The effect of holding time of double annealing process on the microstructure and mechanical properties of Ti-5Al-5Mo-5V1Cr-1Fe(Ti55511)alloy was investigated.Results reveal that the shape and size of the primaryα(α_...The effect of holding time of double annealing process on the microstructure and mechanical properties of Ti-5Al-5Mo-5V1Cr-1Fe(Ti55511)alloy was investigated.Results reveal that the shape and size of the primaryα(α_(p))phase are predominantly influenced by the holding time at the first stage.With the prolongation of holding time,the long strip of α_(p) is transformed into a short rod due to the terminal migration mechanism,leading to the broadening growth,and the growth of α_(p) slows down when the holding time is over 2 h.The volume fraction of α_(p) is mainly affected by the holding time of the second stage:with the prolongation of holding time,the volume fraction of α_(p) is increased,which is accompanied by the precipitation of the secondaryα(α_(s)).The mechanical properties of Ti55511 alloy are influenced by bothα_(p) andαs.Tensile results indicate that the optimal holding time of double annealing is 1-4 h for the first stage and 0.5-2 h for the second stage.展开更多
Four different types of film-forming agents were added to the foundation formulations,and their effects on the makeup-holding properties of the foundations on human facial skin were determined by Visia-CR.The study sh...Four different types of film-forming agents were added to the foundation formulations,and their effects on the makeup-holding properties of the foundations on human facial skin were determined by Visia-CR.The study showed that there was a significant difference between the sample group with film-forming agent and the blank control group,indicating that the addition of film-forming agent had an effect on the makeup-holding performance of the foundation;the makeup-holding effect of the foundation formulated with trimethylsiloxysilicate or(acrylates/dimethicone copolymer,cyclopentasiloxane)was better than that of the foundation formulated with polymethylsilsesquioxane or VP/hexadecene copolymer.This experiment is of guidance significance for the formulation design of long-lasting foundation.展开更多
[ Objective] To explore the effects of different proportion of bee pollen on the water holding capacity of pork in Duroc Landrace x Yorkshire growing-finishing pigs in order to determine the optimal proportion. [ Met...[ Objective] To explore the effects of different proportion of bee pollen on the water holding capacity of pork in Duroc Landrace x Yorkshire growing-finishing pigs in order to determine the optimal proportion. [ Method] A total of 80 Duroc x Landrace x Yorkshire growing-finishing pigs, weighing （10.0 ± 1.0） kg, were randomly divided into five groups. The experimental period was 120 d including the 5-day pre-feecling period. The corn-soybean meal was not replaced during the whole period. All pigs had free access to feed and water. The pigs were fasting for 24 h but not prohibited from feed before the beginning. Group I was the control group reared with the diet not supplemented bee pollen. The pigs in group II, III ,IV and V were reared with the diet supplemented bee pollen at the concentration of 1%, 3%, 5% and 7%, respectively. After slaughtering, eye muscle was used for determination of water holding capacity through fast filter paper method, drip loss method, cooking loss method and Na- pole yield determination method. [ Resultl With the increase of the proportion of bee pollen, the water holding capacity of pork was first good and then poor. The addition of bee pollen at the concentration of 5% significantly reduced the drip loss of pork and the water holding capacity which was detected by fast filter paper method, but the cooking loss and Napole yield were not significantly influenced. [ Condmion] The bee pollen can effectively improve the water holding capacity of pork in Duroc x Landrace x Yorkshire growing-finishing pigs, and the optimal proportion is 5%.展开更多
Effect of isothermal holding treatment in the solidification process on the microstructure of Ti-6Al-4V alloy was studied by temperature controlled induced melting apparatus. The result shows that with isothermal hold...Effect of isothermal holding treatment in the solidification process on the microstructure of Ti-6Al-4V alloy was studied by temperature controlled induced melting apparatus. The result shows that with isothermal holding treatment above the β transus temperature during solidification, the colony structure consisting of parallel lamellae was obtained. While the isothermal holding treatment was set at 960 °C, a unique bi-modal microstructure consisting of coarse primary α and fine secondary lamellar α was obtained. The primary lamellar α tended to break into several pieces, globularize and present equiaxed morphology. The formation mechanism of the equiaxed α can be explained with the atom immigration, high density dislocations, combined action with the interface tension of formed α phase during the isothermal holding treatment. After the isothermal holding, the retained β matrix transformed into fine lamellar α, thus, bi-modal microstructure was acquired. Compared with the lamellar structure, the grain boundary α presented discontinuously and cannot be distinguished from the primary α lamellae easily. The size of colonies α was greatly decreased. The microstructure tended to be much more homogeneous in the whole section of the samples.展开更多
