To objectively verify microstructural heredity in a rare-earth magnesium alloy during heat-treatment and deformation processes under pulsed current condition,we proposed a pulsed current method during homogenization a...To objectively verify microstructural heredity in a rare-earth magnesium alloy during heat-treatment and deformation processes under pulsed current condition,we proposed a pulsed current method during homogenization and rolling processes.We then compared the macroscopic edge cracks,microstructures,and mechanical properties of sheets which were formed using pulsed homogenization(PH)/industrial homogenization(IH)followed by hot rolling(HR)/electroplastic rolling(ER).The results showed that the PH+ER forming method produced an alloy with the most obviously enhanced deformation ability,with the tensile strength increasing from 145 MPa(IH+HR)to 266 MPa(PH+ER).Inside the PH+ER sample,the nonthermal and thermal effects of the pulsed current promoted atomic diffusion,regulating the proportion and morphology of the secondary phase,thereby improving the forming ability of the material.展开更多
The complex characteristics of thin-walled parts fabricated by laser powder bed fusion(LPBF),particularly the dependence of their microstructures on wall thickness and scanning strategies,pose significant challenges f...The complex characteristics of thin-walled parts fabricated by laser powder bed fusion(LPBF),particularly the dependence of their microstructures on wall thickness and scanning strategies,pose significant challenges for this technology.This paper presents a predictive model for microstructural evolution of LPBF-fabricated thin-walled components,integrating three-dimensional cellular automaton(CA)with finite element(FE)analysis.The FE method is employed to solve the temperature field of thin-walled components during LPBF,and the resulting temperature history is used to predict micro-structural evolution in the CA model.Experimental validation via electron back scatter diffraction(EBSD)on a 4 mm-thick specimen confirms a high degree of agreement between model predictions and experimental results.The study reveals that when the thickness of samples prepared by LPBF is reduced from 4 mm to 0.4 mm,there is a significant coarsening of grain size.Additionally,grains at the bottom are observed to be coarser compared to those at the top,which is attributed to epitaxial growth and remelting.Furthermore,the study explores microstructural changes induced by manipulating laser power and scanning speed,while maintaining constant energy density.The findings indicate that grain morphology and size remain consistent across varying parameters,emphasizing the dominant influence of energy density.Within a predefined scanning strategy,an upsurge in laser energy density leads to an enlargement of the average grain size.Notably,the implementation of a cross-scanning strategy alters the melt pool orientation,disrupting the directional grain growth and fostering the formation of finer grains.This underscores the crucial significance of processing techniques in LPBF.展开更多
As demand grows for low-carbon ironmaking,it is essential to understand how hydrogen reduces iron ore pellets under vary-ing gangue compositions and gas atmospheres.In this work,fired hematite pellets with a basicity(...As demand grows for low-carbon ironmaking,it is essential to understand how hydrogen reduces iron ore pellets under vary-ing gangue compositions and gas atmospheres.In this work,fired hematite pellets with a basicity(mass ratio of CaO to SiO2)of 0.3 and SiO2contents ranging from 1wt%to 4wt%were systematically investigated under three typical shaft furnace atmospheres(Midrex,HYL,and coke oven gas(COG))as well as under 100%H2,to clarify the reduction kinetics,reaction mechanism,and microstructural evolution of the fired pellets.The results indicate that a higher hydrogen proportion significantly accelerates the reduction rate of the fired pellets,while an increase in SiO2content generally leads to a decrease in the overall reaction rate.However,the effect of hydrogen concentration on the reduction behavior of the fired pellets varied markedly with their silicon content.For the fired pellets containing 1wt%and 2wt%SiO2,an increase in hydrogen concentration causes deterioration in reduced pellet characteristics,as evidenced by the increase in reduc-tion swelling index from 26.14%to 34.26%and the decrease in cold compressive strength from 110 to 78 N.In contrast,fired pellets with 3wt%and 4wt%SiO2exhibit the opposite trend,with the reduction swelling index decreasing from 15.26%to 9.23%and cold compress-ive strength improving from 179 to 271 N.Kinetics analysis indicates that under 100%H2,the reduction of fired pellets with 1wt%SiO2is governed by a mixed gas-diffusion and uniform reaction model,whereas fired pellets with 4wt%SiO2follow an unreacted core model.These differences in reduction kinetics,reduction behavior,and post-reduction properties are closely associated with the formation of more Al-bearing calcium silicate slag phases in high-SiO2reduced pellets,which strengthen intergranular bonding,buffer phase-trans-formation-induced stress,and promote the evolution of metallic iron from whisker-like to granular or layered morphologies.展开更多
Friction stir processing(FSP) has emerged as a transformative solid-state technique for enhancing the mechanical performance and microstructural integrity of metallic materials,particularly in the context of additive ...Friction stir processing(FSP) has emerged as a transformative solid-state technique for enhancing the mechanical performance and microstructural integrity of metallic materials,particularly in the context of additive manufacturing(AM).This study demonstrates the effectiveness of FSP as a post-processing strategy for two distinct AM systems:wire arc additive manufacturing(WAAM) of low-carbon steel and selective laser melting(SLM) of Ti6Al4V alloy.In the case of WAAM fabricated steel,FSP significantly refined the coarse dendritic microstructure into ultrafine equiaxed grains,resulting in a 21 %-24 % increase in hardness and enhanced tensile properties at the overlapping regions.Similarly,for SLM fabricated Ti6Al4V,FSP eliminated the columnar prior-β grains and residual porosity,yielding a homogenous α+β structure with improved strengthductility balance and reduced anisotropy.These improvements were attributed to the dynamic recrystallization,conversion of low-angle to high-angle grain boundaries,and homogenization of phase constituents induced by FSP.Despite challenges such as tool wear and fixturing complexity,the study confirms that FSP can reliably bridge the performance gap in AM components by healing solidification defects,mitigating anisotropy,and tailoring the local microstructure.The findings position FSP as a versatile and scalable post-processing technique,crucial for advancing high-performance,application-ready components in aerospace,biomedical,and structural applications.展开更多
Loess landslides are major hazards in the Chinese Loess Plateau(CLP).The loess in this region is frequently subjected to repeated wetting–drying(W-D)cycles due to climatic factors,which significantly increases the li...Loess landslides are major hazards in the Chinese Loess Plateau(CLP).The loess in this region is frequently subjected to repeated wetting–drying(W-D)cycles due to climatic factors,which significantly increases the likelihood of landslides.Therefore,investigating the shear behavior and microstructural evolution of loess under climate-induced W-D cycles is crucial to understanding the mechanisms of loess landslides.In this study,Malan loess is analyzed using unsaturated triaxial tests,resistivity tests,scanning electron microscopy,and mercury intrusion porosimetry.The test results show that shear strength decreases with increased W-D cycles,and the degradation effect is more pronounced under lower confining pressure.The variations in conductive pathways indicate that electrical resistivity can effectively reflect the structural damage of loess during W-D cycles,which is associated with increased direct point contacts and spaced pores.Aggregation of clay particles and growth of cracks during the W-D cycles can further destabilize the loess microstructure.As the confining pressure increases,crushed particles rearrange and convert spaced pores into intergranular pores.The number and peak intensity of dominant spaced pores decrease,resulting in a more stable structure.This study clarifies the mechanisms of loess landslides under W-D cycles and provides theoretical support for landslide prevention and control in the CLP.展开更多
