Royal jelly(RJ)is rich in various nutrients with multiple health-promoting properties.This study aims to evaluate whether RJ can modulate related metabolite in the natural aging mice.Male C57BL/6J mice drank RJ soluti...Royal jelly(RJ)is rich in various nutrients with multiple health-promoting properties.This study aims to evaluate whether RJ can modulate related metabolite in the natural aging mice.Male C57BL/6J mice drank RJ solution daily for 9 months.Determination of serum lipids and pathological analysis exhibited that triglycerides,serum cholesterol,and low-density lipoprotein cholesterol were decreased by 31.15%,9.96%,and 22.58%,respectively,the morphology of brain nerve cells was also effectively recovered after RJ intervention.Lipidomic analysis showed that RJ could improve the levels of different kinds of lipids in aging mice brain,especially by increasing the content of antioxidant ether ester,and that the ratio of monounsaturated fatty acid to polyunsaturated fatty acid was up by 23.46%,which could alleviate oxidative stress.Moreover,the metabolism of glycerol phospholipids,glycerols,and fatty acids in aging mice could be regulated by RJ.RJ intervention can effectively improve lipid metabolism disorders caused by aging.展开更多
The influences of high temperature pre-straining (HT-PS) on the natural aging and bake hardening of Al?Mg?Si alloys were investigated by Vickers microhardness measurements, differential scanning calorimetry (DSC) anal...The influences of high temperature pre-straining (HT-PS) on the natural aging and bake hardening of Al?Mg?Si alloys were investigated by Vickers microhardness measurements, differential scanning calorimetry (DSC) analysis and transmission electron microscopy (TEM) characterization. The results show that pre-straining at 170 °C immediately after quenching can effectively resolve the rather high T4 temper hardness caused by the conventional room temperature (RT) pre-straining treatment, and give a better bake hardening response (BHR) after paint-bake cycle. HT-PS 7% at 170 °C for 10 min is chosen as the optimum process as it provides lower T4 temper hardness and better BHR. The simultaneous introduction of dislocations and Cluster (2) can significantly suppress the natural aging and promote the precipitation of β″ phase, and reduce the effects of deformation hardening by dynamic recovery.展开更多
Seed storability （SS） is an important trait for agronomic production and germplasm preservation in rice （Oryza sativa L.）. Quantitative trait locus （QTL） for seed storability in three storage periods was identif...Seed storability （SS） is an important trait for agronomic production and germplasm preservation in rice （Oryza sativa L.）. Quantitative trait locus （QTL） for seed storability in three storage periods was identified using two sets of recombinant inbred lines （RILs） derived from the crosses with a colnmon female parent Shennong 265 （SN265）. Ten QTLs for seed storability were detected on chromosomes 1, 2, 3, 4, 6, 8, and 12in SL-RILs （SN265/Lijiangxingtuanheigui （LTH））, and a total of 12 QTLs were identified on chromosomes 2, 3, 4, 6, 9, and 10 in SH-RILs （SN265/Luhui 99 （LH99））in different storage periods. Among these QTLs, five major QTLs were identified in more than one storage period. The qSS3-1, qSS3-2, qSS12-1, and qSS12-2 were detected in SL-RILs. Similarly, qSS2-2, qSS2-3, qSS6-2, qSS6-3, qSS6-4, qSS9-1, and qSS9-2 were detected in SH-RILs. In addition, the maximum phenotypic variation was derived from the qSS6-1 and qSS9-2, explaining 53.58 and 29.09%, respectively, while qSS6-1 was a new stable QTL for seed storability. These results provide an opportunity for pyramiding and map-based cloning major QTLs for seed storability in rice.展开更多
For a series of Al-0.34／%Mg-1.05／%Si-0.08／%Cu alloys, the effects of pre-treatment on natural aging, bake hardening response and plasticity were investigated using Vickers hardness test and tensile test. Differenti...For a series of Al-0.34／%Mg-1.05／%Si-0.08／%Cu alloys, the effects of pre-treatment on natural aging, bake hardening response and plasticity were investigated using Vickers hardness test and tensile test. Differential scanning calorimetry （DSC） analysis was conducted to reveal corresponding precipitation mechanisms. The results showed that pre-straining and pre-aging alone couldn＇t completely suppress natural aging and improve bake hardening response simultaneously. The sensitivity of the pre-straining and pre-aging on the mechanical properties was evaluated. It was found that pre-aging was the main factor which greatly improved bake hardening response and pre-treatment had a weak influence on plasticity in pre-treated samples. DSC analysis showed that the dissolution trough of clusters disappeared in pre-treated samples, both β”and β＇ precipitation peak shifted to lower temperature and were reduced in pre-strained and pre-aged samples. It was concluded that the formation of Mg/Si clusters was replaced by the accelerated precipitation ofβ” andβ＇ phases, which caused the suppression of natural aging and the improvement of bake hardening response （BHR）.展开更多
The microstructure and mechanical properties of friction stir welded 2. 5 mm 7050-T7451 aluminum alloy natural aging 72 h and 17 520 h were investigated, respectively. The uniaxial tensile test showed that yield stren...The microstructure and mechanical properties of friction stir welded 2. 5 mm 7050-T7451 aluminum alloy natural aging 72 h and 17 520 h were investigated, respectively. The uniaxial tensile test showed that yield strength, tensile strength and elongation of the joints 17 520 h natural aging were about 20%, 12% and 24% higher than those joints natural aging 72 h. Hardness profile of natural aging 17 520 h joint witnessed significant enhancement in nugget zone, compared with 72 h natural aging. Differential scanning calorimetry （ DSC ） and transmission electron microscopy （TEM） test revealed that more Guinier-Preston zone, η＇ and 71 phase emerged in nugget zone as natural aging duration increased, high density of dislocation located within grain boundary in nugget zone of joints natural aging 72 h. It is concluded that natural aging was feasible to enhalwe strength and plasticity of FSW joints simultaneously.展开更多
Enhancing the strength of Al-Zn-Mg alloys is critical to the weight-lightening of structural components in the application of high-speed trains and aerospace industries,while high stress corrosion cracking(SCC)suscept...Enhancing the strength of Al-Zn-Mg alloys is critical to the weight-lightening of structural components in the application of high-speed trains and aerospace industries,while high stress corrosion cracking(SCC)susceptibility of Al-Zn-Mg alloys(especially the alloy with high recrystallization fraction)with high strength makes it difficult.In this study,the influence of tensile stress-aging coupled with natural aging pre-treatment on the mechanical properties and SCC resistance of Al-Zn-Mg alloy with high recrystallization fraction has been investigated.The results show that tensile stress-aging at 160℃can inhibit the dissolution of clusters/Guinier-Preston(GP)zones formed during long-term natural aging pre-treatment,which increases the number density of matrix precipitates(MPts),narrow the width of precipitate free zone(PFZ),and dramatically improve the mechanical properties of the experimental Al-Zn-Mg alloy.Meanwhile,the precipitation of the high density of MPts within the matrix will assume a large number of solute atoms during artificial aging,which will reduce the supplement of solute atoms to grain boundaries.As a result,the volume of anodic active grain boundary precipitates(GBPs)and the content of free solute atoms at grain boundaries are reduced,which reduces the possibility of initial nucleation and propagation of SCC crack.The coupled treatment method proposed in this study proves efficient in resolving the contradiction between the strength and SCC resistance in Al-Zn-Mg alloy.展开更多