Holding temperature and holding thickness are main parameters for two-phase controlled rolling on plate mill. The optimization of holding temperature and holding thickness for pass schedule calculation of two-phase co...Holding temperature and holding thickness are main parameters for two-phase controlled rolling on plate mill. The optimization of holding temperature and holding thickness for pass schedule calculation of two-phase controlled rolling on plate mill was presented and its feature is as follows： （1） Determination of holding thickness can be automatically obtained based on the influence of mill safety limits, tracking zone length and holding time on holding thickness; （2） Determination of holding temperature can be automatically obtained and the holding time can be reduced as much as possible; （3） Algorithm can modify the holding temperature and thickness depending on slab size and product size.展开更多
We aim in this research at synthesizing high-purity aluminium titanate with sludge from the aluminium profile factory by shock cooling method, and mainly discuss the effect of calcining reaction temperature and holdin...We aim in this research at synthesizing high-purity aluminium titanate with sludge from the aluminium profile factory by shock cooling method, and mainly discuss the effect of calcining reaction temperature and holding time on crystalline, microstructure and content of aluminum titanate materials to determine the preferred calcining temperature and holding time. XRD and SEM methods were utilized to characterize the crystalline and microstructure of each specimen, Rietveld Quantification software was used for the determination of different crystalline contents of specimens, and Philips plus software was applied to determine the cell parameters of aluminium titanate in different specimens. According to the experimental results, preferred calcining temperature is determined as 1400℃ and preferred holding time is 2 h, at which the grains of aluminum titanate grow completely and the purity of aluminum titanate is 97.2wt%.展开更多
In order to develop a comprehensive understanding about the effect of different holding time under rapid heating on the microstructural evolution and mechanical properties of transformation-induced plasticity （TRIP）...In order to develop a comprehensive understanding about the effect of different holding time under rapid heating on the microstructural evolution and mechanical properties of transformation-induced plasticity （TRIP） steel, continuous annealing process simulations were performed using a thermal system with resistance heating method. The morphology and distribution of all phases present in the microstructure and the mechanical properties of TRIP steel were revealed. It appeared that the final tensile strength of the TRIP steel increased and retained austenite car bon content decreased with increasing holding time. An overlap between ferrite recrystallization and austenitization was observed during intercritical holding. In addition, the work hardening of the samples was evaluated by calculat ing the instantaneous ~l value as a function of the true strain. The difference in work hardening behavior corresponds to the rate of the retained austenite transformation during straining, which can be attributed to the carbon content and the morphology of the retained austenite.展开更多
Continuous annealing simulation tests were conducted by using a continuous annealing thermomechanical simulator. Holding times of 5, 60, 180, and 480 seconds for an intercritical annealing temperature of 820℃ were ad...Continuous annealing simulation tests were conducted by using a continuous annealing thermomechanical simulator. Holding times of 5, 60, 180, and 480 seconds for an intercritical annealing temperature of 820℃ were adopted to investigate the evolution of the mierostructure and mechanical properties of ferrite-bainite dual-phase steel. The ferrite-bainite dual-phase steel was characterized by high strength and low yield ratio due to the presence of the constituents （polygonal ferrite, bainite, martensite and retained austenite） of the steel microstructure. Specimen 3 exhibits the highest value of A50 （7.67%） and a product of Rm × A50 （10453MPa%） after a 180s holding. This is likely attributed to the presence of a C-enriched retained anstenite in the microstructure. And the effect of martensite islands and carbide precipitate is thought to be able to contribute in strengthening the present steel. It is expected that equilibrium of anstenite fraction would be reached for reasonable intercritical holding period, regardless of the heating temperature. The results suggest that long increasing holding times may not be needed because the major phase of the microstructure does not change very significantly. It is favorable for industrial production of DP steels to shorten holding times. Key words： ferrite-bainite dual-phase steel; holding time; martensite islands; mechanical properties展开更多