Silicon carbide fibers are considered ideal reinforcing materials for ceramic matrix composites due to their excellent mechanical properties and high-temperature performance.Different types of fibers necessitate indiv...Silicon carbide fibers are considered ideal reinforcing materials for ceramic matrix composites due to their excellent mechanical properties and high-temperature performance.Different types of fibers necessitate individual investigation due to variations in their composition and fabrication processes.This study presents a comprehensive investigation into evolution of the mechanical properties,surface microstructure,and composition of Shicolon-Ⅱ fibers subjected to argon heat treatment at temperatures ranging from 1300℃to 1700℃.The Shicolon-Ⅱ fibers are composed of small-sized β-SiC grains,SiCxOy amorphous phase,and a minor amount of graphite microcrystals.Following treatment in an argon atmosphere at 1300℃,the fibers maintain a monofilament tensile strength of 3.620 GPa,corresponding to a retention of 98.32%.This strength diminishes to 2.875 GPa,equating to a retention of 78.08%,after treatment at 1500℃.The reduction in mechanical properties of the fibers can be ascribed to the decomposition of the amorphous phase and the growth of β-SiC grains.Furthermore,creep resistance is an essential factor influencing the long-term performance of composite materials.After treatment at temperatures above 1400℃,the high-temperature creep resistance of the fibers is significantly enhanced due to growth of β-SiC grains.This study offers valuable theoretical insights into high-temperature applications of second-generation fibers,contributing to an enhanced understanding of their performance under extreme conditions.展开更多
This study investigated the effects of direct aging(DA),solution treatment(ST),and ST followed by DA(T6)on the microstructural,mechanical,and corrosion properties of direct powder forged Al–10 Si–0.3 Mg alloy specim...This study investigated the effects of direct aging(DA),solution treatment(ST),and ST followed by DA(T6)on the microstructural,mechanical,and corrosion properties of direct powder forged Al–10 Si–0.3 Mg alloy specimens.Microstructural analyses conducted using optical microscopy,scanning electron microscopy,and electron backscatter diffraction revealed that among DA specimens,direct aging at 200℃(DA-2)exhibited significantly enhanced silicon(Si)particle distribution uniformity and minimal interparticle boundaries owing to increased diffusion bonding;ST specimens exhibited partial Si dissolution,higher porosity,and retained the interparticle boundaries;and T6 specimens exhibited improved microstructural uniformity and enhanced Si precipitation.Furthermore,mechanical property evaluations indicated that T6 treatment comprising ST at 500℃for 180 min followed by DA at 200℃for 360 min resulted in the highest tensile strength(207.15 MPa)and elongation(5.02%),followed closely by DA at 200℃for 360 min(203.13 MPa and4.39%).These improvements were attributed to the lower residual stress,higher diffusion distances,and well-dispersed Si particles induced by DA-2 treatment.Corrosion analyses conducted using cyclic polarization and impedance spectroscopy indicated varied electrochemical responses,with DA-2 resulting in the lowest corrosion current and highest impedance,and ST resulting in the lowest corrosion resistance.Overall,DA at 200℃for 360 min was the most effective heat treatment,offering the optimal balance between mechanical and corrosion-resistance properties.展开更多
A fine-grained metastable dual-phase Fe40Mn20Co20Cr15Si5high entropy alloy(CS-HEA)with excellent strength and ductility was successfully prepared by friction stir processing(FSP).The microstructural and...A fine-grained metastable dual-phase Fe40Mn20Co20Cr15Si5high entropy alloy(CS-HEA)with excellent strength and ductility was successfully prepared by friction stir processing(FSP).The microstructural and mechanical properties of the fine-grained CS-HEA were characterized.The results showed that as-cast shrinkage cavities and elemental segregation were eliminated.The average grain size was refined from 121.1 to 5.4μm.The face-centered cubic phase fraction increased from 23%to 82%.During tensile deformation,dislocation slip dominated at strains ranging from 5%to 17%,followed by transformation induced plasticity(TRIP)from 17%to 26%,and twin induced plasticity(TWIP)from 26%to 37%.The yield strength,ultimate tensile strength,and elongation of the fine-grained CS-HEA were 503 MPa,1120 MPa,and 37%,respectively.The strength-ductility synergy of fine-grained CS-HEA was attributed to the combined effects of TRIP,TWIP,dislocation strengthening,and fine-grained strengthening.展开更多
A thick-section GH4169 superalloy joint for safety-critical hot-section components was welded via a novel vacuum laser welding process.This process utilizes a vacuum environment to enhance laser welding penetration ab...A thick-section GH4169 superalloy joint for safety-critical hot-section components was welded via a novel vacuum laser welding process.This process utilizes a vacuum environment to enhance laser welding penetration ability.The microstructure and mechanical properties of the deep-penetration welded GH4169 superalloy were systematically investigated.The volume fraction of brittle Laves precipitate reached an exceptionally low level due to lower heat input and faster cooling rate involved in vacuum laser beam welding.The results indicated that a more than 17.5 mm-deep defect-free laser weld with a sound weld appearance was prepared.The yield strength and ultimate tensile strength of the weld joint in the as-welded condition were 434.6 and 775.9 MPa,respectively.Post-weld heat treatment promoted the precipitation ofγ″phase,which greatly improved the strength of the joint.展开更多
The transformation of the dissimilar metals in the welding area into a single metal is an important method for achieving high-quality welded connection in the dissimilar metal laminated composite plate.In this study,a...The transformation of the dissimilar metals in the welding area into a single metal is an important method for achieving high-quality welded connection in the dissimilar metal laminated composite plate.In this study,a high-performance titanium/steel composite plate(TSCP)with pure titaniumization in the welding area was prepared by cold spraying,hot rolling and heat treatment processes.The results indicate that cold spraying achieves effective pre-composite deposition of titanium particles while inhibiting interfacial oxidation and Fe-Ti alloying reactions,producing a relatively dense pure titanium coating with a low porosity of only 1.2%.Hot rolling eliminates internal defects and promotes strong metallurgical bonding of the composite interface.The heat treatment promotes the recrystallization and reduces the dislocation density within the coating.The interfacial bonding strength of the welding area with pure titaniumization of TSCP is 257 MPa,and the tensile strength of that is 414 MPa,reaching 95.6%of the TSCP’s base material.展开更多
To reveal the microstructural characteristics at specific locations of a TiAl turbocharger turbine under gravity casting conditions,metallographic observations were conducted on characteristic regions of its longitudi...To reveal the microstructural characteristics at specific locations of a TiAl turbocharger turbine under gravity casting conditions,metallographic observations were conducted on characteristic regions of its longitudinal section.The turbine hub exhibits primarily a columnar microstructure,with an average grain size significantly larger than that of the blade,which exhibits an equiaxed microstructure.The cooling rate varies significantly across the turbine,decreasing from the blade tip to the hub bottom,resulting in a negative correlation with grain size.The center of the turbine hub and the blade tips show higherγphase volume fractions(14.028% and 10.009%,respectively).In terms of phase constitution,both a low Ti/Al atomic ratio and a high cooling rate shift the solidification path to the Al side of the phase diagram,promoting the precipitation of massiveγphase.The average hardness of the blade body(273.89 HV)is higher than that of the turbine hub(238.40 HV),while the blade root(282.66 HV)exhibits similar average hardness to the blade body.展开更多
