The microstructure evolution of a new directionally solidified（DS） Ni-based superalloy used for gas turbine blades after long-term aging at 950 ℃ was investigated.The results show that the γ ＇ phase becomes more ...The microstructure evolution of a new directionally solidified（DS） Ni-based superalloy used for gas turbine blades after long-term aging at 950 ℃ was investigated.The results show that the γ ＇ phase becomes more regular in dendritic arm and interdendritic area,while both the mass fraction and the size of γ ＇ phase increase gradually with increasing aging time.During long-term aging,the MC carbide dissolves on the edge to provide the carbon for the formation of M23C6 carbide by the precipitation of Cr at the grain boundary.The rose-shaped γ ＇/γ eutectic partly dissolves into γ matrix and the aging promotes it transform into raft-shape γ ＇.The microstructure is generally stable and no needle-like topologically close-packed phase（TCP） can be found after aging for 1 000 h.展开更多
The relationship among B content,microstructure evolution and stress rupture properties of K4750 alloy during long-term aging were investigated.After aging at 800℃for 1000 h,the decomposition degree of MC carbides of...The relationship among B content,microstructure evolution and stress rupture properties of K4750 alloy during long-term aging were investigated.After aging at 800℃for 1000 h,the decomposition degree of MC carbides of K4750 alloys with 0 B,0.007 wt.%B and 0.010 wt.%B were basically identical,which indicated that B has no inhibition on MC carbide decomposition during long-term aging.The MC carbide decomposition was accompanied by the formation of M_(23)C_(6) carbides and a small number ofηphases,which was controlled by the outward diffusion of C and Ti combined with the inward diffusion of Ni and Cr from theγmatrix.In addition,M_(23)C_(6) carbides in boron-free alloy were in continuous chain and needle-likeηphases were precipitated near them,while M_(23)C_(6) carbides in boron-containing alloys remained in granular distribution and noηphases precipitation around them.Adding B could delay the agglomeration and coarsening of M_(23)C_(6) carbides during long-term aging,which was because the segregation of B at grain boundary retarded the diffusion of alloy elements,thus weakened the local fluctuation of chemical composition near grain boundary.The stress rupture samples of K4750 alloys with various B contents after aging at 800℃for 1000 h were tested at 750℃/380 MPa.The results indicated that the stress rupture properties of bo ron-containing alloys were significantly better than that of boron-free alloy,which could be attributed to the increase of grain boundary cohesion strength and the optimization of M_(23)C_(6) carbide distribution due to the addition of B.展开更多
Thermal stabilities of microstructure and mechanical property have been investigated on superalloy U720Li, which is of great interest of application for jet engine and land-based turbine disc. The results showed that,...Thermal stabilities of microstructure and mechanical property have been investigated on superalloy U720Li, which is of great interest of application for jet engine and land-based turbine disc. The results showed that, the primary and secondary gamma' particles maintain good thermal stability at 650 and 700 degreesC with aging time up to 3000 h, while the tertiary gamma' is apparently dependent on aging temperature and time. The tertiary gamma' particles undergo a procedure of coarsening, dissolution and eventually complete disappearance with the increasing of aging time and temperature. They exhibit unusual high sensibility upon aging temperature, which is attributed to the lattice misfit between the gamma' precipitates and the matrix in the alloy. The grain boundary phase M23C6 remains stable without forming of sigma phase even with aging time up to 3000 h at 700 degreesC. Microhardness decreases apparently with increasing aging time and aging temperature. Theoretical analysis based on dislocation mechanism indicates that the change of microhardness should be attributed to the evolution of the tertiary gamma' during aging.展开更多
In K4750 alloy,the evolution of grain boundary(GB)precipitates,including the degradation of blocky MC carbide particles and the precipitation of granular/needle-likeηphase particles,were observed after longterm aging...In K4750 alloy,the evolution of grain boundary(GB)precipitates,including the degradation of blocky MC carbide particles and the precipitation of granular/needle-likeηphase particles,were observed after longterm aging(LA)at 750℃for 8000 h.During MC degradation,the Ti and C released from the MC carbide combined with Ni and Cr,respectively,in theγ’matrix to formη-Ni_(3)Ti phase and Cr-rich M_(23)C_(6)carbide.Large amounts of granularηphase precipitated at GBs and the needle-likeηphase grew gradually from GBs toward the grain interior.Because of the growth of theηphase through absorbingγ’phase,γ-depleted zones were formed around theηphase.The evolution of the MC carbide andηphase was primarily responsible for the decrease of the stress rupture life and the increase of elongation.After an LA sample was tested at 750℃and 360 MPa,the residual strain distribution was investigated by electron backscatter diffraction(EBSD).The results showed that the residual strain mainly distributed at GBs,especially in the region of MC degradation and at the edges ofηphases,which was closely related to the appearance of phase interfaces.Microvoids/cracks easily initiated at phase interfaces,then easily extended along theγ-depleted zones,thus the stress rupture life of LA samples was substantially shorter than that of samples subjected to the standard treatment.In particular,because of large amounts of fine degraded MC,granular M_(23)C_(6)and granularηphase particles distributed at GBs after 750℃/8000 h LA and microvoid/crack formation could be hindered by the formation of dimples,which led to an increase of elongation.展开更多
The service performance of heat resistance steels is largely determined by the precipitation kinetics.The nucleation-growth-coarsening behaviors of precipitates in G115 martensitic heat resistance steel during long-te...The service performance of heat resistance steels is largely determined by the precipitation kinetics.The nucleation-growth-coarsening behaviors of precipitates in G115 martensitic heat resistance steel during long-term aging at 650℃ have been systemically investigated.The microstructural characteristics,precipitate morphology and alloying element distribution were studied by scanning electron microscopy,transmission electron microscopy and scanning transmission electron microscopy.The lognormal distribution fitting combined with the multiple regression analysis was adopted to evaluate the precipitate size distributions.Laves phase has longer incubation time,and its coarsening rate is almost one order of magnitude higher in comparison with that of M_(23)C_(6) carbide.Furthermore,the nucleation rate,number density,average radius,and volume fraction of two precipitates are simulated based on the classical nucleation theory and the modified Langer-Schwartz model.The precipitation behavior of Laves phase can be well explained with the Fe-W system as the interfacial energy takes 0.10 J/m^(2).In contrast,the simulation results of M_(23)C_(6) carbide in the Fe-Cr-C system are significantly overestimated,which results from the inhibitory effect of boron on coarsening.展开更多