The cast Al-Si alloy was fabricated using the Additive Pressure Casting(APC)method.The effects of holding pressure from 50 to 400 k Pa on the density,cooling rate,and mechanical properties of the alloy,and the corresp...The cast Al-Si alloy was fabricated using the Additive Pressure Casting(APC)method.The effects of holding pressure from 50 to 400 k Pa on the density,cooling rate,and mechanical properties of the alloy,and the corresponding mechanism were discussed.The results indicate that the application of high holding pressure(300 k Pa)enhances the feeding ability of the alloy,leading to an increase of the density.Meanwhile,the cooling rate of the alloy is increased by 100%.In addition,the tensile testing results show that the increase of holding pressure from 50 to 300 k Pa improves the tensile strength and elongation of the alloy by 6.2%and 81.3%,respectively.However,excessive holding pressure(400 k Pa)might lower the density and cooling rate of the alloy due to the feeding channels being blocked.展开更多
Developing an electrostatic discharge（ESD） protection device with a better latch-up immunity has been a challenging issue for the nanometer complementary metal-oxide semiconductor（CMOS） technology. In this work, a...Developing an electrostatic discharge（ESD） protection device with a better latch-up immunity has been a challenging issue for the nanometer complementary metal-oxide semiconductor（CMOS） technology. In this work, an improved grounded-gate N-channel metal-oxide semiconductor（GGNMOS） transistor triggered silicon-controlled rectifier（SCR）structure, named GGSCR, is proposed for high holding voltage ESD protection applications. The GGSCR demonstrates a double snapback behavior as a result of progressive trigger-on of the GGNMOS and SCR. The double snapback makes the holding voltage increase from 3.43 V to 6.25 V as compared with the conventional low-voltage SCR. The TCAD simulations are carried out to verify the modes of operation of the device.展开更多
The decomposition rate and the water-holding capacity of 6 kinds of grass litters were studied in the Jinshajiang river dry-hot valley. The results showed that the dry weight remains reduced with time but did not have...The decomposition rate and the water-holding capacity of 6 kinds of grass litters were studied in the Jinshajiang river dry-hot valley. The results showed that the dry weight remains reduced with time but did not have a direct correlation with time. The decomposition litters were affected by climate, character of litter, animalcule and soil animal. The climate factors of temperature and humidity were important especially. The water-holding capacity was in the sequence ofN. wightii （336%）, P. notatum Flugge （248%）, H. contortus （L.） Beauv （209%）, B. pertusa （L.） A. Camus（206%）, L endecaphylla Jacq （174%）, D. annulatum （Forsk.） Stapf （168%）. After 24 months decomposition the remaining dry weight of the litter was in the sequence as follows： 15.12% for N. wightii, 26.38% for I. endecaphylla Jacq, 27.23% for B. pertusa （L.） A. Camus, 30.78% for P. notatum Flugge, 39.72% for H. contortus （L.） Beauv and 39.76% for D. annulatum （Forsk.） Stapf. The decomposition rate and water-holding capacity ofN. wightii are at the highest level. It is important for the development, improvement and conservation of the grassland soil.展开更多
To predict three-dimensional temperature distribution of molten aluminum and its influencing factors inside an industrial aluminum holding furnace,a fluid-solid coupled method was presented.The fluid-solid coupled mat...To predict three-dimensional temperature distribution of molten aluminum and its influencing factors inside an industrial aluminum holding furnace,a fluid-solid coupled method was presented.The fluid-solid coupled mathematics models of aluminum holding furnace in the premixed combustion processing were established based on mass conservation,moment conservation,momentum conservation,energy conservation and chemistry species conservation.Computational results agree well with the test data of the typical condition.The maximum combustion temperature is 1 850 K.The average temperature of the molten aluminum is 1 158 K,and the maximum temperature difference is about 240 K.The average temperature increases 0.3 ℃ while the temperature of combustion air increases 1 ℃.The optimal excess air ratio is 1.25-1.30.展开更多
The effect of the melt holding temperature on the morphological evolution and sedimentation behavior of iron-rich intermetallics in Al-7.0 Si-1.0 Fe-1.2 Mn-0.25 Mg alloy was investigated using an optical microscope,sc...The effect of the melt holding temperature on the morphological evolution and sedimentation behavior of iron-rich intermetallics in Al-7.0 Si-1.0 Fe-1.2 Mn-0.25 Mg alloy was investigated using an optical microscope,scanning electron microscope and differential thermal analyzer.The results show that as the holding temperature decreases,the morphologies of the primary iron-rich phase in matrix change from star-like to polygonal,and the number of the primary phases gradually decreases and disappears at 615°C.Finally,the Chinese script phases with small size,high compact and uniform distribution are obtained.In contrast,the primary iron-rich phases in slag transform into a coarser polygonal shape with lower roundness,and some of them have hollow structures.Furthermore,the area fraction of intermetallics and Fe content in the matrix decrease gradually due to the formation and growth of sludge and subsequent natural sedimentation during melt holding.With the decrease of holding temperature,the main factors hindering the settlement of the primary phases are morphology,size,and density in turn.展开更多