A deep-undercooling rapid-solidification technique combining cyclic superheating and molten glass purification was employed to successfully prepare Cu60Ni40 and Cu65Ni35 alloys at various undercooling levels.Furthermo...A deep-undercooling rapid-solidification technique combining cyclic superheating and molten glass purification was employed to successfully prepare Cu60Ni40 and Cu65Ni35 alloys at various undercooling levels.Furthermore,through precise compositional regulation by adjusting the Cu content and introducing Co,the Cu60Ni35Co5 alloy was obtained.The morphological evolution of the solidification front and the variation in solidification rate with undercooling were systematically investigated.By combining metallographic analysis,the BCT model,electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM),the microstructural evolution and grain refinement mechanisms of the undercooled alloys were revealed.This work aims to establish the intrinsic relationship among undercooling,solidification behavior,and microstructure,thereby provides both experimental and theoretical foundations for a deeper understanding of the deep undercooling solidification mechanism and microstructural control.展开更多
This study investigates the effect of Zn addition(1,5,and 10 wt.%)to the Mg melt on the microstructure and mechanical properties of Mg-Ti composites fabricated via liquid metal dealloying(LMD).The addition of Zn effec...This study investigates the effect of Zn addition(1,5,and 10 wt.%)to the Mg melt on the microstructure and mechanical properties of Mg-Ti composites fabricated via liquid metal dealloying(LMD).The addition of Zn effectively refines the Ti matrix while preserving the characteristic three-dimensional bicontinuous structure of dealloyed composites.Quantitative analysis shows that increasing Zn content reduces the Ti matrix width and effective grain size by up to 18%and 44%,respectively.Microstructural observations further reveal the formation of lamellar{11-22}contraction twins within the Ti matrix,with twin density increasing proportionally with Zn addition in the absence of external mechanical loading.As a result,the Vickers hardness increases monotonically from 130 HV in the Zn-free composite to 203 HV in the Mg-10Zn composite,corresponding to a 56%improvement.These results demonstrate that Zn alloying of the Mg melt is an effective strategy for enhancing the mechanical performance of bicontinuous Mg-Ti composites produced by LMD.展开更多
A systematic investigation was conducted into the influence of thermal treatment on the microstructure evolution and mechanical properties of additively manufactured Ni-based GH4099 superalloy,with specific focus on t...A systematic investigation was conducted into the influence of thermal treatment on the microstructure evolution and mechanical properties of additively manufactured Ni-based GH4099 superalloy,with specific focus on the selective laser melting(SLM)fabrication process.The as-fabricated GH4099 alloy demonstrated characteristic columnar grain structures with pronounced residual stresses,predominantly attributed to the steep thermal gradients inherent in the SLM process.Through solution treatment at 1110℃,a significant microstructural transformation was observed,characterized by recrystallization that converted the columnar grains into equiaxed structures while effectively mitigating residual stresses.Concurrently,this treatment facilitated the precipitation of fine γ′phases,thereby enhancing the material’s strength.Subsequent aging treatments at 800 and 900℃,however,led to γ′phase coarsening,which diminished the precipitation strengthening effect,but concurrently improved the alloy’s plasticity.These findings highlight the pivotal role of thermal processing in optimizing the strength-ductility balance for SLM-manufactured superalloys under high-temperature service conditions.This work contributes to a comprehensive understanding of the microstructure-property relationships in thermally processed SLM GH4099 superalloy,providing critical insights for the development of advanced Ni-based superalloys and contributing to the refinement of SLM manufacturing protocols for high-performance applications.展开更多
Rational interlayer cooling time management emerges as a critical yet underexplored parameter for controlling microstructural evolution and mechanical performance in wire-arc additive manufacturing(WAAM)of rare-earth ...Rational interlayer cooling time management emerges as a critical yet underexplored parameter for controlling microstructural evolution and mechanical performance in wire-arc additive manufacturing(WAAM)of rare-earth magnesium alloys.The present work systematically investigates,through integrated experiment and simulation,how varying cooling intervals(45–180 s)affect grain morphology,phase precipitation,and tensile properties in CMT-WAAM fabricated Mg-Gd-Y-Zn-Zr components.Repetitive thermal cycling during deposition induces solid-state transformations,notably promoting the formation of long-period stacking ordered(18R-LPSO)phases.The phases volume fractions were determined by quantitative metallography,reach a maximum of 1.43%at a cooling time of 120 s and a minimum of 0.41%at 45 s.Microstructural characterization reveals a characteristic bimodal grain structure comprising alternating coarse(15–35μm)and fine(5–12μm)equiaxed grains,with average sizes ranging from 11.32±5.35μm(180 s)to 15.62±6.94μm(45 s).Mechanical testing demonstrates strength-ductility trade-off:samples with 90 s cooling duration exhibit peak ultimate tensile strength(259.7±12.7 MPa)and yield strength(224.3±2.5 MPa),while 120s-cooled samples display superior elongation(8.5±0.54%)but reduced strength.These findings establish interlayer cooling time as an effective microstructural engineering tool for tailoring mechanical properties in WAAM-processed Mg-RE alloy systems through controlled thermal management.展开更多
Thin-walled Mg-8.5Gd-2.5Y-1.8Zn-0.5Zr(GWZ932)alloy component was successfully fabricated by the cold metal transfer(CMT)based wire-arc additive manufacturing(WAAM)process.Considering the significant influence of secon...Thin-walled Mg-8.5Gd-2.5Y-1.8Zn-0.5Zr(GWZ932)alloy component was successfully fabricated by the cold metal transfer(CMT)based wire-arc additive manufacturing(WAAM)process.Considering the significant influence of secondary phases on mechanical properties,we regulated the secondary phases through heat treatment.As-deposited sample exhibits the typical layered microstructure with alternating coarse/fine grains,along with a lot of Mg3(RE,Zn)eutectic phases at grain boundaries(GBs).After solid-solution treatment,these eutectic phases are transformed into coarse X phase at GBs and fine lamellar 14H long period ordered stacking(14H-LPSO)phases in grain interiors.Further peak-aging induces amounts of prismaticβ'phases precipitated in theα-Mg matrix,which produces the strong precipitation hardening effect.Note that prismaticβ'phases are perpendicular to basal 14H-LPSO phase in space,which can form a closed space that blocks dislocation motions more effectively.Thus,peakaged sample exhibits a high tensile strength of(314±3)MPa and an acceptable ductility of4.3%±0.6%,which outperforms most Mg-Gd-Y series alloys prepared by WAAM reported previously.Our work provides a basis for forming thin-walled Mg-Gd-Y series components with high strength via WAAM process,but the deposition process should be further optimized.展开更多