Currently,accelerated aging tests are widely used to study the aging process of polyethylene pipelines.However,this approach can only simulate one or several main influencing factors in the natural environment,which a...Currently,accelerated aging tests are widely used to study the aging process of polyethylene pipelines.However,this approach can only simulate one or several main influencing factors in the natural environment,which are often quite different from the actual environment of the buried pipelines.In this study,five types of PE80 buried pipelines in service for 9e18 years were taken as the research object,while new PE80 pipelines were taken as the reference group.The aging process and mechanism of polyethylene buried pipelines were studied through mechanical and chemical property tests and microstructural analysis.The results showed that the pipeline exhibited cross-linking as the main aging mechanism after being in service for 0e18 years.The aging degree and law of the inner and outer surface of the pipeline were compared,and the observed mechanism of both surfaces was explained.After 18 years in service,the elongation at the break of the pipe decreased by 16.2%,and the toughness of the matrix in the main collapse area of the tensile sample was the fundamental reason responsible for changes in the mechanical properties.Finally,after 18 years in service,the oxidation induction time of the pipeline was 25.7 min,which was 28.5% higher than the national standard value.There were no potential safety hazards during continuous long-term service.The results of this paper provide reference data and theoretical guidance for the aging process study of buried polyethylene pipelines.展开更多
Two kinds of high pure silver materials with 5.3 ppm oxygen and 32.7 ppm oxygen were prepared by various melting processes, both samples were subjected to accumulative rolling with 95% thickness reduction. Their mecha...Two kinds of high pure silver materials with 5.3 ppm oxygen and 32.7 ppm oxygen were prepared by various melting processes, both samples were subjected to accumulative rolling with 95% thickness reduction. Their mechanical properties were tested during long natural aging. Results showed that the Ag sheet with 5.3 ppm oxygen is at full annealed state when natural aging 58 days or kept at 150℃ for 30 minutes, and the Ag sheet with 32.7 ppm oxygen is a little of recovery when natural aging a year. It is suggested that appropriate oxygen interstitial solute in Ag solid solution and a few of Ag2O particles at Ag grain boundaries impede the recovery and recrystallization of Ag sheets.展开更多
The microstructures and damping property of supersaturated ZnA127Ce alloy during natural aging have been investigated. H-800 TEM was mainly used to research the microstructures. The relationship between microstructure...The microstructures and damping property of supersaturated ZnA127Ce alloy during natural aging have been investigated. H-800 TEM was mainly used to research the microstructures. The relationship between microstructure and damping property was primarily studied. The results showed that solution plus natural aging was the best heat treatment, which could improve the damping property. Both continuous precipitation and cellular reaction occurred during the aging. Continuous precipitation follows the sequence: β→spherical GP zones→elliptical GP zones→intermediate phase R→n. The cellular reaction can be written as follows:β→a+n+ε.展开更多
This paper describes pre-treatment methods to improve the bake-hardening response of naturally aged AA6022 （Al-0.6Mg-1.0Si）, which is an alloy used in automotive body panels. These methods are used to accelerate the...This paper describes pre-treatment methods to improve the bake-hardening response of naturally aged AA6022 （Al-0.6Mg-1.0Si）, which is an alloy used in automotive body panels. These methods are used to accelerate the artificial aging process, which proceeds 30-day period of natural aging. The precipitation behavior of the sheets of this aluminum alloy was analyzed by differential scanning calorimetry （DSC） and electrical conductivity measurements, and subsequently confirmed by microstructure observations by transmission electron microscopy （TEM）. Tensile tests and microhardness measurements were performed to determine the mechanical properties of the samples. Under simulated paint-baking conditions （30 min at 170℃）, the microhardness and the yield strength （YS） of the pre-strained ＋ pre-aged samples were found to be I13 HV and 225 MPa, respectively. These values are considerably higher than those of pre-aged samples, and they did not decrease significantly during the initial stage of artificial aging.展开更多
The accelerating pace of global aging underscores the need for a deeper understanding of the aging process and the identification of effective anti-aging substances,whether from natural sources or synthetic compounds....The accelerating pace of global aging underscores the need for a deeper understanding of the aging process and the identification of effective anti-aging substances,whether from natural sources or synthetic compounds.Currently,most drugs aimed at preventing or treating ageing,such as metformin,nicotinamide adenine dinucleotide(NAD*)precursors,etc.,are still in the research phase and come with safety concerns and side effects.展开更多
Hydrochar has potential applications in soil improvement and heavy metal remediation.Hydrochar would undergo the process of aging when introduced into the soil,altering its properties.However,recent studies have focus...Hydrochar has potential applications in soil improvement and heavy metal remediation.Hydrochar would undergo the process of aging when introduced into the soil,altering its properties.However,recent studies have focused mainly on the artificial aging of hydrochar,which could not reveal the cumulative effect of multiple environmental factors.Therefore,the periodical monitoring of the property and sorption behavior of hydrochar after amending soils is necessary to better understand the multifaceted mechanisms associated with the natural aging of hydrochar.This study selected the sludge-derived hydrochar(SLHC)as a typical hydrochar and applied a 16-month rice-wheat-rice rotation to mimic the natural aging of hydrochar,focusing on changing properties and cadmium(Cd)sorption and literature contrast between aging strategies and biochar types.The porosity,O abundance,and ash content of 16-month aged SLHC increased by 37%,47%,and 8.5%,respectively,facilitating Cd sorption due to surface complexation,pore sorption,and precipitation.The sorption percentage of Cd to SLHC was in the range of 11-14%for SLHC-A0 and increased to 17-31%for SLHC-A4 and 20-32%for SLHC-A16 after natural aging.The natural aging of SLHC induced by ash content played an essential role in Cd sorption site heterogeneity.Linear regression analysis showed that aging strategies on sorption behavior significantly differed between biochars.Thus,studies involving natural aging with multiple environmental factors are preferred over those involving chemical or biological aging.Future studies should continue to explore the mechanisms of natural aging-induced heavy metal sorption between hydrochar and pyrochar.These results improve insights to appraise the potential of SLHC as soil amendments to alleviate the adverse effects of heavy metal contamination and provide an essential basis for researchers and staff in soil management and environmental prevention.展开更多