Intensive melt shearing has a significant grain refining effect on some light alloys.However,the persistence of the grain refining effect during isothermal holding and remelting is still unclear,although it is very im...Intensive melt shearing has a significant grain refining effect on some light alloys.However,the persistence of the grain refining effect during isothermal holding and remelting is still unclear,although it is very important for the practical application.In this study,intensive melt shearing was achieved in a twin-screw mechanism to investigate its grain refining effect on AZ91D magnesium alloy.The refinement mechanism was discussed and the persistence of grain refinement after remelting and isothermal holding was also studied.A Zeiss imaging system with polarized light was used for quantitative measurement of grain size.The results show that the intensive melt shearing has a significant grain refining effect on AZ91D magnesium alloy.With the application of intensive melt shearing,the grain size of AZ91D magnesium alloy can be reduced from 530 μm(for a typical as-cast microstructure) to 170 μm,which is about 70% size reduction.The grain refinement achieved by the intensive melt shearing can be partially kept after isothermal holding and remelting.It is believed that the refinement effect was mainly due to the finer and well dispersed oxide particles formed by high intensive shearing.The smaller size of oxide particles and their slow motion velocity in the sheared melt could make important contributions to the remained grain refinement.展开更多
Coarse woody debris( CWD) has an important role in hydrological function and water and soil conservation function of forest ecosystem especially mountain forest ecosystem. To understand water holding capacity of CWD i...Coarse woody debris( CWD) has an important role in hydrological function and water and soil conservation function of forest ecosystem especially mountain forest ecosystem. To understand water holding capacity of CWD in subalpine forest of southeast Tibet,CWD reserve of primitive A. fabri forest in Sygera Mountain was investigated by sample plot method,and water absorption and storage capacity of CWD was studied by using soaking method. The results showed that decay grade was positively related to water storage potential,that is to say,the higher the decay grade,the larger the water storage potential. Saturated water holding capacity,saturated water holding rate,effective water holding capacity and effective water holding rate of A. fabri CWD all rose with decay grade increased,and the order was Ⅴ>Ⅳ>Ⅲ>Ⅱ>Ⅰ. CWD reserve was 51.555 t/hm^2,and the maximum water storage capacity was 71.601 t/hm^2,while effective water storage capacity was 60.861 t/hm2,which was equivalent to 6.086 mm of rainfall.展开更多
For acquiring the details in aluminum holding furnace with bottom porous brick purging system,efforts were performed to try to find out the potential optimal operation schemes.By adopting transient analysis scheme and...For acquiring the details in aluminum holding furnace with bottom porous brick purging system,efforts were performed to try to find out the potential optimal operation schemes.By adopting transient analysis scheme and constant boundary temperature,combustion in the furnace was investigated numerically using computational fluid dynamics(CFD).The predicted gas temperature shows good agreement with the measured results,and the predicted energy distribution of the furnace is consistent with that obtained from energy balance experiment,which confirms the reliability of the numerical solution.The results show that as the fuel-air mixture temperature rises up from 300 K to 500 K,the energy utilization of the furnace could increase from 34.55% to 37.14%.However,as the excess air coefficient increases from 1.0 to 1.4,energy utilization drops from 34.55% to 29.56%.Increasing the combustion temperature is the most effective way to improve the energy efficiency of the furnace.High reactant temperature and medium excess air coefficient are recommended for high operation performance,and keeping the furnace jamb sealed well for avoiding leakage has to be emphasized.展开更多
The effects of Cr contents(0.3 and 1.0 wt.%)and isothermal holding temperatures(400,440,and 480℃)on the microstructure evolution and properties of complex phase steel with high formability(CH steel)were investigated ...The effects of Cr contents(0.3 and 1.0 wt.%)and isothermal holding temperatures(400,440,and 480℃)on the microstructure evolution and properties of complex phase steel with high formability(CH steel)were investigated using dilatometry,scanning electron microscopy,transmission electron microscopy(TEM),and X-ray diffraction.The results show that the microstructures of CH steel with 0.3 wt.%Cr are ferrite,granular bainite,martensite,and retained austenite,while no ferrite is observed in the microstructure of CH steel with 1.0 wt.%Cr in the same process.Cr promotes the precipitation of(Nb,Ti)C in the high-temperature austenite region through theoretical calculations and TEM observations.Cr retards the bainite transformation and refines the grain size of CH steel.Furthermore,as isothermal holding temperature increases from 400 to 480℃,the bainite and retained austenite fractions of two CH steels decrease,while the martensite fraction increases in the steels after final quenching.Consequently,the strength has an increasing tendency and the total elongation has a decreasing tendency with increasing isothermal temperature.展开更多