Microstructure evolution and the changes in mechanical properties of HR3 Csteel during long-term aging at650,700 and 750℃ were investigated.The precipitated phases of the aging steel included M23C6 carbides,Z-phase a...Microstructure evolution and the changes in mechanical properties of HR3 Csteel during long-term aging at650,700 and 750℃ were investigated.The precipitated phases of the aging steel included M23C6 carbides,Z-phase and a trace amount of Nb（C,N）.The M23C6 carbides were distributed mainly at the grain boundary,while Z-phase was mainly inside the grains.Amounts of both M23C6 carbides and Z-phase during the aging process increased with increasing aging period and temperature.Coarsening of M23C6 carbides was influenced significantly by aging time and temperature,while the size of the Z-phase was relatively less affected by the aging time and temperature,which had a steady strengthening effect.Coarsening of the M23C6 carbides was the main reason for the decline in high temperature yield strength during long-term aging at 750℃.The M23C6 carbides were linked into a continuous chain along the grain boundary which accounted for the decrease of toughness during aging.展开更多
Aging of polyaluminum chloride(PACl) coagulants could significantly influence hydrolyzed Al speciation ruling coagulation performance.The goal of this study was to investigate Al species transformation through long-te...Aging of polyaluminum chloride(PACl) coagulants could significantly influence hydrolyzed Al speciation ruling coagulation performance.The goal of this study was to investigate Al species transformation through long-term aging and its impact on coagulation performance.Two kinds of commercial coagulants(PACl-1 and PACl-2) were stored for in-situ aging tests in six months to evaluate Al species variation with time and the performance of coagulation with natural turbid waters.The results showed that CaSO4 precipitation easily occur in a commercial PACl coagulant with time as it contains SO4^2- and Ca^2+.It also activates the precipitation of gibbsite Al(OH)3 in PACl with aging.Through 180 days aging,both monomeric Al(Ala) and polymeric Al(Alb) substantially transform into colloidal Al(Alc) and precipitated for both PACl coagulants.At low turbidity(10 NTU),PACl-1 has a superior turbidity reduction rate than PACl-2,while PACl-2 performs a little better turbidity re duction at high turbidity(1000 NTU) regardless of aging time.With aging time,an obvious decrease in turbidity reduction for PACl-1 coagulation is observed at low turbidity of 10 NTU,while the improvement in turbidity reduction for PACl-2 coagulation by enhanced sweep flocculation can be achieved as Alb mostly transform into Alc after 150 days aging.It is concluded that dominant in-situ formed Alc after a long time hydrolysis can improve PACl coagulation efficiency in turbidity reduction by enhanced sweep flocculation,especially for low turbidity water,but the increase in preformed Alc in PACl would worsen particle destabilization after aging.展开更多
Microstructures of a CuZnAlMnNi shape memory alloy in the as-quenched andlong-term aged conditions were investigated by transmission electron microscopy. Aged for one yearin martensite phase, an equilibrium α-phase w...Microstructures of a CuZnAlMnNi shape memory alloy in the as-quenched andlong-term aged conditions were investigated by transmission electron microscopy. Aged for one yearin martensite phase, an equilibrium α-phase with fcc structure was observed in the M18R martensitematrix, accompanied by the appearance of a novel diffraction pattern. By analysis, it was suggestedthat the novel pattern results from the α-phase and the martensite matrix remaining in seven fineplates which produce intense secondary diffraction effect when the diffraction beams enter from onephase into another.展开更多
In view of developing novel alloys for applications in supercritical water-cooled reactor fuel cladding and in-core components, a 12%Cr reduced activation ferrite/martensite(RAFM) steel with good corrosion resistance ...In view of developing novel alloys for applications in supercritical water-cooled reactor fuel cladding and in-core components, a 12%Cr reduced activation ferrite/martensite(RAFM) steel with good corrosion resistance and irradiation performance was developed. V and Ta were added to form fine MX type carbonitrides and enhance the high temperature creep rupture strength. Microstructure stability of the steel during long-term aging at 650 C was studied experimentally combined with the simulation of ThermoCalc and DICTRA software. The results show that the precipitates in the steel during long-term aging contain M23C6, MX and Laves phase. M23C6 carbides play a major role in the stabilization of the tempered martensite lath structure by exerting a large Zener pinning force as compared with MX and Laves phase.Adding V and Ta in the steel can not only promote MX precipitation, but also refine M23C6 carbides and thus improve the thermal stability of lath/subgrains, which is beneficial to the improvement of high temperature microstructure stability of the 12%Cr RAFM steel.展开更多
The effects of electric field intensity and treatment temperature on the microstructures of GH4199 superalloy after long-term aging were investigated. The results show that the number and size of carbides and TCP(σph...The effects of electric field intensity and treatment temperature on the microstructures of GH4199 superalloy after long-term aging were investigated. The results show that the number and size of carbides and TCP(σphase andμphase) phase in the alloy increase with increasing electric field intensity at the same heat treatment temperature and holding time. While the number and size of carbides and TCP phase are weekly influenced by treatment temperature with lower electric field intensity of 2 kV/cm. When the treat temperature is up to 1 093 K, annealing twins appear in the alloy, and the number of twins increases with increasing holding time. Since the electric field can provide the enough energy for the movement of vacancies and atom, it is considered that the nucleus of the twins formed with formation stack faults due to the mismatch of local atom in crystal caused by the vacancies, and the twins will grow with the increase of holding time. Meanwhile, such promoting effects on atom movement of the electric field increase with the increase of the electric field intensity, meantime the carbides and TCP phase grow fast with the increase of electric field intensity.展开更多