Artificial ageing above 165℃directly after quenching induces the formation of^50 nm wide precipitatefree zone(PFZ)and^100 nm wide precipitate-sparse zone(PSZ)consisting of coarse precipitates with a gradient in size ...Artificial ageing above 165℃directly after quenching induces the formation of^50 nm wide precipitatefree zone(PFZ)and^100 nm wide precipitate-sparse zone(PSZ)consisting of coarse precipitates with a gradient in size and density toward the grain center in a commercial Al-Zn-Mg-Cu alloy.With the grain size decreasing,the fraction of PFZ and PSZ in a grain becomes larger and could even occupy the entire volume of the grain.This undesirable microstructure near the grain boundary is mitigated substantially by natural pre-ageing,leading to an exceptional enhancement of the age hardening potential at elevated temperatures.Natural ageing could fundamentally alter the precipitation near grain boundary,and is a promising method to optimize the precipitation hardening in high strength aluminum alloys with unconventionally small grains.展开更多
The high-strength Al-Zn-Mg-Cu alloy provides much better dent resistance and weight-reduction potential compared to the conventional Al alloys used for the automobile body panels.However,natural ageing(NA)significantl...The high-strength Al-Zn-Mg-Cu alloy provides much better dent resistance and weight-reduction potential compared to the conventional Al alloys used for the automobile body panels.However,natural ageing(NA)significantly reduces the formability of Al-Zn-Mg-Cu alloy.The reversion of natural ageing has been systematically investigated by hardness test,tensile test,differential scanning calorimetry(DSC)and transmission electron microscopy(TEM).Substantial reversion of natural ageing and thus hardness decrease occurs immediately upon thermal treatment at 120–210℃in an Al-Zn-Mg-Cu alloy.Although the hardness of the most reverted state decreases with increasing temperature,the lowest hardness is still higher than the as-quenched state by 30 HV.As revealed by the complementary DSC and TEM observations,this is ascribed to the synchronization of the dissolution and the re-precipitation of the solutes in the NA clusters during reversion ageing.Reversion at 180–210℃for less than 30 s leads to a hardness decline of 40 HV.The hardening kinetics during NA after reversion is slower than that during first-time NA due to the reduced vacancy concentration.Artificial ageing at 180℃for 30 min after secondary NA of less than 24 h induces intensive precipitation of plate-like pre-ηphases and a giant strength increase of 188–204 MPa.Potential use of high strength Al-Zn-Mg-Cu alloy in automobile body panels could be realized by appropriate reversion treatment improving the formability and the quick bake hardening response.展开更多
In situ testing provides accurate characterization of existing degradation mechanisms of materials and building systems which helps reducing the subjectivity of visual inspections especially when ageing under natural ...In situ testing provides accurate characterization of existing degradation mechanisms of materials and building systems which helps reducing the subjectivity of visual inspections especially when ageing under natural ageing conditions is carried out over significant periods of time. In this work, data collected from field experimental campaigns over 10 years after construction using several premixed one-coat rendered walls and over 4 and 6 years after construction in the case of ETICS （external thermal insulation composite systems） are presented and discussed. The influence of hydrophobic agents on the performance of both types of facades in terms of surface condition and water penetration was assessed by visual inspections, Karsten test and capillary tests. Additionally, adhesion tests and subsequent evaluation of porosity were also carried out for premixed one-coat mortars. The results obtained have shown that ageing of the rendering solutions, especially after 5 or 6 years in-service, results from the loss of resistance to liquid water penetration, especially at the surface. Yet, additional mechanisms such as leaching of hydrophobic agents and photochemical degradation are thought to be involved, too. Moreover, the results obtained using the Karsten test proved to be the most reliable method to determine the loss of water penetration resistance and predict the ageing of facade solutions. The information collected and the correlations established can help developing solutions to prevent early ageing and implement appropriate maintenance plans to delay their effect.展开更多
The stability of the microstructure and mechanical properties of the pre-hardened sheets during the pre-hardening forming(PHF)process directly determines the quality of the formed components.The microstructure stabili...The stability of the microstructure and mechanical properties of the pre-hardened sheets during the pre-hardening forming(PHF)process directly determines the quality of the formed components.The microstructure stability of the pre-hardened sheets was in-vestigated by differential scanning calorimetry(DSC),transmission electron microscopy(TEM),and small angle X-ray scattering(SAXS),while the mechanical properties and formability were analyzed through uniaxial tensile tests and formability tests.The results in-dicate that the mechanical properties of the pre-hardened alloys exhibited negligible changes after experiencing 1-month natural aging(NA).The deviations of ultimate tensile strength(UTS),yield strength(YS),and sheet formability(Erichsen value)are all less than 2%.Also,after different NA time(from 48 h to 1 month)is applied to alloys before pre-hardening treatment,the pre-hardened alloys possess stable microstructure and mechanical properties as well.Interestingly,with the extension of NA time before pre-hardening treatment from 48 h to 1 month,the contribution of NA to the pre-hardening treatment is limited.Only a yield strength increment of 20 MPa is achieved,with no loss in elongation.The limited enhancement is mainly attributed to the fact that only a limited number of clusters are transformed into Guinier-Preston(GP)zones at the early stage of pre-hardening treatment,and the formation ofθ''phase inhibits the nucleation and growth of GP zones as the precipitated phase evolves.展开更多