In this present paper, an inventory model with a generalised exponential decreasing demand is considered. A numerical example is used to illustrate the application of the model. Sensitivity analysis of the optimal sol...In this present paper, an inventory model with a generalised exponential decreasing demand is considered. A numerical example is used to illustrate the application of the model. Sensitivity analysis of the optimal solution with respect to various parameters is carried out to see the effect of parameter changes on the solution.展开更多
文摘The effect of holding time of double annealing process on the microstructure and mechanical properties of Ti-5Al-5Mo-5V1Cr-1Fe(Ti55511)alloy was investigated.Results reveal that the shape and size of the primaryα(α_(p))phase are predominantly influenced by the holding time at the first stage.With the prolongation of holding time,the long strip of α_(p) is transformed into a short rod due to the terminal migration mechanism,leading to the broadening growth,and the growth of α_(p) slows down when the holding time is over 2 h.The volume fraction of α_(p) is mainly affected by the holding time of the second stage:with the prolongation of holding time,the volume fraction of α_(p) is increased,which is accompanied by the precipitation of the secondaryα(α_(s)).The mechanical properties of Ti55511 alloy are influenced by bothα_(p) andαs.Tensile results indicate that the optimal holding time of double annealing is 1-4 h for the first stage and 0.5-2 h for the second stage.
文摘Four different types of film-forming agents were added to the foundation formulations,and their effects on the makeup-holding properties of the foundations on human facial skin were determined by Visia-CR.The study showed that there was a significant difference between the sample group with film-forming agent and the blank control group,indicating that the addition of film-forming agent had an effect on the makeup-holding performance of the foundation;the makeup-holding effect of the foundation formulated with trimethylsiloxysilicate or(acrylates/dimethicone copolymer,cyclopentasiloxane)was better than that of the foundation formulated with polymethylsilsesquioxane or VP/hexadecene copolymer.This experiment is of guidance significance for the formulation design of long-lasting foundation.
文摘[ Objective] To explore the effects of different proportion of bee pollen on the water holding capacity of pork in Duroc Landrace x Yorkshire growing-finishing pigs in order to determine the optimal proportion. [ Method] A total of 80 Duroc x Landrace x Yorkshire growing-finishing pigs, weighing （10.0 ± 1.0） kg, were randomly divided into five groups. The experimental period was 120 d including the 5-day pre-feecling period. The corn-soybean meal was not replaced during the whole period. All pigs had free access to feed and water. The pigs were fasting for 24 h but not prohibited from feed before the beginning. Group I was the control group reared with the diet not supplemented bee pollen. The pigs in group II, III ,IV and V were reared with the diet supplemented bee pollen at the concentration of 1%, 3%, 5% and 7%, respectively. After slaughtering, eye muscle was used for determination of water holding capacity through fast filter paper method, drip loss method, cooking loss method and Na- pole yield determination method. [ Resultl With the increase of the proportion of bee pollen, the water holding capacity of pork was first good and then poor. The addition of bee pollen at the concentration of 5% significantly reduced the drip loss of pork and the water holding capacity which was detected by fast filter paper method, but the cooking loss and Napole yield were not significantly influenced. [ Condmion] The bee pollen can effectively improve the water holding capacity of pork in Duroc x Landrace x Yorkshire growing-finishing pigs, and the optimal proportion is 5%.
基金Project(3102014JCQ01026)supported by the Fundamental Research Fund for the Central Universities,ChinaProject(B08040)supported by the Program of Introducing Talents of Discipline to Universities,China
文摘Effect of isothermal holding treatment in the solidification process on the microstructure of Ti-6Al-4V alloy was studied by temperature controlled induced melting apparatus. The result shows that with isothermal holding treatment above the β transus temperature during solidification, the colony structure consisting of parallel lamellae was obtained. While the isothermal holding treatment was set at 960 °C, a unique bi-modal microstructure consisting of coarse primary α and fine secondary lamellar α was obtained. The primary lamellar α tended to break into several pieces, globularize and present equiaxed morphology. The formation mechanism of the equiaxed α can be explained with the atom immigration, high density dislocations, combined action with the interface tension of formed α phase during the isothermal holding treatment. After the isothermal holding, the retained β matrix transformed into fine lamellar α, thus, bi-modal microstructure was acquired. Compared with the lamellar structure, the grain boundary α presented discontinuously and cannot be distinguished from the primary α lamellae easily. The size of colonies α was greatly decreased. The microstructure tended to be much more homogeneous in the whole section of the samples.
