Grain-oriented silicon steels were prepared at different heating rates during high temperature annealing,in which the evolution of magnetic properties,grain orientations and precipitates were studied.To illustrate the...Grain-oriented silicon steels were prepared at different heating rates during high temperature annealing,in which the evolution of magnetic properties,grain orientations and precipitates were studied.To illustrate the Zener factor,the diameter and number density of precipitates of interrupted testing samples were statistically calculated.The effect of precipitate ripening on the Goss texture and magnetic property was investigated.Data indicated that the trend of Zener factor was similar under different heating rates,first increasing and then decreasing,and that the precipitate maturing was greatly inhibited as the heating rate increased.Secondary recrystallization was developed at the temperature of 1010℃when a heating rate of 5℃/h was used,resulting in Goss,Brass and{110}<227>oriented grains growing abnormally and a magnetic induction intensity of 1.90T.Furthermore,increasing the heating rate to 20℃/h would inhibit the development of undesirable oriented grains and obtain a sharp Goss texture.However,when the heating rate was extremely fast,such as 40℃/h,poor secondary recrystallization was developed with many island grains,corresponding to a decrease in magnetic induction intensity to 1.87 T.At a suitable heating rate of 20℃/h,the sharpest Goss texture and the highest magnetic induction of 1.94 T with an onset secondary recrystallization temperature of 1020℃were found among the experimental variables in this study.The heating rate affected the initial temperature of secondary recrystallization by controlling the maturation of precipitates,leading to the deviation and dispersion of Goss texture,thereby reducing the magnetic properties.展开更多
The effects of heating rate （ranging from 50 to 300 ℃/s） during the final annealing process on microstructure evolution and magnetic properties of cold rolled non-oriented electrical steel were investigated. It was...The effects of heating rate （ranging from 50 to 300 ℃/s） during the final annealing process on microstructure evolution and magnetic properties of cold rolled non-oriented electrical steel were investigated. It was found that increasing heating rate increased the nucleation temperature and complete recrystallization temperature. At the same time, heating rate increasing could cause the substantially refined structures for the recrystallization grains and this grain refinement would decline when the heating rate was beyond 50 ℃/s. The recrystallization texture exhibited pronounced improvement with heating rate, such as the intensity decrease of 〈111〉//ND （normal direction） fiber and the intensity increase of { 110}%〈001〉 Goss texture component. The texture improvement and grain size refinement caused by heating rate increasing resulted in complicated variation of the magnetic properties. The magnetic induction （B50） keeps increasing while heating rate increases from 15 to 300 ℃/s which is due to the recrystallized texture optimization caused by rapid heating. The core losses （P1.5/50） decrease while heating rate increases from 15 to 100 ℃/s; however, the core losses would increase when heating rate is higher than 100 ℃/s, which is caused by the mean grain size refinement after rapid heating annealing. The results indicate that recrystallization texture and the magnetic properties of the non-oriented electrical steel can be improved definitely by rapid heating during the final annealing treatment.展开更多
The effect of heating rates during vacuum debinding on the microstructure and mechanical properties of alumina ceramics are discussed in this paper.The threedimensional(3D)-printed alumina ceramics examined in this st...The effect of heating rates during vacuum debinding on the microstructure and mechanical properties of alumina ceramics are discussed in this paper.The threedimensional(3D)-printed alumina ceramics examined in this study were found to have a layered structure,and interlayer spacing increased as the heating rate increased The pore diameter,shrinkage,flexural strength and hardness were found to decrease as the heating rate increased due to weak interfacial bonding between alumina particles Shrinkage was found to be much larger along the Z direction than along the X or Y directions due to the layer-bylayer forming mode during 3D printing.0.5°C·min-1is considered the optimum heating rate,yielding ceramics with interlayer spacing of 0.65 lm,shrinkage of 2.6%2.3%and 4.0%along the X,Y and Z directions,respectively,flexural strength of 27.5 MPa,hardness of29.8 GPa,Vickers hardness of HV 266.5,pore diameter of356.8 nm,bulk density of 2.5 g·cm-3,and open porosity of38.4%.The debinding procedure used in this study could be used to produce a high-quality ceramic which can be used for fabricating alumina ceramic cores.展开更多