A novel porous metal fiber sintered sheet （PMFSS） with a three-dimensional reticulated structure was fabricated by multi-tooth cutting and high-temperature solid-phase sintering process with copper fibers. A uniaxia...A novel porous metal fiber sintered sheet （PMFSS） with a three-dimensional reticulated structure was fabricated by multi-tooth cutting and high-temperature solid-phase sintering process with copper fibers. A uniaxial tensile test was conducted to investigate the effect of fiber length and natural aging factor on the tensile properties of the PMFSS. Results indicated that, under given stress, the increase of fiber length helped reinforce the tensile strength. The elongation of the PMFSS with medium length fiber of 15 mm exhibited the optimal performance, reaching about 13.5%. After natural aging treatment for a month, the tensile strength of PMFSS significantly decreased, but the change of elongation was negligible except for the one with the shortest fiber length of 5 mm, whose elongation was effectively improved. The morphological fracture features of PMFSSs were also characterized.展开更多
Conventional friction stir welding(FSW)and ultrasonic assisted friction stir welding(UAFSW)were employed to weld 6-mm thick 7 N01-T4 aluminum alloy plates.Weld forming characteristics and material flow behavior in the...Conventional friction stir welding(FSW)and ultrasonic assisted friction stir welding(UAFSW)were employed to weld 6-mm thick 7 N01-T4 aluminum alloy plates.Weld forming characteristics and material flow behavior in these two different welding processes were studied and compared.Ultrasonic vibration was applied directly on the weld in axial direction through the welding tool.Metal flow behavior,microstructure characteristics in the nugget zone(NZ)and evolution of the mechanical properties of naturally aged joints were studied.Results show that the ultrasonic vibration can significantly increase the welding speed of defect-free welded joint.At the rotation speed of 1200 rpm,the UAFSW can produce defect-free welded joints at a welding speed that is 50%higher than that of the conventional FSW.Ultrasonic vibrations can also improve surface quality of the joints and reduce axial force by 9%.Moreover,ultrasonic vibrations significantly increase the volume of the pin-driven zone(PDZ)and decrease the thickness of the transition zone(TZ).The number of subgrains and deformed grains resulting from the UAFSW is higher than that from the FSW.By increase the strain level and strain gradient in the NZ,the ultrasonic vibrations can refine the grains.Ultrasonic energy is the most at the top of the NZ,and gradually reduces along the thickness of the plate.The difference in strengths between the FSW and the UAFSW joints after post-weld natural aging(PWNA)is small.However,the elongation of the UAFSW is8.8%higher than that of the FSW(PWNA for 4320 h).Fracture surface observation demonstrates that all the specimens fail by ductile fracture,and the fracture position of the UAFSW joint changes from HAZ(PWNA for 120 h)to NZ(PWNA for 720 and 4320 h).展开更多
The effect of Er on the microhardness and precipitation behavior of the heat-treated Al−Si−Mg alloy was investigated by microhardness tester and TEM.As a comparison,the influence of natural aging was also studied.It i...The effect of Er on the microhardness and precipitation behavior of the heat-treated Al−Si−Mg alloy was investigated by microhardness tester and TEM.As a comparison,the influence of natural aging was also studied.It is shown that the thermal stability of the over-aged Al−Si−Mg−Er alloy is highly related to the average size of the precipitates.The average size ofβ''precipitates in Al−Si−Mg−Er alloy is smaller than that in Al−Si−Mg alloy,and the distribution is more localized under condition of without introducing natural aging.However,when natural aging is introduced before artificial aging,the Al−Si−Mg−Er alloy has similar average size and distribution of precipitates with the Al−Si−Mg alloy,resulting in similar mechanical properties.The effect of Er on the precipitation kinetics in the alloy was also discussed in detail to explain these phenomena.展开更多
Effects of natural aging and test temperature on the tensile behaviors have been studied for a highperformance cast aluminum alloy Al–10Si–1.2Cu–0.7Mn. Based on self-strengthening mechanism and spheroidization micr...Effects of natural aging and test temperature on the tensile behaviors have been studied for a highperformance cast aluminum alloy Al–10Si–1.2Cu–0.7Mn. Based on self-strengthening mechanism and spheroidization microstructures, the alloy tested at room temperature（RT） exhibits higher 0.2% proof stress（YS） of 206 MPa, ultimate tensile strength（UTS） of 331 MPa and elongation of 10%. Increasing aging time improves the YS and UTS and reduces the ductility of the alloy. Further increasing aging time beyond72 h does not signi？cantly increase the tensile strengths. Increasing test temperature significantly decreases the tensile strengths and increases the ductility of the alloy. The UTS of the alloy can be estimated by using the hardness. The Portevin–Le Chatelier effect occurs at RT due to the interactions between solid solution atoms and dislocations. Similar behaviors occurring at 250℃ are attributed to dynamic strain aging mechanism. Increasing aging time leads to decrease in the strain-hardening exponent（n） value and increase in the strain-hardening coeficient（k） value. Increasing test temperature apparently decreases the n and k values. Eutectic phase particles cracking and debonding determine the fracture mechanism of the alloy. Final failure of the alloy mainly depends on the global instability（high temperature, necking） and local instability（RT, shearing）. Different tensile behaviors of the alloy are mainly attributed to different matrix strengths, phase particle strengths and damage rate.展开更多
基金supported by the Science and Technology Department of Jiangxi Province(20212AEI91010)National Natural Science Foundation of China(31772067)+1 种基金Jiangxi Agriculture Research System(JXARS-14)Research Project of State Key Laboratory of Food Science and Technology(SKFL-ZZB-2)。
文摘Royal jelly(RJ)is rich in various nutrients with multiple health-promoting properties.This study aims to evaluate whether RJ can modulate related metabolite in the natural aging mice.Male C57BL/6J mice drank RJ solution daily for 9 months.Determination of serum lipids and pathological analysis exhibited that triglycerides,serum cholesterol,and low-density lipoprotein cholesterol were decreased by 31.15%,9.96%,and 22.58%,respectively,the morphology of brain nerve cells was also effectively recovered after RJ intervention.Lipidomic analysis showed that RJ could improve the levels of different kinds of lipids in aging mice brain,especially by increasing the content of antioxidant ether ester,and that the ratio of monounsaturated fatty acid to polyunsaturated fatty acid was up by 23.46%,which could alleviate oxidative stress.Moreover,the metabolism of glycerol phospholipids,glycerols,and fatty acids in aging mice could be regulated by RJ.RJ intervention can effectively improve lipid metabolism disorders caused by aging.