文摘Holding temperature and holding thickness are main parameters for two-phase controlled rolling on plate mill. The optimization of holding temperature and holding thickness for pass schedule calculation of two-phase controlled rolling on plate mill was presented and its feature is as follows： （1） Determination of holding thickness can be automatically obtained based on the influence of mill safety limits, tracking zone length and holding time on holding thickness; （2） Determination of holding temperature can be automatically obtained and the holding time can be reduced as much as possible; （3） Algorithm can modify the holding temperature and thickness depending on slab size and product size.
基金supported by the Natural Science Foundation of Fujian Province (No. T08J0129)the Science and Technology Developing Foundation of Fuzhou University (No. 2008-XQ-001)2007-year New Century Talents Supporting Program of Fujian Province (No.XSJRC2007-17)
文摘We aim in this research at synthesizing high-purity aluminium titanate with sludge from the aluminium profile factory by shock cooling method, and mainly discuss the effect of calcining reaction temperature and holding time on crystalline, microstructure and content of aluminum titanate materials to determine the preferred calcining temperature and holding time. XRD and SEM methods were utilized to characterize the crystalline and microstructure of each specimen, Rietveld Quantification software was used for the determination of different crystalline contents of specimens, and Philips plus software was applied to determine the cell parameters of aluminium titanate in different specimens. According to the experimental results, preferred calcining temperature is determined as 1400℃ and preferred holding time is 2 h, at which the grains of aluminum titanate grow completely and the purity of aluminum titanate is 97.2wt%.
基金Item Sponsored by National Twelfth Five-year Science and Technology Support Program of China(2011BAE13B01,2011BAE13B03)
文摘In order to develop a comprehensive understanding about the effect of different holding time under rapid heating on the microstructural evolution and mechanical properties of transformation-induced plasticity （TRIP） steel, continuous annealing process simulations were performed using a thermal system with resistance heating method. The morphology and distribution of all phases present in the microstructure and the mechanical properties of TRIP steel were revealed. It appeared that the final tensile strength of the TRIP steel increased and retained austenite car bon content decreased with increasing holding time. An overlap between ferrite recrystallization and austenitization was observed during intercritical holding. In addition, the work hardening of the samples was evaluated by calculat ing the instantaneous ~l value as a function of the true strain. The difference in work hardening behavior corresponds to the rate of the retained austenite transformation during straining, which can be attributed to the carbon content and the morphology of the retained austenite.
基金Founded by National Natural Science Foundation of China(No.51004037)Shenyang City Application Basic Research Project(No.F13-316-1-15)State Key Laboratory Opening Project of Northeastern University(No.12SYS05)
文摘Continuous annealing simulation tests were conducted by using a continuous annealing thermomechanical simulator. Holding times of 5, 60, 180, and 480 seconds for an intercritical annealing temperature of 820℃ were adopted to investigate the evolution of the mierostructure and mechanical properties of ferrite-bainite dual-phase steel. The ferrite-bainite dual-phase steel was characterized by high strength and low yield ratio due to the presence of the constituents （polygonal ferrite, bainite, martensite and retained austenite） of the steel microstructure. Specimen 3 exhibits the highest value of A50 （7.67%） and a product of Rm × A50 （10453MPa%） after a 180s holding. This is likely attributed to the presence of a C-enriched retained anstenite in the microstructure. And the effect of martensite islands and carbide precipitate is thought to be able to contribute in strengthening the present steel. It is expected that equilibrium of anstenite fraction would be reached for reasonable intercritical holding period, regardless of the heating temperature. The results suggest that long increasing holding times may not be needed because the major phase of the microstructure does not change very significantly. It is favorable for industrial production of DP steels to shorten holding times. Key words： ferrite-bainite dual-phase steel; holding time; martensite islands; mechanical properties
基金National Key Research Project of China(No.2016YFB0300901).
文摘The cast Al-Si alloy was fabricated using the Additive Pressure Casting(APC)method.The effects of holding pressure from 50 to 400 k Pa on the density,cooling rate,and mechanical properties of the alloy,and the corresponding mechanism were discussed.The results indicate that the application of high holding pressure(300 k Pa)enhances the feeding ability of the alloy,leading to an increase of the density.Meanwhile,the cooling rate of the alloy is increased by 100%.In addition,the tensile testing results show that the increase of holding pressure from 50 to 300 k Pa improves the tensile strength and elongation of the alloy by 6.2%and 81.3%,respectively.However,excessive holding pressure(400 k Pa)might lower the density and cooling rate of the alloy due to the feeding channels being blocked.