Countries around the world have been making efforts to reduce pollutant emissions. However, the response of global black carbon(BC) aging to emission changes remains unclear. Using the Community Atmosphere Model versi...Countries around the world have been making efforts to reduce pollutant emissions. However, the response of global black carbon(BC) aging to emission changes remains unclear. Using the Community Atmosphere Model version 6 with a machine-learning-integrated four-mode version of the Modal Aerosol Module, we quantify global BC aging responses to emission reductions for 2011–2018 and for 2050 and 2100 under carbon neutrality. During 2011–18, global trends in BC aging degree(mass ratio of coatings to BC, R_(BC)) exhibited marked regional disparities, with a significant increase in China(5.4% yr^(-1)), which contrasts with minimal changes in the USA, Europe, and India. The divergence is attributed to opposing trends in secondary organic aerosol(SOA) and sulfate coatings, driven by regional changes in the emission ratios of corresponding coating precursors to BC(volatile organic compounds-VOCs/BC and SO_(2)/BC). Projections under carbon neutrality reveal that R_(BC) will increase globally by 47%(118%) in 2050(2100), with strong convergent increases expected across major source regions. The R_(BC) increase, primarily driven by enhanced SOA coatings due to sharper BC reductions relative to VOCs, will enhance the global BC mass absorption cross-section(MAC) by 11%(17%) in 2050(2100).Consequently, although the global BC burden will decline sharply by 60%(76%), the enhanced MAC partially offsets the magnitude of the decline in the BC direct radiative effect, resulting in the moderation of global BC DRE decreases to 88%(92%) of the BC burden reductions in 2050(2100). This study highlights the globally enhanced BC aging and light absorption capacity under carbon neutrality, thereby partly offsetting the impact of BC direct emission reductions on future changes in BC radiative effects globally.展开更多
Subarachnoid hemorrhage is a subtype of stroke that causes severe neurological damage and is associated with poor long-term prognosis.Cognitive impairment is a major manifestation of long-term neurological dysfunction...Subarachnoid hemorrhage is a subtype of stroke that causes severe neurological damage and is associated with poor long-term prognosis.Cognitive impairment is a major manifestation of long-term neurological dysfunction in patients with subarachnoid hemorrhage.However,there is notable absence of biological markers to predict long-term prognosis in this patient population.Given the aging-like neurocognitive phenomena associated with subarachnoid hemorrhage,this study postulates that telomere length,a recognized biomarker for aging,could be used as a prognostic indicator for subarachnoid hemorrhage.A left internal carotid artery intravascular puncture mouse model was used to simulate subarachnoid hemorrhage.Comprehensive neurological test scores were obtained through neurobehavioral assessments conducted at one-month intervals.Concurrently,the relative telomere length was analyzed by quantitative polymerase chain reaction,which was performed using DNA extracted from ear notch and brain tissue after each assessment.Furthermore,proteomic analysis was employed to investigate differential protein expression in hippocampal tissue.Subarachnoid hemorrhage mice exhibited persistent neurocognitive impairment over a prolonged period of time.There was a significant positive correlation between telomere length and neurological test scores,confirming the usefulness of telomere length as a prognostic indicator in subarachnoid hemorrhage.Hippocampal tissue from subarachnoid hemorrhage mice showed reduced expression of acetyl-coenzyme A synthetase-2 and abnormalities in the expression of proteins related to ribosomes,energy metabolism,and cellular signal transduction.This study confirmed telomere shortening in the brain and metabolic disturbances in the hippocampi of subarachnoid hemorrhage mice.Thus,telomere length is a predictive marker for long-term impairment of cognitive function in mice following experimental subarachnoid hemorrhage.展开更多
The Cu0.9Cr0.1Zr alloy was deformed through continuous equal channel angular pressing(C-ECAP)through Route A,followed by liquid nitrogen cryogenic rolling(CR)and aging treated at 450℃.The microstructure,mechanical pr...The Cu0.9Cr0.1Zr alloy was deformed through continuous equal channel angular pressing(C-ECAP)through Route A,followed by liquid nitrogen cryogenic rolling(CR)and aging treated at 450℃.The microstructure,mechanical properties,and conductivity of the alloy were detected by electron back-scattered diffractometer,energy dispersive spectroscope,X-ray diffractometer,scanning electron microscope,and transmission electron microscope.The evolution mechanism of the texture during the deformation process and its influence on mechanical properties were analyzed.The results show that directional shear bands form in the CuCrZr alloy during the C-ECAP process,and the preferred orientation of the microstructure is consistent with the rolling direction.After deformation,the number of precipitated phases(mainly Cr)increases with the prolongation of aging time,accompanied by the appearance of micro-nanostructured fibrous structure in the alloy.After C-ECAP for three passes,75%CR deformation,and aging at 450℃ for 2 h,the tensile strength,microhardness,and conductivity reach 538 MPa,168 HV,and 80%IACS,respectively.CR,aging heat treatment,and formation of recrystallization texture are all conducive to the improvement of conductivity.展开更多
To investigate the effect of solution treatment and aging process parameters on the microstructure and mechanical properties of TB18 titanium alloy,process optimization research was conducted based on the mixed-level ...To investigate the effect of solution treatment and aging process parameters on the microstructure and mechanical properties of TB18 titanium alloy,process optimization research was conducted based on the mixed-level orthogonal experiment design of factor levels.Results show that through range analysis,the significance order of process parameters is determined as follows:solution cooling method>solution temperature>aging time>aging temperature>solution time.Considering the strength-ductility matching and engineering application requirements,the benchmark parameters are selected as solution time of 1 h,solution cooling method of air cooling(AC),aging temperature of 525℃,and aging time of 4 h.Furthermore,the effects of solution temperature in the range of 790–870℃ on the impact toughness and micro-fracture characteristics of the alloy were studied.The results reveal that the larger the area of shear lip and fibrous zone,and the smaller the area of radiation zone,the better the toughness of the alloy.With the increase in solution temperature,the length of secondary cracks on the fracture surface increases,the number of dimples increases,and the toughness is enhanced.Based on the collaborative optimization of strength and toughness,the optimal heat treatment process for TB18 alloy is determined as 870℃/1 h,AC+525℃/4 h,AC.展开更多
With the rapid increase in the aging population comes a rise in the incidence and prevalence of neurodegenerative diseases.Therefore,it is critical to understand the molecular changes that occur,which can either cause...With the rapid increase in the aging population comes a rise in the incidence and prevalence of neurodegenerative diseases.Therefore,it is critical to understand the molecular changes that occur,which can either cause disease or make brains resilient.Epigenetic changes are a common suspect and target,not only because they are among the hallmarks of aging,but also because they are flexible and could potentially be reversed.展开更多
SKI family transcriptional corepressor 1(SKOR1also known as LbxCor1, Fussel15, or CORL1), is a member of the SKI family of proteins and is transcribed from a protein-coding gene located on chromosome 15 in humans, tha...SKI family transcriptional corepressor 1(SKOR1also known as LbxCor1, Fussel15, or CORL1), is a member of the SKI family of proteins and is transcribed from a protein-coding gene located on chromosome 15 in humans, that has a molecular weight of approximately 100 kDa. Skor1 is highly expressed in neurons in the central nervous system of both humans and rodents.展开更多