基金Project(2014DFA51270)supported by the International Science and Technology Cooperation Program of ChinaProject(51421001)supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China
文摘The influences of high temperature pre-straining (HT-PS) on the natural aging and bake hardening of Al?Mg?Si alloys were investigated by Vickers microhardness measurements, differential scanning calorimetry (DSC) analysis and transmission electron microscopy (TEM) characterization. The results show that pre-straining at 170 °C immediately after quenching can effectively resolve the rather high T4 temper hardness caused by the conventional room temperature (RT) pre-straining treatment, and give a better bake hardening response (BHR) after paint-bake cycle. HT-PS 7% at 170 °C for 10 min is chosen as the optimum process as it provides lower T4 temper hardness and better BHR. The simultaneous introduction of dislocations and Cluster (2) can significantly suppress the natural aging and promote the precipitation of β″ phase, and reduce the effects of deformation hardening by dynamic recovery.
基金supported by the Major Project of Education Department in Liaoning,China(LSNZD201604)
文摘Seed storability （SS） is an important trait for agronomic production and germplasm preservation in rice （Oryza sativa L.）. Quantitative trait locus （QTL） for seed storability in three storage periods was identified using two sets of recombinant inbred lines （RILs） derived from the crosses with a colnmon female parent Shennong 265 （SN265）. Ten QTLs for seed storability were detected on chromosomes 1, 2, 3, 4, 6, 8, and 12in SL-RILs （SN265/Lijiangxingtuanheigui （LTH））, and a total of 12 QTLs were identified on chromosomes 2, 3, 4, 6, 9, and 10 in SH-RILs （SN265/Luhui 99 （LH99））in different storage periods. Among these QTLs, five major QTLs were identified in more than one storage period. The qSS3-1, qSS3-2, qSS12-1, and qSS12-2 were detected in SL-RILs. Similarly, qSS2-2, qSS2-3, qSS6-2, qSS6-3, qSS6-4, qSS9-1, and qSS9-2 were detected in SH-RILs. In addition, the maximum phenotypic variation was derived from the qSS6-1 and qSS9-2, explaining 53.58 and 29.09%, respectively, while qSS6-1 was a new stable QTL for seed storability. These results provide an opportunity for pyramiding and map-based cloning major QTLs for seed storability in rice.
基金supported by the Fundamental Research Fund for the Central Universities(No.CDJZR10130018)the Chongqing Science and Technology Commission (No.2011GZ0039)
文摘For a series of Al-0.34／%Mg-1.05／%Si-0.08／%Cu alloys, the effects of pre-treatment on natural aging, bake hardening response and plasticity were investigated using Vickers hardness test and tensile test. Differential scanning calorimetry （DSC） analysis was conducted to reveal corresponding precipitation mechanisms. The results showed that pre-straining and pre-aging alone couldn＇t completely suppress natural aging and improve bake hardening response simultaneously. The sensitivity of the pre-straining and pre-aging on the mechanical properties was evaluated. It was found that pre-aging was the main factor which greatly improved bake hardening response and pre-treatment had a weak influence on plasticity in pre-treated samples. DSC analysis showed that the dissolution trough of clusters disappeared in pre-treated samples, both β”and β＇ precipitation peak shifted to lower temperature and were reduced in pre-strained and pre-aged samples. It was concluded that the formation of Mg/Si clusters was replaced by the accelerated precipitation ofβ” andβ＇ phases, which caused the suppression of natural aging and the improvement of bake hardening response （BHR）.
文摘The microstructure and mechanical properties of friction stir welded 2. 5 mm 7050-T7451 aluminum alloy natural aging 72 h and 17 520 h were investigated, respectively. The uniaxial tensile test showed that yield strength, tensile strength and elongation of the joints 17 520 h natural aging were about 20%, 12% and 24% higher than those joints natural aging 72 h. Hardness profile of natural aging 17 520 h joint witnessed significant enhancement in nugget zone, compared with 72 h natural aging. Differential scanning calorimetry （ DSC ） and transmission electron microscopy （TEM） test revealed that more Guinier-Preston zone, η＇ and 71 phase emerged in nugget zone as natural aging duration increased, high density of dislocation located within grain boundary in nugget zone of joints natural aging 72 h. It is concluded that natural aging was feasible to enhalwe strength and plasticity of FSW joints simultaneously.