The relationship among heating rate, mechanical properties, microstructure and texture of Al-Mg-Si-Cu alloy during solution treatment was investigated through tensile test, scanning electron microscope, X-ray diffract...The relationship among heating rate, mechanical properties, microstructure and texture of Al-Mg-Si-Cu alloy during solution treatment was investigated through tensile test, scanning electron microscope, X-ray diffractometer and EBSD technology. The experimental results reveal that there is a non-monotonic relationship among solution heating rate, mechanical properties, microstructure and texture. As the solution heating rate increases, the strength variations are dependent on the tensile direction;work hardening exponent n decreases first, and then increases;plastic strain ratio r increases first, and then decreases, and finally increases. The final microstructure and texture are also affected by heating rate. As heating rate increases, the microstructure transforms from elongated grain structure to equiaxed grain structure, and the average grain size decreases first, and then increases, and decreases finally. Although the texture components including CubeND{001}<310> and P{011}<122> orientations almost have no change with the increase of heating rate, the texture intensity and volume fraction decrease first, and then increase, and finally decrease. Both microstructure and texture evolutions are weakly affected by heating rate. Improving heating rate is not always favorable for the development of fine equiaxed grain structure, weak texture and high average r value, which may be related to the recrystallization behavior.展开更多
The effects of heating rate on the alloy element partitioning and mechanical properties during the phase transformation ofα→βin Ti-6Al-4 V alloy under solution treatment have been investigated by the experiments an...The effects of heating rate on the alloy element partitioning and mechanical properties during the phase transformation ofα→βin Ti-6Al-4 V alloy under solution treatment have been investigated by the experiments and phase field simulations,which reveal the evolutions of microstructure and compositions at the non-equilibrium state and well verify the experimental results.The specific results indicate that the compositions measured through electron probe micro-analysis(EPMA)under a lower heating rate are close to the equilibrium ones corresponding to the solution temperature.Heating up to the target solution temperature,as the heating rate increases,the Al content decreases and V increases in the primaryα(α_(p))grain with a larger size,the volume fraction ofα_(p)increases and the composition gradient betweenα_(p)andβphases gets steeper.The interrelated relationship among the diffusion,compositions,solution temperature and free energy of the system has been discussed in detail.Moreover,increasing the heating rate(~20.0 K/min)may help to improve the mechanical properties of the alloy by mainly adjusting theα_(p)/β;volume fractions,α_(p)particle size and secondaryα(α_(p))size during the process of heating up to the solution temperature.These results may shed some light on the optimization of the knowledge-based heat treatment route.展开更多
The alloy was reheated to 580℃ for tempering at rates of 2 , 5 , 10 , 20 , and 40℃ / s , respectively , after quenching.The amount , distribution , and stability of reversed austenite were investigated by X-ray diff...The alloy was reheated to 580℃ for tempering at rates of 2 , 5 , 10 , 20 , and 40℃ / s , respectively , after quenching.The amount , distribution , and stability of reversed austenite were investigated by X-ray diffraction ( XRD ) and electron back scatter diffraction ( EBSD ) .The microstructure and cryogenic impact energy were studied by scanning electron microscope ( SEM ), transmission electron microscope ( TEM ) and Charpy V-notch ( CVN ) tests.The results showed that when the sample was heated at 10℃ / s , the volume fraction of reversed austenite exhibited maximum of 8% ; the reversed austenite was uniform along all kinds of boundaries ; the reversed austenite contained higher concentration of carbon which enabled it to be more stable.The cryogenic toughness of the alloy was greatly improved when heated at 10℃ / s , as the fracture surface observation showed that it mainly fractured in ductile rupture mode , which was consistent with the results of cryogenic impact energy.展开更多