In modern ZnO varistors,traditional aging mechanisms based on increased power consumption are no longer relevant due to reduced power consumption during DC aging.Prolonged exposure to both AC and DC voltages results i...In modern ZnO varistors,traditional aging mechanisms based on increased power consumption are no longer relevant due to reduced power consumption during DC aging.Prolonged exposure to both AC and DC voltages results in increased leakage current,decreased breakdown voltage,and lower nonlinearity,ultimately compromising their protective performance.To investigate the evolution in electrical properties during DC aging,this work developed a finite element model based on Voronoi networks and conducted accelerated aging tests on commercial varistors.Throughout the aging process,current-voltage characteristics and Schottky barrier parameters were measured and analyzed.The results indicate that when subjected to constant voltage,current flows through regions with larger grain sizes,forming discharge channels.As aging progresses,the current focus increases on these channels,leading to a decline in the varistor’s overall performance.Furthermore,analysis of the Schottky barrier parameters shows that the changes in electrical performance during aging are non-monotonic.These findings offer theoretical support for understanding the aging mechanisms and condition assessment of modern stable ZnO varistors.展开更多
Aging is a physiological and complex process produced by accumulative age-dependent cellular damage,which significantly impacts brain regions like the hippocampus,an essential region involved in memory and learning.A ...Aging is a physiological and complex process produced by accumulative age-dependent cellular damage,which significantly impacts brain regions like the hippocampus,an essential region involved in memory and learning.A crucial factor contributing to this decline is the dysfunction of mitochondria,particularly those located at synapses.Synaptic mitochondria are specialized organelles that produce the energy required for synaptic transmission but are also important for calcium homeostasis at these sites.In contrast,non-synaptic mitochondria primarily involve cellular metabolism and long-term energy supply.Both pools of mitochondria differ in their form,proteome,functionality,and cellular role.The proper functioning of synaptic mitochondria depends on processes such as mitochondrial dynamics,transport,and quality control.However,synaptic mitochondria are particularly vulnerable to age-associated damage,characterized by oxidative stress,impaired energy production,and calcium dysregulation.These changes compromise synaptic transmission,reducing synaptic activity and cognitive decline during aging.In the context of neurodegenerative diseases such as Alzheimer’s,Parkinson’s,and Huntington’s,the decline of synaptic mitochondrial function is even more pronounced.These diseases are marked by pathological protein accumulation,disrupted mitochondrial dynamics,and heightened oxidative stress,accelerating synaptic dysfunction and neuronal loss.Due to their specialized role and location,synaptic mitochondria are among the first organelles to exhibit dysfunction,underscoring their critical role in disease progression.This review delves into the main differences at structural and functional levels between synaptic and non-synaptic mitochondria,emphasizing the vulnerability of synaptic mitochondria to the aging process and neurodegeneration.These approaches highlight the potential of targeting synaptic mitochondria to mitigate age-associated cognitive impairment and synaptic degeneration.This review emphasizes the distinct vulnerabilities of hippocampal synaptic mitochondria,highlighting their essential role in sustaining brain function throughout life and their promise as therapeutic targets for safeguarding the cognitive capacities of people of advanced age.展开更多
Biological aging is a complex physiological process characterized by a decline in tissue function and the loss of cellular capabilities,which increase an individual's risk of various diseases[1].While genetic fact...Biological aging is a complex physiological process characterized by a decline in tissue function and the loss of cellular capabilities,which increase an individual's risk of various diseases[1].While genetic factors and lifestyle are key influences on biological aging,environmental factors also play a significant role.Given the rapid aging of the global population,elucidating the factors that influence biological aging is crucial for promoting healthy aging.展开更多
Glassy polymers are widely used in biomedical applications in a solvent environment,yet their long-term performance is governed by the competing effects of physical aging and solvent-induced plasticization.Here,we dev...Glassy polymers are widely used in biomedical applications in a solvent environment,yet their long-term performance is governed by the competing effects of physical aging and solvent-induced plasticization.Here,we develop a constitutive model that explicitly couples the solvent concentration,structural relaxation,and mechanical response.This framework is built on a multiplicative decomposition of deformation and an Eyring-type flow rule,with structural evolution described by an effective temperature.A generalized shift factor is introduced to quantify how the solvent concentration and effective temperature jointly affect the relaxation time,thereby integrating physical aging and plasticization.The model is subsequently applied to methacrylate(MA)-based copolymer networks immersed in phosphate-buffered saline for up to nine months.Simulations accurately capture key experimental features,including the strong softening of highly swellable networks,the partial recovery due to aging,and the mitigating role of hydrophobic crosslinking in reducing solvent uptake.While the current single-mode description cannot reproduce the full relaxation spectrum,it establishes an efficient framework for predicting the long-term mechanical performance under coupled environmental and mechanical loading.This study provides a constitutive description of solvent-swollen glassy polymers,offering mechanistic insight into the interplay between plasticization and aging.Beyond biomedical MA networks,this framework establishes a foundation for predicting the long-term performance of polymer glasses under coupled aqueous environmental and mechanical loading.展开更多
基金Projects(2006CB605005,2010CB631203) supported by the National Basic Research Program of ChinaProject(IRT0713) supported by Changjiang Scholars and Innovative Research Team in University,China
文摘The microstructure evolution of a new directionally solidified（DS） Ni-based superalloy used for gas turbine blades after long-term aging at 950 ℃ was investigated.The results show that the γ ＇ phase becomes more regular in dendritic arm and interdendritic area,while both the mass fraction and the size of γ ＇ phase increase gradually with increasing aging time.During long-term aging,the MC carbide dissolves on the edge to provide the carbon for the formation of M23C6 carbide by the precipitation of Cr at the grain boundary.The rose-shaped γ ＇/γ eutectic partly dissolves into γ matrix and the aging promotes it transform into raft-shape γ ＇.The microstructure is generally stable and no needle-like topologically close-packed phase（TCP） can be found after aging for 1 000 h.