Niobium alloy and nickel-based superalloy exhibit high strength and remarkable corrosion resistance,joining them to fabricate composite structures could help to realize their potential.Nevertheless,research attention ...Niobium alloy and nickel-based superalloy exhibit high strength and remarkable corrosion resistance,joining them to fabricate composite structures could help to realize their potential.Nevertheless,research attention devoted to the joining of niobium alloy with nickel-based superalloy remains scarce.This study investigates direct diffusion bonding of these two materials.The microstructure of the joint is characterized in detail,with the typical joint microstructure being identified as GH4099/(Ni,Cr)ss+Ni3Nb+Cr2Nb/Ni3Nb/Ni6Nb7/Nb alloy.With holding time fixed at 60 min and diffusion pressure maintained at 15 MPa,the effects of diffusion bonding temperature on the microstructure and mechanical properties of joints are examined within the range of 900–1150℃.An increase in bonding temperature results in the formation of different intermetallic compounds within the joint.The primary cause of joint fracture is the presence of Cr2Nb and Ni6Nb7.The tensile strength of the joint initially increases and then decreases with increasing temperature,reaching a maximum value of 204 MPa.This work expands the range of methods for joining niobium alloys to nickel-based superalloys,enabling bonding without the introduction of additional elements.展开更多
With the increasing mining depth,heat hazards have become a critical challenge in deep underground operations.This study explores the incorporation of polyvinyl chloride(PVC)powder as a partial cement replacement in c...With the increasing mining depth,heat hazards have become a critical challenge in deep underground operations.This study explores the incorporation of polyvinyl chloride(PVC)powder as a partial cement replacement in cemented backfill to improve thermal insulation and promote sustainable waste utilization.Five mix designs were prepared with 0,5wt%,10wt%,15wt%,and 20wt%PVC,and their thermomechanical behaviors were systematically evaluated through uniaxial compressive strength(UCS)testing,thermal parameter measurements,energy evolution analysis,and micro structural characterization via scanning electron microscopy.The results showed that the UCS and energy absorption capacity first increased and then decreased with PVC addition,reaching an optimum at10wt%PVC,which achieved an 87.5% higher strength and improved energy dissipation compared with the control.The thermal conductivity and specific heat capacity progressively decreased with increasing PVC content,with the maximum reductions of 23.0% and 40.2%,respectively,for 20wt%PVC.Microstructural analysis confirmed that moderate PVC addition reduced the porosity and enhanced the internal compactness,whereas excessive PVC likely inhibited calcium silicate hydrate gel formation and weakened the structural integrity.A PVC dosage of 10wt% was identified as the optimal replacement level,providing a favorable balance between strength and thermal insulation.This study provides new insights into sustainable backfill design and offers a practical strategy for mitigating thermal hazards in deep mining environments.展开更多
Some patients with systemic lupus erythematosus experience neuropsychiatric symptoms.Although magnetic resonance imaging can detect abnormal signals in the white matter of the brain,conventional methods often struggle...Some patients with systemic lupus erythematosus experience neuropsychiatric symptoms.Although magnetic resonance imaging can detect abnormal signals in the white matter of the brain,conventional methods often struggle to accurately capture microstructural changes.Various diffusion models have been used to study white matter in systemic lupus erythematosus;however,comparative analyses of their sensitivity and specificity for detecting microstructural changes remain insufficient.To address this,our team designed a diagnostic trial that used multimodal diffusion imaging techniques to observe white matter microstructural changes in patients with systemic lupus erythematosus who had neuropsychiatric symptoms,with an aim to identify key diagnostic biomarkers for these patients.Patients with active lupus who received treatment at the Department of Rheumatology and Immunology,The First Affiliated Hospital of China Medical University,from September 2023 to March 2024 were recruited.According to the standards of the American College of Rheumatology,patients with systemic lupus erythematosus who had neuropsychiatric symptoms were assigned to the systemic lupus erythematosus group,whereas those without neuropsychiatric symptoms were assigned to the non-systemic lupus erythematosus group.Additionally,healthy volunteers matched by region,sex,and age were recruited as controls.All three groups underwent the same diffusion magnetic resonance imaging examination protocol to compare differences in diffusion parameters.Advanced diffusion imaging models were able to sensitively detect microstructural changes in the white matter fibers of patients with systemic lupus erythematosus who had neuropsychiatric symptoms,with specific diffusion parameters showing significant abnormalities in key brain regions.In the left superior longitudinal fasciculus subregion and the right thalamic radiations of patients with systemic lupus erythematosus who had neuropsychiatric symptoms,we also identified abnormal diffusion characteristics that were clearly correlated with disease activity,suggesting that microstructural changes in these areas may reflect the dynamic process of neuroinflammatory damage.The present study addresses critical challenges in the diagnosis of systemic lupus erythematosus by identifying specific white matter imaging biomarkers and elucidating the association between microstructural damage and clinical manifestations.The main contributions of our study include:1)establishing axial regression probability parameters from mean apparent propagator magnetic resonance imaging as sensitive biomarkers for systemic lupus erythematosus,particularly in the third subregion of the left superior longitudinal fasciculus;2)demonstrating that multimodal diffusion imaging may be superior to conventional diffusion tensor imaging for detecting white matter microstructural abnormalities in patients with systemic lupus erythematosus;and 3)integrating tract-based spatial statistics with clinically relevant analyses to link imaging findings to pathological mechanisms.展开更多
The synergistic CO2 sequestration via solid waste backfilling in goafs can simultaneously address the issues of CO2 emissions,accumulation of coal-based solid wastes,and safety hazards in goafs under China's...The synergistic CO2 sequestration via solid waste backfilling in goafs can simultaneously address the issues of CO2 emissions,accumulation of coal-based solid wastes,and safety hazards in goafs under China's coal-dominated energy structure.In this study,a modified magnesium-coal-based all-solid-waste carbon-sequestering backfill material(MFCC,prepared from modified magnesium slag(MMS),fly ash(FA),coal gangue(CG),and coal gasification slag(CGS))was fabricated.The fluidity of the fresh slurry was characterized using the mini slump test,and its carbonation curing performance was investigated via uniaxial compressive strength(UCS),carbonation depth(CD),X-ray diffraction(XRD),scanning electron microscopy(SEM),thermogravimetrydifferential thermogravimetry(TGDTG),and computed tomography(CT)tests,aiming to achieve the synergistic goals of high-value utilization of solid wastes and CO2 sequestration.The results indicate that the fresh MFCC sluny exhibits excellent fluidity with a mini slump ranging from 121.5 to 135 mm.The fluidity increases with the rise in CGS content,which fully meets the requirements for industrial pipeline pumping.During the carbonation curing process,the UCS of the material increases continuously with the extension of curing age,with the 28-d UCS ranging from 7.36 to 8.71 MPa,which fully meets the strength design requirements for coal mine backfilling engineering.Microscopic analyses reveal that the filling and cementation effects of hydration and carbonation products on pores render the material's microstructure denser,significantly reducing pore volume and connectivity,which is the key reason for the strength improvement.After 28 d of carbonation curing,when the CGS content is 20wt%,the UCS reaches a maximum value of 8.71 MPa,and the CO2 uptake also attains a peak of 13.94%.In summary,after carbonation curing,the MFCC material not only exhibits excellent mechanical properties but also enables the simultaneous realization of resource utilization of solid wastes and efficient CO2 sequestration thus holding broad application prospects in backfilling engineering.展开更多
基金supported by the National Natural Science Foundation of China(Nos.U20A20230,52375390,52201144)and the Hebei Provincial Natural Science Foundation,China(Nos.E2023203260,E2023203189).