基金the National Key R&D Program of China(No.2016YFB1200602)the Strategic Priority Program of the Chinese Academy of Sciences(No.XDB22020200)the Shenyang Key R&D and Technology Transfer program(No.Z19–1–004)。
文摘Enhancing the strength of Al-Zn-Mg alloys is critical to the weight-lightening of structural components in the application of high-speed trains and aerospace industries,while high stress corrosion cracking(SCC)susceptibility of Al-Zn-Mg alloys(especially the alloy with high recrystallization fraction)with high strength makes it difficult.In this study,the influence of tensile stress-aging coupled with natural aging pre-treatment on the mechanical properties and SCC resistance of Al-Zn-Mg alloy with high recrystallization fraction has been investigated.The results show that tensile stress-aging at 160℃can inhibit the dissolution of clusters/Guinier-Preston(GP)zones formed during long-term natural aging pre-treatment,which increases the number density of matrix precipitates(MPts),narrow the width of precipitate free zone(PFZ),and dramatically improve the mechanical properties of the experimental Al-Zn-Mg alloy.Meanwhile,the precipitation of the high density of MPts within the matrix will assume a large number of solute atoms during artificial aging,which will reduce the supplement of solute atoms to grain boundaries.As a result,the volume of anodic active grain boundary precipitates(GBPs)and the content of free solute atoms at grain boundaries are reduced,which reduces the possibility of initial nucleation and propagation of SCC crack.The coupled treatment method proposed in this study proves efficient in resolving the contradiction between the strength and SCC resistance in Al-Zn-Mg alloy.
基金Special technical support program of the State Administration of Market Supervision(2021YJ021)Science and technology program of the State Administration of Market Supervision(2021MK118,2021MK119).
文摘Currently,accelerated aging tests are widely used to study the aging process of polyethylene pipelines.However,this approach can only simulate one or several main influencing factors in the natural environment,which are often quite different from the actual environment of the buried pipelines.In this study,five types of PE80 buried pipelines in service for 9e18 years were taken as the research object,while new PE80 pipelines were taken as the reference group.The aging process and mechanism of polyethylene buried pipelines were studied through mechanical and chemical property tests and microstructural analysis.The results showed that the pipeline exhibited cross-linking as the main aging mechanism after being in service for 0e18 years.The aging degree and law of the inner and outer surface of the pipeline were compared,and the observed mechanism of both surfaces was explained.After 18 years in service,the elongation at the break of the pipe decreased by 16.2%,and the toughness of the matrix in the main collapse area of the tensile sample was the fundamental reason responsible for changes in the mechanical properties.Finally,after 18 years in service,the oxidation induction time of the pipeline was 25.7 min,which was 28.5% higher than the national standard value.There were no potential safety hazards during continuous long-term service.The results of this paper provide reference data and theoretical guidance for the aging process study of buried polyethylene pipelines.
文摘Two kinds of high pure silver materials with 5.3 ppm oxygen and 32.7 ppm oxygen were prepared by various melting processes, both samples were subjected to accumulative rolling with 95% thickness reduction. Their mechanical properties were tested during long natural aging. Results showed that the Ag sheet with 5.3 ppm oxygen is at full annealed state when natural aging 58 days or kept at 150℃ for 30 minutes, and the Ag sheet with 32.7 ppm oxygen is a little of recovery when natural aging a year. It is suggested that appropriate oxygen interstitial solute in Ag solid solution and a few of Ag2O particles at Ag grain boundaries impede the recovery and recrystallization of Ag sheets.
文摘The microstructures and damping property of supersaturated ZnA127Ce alloy during natural aging have been investigated. H-800 TEM was mainly used to research the microstructures. The relationship between microstructure and damping property was primarily studied. The results showed that solution plus natural aging was the best heat treatment, which could improve the damping property. Both continuous precipitation and cellular reaction occurred during the aging. Continuous precipitation follows the sequence: β→spherical GP zones→elliptical GP zones→intermediate phase R→n. The cellular reaction can be written as follows:β→a+n+ε.
文摘This paper describes pre-treatment methods to improve the bake-hardening response of naturally aged AA6022 （Al-0.6Mg-1.0Si）, which is an alloy used in automotive body panels. These methods are used to accelerate the artificial aging process, which proceeds 30-day period of natural aging. The precipitation behavior of the sheets of this aluminum alloy was analyzed by differential scanning calorimetry （DSC） and electrical conductivity measurements, and subsequently confirmed by microstructure observations by transmission electron microscopy （TEM）. Tensile tests and microhardness measurements were performed to determine the mechanical properties of the samples. Under simulated paint-baking conditions （30 min at 170℃）, the microhardness and the yield strength （YS） of the pre-strained ＋ pre-aged samples were found to be I13 HV and 225 MPa, respectively. These values are considerably higher than those of pre-aged samples, and they did not decrease significantly during the initial stage of artificial aging.
基金Supported by Traditional Chinese Medicine Inheritance and Innovation“Thousand”Talents(the first batch of National TCM[Xi Xue Zhong]outstanding talents)Training Program(No.NATCM Department of Personnel and Education[2019]13)the Irma and Paul Milstein Program for Senior Health of Milstein Medical Asian American Partnership Foundation(No.20220914)the National Natural Science Foundation of China(No.82004193 and No.82104680)。
文摘The accelerating pace of global aging underscores the need for a deeper understanding of the aging process and the identification of effective anti-aging substances,whether from natural sources or synthetic compounds.Currently,most drugs aimed at preventing or treating ageing,such as metformin,nicotinamide adenine dinucleotide(NAD*)precursors,etc.,are still in the research phase and come with safety concerns and side effects.
基金the National Natural Science Foundation of China(Nos.41877090 and 42107398)Natural Science Foundation of Jiangsu Province(BK20181165 and BK20210358)+1 种基金China Postdoctoral Science Foundation(2020M68618)Yunnan Branch of China National Tobacco Corporation(2022530000241022).