文摘The relationship among B content,microstructure evolution and stress rupture properties of K4750 alloy during long-term aging were investigated.After aging at 800℃for 1000 h,the decomposition degree of MC carbides of K4750 alloys with 0 B,0.007 wt.%B and 0.010 wt.%B were basically identical,which indicated that B has no inhibition on MC carbide decomposition during long-term aging.The MC carbide decomposition was accompanied by the formation of M_(23)C_(6) carbides and a small number ofηphases,which was controlled by the outward diffusion of C and Ti combined with the inward diffusion of Ni and Cr from theγmatrix.In addition,M_(23)C_(6) carbides in boron-free alloy were in continuous chain and needle-likeηphases were precipitated near them,while M_(23)C_(6) carbides in boron-containing alloys remained in granular distribution and noηphases precipitation around them.Adding B could delay the agglomeration and coarsening of M_(23)C_(6) carbides during long-term aging,which was because the segregation of B at grain boundary retarded the diffusion of alloy elements,thus weakened the local fluctuation of chemical composition near grain boundary.The stress rupture samples of K4750 alloys with various B contents after aging at 800℃for 1000 h were tested at 750℃/380 MPa.The results indicated that the stress rupture properties of bo ron-containing alloys were significantly better than that of boron-free alloy,which could be attributed to the increase of grain boundary cohesion strength and the optimization of M_(23)C_(6) carbide distribution due to the addition of B.
文摘Thermal stabilities of microstructure and mechanical property have been investigated on superalloy U720Li, which is of great interest of application for jet engine and land-based turbine disc. The results showed that, the primary and secondary gamma' particles maintain good thermal stability at 650 and 700 degreesC with aging time up to 3000 h, while the tertiary gamma' is apparently dependent on aging temperature and time. The tertiary gamma' particles undergo a procedure of coarsening, dissolution and eventually complete disappearance with the increasing of aging time and temperature. They exhibit unusual high sensibility upon aging temperature, which is attributed to the lattice misfit between the gamma' precipitates and the matrix in the alloy. The grain boundary phase M23C6 remains stable without forming of sigma phase even with aging time up to 3000 h at 700 degreesC. Microhardness decreases apparently with increasing aging time and aging temperature. Theoretical analysis based on dislocation mechanism indicates that the change of microhardness should be attributed to the evolution of the tertiary gamma' during aging.
基金supported by the National Natural Science Foundation of China under Grant No.52001314the Natural Science Foundation of Liaoning Province of China under Grant No.2020BS-008the China Postdoctoral Science Foundation under Grant No.2020M671403。
文摘In K4750 alloy,the evolution of grain boundary(GB)precipitates,including the degradation of blocky MC carbide particles and the precipitation of granular/needle-likeηphase particles,were observed after longterm aging(LA)at 750℃for 8000 h.During MC degradation,the Ti and C released from the MC carbide combined with Ni and Cr,respectively,in theγ’matrix to formη-Ni_(3)Ti phase and Cr-rich M_(23)C_(6)carbide.Large amounts of granularηphase precipitated at GBs and the needle-likeηphase grew gradually from GBs toward the grain interior.Because of the growth of theηphase through absorbingγ’phase,γ-depleted zones were formed around theηphase.The evolution of the MC carbide andηphase was primarily responsible for the decrease of the stress rupture life and the increase of elongation.After an LA sample was tested at 750℃and 360 MPa,the residual strain distribution was investigated by electron backscatter diffraction(EBSD).The results showed that the residual strain mainly distributed at GBs,especially in the region of MC degradation and at the edges ofηphases,which was closely related to the appearance of phase interfaces.Microvoids/cracks easily initiated at phase interfaces,then easily extended along theγ-depleted zones,thus the stress rupture life of LA samples was substantially shorter than that of samples subjected to the standard treatment.In particular,because of large amounts of fine degraded MC,granular M_(23)C_(6)and granularηphase particles distributed at GBs after 750℃/8000 h LA and microvoid/crack formation could be hindered by the formation of dimples,which led to an increase of elongation.
基金financially supported by the National Key Research and Development Program of China(Grant Nos.2020YFB0311000 and 2017YFB0305201)the Fund of Key Laboratory of Advanced Materials of Ministry of Education(ADV22-12)the Jiangsu Funding Program for Excellent Postdoctoral Talent.