This study introduces a novel method of electric field sintering for preparing NdFeB magnets. NdFeB alloy compacts were all sintered by electric fields for 8 min at 1000~C with different preset heating rates. The char...This study introduces a novel method of electric field sintering for preparing NdFeB magnets. NdFeB alloy compacts were all sintered by electric fields for 8 min at 1000~C with different preset heating rates. The characteristics of electric field sintering and the effects of heating rate on the sintering densification of NdFeB alloys were also studied. It is found that electric field sintering is a new non-pressure rapid sintering method for preparing NdFeB magnets with fine grains at a relatively lower sintering temperature and in a shorter sintering time. Using this method, the sintering temperature and process of the compacts can be controlled accurately. When the preset heating rate in- creasing from 5 to 2000~C/s the densification of NdFeB sintered compacts gradHally improves. As the preset heating rate is 2000C/s, Nd-rich phases are small, dispersed and uniformly distributed in the sintered compact, and the magnet has a better microstructure than that made by conventional vacuum sintering. Also, the maximum energy product of the sintered magnet reaches 95% of conventionally vacuum sintered magnets.展开更多
Oxide scale formation on a C-steel surface has been investigated using linear heating rates ranging from 0.1℃/min to 10℃/min at high temperatures. The studies on the oxide scale formation at high temperature (650℃)...Oxide scale formation on a C-steel surface has been investigated using linear heating rates ranging from 0.1℃/min to 10℃/min at high temperatures. The studies on the oxide scale formation at high temperature (650℃) at slower heating rate (0.1℃/min) shows that the kinetic regime is linear. X-ray diffraction measurements revealed that the scale constituents are significantly influenced by the heating rate. The adherence of the scale was improved by using slower heating rate (0.1℃/min-≤650℃), while above such degree the scale was susceptible to cracking and flaking out of the alloy surface. In fact, the development of oxide growth stresses can cause considerable scale cracking. As well, variation of the crystallite sizes under the aforementioned conditions might affect the scale stacking to the alloy surface. The secondary electron detector images of the oxide scale shows that the scale was imperfectly smooth and there were a number of voids and defects in the scale skin, especially at fast heating rate. This observation could be attributed to defects of the as-received alloy. In general, slower heating rate reduced the defects of the scale and improved its adherence.展开更多
Effects of temperature and heating rate on the mechanical properties of the tensile specimens of magnesium alloy AZ31 were experimentally investigated using a Gleeble-1500 thermo-mechanical material testing system.The...Effects of temperature and heating rate on the mechanical properties of the tensile specimens of magnesium alloy AZ31 were experimentally investigated using a Gleeble-1500 thermo-mechanical material testing system.The metallurgraphs of the fracture section of the specimens were also experimentally observed and analyzed for exploring their failure mechanism under different temperatures and heating rates.The results show that the higher the temperature,the lower the ultimate strength of the specimens.And the higher the heating rate,the higher the ultimate strength of the specimens.The high temperatures and high heating rates will induce microvoids in the specimens which make the specimens failure under relatively low loads.展开更多
The release characteristics of CH_(4),H_(2),CO and CO_(2) from iron coke hot briquette(ICHB)during carbonization were studied.The results show that compared with briquette without iron ore,Fe_(3)O_(4) can inhibit the ...The release characteristics of CH_(4),H_(2),CO and CO_(2) from iron coke hot briquette(ICHB)during carbonization were studied.The results show that compared with briquette without iron ore,Fe_(3)O_(4) can inhibit the release rate of H2 and promote the production of CO and CO_(2).In addition,when the heating rate increases from 3 to 7℃/min,the release rates of CH4 and H2 increase,while the release rates of CO and CO_(2) first increase and then decrease.The carbonization process of ICHB was segmented,and corresponding kinetic analysis was carried out.The results show that the activation energy of StageⅡand StageⅣis higher in the carbonization process