摘要To objectively verify microstructural heredity in a rare-earth magnesium alloy during heat-treatment and deformation processes under pulsed current condition,we proposed a pulsed current method during homogenization and rolling processes.We then compared the macroscopic edge cracks,microstructures,and mechanical properties of sheets which were formed using pulsed homogenization(PH)/industrial homogenization(IH)followed by hot rolling(HR)/electroplastic rolling(ER).The results showed that the PH+ER forming method produced an alloy with the most obviously enhanced deformation ability,with the tensile strength increasing from 145 MPa(IH+HR)to 266 MPa(PH+ER).Inside the PH+ER sample,the nonthermal and thermal effects of the pulsed current promoted atomic diffusion,regulating the proportion and morphology of the secondary phase,thereby improving the forming ability of the material.
基金supported by the National Natural Science Foundation of China(Grant Nos.12462006 and 12062016)received crucial support from the high-performance computing services offered by the Information Center of Nanchang Hangkong University.
摘要The complex characteristics of thin-walled parts fabricated by laser powder bed fusion(LPBF),particularly the dependence of their microstructures on wall thickness and scanning strategies,pose significant challenges for this technology.This paper presents a predictive model for microstructural evolution of LPBF-fabricated thin-walled components,integrating three-dimensional cellular automaton(CA)with finite element(FE)analysis.The FE method is employed to solve the temperature field of thin-walled components during LPBF,and the resulting temperature history is used to predict micro-structural evolution in the CA model.Experimental validation via electron back scatter diffraction(EBSD)on a 4 mm-thick specimen confirms a high degree of agreement between model predictions and experimental results.The study reveals that when the thickness of samples prepared by LPBF is reduced from 4 mm to 0.4 mm,there is a significant coarsening of grain size.Additionally,grains at the bottom are observed to be coarser compared to those at the top,which is attributed to epitaxial growth and remelting.Furthermore,the study explores microstructural changes induced by manipulating laser power and scanning speed,while maintaining constant energy density.The findings indicate that grain morphology and size remain consistent across varying parameters,emphasizing the dominant influence of energy density.Within a predefined scanning strategy,an upsurge in laser energy density leads to an enlargement of the average grain size.Notably,the implementation of a cross-scanning strategy alters the melt pool orientation,disrupting the directional grain growth and fostering the formation of finer grains.This underscores the crucial significance of processing techniques in LPBF.
基金the financial support from the National Natural Science Foundation of China(No.52474370)the China Baowu Low Carbon Metallurgy Innovation Foundation(Nos.BWLCF202216 and BWLCF202313)。
摘要As demand grows for low-carbon ironmaking,it is essential to understand how hydrogen reduces iron ore pellets under vary-ing gangue compositions and gas atmospheres.In this work,fired hematite pellets with a basicity(mass ratio of CaO to SiO2)of 0.3 and SiO2contents ranging from 1wt%to 4wt%were systematically investigated under three typical shaft furnace atmospheres(Midrex,HYL,and coke oven gas(COG))as well as under 100%H2,to clarify the reduction kinetics,reaction mechanism,and microstructural evolution of the fired pellets.The results indicate that a higher hydrogen proportion significantly accelerates the reduction rate of the fired pellets,while an increase in SiO2content generally leads to a decrease in the overall reaction rate.However,the effect of hydrogen concentration on the reduction behavior of the fired pellets varied markedly with their silicon content.For the fired pellets containing 1wt%and 2wt%SiO2,an increase in hydrogen concentration causes deterioration in reduced pellet characteristics,as evidenced by the increase in reduc-tion swelling index from 26.14%to 34.26%and the decrease in cold compressive strength from 110 to 78 N.In contrast,fired pellets with 3wt%and 4wt%SiO2exhibit the opposite trend,with the reduction swelling index decreasing from 15.26%to 9.23%and cold compress-ive strength improving from 179 to 271 N.Kinetics analysis indicates that under 100%H2,the reduction of fired pellets with 1wt%SiO2is governed by a mixed gas-diffusion and uniform reaction model,whereas fired pellets with 4wt%SiO2follow an unreacted core model.These differences in reduction kinetics,reduction behavior,and post-reduction properties are closely associated with the formation of more Al-bearing calcium silicate slag phases in high-SiO2reduced pellets,which strengthen intergranular bonding,buffer phase-trans-formation-induced stress,and promote the evolution of metallic iron from whisker-like to granular or layered morphologies.
基金funded by the National Natural Science Foundation of China(Grant No.52322508)the R&D Program of Beijing Municipal Education Commission(Grant No.KZ20231000519).
摘要Friction stir processing(FSP) has emerged as a transformative solid-state technique for enhancing the mechanical performance and microstructural integrity of metallic materials,particularly in the context of additive manufacturing(AM).This study demonstrates the effectiveness of FSP as a post-processing strategy for two distinct AM systems:wire arc additive manufacturing(WAAM) of low-carbon steel and selective laser melting(SLM) of Ti6Al4V alloy.In the case of WAAM fabricated steel,FSP significantly refined the coarse dendritic microstructure into ultrafine equiaxed grains,resulting in a 21 %-24 % increase in hardness and enhanced tensile properties at the overlapping regions.Similarly,for SLM fabricated Ti6Al4V,FSP eliminated the columnar prior-β grains and residual porosity,yielding a homogenous α+β structure with improved strengthductility balance and reduced anisotropy.These improvements were attributed to the dynamic recrystallization,conversion of low-angle to high-angle grain boundaries,and homogenization of phase constituents induced by FSP.Despite challenges such as tool wear and fixturing complexity,the study confirms that FSP can reliably bridge the performance gap in AM components by healing solidification defects,mitigating anisotropy,and tailoring the local microstructure.The findings position FSP as a versatile and scalable post-processing technique,crucial for advancing high-performance,application-ready components in aerospace,biomedical,and structural applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.42177138 and 41907239)the Central Guidance Funds for Local Science and Technology Development of China(Grant No.YDZJSX2025D031).
摘要Loess landslides are major hazards in the Chinese Loess Plateau(CLP).The loess in this region is frequently subjected to repeated wetting–drying(W-D)cycles due to climatic factors,which significantly increases the likelihood of landslides.Therefore,investigating the shear behavior and microstructural evolution of loess under climate-induced W-D cycles is crucial to understanding the mechanisms of loess landslides.In this study,Malan loess is analyzed using unsaturated triaxial tests,resistivity tests,scanning electron microscopy,and mercury intrusion porosimetry.The test results show that shear strength decreases with increased W-D cycles,and the degradation effect is more pronounced under lower confining pressure.The variations in conductive pathways indicate that electrical resistivity can effectively reflect the structural damage of loess during W-D cycles,which is associated with increased direct point contacts and spaced pores.Aggregation of clay particles and growth of cracks during the W-D cycles can further destabilize the loess microstructure.As the confining pressure increases,crushed particles rearrange and convert spaced pores into intergranular pores.The number and peak intensity of dominant spaced pores decrease,resulting in a more stable structure.This study clarifies the mechanisms of loess landslides under W-D cycles and provides theoretical support for landslide prevention and control in the CLP.