文摘The service performance of heat resistance steels is largely determined by the precipitation kinetics.The nucleation-growth-coarsening behaviors of precipitates in G115 martensitic heat resistance steel during long-term aging at 650℃ have been systemically investigated.The microstructural characteristics,precipitate morphology and alloying element distribution were studied by scanning electron microscopy,transmission electron microscopy and scanning transmission electron microscopy.The lognormal distribution fitting combined with the multiple regression analysis was adopted to evaluate the precipitate size distributions.Laves phase has longer incubation time,and its coarsening rate is almost one order of magnitude higher in comparison with that of M_(23)C_(6) carbide.Furthermore,the nucleation rate,number density,average radius,and volume fraction of two precipitates are simulated based on the classical nucleation theory and the modified Langer-Schwartz model.The precipitation behavior of Laves phase can be well explained with the Fe-W system as the interfacial energy takes 0.10 J/m^(2).In contrast,the simulation results of M_(23)C_(6) carbide in the Fe-Cr-C system are significantly overestimated,which results from the inhibitory effect of boron on coarsening.
基金Item Sponsored by National High-Tech Research and Development Program(863Program)of China(2012AA03A501)International Science and Technology Cooperation Program of China(2012DFG51670)
文摘Microstructure evolution and the changes in mechanical properties of HR3 Csteel during long-term aging at650,700 and 750℃ were investigated.The precipitated phases of the aging steel included M23C6 carbides,Z-phase and a trace amount of Nb（C,N）.The M23C6 carbides were distributed mainly at the grain boundary,while Z-phase was mainly inside the grains.Amounts of both M23C6 carbides and Z-phase during the aging process increased with increasing aging period and temperature.Coarsening of M23C6 carbides was influenced significantly by aging time and temperature,while the size of the Z-phase was relatively less affected by the aging time and temperature,which had a steady strengthening effect.Coarsening of the M23C6 carbides was the main reason for the decline in high temperature yield strength during long-term aging at 750℃.The M23C6 carbides were linked into a continuous chain along the grain boundary which accounted for the decrease of toughness during aging.
基金the assistances from Taiwan Water Corporation in sampling as well as the financial support。
文摘Aging of polyaluminum chloride(PACl) coagulants could significantly influence hydrolyzed Al speciation ruling coagulation performance.The goal of this study was to investigate Al species transformation through long-term aging and its impact on coagulation performance.Two kinds of commercial coagulants(PACl-1 and PACl-2) were stored for in-situ aging tests in six months to evaluate Al species variation with time and the performance of coagulation with natural turbid waters.The results showed that CaSO4 precipitation easily occur in a commercial PACl coagulant with time as it contains SO4^2- and Ca^2+.It also activates the precipitation of gibbsite Al(OH)3 in PACl with aging.Through 180 days aging,both monomeric Al(Ala) and polymeric Al(Alb) substantially transform into colloidal Al(Alc) and precipitated for both PACl coagulants.At low turbidity(10 NTU),PACl-1 has a superior turbidity reduction rate than PACl-2,while PACl-2 performs a little better turbidity re duction at high turbidity(1000 NTU) regardless of aging time.With aging time,an obvious decrease in turbidity reduction for PACl-1 coagulation is observed at low turbidity of 10 NTU,while the improvement in turbidity reduction for PACl-2 coagulation by enhanced sweep flocculation can be achieved as Alb mostly transform into Alc after 150 days aging.It is concluded that dominant in-situ formed Alc after a long time hydrolysis can improve PACl coagulation efficiency in turbidity reduction by enhanced sweep flocculation,especially for low turbidity water,but the increase in preformed Alc in PACl would worsen particle destabilization after aging.
基金This project is financially supported by the Natural Science Foundation of Shandong Province ( Y2001F06) and the Fund for Outstanding Young Researcher of Shandong Province
文摘Microstructures of a CuZnAlMnNi shape memory alloy in the as-quenched andlong-term aged conditions were investigated by transmission electron microscopy. Aged for one yearin martensite phase, an equilibrium α-phase with fcc structure was observed in the M18R martensitematrix, accompanied by the appearance of a novel diffraction pattern. By analysis, it was suggestedthat the novel pattern results from the α-phase and the martensite matrix remaining in seven fineplates which produce intense secondary diffraction effect when the diffraction beams enter from onephase into another.
基金supported by the National Basic Research Program of China (Grant No. 2007CB209801)the National Natural Science Fundation of China (Grant No. 51371030)the National High Technology Research and Development Program of China (Grant No. 2013AA031601)
文摘In view of developing novel alloys for applications in supercritical water-cooled reactor fuel cladding and in-core components, a 12%Cr reduced activation ferrite/martensite(RAFM) steel with good corrosion resistance and irradiation performance was developed. V and Ta were added to form fine MX type carbonitrides and enhance the high temperature creep rupture strength. Microstructure stability of the steel during long-term aging at 650 C was studied experimentally combined with the simulation of ThermoCalc and DICTRA software. The results show that the precipitates in the steel during long-term aging contain M23C6, MX and Laves phase. M23C6 carbides play a major role in the stabilization of the tempered martensite lath structure by exerting a large Zener pinning force as compared with MX and Laves phase.Adding V and Ta in the steel can not only promote MX precipitation, but also refine M23C6 carbides and thus improve the thermal stability of lath/subgrains, which is beneficial to the improvement of high temperature microstructure stability of the 12%Cr RAFM steel.
文摘The effects of electric field intensity and treatment temperature on the microstructures of GH4199 superalloy after long-term aging were investigated. The results show that the number and size of carbides and TCP(σphase andμphase) phase in the alloy increase with increasing electric field intensity at the same heat treatment temperature and holding time. While the number and size of carbides and TCP phase are weekly influenced by treatment temperature with lower electric field intensity of 2 kV/cm. When the treat temperature is up to 1 093 K, annealing twins appear in the alloy, and the number of twins increases with increasing holding time. Since the electric field can provide the enough energy for the movement of vacancies and atom, it is considered that the nucleus of the twins formed with formation stack faults due to the mismatch of local atom in crystal caused by the vacancies, and the twins will grow with the increase of holding time. Meanwhile, such promoting effects on atom movement of the electric field increase with the increase of the electric field intensity, meantime the carbides and TCP phase grow fast with the increase of electric field intensity.