文摘Hydrochar has potential applications in soil improvement and heavy metal remediation.Hydrochar would undergo the process of aging when introduced into the soil,altering its properties.However,recent studies have focused mainly on the artificial aging of hydrochar,which could not reveal the cumulative effect of multiple environmental factors.Therefore,the periodical monitoring of the property and sorption behavior of hydrochar after amending soils is necessary to better understand the multifaceted mechanisms associated with the natural aging of hydrochar.This study selected the sludge-derived hydrochar(SLHC)as a typical hydrochar and applied a 16-month rice-wheat-rice rotation to mimic the natural aging of hydrochar,focusing on changing properties and cadmium(Cd)sorption and literature contrast between aging strategies and biochar types.The porosity,O abundance,and ash content of 16-month aged SLHC increased by 37%,47%,and 8.5%,respectively,facilitating Cd sorption due to surface complexation,pore sorption,and precipitation.The sorption percentage of Cd to SLHC was in the range of 11-14%for SLHC-A0 and increased to 17-31%for SLHC-A4 and 20-32%for SLHC-A16 after natural aging.The natural aging of SLHC induced by ash content played an essential role in Cd sorption site heterogeneity.Linear regression analysis showed that aging strategies on sorption behavior significantly differed between biochars.Thus,studies involving natural aging with multiple environmental factors are preferred over those involving chemical or biological aging.Future studies should continue to explore the mechanisms of natural aging-induced heavy metal sorption between hydrochar and pyrochar.These results improve insights to appraise the potential of SLHC as soil amendments to alleviate the adverse effects of heavy metal contamination and provide an essential basis for researchers and staff in soil management and environmental prevention.
基金the National Natural Science Foundation of China(Nos.51601060,51675538 and 11872380)the Natural Science Foundation of Hunan Province(No.2018JJ3655)+3 种基金the National Key R&D Program of China(No.2017YFB0306300)the Innovation-driven Plan in Central South University(No.2015CX002)the Science and Technology Plan in Hunan Province(No.2016RS2015)the Fundamental Research Funds for the Central Universities of Central South University(No.2018zzts154)。
文摘Artificial ageing above 165℃directly after quenching induces the formation of^50 nm wide precipitatefree zone(PFZ)and^100 nm wide precipitate-sparse zone(PSZ)consisting of coarse precipitates with a gradient in size and density toward the grain center in a commercial Al-Zn-Mg-Cu alloy.With the grain size decreasing,the fraction of PFZ and PSZ in a grain becomes larger and could even occupy the entire volume of the grain.This undesirable microstructure near the grain boundary is mitigated substantially by natural pre-ageing,leading to an exceptional enhancement of the age hardening potential at elevated temperatures.Natural ageing could fundamentally alter the precipitation near grain boundary,and is a promising method to optimize the precipitation hardening in high strength aluminum alloys with unconventionally small grains.
基金financial support from National Natural Science Foundation of China(Nos.U2032117,51675538,11872380)the National Key R&D Program of China(No.2017YFB0306300)+3 种基金Natural Science Foundation of Hunan Province(No.2018JJ3655)National Science and Technology Major Project(No.2017ZX04005001)the Fundamental Research Funds for the Central Universities of Central South University(2021zzts0638)the Innovation fund of National commercial aircraft manufacturing engineering technology centre(No.COMAC-SFGS-2019-4284)。
文摘The high-strength Al-Zn-Mg-Cu alloy provides much better dent resistance and weight-reduction potential compared to the conventional Al alloys used for the automobile body panels.However,natural ageing(NA)significantly reduces the formability of Al-Zn-Mg-Cu alloy.The reversion of natural ageing has been systematically investigated by hardness test,tensile test,differential scanning calorimetry(DSC)and transmission electron microscopy(TEM).Substantial reversion of natural ageing and thus hardness decrease occurs immediately upon thermal treatment at 120–210℃in an Al-Zn-Mg-Cu alloy.Although the hardness of the most reverted state decreases with increasing temperature,the lowest hardness is still higher than the as-quenched state by 30 HV.As revealed by the complementary DSC and TEM observations,this is ascribed to the synchronization of the dissolution and the re-precipitation of the solutes in the NA clusters during reversion ageing.Reversion at 180–210℃for less than 30 s leads to a hardness decline of 40 HV.The hardening kinetics during NA after reversion is slower than that during first-time NA due to the reduced vacancy concentration.Artificial ageing at 180℃for 30 min after secondary NA of less than 24 h induces intensive precipitation of plate-like pre-ηphases and a giant strength increase of 188–204 MPa.Potential use of high strength Al-Zn-Mg-Cu alloy in automobile body panels could be realized by appropriate reversion treatment improving the formability and the quick bake hardening response.
文摘In situ testing provides accurate characterization of existing degradation mechanisms of materials and building systems which helps reducing the subjectivity of visual inspections especially when ageing under natural ageing conditions is carried out over significant periods of time. In this work, data collected from field experimental campaigns over 10 years after construction using several premixed one-coat rendered walls and over 4 and 6 years after construction in the case of ETICS （external thermal insulation composite systems） are presented and discussed. The influence of hydrophobic agents on the performance of both types of facades in terms of surface condition and water penetration was assessed by visual inspections, Karsten test and capillary tests. Additionally, adhesion tests and subsequent evaluation of porosity were also carried out for premixed one-coat mortars. The results obtained have shown that ageing of the rendering solutions, especially after 5 or 6 years in-service, results from the loss of resistance to liquid water penetration, especially at the surface. Yet, additional mechanisms such as leaching of hydrophobic agents and photochemical degradation are thought to be involved, too. Moreover, the results obtained using the Karsten test proved to be the most reliable method to determine the loss of water penetration resistance and predict the ageing of facade solutions. The information collected and the correlations established can help developing solutions to prevent early ageing and implement appropriate maintenance plans to delay their effect.