基金National Natural Science Foundation of China(52172108)National Key R&D Program of China(2022YFB3707700)Strategic Priority Research Program of the Chinese Academy of Sciences(XDC0144005)。
摘要Silicon carbide fibers are considered ideal reinforcing materials for ceramic matrix composites due to their excellent mechanical properties and high-temperature performance.Different types of fibers necessitate individual investigation due to variations in their composition and fabrication processes.This study presents a comprehensive investigation into evolution of the mechanical properties,surface microstructure,and composition of Shicolon-Ⅱ fibers subjected to argon heat treatment at temperatures ranging from 1300℃to 1700℃.The Shicolon-Ⅱ fibers are composed of small-sized β-SiC grains,SiCxOy amorphous phase,and a minor amount of graphite microcrystals.Following treatment in an argon atmosphere at 1300℃,the fibers maintain a monofilament tensile strength of 3.620 GPa,corresponding to a retention of 98.32%.This strength diminishes to 2.875 GPa,equating to a retention of 78.08%,after treatment at 1500℃.The reduction in mechanical properties of the fibers can be ascribed to the decomposition of the amorphous phase and the growth of β-SiC grains.Furthermore,creep resistance is an essential factor influencing the long-term performance of composite materials.After treatment at temperatures above 1400℃,the high-temperature creep resistance of the fibers is significantly enhanced due to growth of β-SiC grains.This study offers valuable theoretical insights into high-temperature applications of second-generation fibers,contributing to an enhanced understanding of their performance under extreme conditions.
基金financially supported by an initiation grant project:IITK/MET/2022094,Indian Institute of Technology Kanpur,India,and SERB(Grant No:EEQ/2020/000306).
摘要This study investigated the effects of direct aging(DA),solution treatment(ST),and ST followed by DA(T6)on the microstructural,mechanical,and corrosion properties of direct powder forged Al–10 Si–0.3 Mg alloy specimens.Microstructural analyses conducted using optical microscopy,scanning electron microscopy,and electron backscatter diffraction revealed that among DA specimens,direct aging at 200℃(DA-2)exhibited significantly enhanced silicon(Si)particle distribution uniformity and minimal interparticle boundaries owing to increased diffusion bonding;ST specimens exhibited partial Si dissolution,higher porosity,and retained the interparticle boundaries;and T6 specimens exhibited improved microstructural uniformity and enhanced Si precipitation.Furthermore,mechanical property evaluations indicated that T6 treatment comprising ST at 500℃for 180 min followed by DA at 200℃for 360 min resulted in the highest tensile strength(207.15 MPa)and elongation(5.02%),followed closely by DA at 200℃for 360 min(203.13 MPa and4.39%).These improvements were attributed to the lower residual stress,higher diffusion distances,and well-dispersed Si particles induced by DA-2 treatment.Corrosion analyses conducted using cyclic polarization and impedance spectroscopy indicated varied electrochemical responses,with DA-2 resulting in the lowest corrosion current and highest impedance,and ST resulting in the lowest corrosion resistance.Overall,DA at 200℃for 360 min was the most effective heat treatment,offering the optimal balance between mechanical and corrosion-resistance properties.
基金the funds of the National Natural Science Fund for Excellent Young Scholars of China(No.52222410)Shaanxi Province National Science Fund for Distinguished Young Scholars,China(No.2022JC-24)the National Natural Science Foundation of China(Nos.52227807,52034005)。
摘要A fine-grained metastable dual-phase Fe40Mn20Co20Cr15Si5high entropy alloy(CS-HEA)with excellent strength and ductility was successfully prepared by friction stir processing(FSP).The microstructural and mechanical properties of the fine-grained CS-HEA were characterized.The results showed that as-cast shrinkage cavities and elemental segregation were eliminated.The average grain size was refined from 121.1 to 5.4μm.The face-centered cubic phase fraction increased from 23%to 82%.During tensile deformation,dislocation slip dominated at strains ranging from 5%to 17%,followed by transformation induced plasticity(TRIP)from 17%to 26%,and twin induced plasticity(TWIP)from 26%to 37%.The yield strength,ultimate tensile strength,and elongation of the fine-grained CS-HEA were 503 MPa,1120 MPa,and 37%,respectively.The strength-ductility synergy of fine-grained CS-HEA was attributed to the combined effects of TRIP,TWIP,dislocation strengthening,and fine-grained strengthening.
基金supported by the National Civil Space Pre-research Project,China。
摘要A thick-section GH4169 superalloy joint for safety-critical hot-section components was welded via a novel vacuum laser welding process.This process utilizes a vacuum environment to enhance laser welding penetration ability.The microstructure and mechanical properties of the deep-penetration welded GH4169 superalloy were systematically investigated.The volume fraction of brittle Laves precipitate reached an exceptionally low level due to lower heat input and faster cooling rate involved in vacuum laser beam welding.The results indicated that a more than 17.5 mm-deep defect-free laser weld with a sound weld appearance was prepared.The yield strength and ultimate tensile strength of the weld joint in the as-welded condition were 434.6 and 775.9 MPa,respectively.Post-weld heat treatment promoted the precipitation ofγ″phase,which greatly improved the strength of the joint.
基金financially supported by the National Key R&D Program of China(No.2018YFA0707300)the National Natural Science Foundation of China(No.52374376)。
摘要The transformation of the dissimilar metals in the welding area into a single metal is an important method for achieving high-quality welded connection in the dissimilar metal laminated composite plate.In this study,a high-performance titanium/steel composite plate(TSCP)with pure titaniumization in the welding area was prepared by cold spraying,hot rolling and heat treatment processes.The results indicate that cold spraying achieves effective pre-composite deposition of titanium particles while inhibiting interfacial oxidation and Fe-Ti alloying reactions,producing a relatively dense pure titanium coating with a low porosity of only 1.2%.Hot rolling eliminates internal defects and promotes strong metallurgical bonding of the composite interface.The heat treatment promotes the recrystallization and reduces the dislocation density within the coating.The interfacial bonding strength of the welding area with pure titaniumization of TSCP is 257 MPa,and the tensile strength of that is 414 MPa,reaching 95.6%of the TSCP’s base material.
摘要To reveal the microstructural characteristics at specific locations of a TiAl turbocharger turbine under gravity casting conditions,metallographic observations were conducted on characteristic regions of its longitudinal section.The turbine hub exhibits primarily a columnar microstructure,with an average grain size significantly larger than that of the blade,which exhibits an equiaxed microstructure.The cooling rate varies significantly across the turbine,decreasing from the blade tip to the hub bottom,resulting in a negative correlation with grain size.The center of the turbine hub and the blade tips show higherγphase volume fractions(14.028% and 10.009%,respectively).In terms of phase constitution,both a low Ti/Al atomic ratio and a high cooling rate shift the solidification path to the Al side of the phase diagram,promoting the precipitation of massiveγphase.The average hardness of the blade body(273.89 HV)is higher than that of the turbine hub(238.40 HV),while the blade root(282.66 HV)exhibits similar average hardness to the blade body.