文摘Developing an electrostatic discharge（ESD） protection device with a better latch-up immunity has been a challenging issue for the nanometer complementary metal-oxide semiconductor（CMOS） technology. In this work, an improved grounded-gate N-channel metal-oxide semiconductor（GGNMOS） transistor triggered silicon-controlled rectifier（SCR）structure, named GGSCR, is proposed for high holding voltage ESD protection applications. The GGSCR demonstrates a double snapback behavior as a result of progressive trigger-on of the GGNMOS and SCR. The double snapback makes the holding voltage increase from 3.43 V to 6.25 V as compared with the conventional low-voltage SCR. The TCAD simulations are carried out to verify the modes of operation of the device.
基金Supported by the National Science and Technology Sup-porting Program in the Eleventh Five-Year Plan of China (2006BAC01A11)
文摘The decomposition rate and the water-holding capacity of 6 kinds of grass litters were studied in the Jinshajiang river dry-hot valley. The results showed that the dry weight remains reduced with time but did not have a direct correlation with time. The decomposition litters were affected by climate, character of litter, animalcule and soil animal. The climate factors of temperature and humidity were important especially. The water-holding capacity was in the sequence ofN. wightii （336%）, P. notatum Flugge （248%）, H. contortus （L.） Beauv （209%）, B. pertusa （L.） A. Camus（206%）, L endecaphylla Jacq （174%）, D. annulatum （Forsk.） Stapf （168%）. After 24 months decomposition the remaining dry weight of the litter was in the sequence as follows： 15.12% for N. wightii, 26.38% for I. endecaphylla Jacq, 27.23% for B. pertusa （L.） A. Camus, 30.78% for P. notatum Flugge, 39.72% for H. contortus （L.） Beauv and 39.76% for D. annulatum （Forsk.） Stapf. The decomposition rate and water-holding capacity ofN. wightii are at the highest level. It is important for the development, improvement and conservation of the grassland soil.
基金Project(2006AA03Z523) supported by the National High-Tech Research and Development Program of ChinaProject(08C26224302178) supported by the Innovation Foundation of Central South University,China
文摘To predict three-dimensional temperature distribution of molten aluminum and its influencing factors inside an industrial aluminum holding furnace,a fluid-solid coupled method was presented.The fluid-solid coupled mathematics models of aluminum holding furnace in the premixed combustion processing were established based on mass conservation,moment conservation,momentum conservation,energy conservation and chemistry species conservation.Computational results agree well with the test data of the typical condition.The maximum combustion temperature is 1 850 K.The average temperature of the molten aluminum is 1 158 K,and the maximum temperature difference is about 240 K.The average temperature increases 0.3 ℃ while the temperature of combustion air increases 1 ℃.The optimal excess air ratio is 1.25-1.30.
基金Project(2017GDASCX-0117)supported by the Guangdong Academy of Sciences,ChinaProject(201806010126)supported by the Pearl River S&T Nova Program of Guangzhou,China+3 种基金Projects(2017A050503004,2017A07071029)supported by the Guangdong Provincial Program of Science and Technology,ChinaProject(18126010)supported by the Guangxi Autonomous Regional Program of Science and Technology,ChinaProject(201802030012)supported by the Guangzhou Municipal Science and Technology Bureau,ChinaProject(2017A0109005)supported by the Sihui Plan Project of Science and Technology,China.
文摘The effect of the melt holding temperature on the morphological evolution and sedimentation behavior of iron-rich intermetallics in Al-7.0 Si-1.0 Fe-1.2 Mn-0.25 Mg alloy was investigated using an optical microscope,scanning electron microscope and differential thermal analyzer.The results show that as the holding temperature decreases,the morphologies of the primary iron-rich phase in matrix change from star-like to polygonal,and the number of the primary phases gradually decreases and disappears at 615°C.Finally,the Chinese script phases with small size,high compact and uniform distribution are obtained.In contrast,the primary iron-rich phases in slag transform into a coarser polygonal shape with lower roundness,and some of them have hollow structures.Furthermore,the area fraction of intermetallics and Fe content in the matrix decrease gradually due to the formation and growth of sludge and subsequent natural sedimentation during melt holding.With the decrease of holding temperature,the main factors hindering the settlement of the primary phases are morphology,size,and density in turn.