基金supported by the National Natural Science Foundation of China (42505149,41925023,U2342223,42105069,and 91744208)the China Postdoctoral Science Foundation (2025M770303)+1 种基金the Fundamental Research Funds for the Central Universities (14380230)the Jiangsu Funding Program for Excellent Postdoctoral Talent,and Jiangsu Collaborative Innovation Center of Climate Change。
文摘Countries around the world have been making efforts to reduce pollutant emissions. However, the response of global black carbon(BC) aging to emission changes remains unclear. Using the Community Atmosphere Model version 6 with a machine-learning-integrated four-mode version of the Modal Aerosol Module, we quantify global BC aging responses to emission reductions for 2011–2018 and for 2050 and 2100 under carbon neutrality. During 2011–18, global trends in BC aging degree(mass ratio of coatings to BC, R_(BC)) exhibited marked regional disparities, with a significant increase in China(5.4% yr^(-1)), which contrasts with minimal changes in the USA, Europe, and India. The divergence is attributed to opposing trends in secondary organic aerosol(SOA) and sulfate coatings, driven by regional changes in the emission ratios of corresponding coating precursors to BC(volatile organic compounds-VOCs/BC and SO_(2)/BC). Projections under carbon neutrality reveal that R_(BC) will increase globally by 47%(118%) in 2050(2100), with strong convergent increases expected across major source regions. The R_(BC) increase, primarily driven by enhanced SOA coatings due to sharper BC reductions relative to VOCs, will enhance the global BC mass absorption cross-section(MAC) by 11%(17%) in 2050(2100).Consequently, although the global BC burden will decline sharply by 60%(76%), the enhanced MAC partially offsets the magnitude of the decline in the BC direct radiative effect, resulting in the moderation of global BC DRE decreases to 88%(92%) of the BC burden reductions in 2050(2100). This study highlights the globally enhanced BC aging and light absorption capacity under carbon neutrality, thereby partly offsetting the impact of BC direct emission reductions on future changes in BC radiative effects globally.
基金National Natural Science Foundation of China,No.81901336(to JM).
文摘Subarachnoid hemorrhage is a subtype of stroke that causes severe neurological damage and is associated with poor long-term prognosis.Cognitive impairment is a major manifestation of long-term neurological dysfunction in patients with subarachnoid hemorrhage.However,there is notable absence of biological markers to predict long-term prognosis in this patient population.Given the aging-like neurocognitive phenomena associated with subarachnoid hemorrhage,this study postulates that telomere length,a recognized biomarker for aging,could be used as a prognostic indicator for subarachnoid hemorrhage.A left internal carotid artery intravascular puncture mouse model was used to simulate subarachnoid hemorrhage.Comprehensive neurological test scores were obtained through neurobehavioral assessments conducted at one-month intervals.Concurrently,the relative telomere length was analyzed by quantitative polymerase chain reaction,which was performed using DNA extracted from ear notch and brain tissue after each assessment.Furthermore,proteomic analysis was employed to investigate differential protein expression in hippocampal tissue.Subarachnoid hemorrhage mice exhibited persistent neurocognitive impairment over a prolonged period of time.There was a significant positive correlation between telomere length and neurological test scores,confirming the usefulness of telomere length as a prognostic indicator in subarachnoid hemorrhage.Hippocampal tissue from subarachnoid hemorrhage mice showed reduced expression of acetyl-coenzyme A synthetase-2 and abnormalities in the expression of proteins related to ribosomes,energy metabolism,and cellular signal transduction.This study confirmed telomere shortening in the brain and metabolic disturbances in the hippocampi of subarachnoid hemorrhage mice.Thus,telomere length is a predictive marker for long-term impairment of cognitive function in mice following experimental subarachnoid hemorrhage.
基金Gansu Provincial Department of Education Industrial Support Program Project(2025CYZC-069)Central Government-Guided Local Science and Technology Development Fund Project(25ZYJE002)National Natural Science Foundation of China(51861022,51261016)。
文摘The Cu0.9Cr0.1Zr alloy was deformed through continuous equal channel angular pressing(C-ECAP)through Route A,followed by liquid nitrogen cryogenic rolling(CR)and aging treated at 450℃.The microstructure,mechanical properties,and conductivity of the alloy were detected by electron back-scattered diffractometer,energy dispersive spectroscope,X-ray diffractometer,scanning electron microscope,and transmission electron microscope.The evolution mechanism of the texture during the deformation process and its influence on mechanical properties were analyzed.The results show that directional shear bands form in the CuCrZr alloy during the C-ECAP process,and the preferred orientation of the microstructure is consistent with the rolling direction.After deformation,the number of precipitated phases(mainly Cr)increases with the prolongation of aging time,accompanied by the appearance of micro-nanostructured fibrous structure in the alloy.After C-ECAP for three passes,75%CR deformation,and aging at 450℃ for 2 h,the tensile strength,microhardness,and conductivity reach 538 MPa,168 HV,and 80%IACS,respectively.CR,aging heat treatment,and formation of recrystallization texture are all conducive to the improvement of conductivity.
基金Key Program of National Natural Science Foundation of China(52431001)。
文摘To investigate the effect of solution treatment and aging process parameters on the microstructure and mechanical properties of TB18 titanium alloy,process optimization research was conducted based on the mixed-level orthogonal experiment design of factor levels.Results show that through range analysis,the significance order of process parameters is determined as follows:solution cooling method>solution temperature>aging time>aging temperature>solution time.Considering the strength-ductility matching and engineering application requirements,the benchmark parameters are selected as solution time of 1 h,solution cooling method of air cooling(AC),aging temperature of 525℃,and aging time of 4 h.Furthermore,the effects of solution temperature in the range of 790–870℃ on the impact toughness and micro-fracture characteristics of the alloy were studied.The results reveal that the larger the area of shear lip and fibrous zone,and the smaller the area of radiation zone,the better the toughness of the alloy.With the increase in solution temperature,the length of secondary cracks on the fracture surface increases,the number of dimples increases,and the toughness is enhanced.Based on the collaborative optimization of strength and toughness,the optimal heat treatment process for TB18 alloy is determined as 870℃/1 h,AC+525℃/4 h,AC.