基金Funded by the Central Government-Guided Local Development Fund Project(No.YDZJSX2025D042)the Key R&D Program of Shanxi Province(No.202202150401018)+1 种基金the Basic Research Program of Shanxi Province(No.202503021211112)the State Key Laboratory of CAD/CG of Zhejiang University(No.A2325)。
摘要A deep-undercooling rapid-solidification technique combining cyclic superheating and molten glass purification was employed to successfully prepare Cu60Ni40 and Cu65Ni35 alloys at various undercooling levels.Furthermore,through precise compositional regulation by adjusting the Cu content and introducing Co,the Cu60Ni35Co5 alloy was obtained.The morphological evolution of the solidification front and the variation in solidification rate with undercooling were systematically investigated.By combining metallographic analysis,the BCT model,electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM),the microstructural evolution and grain refinement mechanisms of the undercooled alloys were revealed.This work aims to establish the intrinsic relationship among undercooling,solidification behavior,and microstructure,thereby provides both experimental and theoretical foundations for a deeper understanding of the deep undercooling solidification mechanism and microstructural control.
基金supported by the National Research Foundation of Korea(NRF)grants funded by the Korea government(MSIT)(Nos.RS-2024-00351052 and RS-2024-00450561).
摘要This study investigates the effect of Zn addition(1,5,and 10 wt.%)to the Mg melt on the microstructure and mechanical properties of Mg-Ti composites fabricated via liquid metal dealloying(LMD).The addition of Zn effectively refines the Ti matrix while preserving the characteristic three-dimensional bicontinuous structure of dealloyed composites.Quantitative analysis shows that increasing Zn content reduces the Ti matrix width and effective grain size by up to 18%and 44%,respectively.Microstructural observations further reveal the formation of lamellar{11-22}contraction twins within the Ti matrix,with twin density increasing proportionally with Zn addition in the absence of external mechanical loading.As a result,the Vickers hardness increases monotonically from 130 HV in the Zn-free composite to 203 HV in the Mg-10Zn composite,corresponding to a 56%improvement.These results demonstrate that Zn alloying of the Mg melt is an effective strategy for enhancing the mechanical performance of bicontinuous Mg-Ti composites produced by LMD.
基金supported by National Key R&D Program of China(Grant No.2021YFB3702500)Guangdong Major Project of Basic and Applied Basic Research(Grant No.2020B0301030001)+1 种基金the Opening Project of Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology(Grant No.2024K003)Guangxi Province Talent Project(Financial support from Science and Technology Department).
摘要A systematic investigation was conducted into the influence of thermal treatment on the microstructure evolution and mechanical properties of additively manufactured Ni-based GH4099 superalloy,with specific focus on the selective laser melting(SLM)fabrication process.The as-fabricated GH4099 alloy demonstrated characteristic columnar grain structures with pronounced residual stresses,predominantly attributed to the steep thermal gradients inherent in the SLM process.Through solution treatment at 1110℃,a significant microstructural transformation was observed,characterized by recrystallization that converted the columnar grains into equiaxed structures while effectively mitigating residual stresses.Concurrently,this treatment facilitated the precipitation of fine γ′phases,thereby enhancing the material’s strength.Subsequent aging treatments at 800 and 900℃,however,led to γ′phase coarsening,which diminished the precipitation strengthening effect,but concurrently improved the alloy’s plasticity.These findings highlight the pivotal role of thermal processing in optimizing the strength-ductility balance for SLM-manufactured superalloys under high-temperature service conditions.This work contributes to a comprehensive understanding of the microstructure-property relationships in thermally processed SLM GH4099 superalloy,providing critical insights for the development of advanced Ni-based superalloys and contributing to the refinement of SLM manufacturing protocols for high-performance applications.
基金financially supported by National Defense Science and Technology Key Laboratory Fund(61420052024KJW02)the National Natural Science Foundation of China(Nos.52275389 and 52405433)+1 种基金Fundamental Research Program of Shanxi Province(202403021212119 and 202403021223005)China Postdoctoral Science Foundation(2024M763031)and the special fund for Science and Technology Innovation Teams of Shanxi Province.
摘要Rational interlayer cooling time management emerges as a critical yet underexplored parameter for controlling microstructural evolution and mechanical performance in wire-arc additive manufacturing(WAAM)of rare-earth magnesium alloys.The present work systematically investigates,through integrated experiment and simulation,how varying cooling intervals(45–180 s)affect grain morphology,phase precipitation,and tensile properties in CMT-WAAM fabricated Mg-Gd-Y-Zn-Zr components.Repetitive thermal cycling during deposition induces solid-state transformations,notably promoting the formation of long-period stacking ordered(18R-LPSO)phases.The phases volume fractions were determined by quantitative metallography,reach a maximum of 1.43%at a cooling time of 120 s and a minimum of 0.41%at 45 s.Microstructural characterization reveals a characteristic bimodal grain structure comprising alternating coarse(15–35μm)and fine(5–12μm)equiaxed grains,with average sizes ranging from 11.32±5.35μm(180 s)to 15.62±6.94μm(45 s).Mechanical testing demonstrates strength-ductility trade-off:samples with 90 s cooling duration exhibit peak ultimate tensile strength(259.7±12.7 MPa)and yield strength(224.3±2.5 MPa),while 120s-cooled samples display superior elongation(8.5±0.54%)but reduced strength.These findings establish interlayer cooling time as an effective microstructural engineering tool for tailoring mechanical properties in WAAM-processed Mg-RE alloy systems through controlled thermal management.
基金Project supported by the National Natural Science Foundation of China(52201111,52275389)Central Guiding Science and Technology Development of Local Fund(YDZJSX2025D051)+1 种基金Reward Funds for Excellent Doctor of Work in Coming To Shanxi(20242068)the Special fund for Science and Technology Innovation Teams of Shanxi Province。
摘要Thin-walled Mg-8.5Gd-2.5Y-1.8Zn-0.5Zr(GWZ932)alloy component was successfully fabricated by the cold metal transfer(CMT)based wire-arc additive manufacturing(WAAM)process.Considering the significant influence of secondary phases on mechanical properties,we regulated the secondary phases through heat treatment.As-deposited sample exhibits the typical layered microstructure with alternating coarse/fine grains,along with a lot of Mg3(RE,Zn)eutectic phases at grain boundaries(GBs).After solid-solution treatment,these eutectic phases are transformed into coarse X phase at GBs and fine lamellar 14H long period ordered stacking(14H-LPSO)phases in grain interiors.Further peak-aging induces amounts of prismaticβ'phases precipitated in theα-Mg matrix,which produces the strong precipitation hardening effect.Note that prismaticβ'phases are perpendicular to basal 14H-LPSO phase in space,which can form a closed space that blocks dislocation motions more effectively.Thus,peakaged sample exhibits a high tensile strength of(314±3)MPa and an acceptable ductility of4.3%±0.6%,which outperforms most Mg-Gd-Y series alloys prepared by WAAM reported previously.Our work provides a basis for forming thin-walled Mg-Gd-Y series components with high strength via WAAM process,but the deposition process should be further optimized.
基金supported by the National Natural Science Foundation of China(Grant Nos.52125502 and 52275323)the Fundamental Research Funds for the Central Universities(Grant Nos.FRFCU5710051121 and FRFCU5710093920)State Key Laboratory of Precision Welding&Joining of Materials and Structures(No.25-R-02).