基金supported by the National Natural Science Foundation of China (Nos.52075400 and 52275368)the 111 Project (No.B17034)+1 种基金the Key Research and Development Program of Hubei Province,China (Nos.2021BAA200 and 2022AAA001)the Independent Innovation Projects of the Hubei Longzhong Laboratory (No.2022ZZ-04)。
文摘The stability of the microstructure and mechanical properties of the pre-hardened sheets during the pre-hardening forming(PHF)process directly determines the quality of the formed components.The microstructure stability of the pre-hardened sheets was in-vestigated by differential scanning calorimetry(DSC),transmission electron microscopy(TEM),and small angle X-ray scattering(SAXS),while the mechanical properties and formability were analyzed through uniaxial tensile tests and formability tests.The results in-dicate that the mechanical properties of the pre-hardened alloys exhibited negligible changes after experiencing 1-month natural aging(NA).The deviations of ultimate tensile strength(UTS),yield strength(YS),and sheet formability(Erichsen value)are all less than 2%.Also,after different NA time(from 48 h to 1 month)is applied to alloys before pre-hardening treatment,the pre-hardened alloys possess stable microstructure and mechanical properties as well.Interestingly,with the extension of NA time before pre-hardening treatment from 48 h to 1 month,the contribution of NA to the pre-hardening treatment is limited.Only a yield strength increment of 20 MPa is achieved,with no loss in elongation.The limited enhancement is mainly attributed to the fact that only a limited number of clusters are transformed into Guinier-Preston(GP)zones at the early stage of pre-hardening treatment,and the formation ofθ''phase inhibits the nucleation and growth of GP zones as the precipitated phase evolves.
基金Projects(51475172,51275180,51375177) supported by the National Natural Science Foundation of ChinaProject(S2013040016899) supported by the Natural Science Foundation of Guangdong Province,ChinaProjects(2013ZM0003,2013ZZ017) supported by the Fundamental Research Funds for the Central Universities,South China University of Technology,China
文摘A novel porous metal fiber sintered sheet （PMFSS） with a three-dimensional reticulated structure was fabricated by multi-tooth cutting and high-temperature solid-phase sintering process with copper fibers. A uniaxial tensile test was conducted to investigate the effect of fiber length and natural aging factor on the tensile properties of the PMFSS. Results indicated that, under given stress, the increase of fiber length helped reinforce the tensile strength. The elongation of the PMFSS with medium length fiber of 15 mm exhibited the optimal performance, reaching about 13.5%. After natural aging treatment for a month, the tensile strength of PMFSS significantly decreased, but the change of elongation was negligible except for the one with the shortest fiber length of 5 mm, whose elongation was effectively improved. The morphological fracture features of PMFSSs were also characterized.
基金funded by the National Key Research and Development Program of China(No.2016YFB1200506–12)Project of Promoting Talents in Liaoning Province(No.XLYC1808038)。
文摘Conventional friction stir welding(FSW)and ultrasonic assisted friction stir welding(UAFSW)were employed to weld 6-mm thick 7 N01-T4 aluminum alloy plates.Weld forming characteristics and material flow behavior in these two different welding processes were studied and compared.Ultrasonic vibration was applied directly on the weld in axial direction through the welding tool.Metal flow behavior,microstructure characteristics in the nugget zone(NZ)and evolution of the mechanical properties of naturally aged joints were studied.Results show that the ultrasonic vibration can significantly increase the welding speed of defect-free welded joint.At the rotation speed of 1200 rpm,the UAFSW can produce defect-free welded joints at a welding speed that is 50%higher than that of the conventional FSW.Ultrasonic vibrations can also improve surface quality of the joints and reduce axial force by 9%.Moreover,ultrasonic vibrations significantly increase the volume of the pin-driven zone(PDZ)and decrease the thickness of the transition zone(TZ).The number of subgrains and deformed grains resulting from the UAFSW is higher than that from the FSW.By increase the strain level and strain gradient in the NZ,the ultrasonic vibrations can refine the grains.Ultrasonic energy is the most at the top of the NZ,and gradually reduces along the thickness of the plate.The difference in strengths between the FSW and the UAFSW joints after post-weld natural aging(PWNA)is small.However,the elongation of the UAFSW is8.8%higher than that of the FSW(PWNA for 4320 h).Fracture surface observation demonstrates that all the specimens fail by ductile fracture,and the fracture position of the UAFSW joint changes from HAZ(PWNA for 120 h)to NZ(PWNA for 720 and 4320 h).
基金The authors are grateful for the financial supports from the National Key Research and Development Program of China(2016YFB0300801)the National Natural Science Foundation of China(11904093,51831004,51671082,51471067 and 11427806).
文摘The effect of Er on the microhardness and precipitation behavior of the heat-treated Al−Si−Mg alloy was investigated by microhardness tester and TEM.As a comparison,the influence of natural aging was also studied.It is shown that the thermal stability of the over-aged Al−Si−Mg−Er alloy is highly related to the average size of the precipitates.The average size ofβ''precipitates in Al−Si−Mg−Er alloy is smaller than that in Al−Si−Mg alloy,and the distribution is more localized under condition of without introducing natural aging.However,when natural aging is introduced before artificial aging,the Al−Si−Mg−Er alloy has similar average size and distribution of precipitates with the Al−Si−Mg alloy,resulting in similar mechanical properties.The effect of Er on the precipitation kinetics in the alloy was also discussed in detail to explain these phenomena.
基金supported by the Project Funded by China Postdoctoral Science Foundation(No.2015M571562)
文摘Effects of natural aging and test temperature on the tensile behaviors have been studied for a highperformance cast aluminum alloy Al–10Si–1.2Cu–0.7Mn. Based on self-strengthening mechanism and spheroidization microstructures, the alloy tested at room temperature（RT） exhibits higher 0.2% proof stress（YS） of 206 MPa, ultimate tensile strength（UTS） of 331 MPa and elongation of 10%. Increasing aging time improves the YS and UTS and reduces the ductility of the alloy. Further increasing aging time beyond72 h does not signi？cantly increase the tensile strengths. Increasing test temperature significantly decreases the tensile strengths and increases the ductility of the alloy. The UTS of the alloy can be estimated by using the hardness. The Portevin–Le Chatelier effect occurs at RT due to the interactions between solid solution atoms and dislocations. Similar behaviors occurring at 250℃ are attributed to dynamic strain aging mechanism. Increasing aging time leads to decrease in the strain-hardening exponent（n） value and increase in the strain-hardening coeficient（k） value. Increasing test temperature apparently decreases the n and k values. Eutectic phase particles cracking and debonding determine the fracture mechanism of the alloy. Final failure of the alloy mainly depends on the global instability（high temperature, necking） and local instability（RT, shearing）. Different tensile behaviors of the alloy are mainly attributed to different matrix strengths, phase particle strengths and damage rate.