基金David and Inez Myers Foundation,the Israeli Ministry of Science and Technology(MOST)The Israel Science Foundation(No.422/23)(to DT).
文摘With the rapid increase in the aging population comes a rise in the incidence and prevalence of neurodegenerative diseases.Therefore,it is critical to understand the molecular changes that occur,which can either cause disease or make brains resilient.Epigenetic changes are a common suspect and target,not only because they are among the hallmarks of aging,but also because they are flexible and could potentially be reversed.
基金supported by Science Foundation Ireland (Grant 19/FFP/6666),Cure Parkinson’s (Grant CP:GO01)a PhD studentship from the Anatomical Society。
文摘SKI family transcriptional corepressor 1(SKOR1also known as LbxCor1, Fussel15, or CORL1), is a member of the SKI family of proteins and is transcribed from a protein-coding gene located on chromosome 15 in humans, that has a molecular weight of approximately 100 kDa. Skor1 is highly expressed in neurons in the central nervous system of both humans and rodents.
文摘In modern ZnO varistors,traditional aging mechanisms based on increased power consumption are no longer relevant due to reduced power consumption during DC aging.Prolonged exposure to both AC and DC voltages results in increased leakage current,decreased breakdown voltage,and lower nonlinearity,ultimately compromising their protective performance.To investigate the evolution in electrical properties during DC aging,this work developed a finite element model based on Voronoi networks and conducted accelerated aging tests on commercial varistors.Throughout the aging process,current-voltage characteristics and Schottky barrier parameters were measured and analyzed.The results indicate that when subjected to constant voltage,current flows through regions with larger grain sizes,forming discharge channels.As aging progresses,the current focus increases on these channels,leading to a decline in the varistor’s overall performance.Furthermore,analysis of the Schottky barrier parameters shows that the changes in electrical performance during aging are non-monotonic.These findings offer theoretical support for understanding the aging mechanisms and condition assessment of modern stable ZnO varistors.
基金supported by ANID FONDECYT No.1221178Centro Ciencia&Vida,FB210008,Financiamiento Basal para Centros Científicos y Tecnológicos de Excelencia de ANID to CTR.
文摘Aging is a physiological and complex process produced by accumulative age-dependent cellular damage,which significantly impacts brain regions like the hippocampus,an essential region involved in memory and learning.A crucial factor contributing to this decline is the dysfunction of mitochondria,particularly those located at synapses.Synaptic mitochondria are specialized organelles that produce the energy required for synaptic transmission but are also important for calcium homeostasis at these sites.In contrast,non-synaptic mitochondria primarily involve cellular metabolism and long-term energy supply.Both pools of mitochondria differ in their form,proteome,functionality,and cellular role.The proper functioning of synaptic mitochondria depends on processes such as mitochondrial dynamics,transport,and quality control.However,synaptic mitochondria are particularly vulnerable to age-associated damage,characterized by oxidative stress,impaired energy production,and calcium dysregulation.These changes compromise synaptic transmission,reducing synaptic activity and cognitive decline during aging.In the context of neurodegenerative diseases such as Alzheimer’s,Parkinson’s,and Huntington’s,the decline of synaptic mitochondrial function is even more pronounced.These diseases are marked by pathological protein accumulation,disrupted mitochondrial dynamics,and heightened oxidative stress,accelerating synaptic dysfunction and neuronal loss.Due to their specialized role and location,synaptic mitochondria are among the first organelles to exhibit dysfunction,underscoring their critical role in disease progression.This review delves into the main differences at structural and functional levels between synaptic and non-synaptic mitochondria,emphasizing the vulnerability of synaptic mitochondria to the aging process and neurodegeneration.These approaches highlight the potential of targeting synaptic mitochondria to mitigate age-associated cognitive impairment and synaptic degeneration.This review emphasizes the distinct vulnerabilities of hippocampal synaptic mitochondria,highlighting their essential role in sustaining brain function throughout life and their promise as therapeutic targets for safeguarding the cognitive capacities of people of advanced age.
基金support from the Shenzhen Science and Technology program(grant number 202208183000115)。
文摘Biological aging is a complex physiological process characterized by a decline in tissue function and the loss of cellular capabilities,which increase an individual's risk of various diseases[1].While genetic factors and lifestyle are key influences on biological aging,environmental factors also play a significant role.Given the rapid aging of the global population,elucidating the factors that influence biological aging is crucial for promoting healthy aging.
基金the funding support from the Smart Medicine and Engineering Interdisciplinary Innovation Project of Ningbo University(No.ZHYG003)。
文摘Glassy polymers are widely used in biomedical applications in a solvent environment,yet their long-term performance is governed by the competing effects of physical aging and solvent-induced plasticization.Here,we develop a constitutive model that explicitly couples the solvent concentration,structural relaxation,and mechanical response.This framework is built on a multiplicative decomposition of deformation and an Eyring-type flow rule,with structural evolution described by an effective temperature.A generalized shift factor is introduced to quantify how the solvent concentration and effective temperature jointly affect the relaxation time,thereby integrating physical aging and plasticization.The model is subsequently applied to methacrylate(MA)-based copolymer networks immersed in phosphate-buffered saline for up to nine months.Simulations accurately capture key experimental features,including the strong softening of highly swellable networks,the partial recovery due to aging,and the mitigating role of hydrophobic crosslinking in reducing solvent uptake.While the current single-mode description cannot reproduce the full relaxation spectrum,it establishes an efficient framework for predicting the long-term mechanical performance under coupled environmental and mechanical loading.This study provides a constitutive description of solvent-swollen glassy polymers,offering mechanistic insight into the interplay between plasticization and aging.Beyond biomedical MA networks,this framework establishes a foundation for predicting the long-term performance of polymer glasses under coupled aqueous environmental and mechanical loading.
