mechanical properties.The P1 sample(350℃,0.1 mm/min)exhibited the lowest yield strength(∼192 MPa)but the highest elongation(∼18.2%),whereas the P3 sample(400℃,0.6 mm/min)showed the highest yield strength(∼241 MPa)and the lowest elongation(∼14.2%).The P2 sample(400℃,0.1 mm/min)demonstrated intermediate behavior(∼226 MPa,∼17.7%).These variations were primarily attributed to differences in c-axis orientations,particularly their alignment with respect to the normal direction(ND)and their slight deviation from the extrusion direction(ED).Microstructural analysis revealed that distinct DRX mechanisms were activated under different extrusion conditions.P1 predominantly exhibited twinning-induced dynamic recrystallization(TDRX)and continuous dynamic recrystallization(CDRX),whereas P3 primarily showed CDRX and discontinuous dynamic recrystallization(DDRX).These DRX mechanisms,in combination with the activated slip systems governed by the evolving local stress state,collectively contributed to orientation rotation and texture development.During the early stage of extrusion,tensile strain along the ED promoted basalslip,rotating the c-axes toward the ND.As deformation progressed,compressive strain along the ND became dominant.In P1,basalslip remained active,aligning the c-axes along the ND and forming a smaller angle with the ED.In contrast,P3 exhibited predominant pyramidal<c+a>slip,resulting in a pronounced deviation of the c-axes from the ND and a slightly larger angle relative to the ED.The P2 sample exhibited a transitional texture state between those of P1 and P3.
文摘In this study,the power generation difference between the east-west and the north-south orientation of the vertically installed heterojunction solar cell(HJT)modules was deeply discussed.East-west oriented HJT module has 30%higher power generation,especially in desert photovoltaic(PV)with a bimodal distribution.While the south-north one has a single peak,the same as normal PV modules.Vertical power generation technology of HJT also has less land occupation,which is of great significance for optimizing the design of photovoltaic systems.
基金supported by National Key Research&Development Program of China[grant number 2022YFE0110600]National Natural Science Foundation[grant number 52220105003]the State Key Laboratory of Advanced Welding and Joining,Harbin Institute of Technology[grant number XNDCQQ2910201124].
文摘Magnesium(Mg)alloys typically suffer from cold brittleness at cryogenic temperatures(CT),where strength significantly increases and ductility decreases with decreasing temperature.This study investigates the improvement of the strength-ductility balance at CT in Mg-3.6Y(wt.%)alloys with a bimodal grain structure,consisting of fine dynamically recrystallized(DRXed)grains and elongated unDRXed grains.The results demonstrate that the sample with∼50%DRXed region fraction achieves a remarkable strength-ductility synergy at CT.Dislocation strengthening in the unDRXed regions and grain boundary strengthening in the DRXed regions increase the tensile yield strength(TYS)by 1.6 times at CT compared to room temperature(RT).Concurrently,activation of{10¯12}tensile twinning and non-basal slip systems in DRXed regions,including prismatic a and pyramidal I c+a slips,along with abnormal pyramidal slip within unDRXed grains,reduces fracture elongation by only 1%relative to RT.Furthermore,the bimodal grain structure effectively alleviates strain localization through strain partitioning between DRXed and unDRXed grains,leading to the formation of interface-affected zones(IAZs)that promote the accumulation of geometrically necessary dislocations(GNDs)and enhance hetero-deformation-induced(HDI)hardening.At CT,the IAZs become wider and more pronounced,indicating enhanced GND accumulation that promotes stronger strain partitioning and more effective HDI strengthening.This work demonstrates that the bimodal grain structure is an effective approach to overcoming the low-temperature brittleness of Mg alloys,providing valuable insights for the design of high-performance materials for cryogenic applications.
基金the financial support from Basic Research Projects of Higher Education Institutions of Liaoning Province(Key Research Projects)(No.JYTZD2023108)General Project of Liaoning Provincial Department of Education(Nos.LJKMZ20220462 and JYTMS20231199).
文摘Through the innovative integration of semi-solid rheo-casting with extrusion shear process,the short-process fabrication of low-alloyed wrought Mg-2Zn-1Mn alloy is achieved in this study.Uniaxial tensile testing of low-temperature extrusion shear specimens(200℃)demonstrates the exceptional strength-ductility synergy,yield strength of 277 MPa,yield strength ratio of 0.95,and elongation of 24%.Microstructural observations reveal the mechanisms underlying its high strength-plasticity synergy at room temperature.This study investigates the effects of different temperature gradients on the microstructure by analyzing experiments conducted at three temperatures:300℃,250℃,and 200◦C.Ultimately,the formation mechanism of the bimodal microstructure obtained at 200℃ is elucidated.The distinctive crystallographic texture oriented at 34°relative to the loading axis direction effectively mitigates stress concentration by inducing the synergistic activation of multiple slip systems.Furthermore,the transition trends of different slip systems and texture evolution during tensile deformation are validated through Visco-Plastic Self-Consistent(VPSC)simulations and corroborated by microstructural analysis.With geometrically necessary dislocation(GND)density(4.28×10^(15)m^(-2))and pyramidal slip activation(~45%).This study has successfully broken through the bottleneck of strength-ductility trade-off in magnesium alloys,providing theoretical support for the development of high-reliability magnesium alloys.
基金the funding supported by the National Natural Science Foundation of China(No.52161145407,52175285,52305335,52171097).
文摘Overcoming the strength and ductility trade-off is conducive to expanding the application prospects of the Mg matrix composites.A new approach of using the master alloy containing particulate reinforcements to achieve the strength and ductility synergy in the Mg matrix composites was proposed,which can induce the grain size bimodal structure by regulating the dynamic recrystallization(DRX).Specifically,a novel AlN-Al master alloy was prepared via powder metallurgy to fabricate the AlN/ZK60 composite,and the effects of adding the AlN-Al master alloy on microstructure evolution related to the strength and ductility synergy in the composite were thoughtfully investigated,involving precipitation,grain size,and DRX behavior.The reaction between the Al in the master alloy and the Zr in the ZK60 Mg alloy suppressed the grain refinement,and the coarse grains were further formed after the solution treatment on the as-cast composite.Subsequently,deformation heterogeneity between the AlN and Mg matrix during the hot extrusion induced discontinuous dynamic recrystallization(DDRX)and promoted fine grain fraction.The combination formed the bimodal structure in the AlN/ZK60 composite,and coarse and fine grains acted as hard and soft zones,respectively,during the room temperature deformation.The hard zone was enhanced by the basal texture strengthening,and the ductility was improved due to the promotion of the basalslipping in the soft zone,jointly leading to the strength and ductility synergy in the AlN/ZK60 composite for the ultimate tensile strength increased by ~7.4%while maintaining the same elongation compared with the ZK60 Mg alloy.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20872135） and the China National Tobacco Corporation （No.110200701007）.
文摘The ordered bimodal mesoporous silica MCM-48 spheres were facile synthesized by mild- temperature post-synthesis H2O2 hydrothermal treatment of as-synthesized MCM-48. The results showed that H2O2 is indispensable for simultaneously removing organic templates and forming ordered bimodal mesoporous silica MCM-48 spheres. The bimodal mesoporous MCM-48 was characterized by X-ray diffraction, transmission electron micrographs, FT-IR, and N2 adsorption-desorption, and a possible mechanism was proposed for the formation of bimodal mesoporous MCM-48.