基金supported by the Engineering and Physical Sciences Research Council(EPSRC) of the UK and the National Natural Science Foundation of China(Grant No.51104043)
文摘Intensive melt shearing has a significant grain refining effect on some light alloys.However,the persistence of the grain refining effect during isothermal holding and remelting is still unclear,although it is very important for the practical application.In this study,intensive melt shearing was achieved in a twin-screw mechanism to investigate its grain refining effect on AZ91D magnesium alloy.The refinement mechanism was discussed and the persistence of grain refinement after remelting and isothermal holding was also studied.A Zeiss imaging system with polarized light was used for quantitative measurement of grain size.The results show that the intensive melt shearing has a significant grain refining effect on AZ91D magnesium alloy.With the application of intensive melt shearing,the grain size of AZ91D magnesium alloy can be reduced from 530 μm(for a typical as-cast microstructure) to 170 μm,which is about 70% size reduction.The grain refinement achieved by the intensive melt shearing can be partially kept after isothermal holding and remelting.It is believed that the refinement effect was mainly due to the finer and well dispersed oxide particles formed by high intensive shearing.The smaller size of oxide particles and their slow motion velocity in the sheared melt could make important contributions to the remained grain refinement.
基金Supported by the National Natural Science Foundation of China(31460122,31360119)
文摘Coarse woody debris( CWD) has an important role in hydrological function and water and soil conservation function of forest ecosystem especially mountain forest ecosystem. To understand water holding capacity of CWD in subalpine forest of southeast Tibet,CWD reserve of primitive A. fabri forest in Sygera Mountain was investigated by sample plot method,and water absorption and storage capacity of CWD was studied by using soaking method. The results showed that decay grade was positively related to water storage potential,that is to say,the higher the decay grade,the larger the water storage potential. Saturated water holding capacity,saturated water holding rate,effective water holding capacity and effective water holding rate of A. fabri CWD all rose with decay grade increased,and the order was Ⅴ>Ⅳ>Ⅲ>Ⅱ>Ⅰ. CWD reserve was 51.555 t/hm^2,and the maximum water storage capacity was 71.601 t/hm^2,while effective water storage capacity was 60.861 t/hm2,which was equivalent to 6.086 mm of rainfall.
基金Project(2009GK2009) supported by the Science and Technology Program of Hunan Province,China
文摘For acquiring the details in aluminum holding furnace with bottom porous brick purging system,efforts were performed to try to find out the potential optimal operation schemes.By adopting transient analysis scheme and constant boundary temperature,combustion in the furnace was investigated numerically using computational fluid dynamics(CFD).The predicted gas temperature shows good agreement with the measured results,and the predicted energy distribution of the furnace is consistent with that obtained from energy balance experiment,which confirms the reliability of the numerical solution.The results show that as the fuel-air mixture temperature rises up from 300 K to 500 K,the energy utilization of the furnace could increase from 34.55% to 37.14%.However,as the excess air coefficient increases from 1.0 to 1.4,energy utilization drops from 34.55% to 29.56%.Increasing the combustion temperature is the most effective way to improve the energy efficiency of the furnace.High reactant temperature and medium excess air coefficient are recommended for high operation performance,and keeping the furnace jamb sealed well for avoiding leakage has to be emphasized.
基金The authors gratefully acknowledge the support from the Key Research and Development Plan of Shandong Province(No.2019TSLH0103)the New Energy Automobile Material Production and Application Demonstration Platform Project(No.TC180A6MR-1)Guangxi Innovation-Driven Development Special Fund Project(No.AA18242012).
文摘The effects of Cr contents(0.3 and 1.0 wt.%)and isothermal holding temperatures(400,440,and 480℃)on the microstructure evolution and properties of complex phase steel with high formability(CH steel)were investigated using dilatometry,scanning electron microscopy,transmission electron microscopy(TEM),and X-ray diffraction.The results show that the microstructures of CH steel with 0.3 wt.%Cr are ferrite,granular bainite,martensite,and retained austenite,while no ferrite is observed in the microstructure of CH steel with 1.0 wt.%Cr in the same process.Cr promotes the precipitation of(Nb,Ti)C in the high-temperature austenite region through theoretical calculations and TEM observations.Cr retards the bainite transformation and refines the grain size of CH steel.Furthermore,as isothermal holding temperature increases from 400 to 480℃,the bainite and retained austenite fractions of two CH steels decrease,while the martensite fraction increases in the steels after final quenching.Consequently,the strength has an increasing tendency and the total elongation has a decreasing tendency with increasing isothermal temperature.
文摘In this present paper, an inventory model with a generalised exponential decreasing demand is considered. A numerical example is used to illustrate the application of the model. Sensitivity analysis of the optimal solution with respect to various parameters is carried out to see the effect of parameter changes on the solution.