摘要Niobium alloy and nickel-based superalloy exhibit high strength and remarkable corrosion resistance,joining them to fabricate composite structures could help to realize their potential.Nevertheless,research attention devoted to the joining of niobium alloy with nickel-based superalloy remains scarce.This study investigates direct diffusion bonding of these two materials.The microstructure of the joint is characterized in detail,with the typical joint microstructure being identified as GH4099/(Ni,Cr)ss+Ni3Nb+Cr2Nb/Ni3Nb/Ni6Nb7/Nb alloy.With holding time fixed at 60 min and diffusion pressure maintained at 15 MPa,the effects of diffusion bonding temperature on the microstructure and mechanical properties of joints are examined within the range of 900–1150℃.An increase in bonding temperature results in the formation of different intermetallic compounds within the joint.The primary cause of joint fracture is the presence of Cr2Nb and Ni6Nb7.The tensile strength of the joint initially increases and then decreases with increasing temperature,reaching a maximum value of 204 MPa.This work expands the range of methods for joining niobium alloys to nickel-based superalloys,enabling bonding without the introduction of additional elements.
基金financially supported by the Shaanxi Provincial Key Research and Development Program,China(No.2025SF-YBXM-535)the National Natural Science Foundation of China(No.52404111)。
摘要With the increasing mining depth,heat hazards have become a critical challenge in deep underground operations.This study explores the incorporation of polyvinyl chloride(PVC)powder as a partial cement replacement in cemented backfill to improve thermal insulation and promote sustainable waste utilization.Five mix designs were prepared with 0,5wt%,10wt%,15wt%,and 20wt%PVC,and their thermomechanical behaviors were systematically evaluated through uniaxial compressive strength(UCS)testing,thermal parameter measurements,energy evolution analysis,and micro structural characterization via scanning electron microscopy.The results showed that the UCS and energy absorption capacity first increased and then decreased with PVC addition,reaching an optimum at10wt%PVC,which achieved an 87.5% higher strength and improved energy dissipation compared with the control.The thermal conductivity and specific heat capacity progressively decreased with increasing PVC content,with the maximum reductions of 23.0% and 40.2%,respectively,for 20wt%PVC.Microstructural analysis confirmed that moderate PVC addition reduced the porosity and enhanced the internal compactness,whereas excessive PVC likely inhibited calcium silicate hydrate gel formation and weakened the structural integrity.A PVC dosage of 10wt% was identified as the optimal replacement level,providing a favorable balance between strength and thermal insulation.This study provides new insights into sustainable backfill design and offers a practical strategy for mitigating thermal hazards in deep mining environments.
基金supported by the National Natural Science Foundation Joint Fund,No.U22A20309(to PY)the Natural Science Foundation of LiaoningProvince,No.2023-MS-07(to HuL)the Unveiling Key Scientific and Technological Projects of Liaoning Province,No.2021JH1/10400051(to HuL).
摘要Some patients with systemic lupus erythematosus experience neuropsychiatric symptoms.Although magnetic resonance imaging can detect abnormal signals in the white matter of the brain,conventional methods often struggle to accurately capture microstructural changes.Various diffusion models have been used to study white matter in systemic lupus erythematosus;however,comparative analyses of their sensitivity and specificity for detecting microstructural changes remain insufficient.To address this,our team designed a diagnostic trial that used multimodal diffusion imaging techniques to observe white matter microstructural changes in patients with systemic lupus erythematosus who had neuropsychiatric symptoms,with an aim to identify key diagnostic biomarkers for these patients.Patients with active lupus who received treatment at the Department of Rheumatology and Immunology,The First Affiliated Hospital of China Medical University,from September 2023 to March 2024 were recruited.According to the standards of the American College of Rheumatology,patients with systemic lupus erythematosus who had neuropsychiatric symptoms were assigned to the systemic lupus erythematosus group,whereas those without neuropsychiatric symptoms were assigned to the non-systemic lupus erythematosus group.Additionally,healthy volunteers matched by region,sex,and age were recruited as controls.All three groups underwent the same diffusion magnetic resonance imaging examination protocol to compare differences in diffusion parameters.Advanced diffusion imaging models were able to sensitively detect microstructural changes in the white matter fibers of patients with systemic lupus erythematosus who had neuropsychiatric symptoms,with specific diffusion parameters showing significant abnormalities in key brain regions.In the left superior longitudinal fasciculus subregion and the right thalamic radiations of patients with systemic lupus erythematosus who had neuropsychiatric symptoms,we also identified abnormal diffusion characteristics that were clearly correlated with disease activity,suggesting that microstructural changes in these areas may reflect the dynamic process of neuroinflammatory damage.The present study addresses critical challenges in the diagnosis of systemic lupus erythematosus by identifying specific white matter imaging biomarkers and elucidating the association between microstructural damage and clinical manifestations.The main contributions of our study include:1)establishing axial regression probability parameters from mean apparent propagator magnetic resonance imaging as sensitive biomarkers for systemic lupus erythematosus,particularly in the third subregion of the left superior longitudinal fasciculus;2)demonstrating that multimodal diffusion imaging may be superior to conventional diffusion tensor imaging for detecting white matter microstructural abnormalities in patients with systemic lupus erythematosus;and 3)integrating tract-based spatial statistics with clinically relevant analyses to link imaging findings to pathological mechanisms.
基金Financial support for this study was jointly given by the National Key R&D Projects of China(No.2017YFC0603106)the General Program of the National Natural Science Foundation of China(No.41772121)+3 种基金the Major Science and Technology project of Petro China Changqing Oilfield Company(No.2024D1JC06)the China Postdoctoral Science Foundation(Nos.BX20240287 and 2024MD764013)the National Natural Science Foundation of China(No.42402186)the Shaanxi Province Youth Talent Support Program Project(No.20250706)。
摘要The synergistic CO2 sequestration via solid waste backfilling in goafs can simultaneously address the issues of CO2 emissions,accumulation of coal-based solid wastes,and safety hazards in goafs under China's coal-dominated energy structure.In this study,a modified magnesium-coal-based all-solid-waste carbon-sequestering backfill material(MFCC,prepared from modified magnesium slag(MMS),fly ash(FA),coal gangue(CG),and coal gasification slag(CGS))was fabricated.The fluidity of the fresh slurry was characterized using the mini slump test,and its carbonation curing performance was investigated via uniaxial compressive strength(UCS),carbonation depth(CD),X-ray diffraction(XRD),scanning electron microscopy(SEM),thermogravimetrydifferential thermogravimetry(TGDTG),and computed tomography(CT)tests,aiming to achieve the synergistic goals of high-value utilization of solid wastes and CO2 sequestration.The results indicate that the fresh MFCC sluny exhibits excellent fluidity with a mini slump ranging from 121.5 to 135 mm.The fluidity increases with the rise in CGS content,which fully meets the requirements for industrial pipeline pumping.During the carbonation curing process,the UCS of the material increases continuously with the extension of curing age,with the 28-d UCS ranging from 7.36 to 8.71 MPa,which fully meets the strength design requirements for coal mine backfilling engineering.Microscopic analyses reveal that the filling and cementation effects of hydration and carbonation products on pores render the material's microstructure denser,significantly reducing pore volume and connectivity,which is the key reason for the strength improvement.After 28 d of carbonation curing,when the CGS content is 20wt%,the UCS reaches a maximum value of 8.71 MPa,and the CO2 uptake also attains a peak of 13.94%.In summary,after carbonation curing,the MFCC material not only exhibits excellent mechanical properties but also enables the simultaneous realization of resource utilization of solid wastes and efficient CO2 sequestration thus holding broad application prospects in backfilling engineering.