of ICHB,and the active pyrolysis of coal and the reduction of iron ore occur in these two stages.In addition,the effect of heating rate on the kinetic parameters of ICHB carbonization process was investigated.It was found that when the heating rate increased,the reaction activation energy of StageⅣdecreased first and then increased,which was consistent with the release law of CO and CO_(2).The analysis showed that the increase in heating rate leads to more reactions at higher temperatures,resulting in an increase in the release rate of some gases.In addition,thermal hysteresis can also cause some processes to fail to fully react at the end of heating.It is also found that the apparent activation energy and preexponential factor have kinetic compensation effect during the car-bonization of ICHB.展开更多
The influence of heating rate on double reversible transformation in CuZnAlMnNi shape memory alloy was investigated by differential scanning calorimetry. It was found that rapid heating inhibits X -->M transformati...The influence of heating rate on double reversible transformation in CuZnAlMnNi shape memory alloy was investigated by differential scanning calorimetry. It was found that rapid heating inhibits X -->M transformation but is favorable to the reverse martensite transformation, giving rise to the approach of the two transformation peaks. With the decrease of heating rate, the two transformation peaks separate gradually.展开更多
The latitude-altitude distributions of radiative fluxes and heating rates are investigated by utilizing CloudSat satellite data over China during summer. The Tibetan Plateau causes the downward shortwave fluxes of the...The latitude-altitude distributions of radiative fluxes and heating rates are investigated by utilizing CloudSat satellite data over China during summer. The Tibetan Plateau causes the downward shortwave fluxes of the lower atmosphere over central China to be smaller than the fluxes over southern and northern China by generating more clouds. The existence of a larger quantity of clouds over central China reflects a greater amount of solar radiation back into space. The vertical gradients of upward shortwave radiative fluxes in the atmosphere below 8 km are greater than those above 8 km. The latitudinal-altitude distributions of downward longwave radiative fluxes show a slantwise decreasing trend from low latitudes to high latitudes that gradually weaken in the downward direction. The upward longwave radiative fluxes also weaken in the upward direction but with larger gradients. The maximum heating rates by solar radiation and cooling rates by longwave infrared radiation are located over 28 40°N at 7 8 km mean sea level (MSL), and they are larger than the rates in the northern and southern regions. The heating and cooling rates match well both vertically and geographically.展开更多
We investigated the effects of heating rate on the process parameters of superplastic forming for Zr55Cu30Al10Ni5 by differential scanning calorimetry. The continuous heating and isothermal annealing analyses suggeste...We investigated the effects of heating rate on the process parameters of superplastic forming for Zr55Cu30Al10Ni5 by differential scanning calorimetry. The continuous heating and isothermal annealing analyses suggested that the temperatures of glass transition and onset crystallization are heating rate-dependent in the supercooled liquid region. Then, the time-temperature-transformation diagram under different heating rates indicates that increasing the heating rate can lead to an increase of the incubation time at the same anneal temperature in the supercooled liquid region. Based on the Arrhenius relationship, we discovered that the incubation time increases by 1.08-1.11 times with double increase of the heating rate at the same anneal temperature, and then verified it by the data of literatures and the experimental results. The obtained curve of the max available incubation time reveals that the incubation time at a certain anneal temperature in the supercooled liquid region is not infinite, and will increase with increasing heating rate until this temperature shifts out of the supercooled liquid region because of exceeding critical heating rate. It is concluded that heating rate must be an important processing parameter of superplastic forming for Zr55Cu30Al10Ni5.展开更多
The effects of heating rate on the aggregate behavior of poly（ethylene oxide）-b-poly（N-isopropylacrylamide） in aqueous solutions were investigated in detail by laser light scattering and TEM. By employing two sepa...The effects of heating rate on the aggregate behavior of poly（ethylene oxide）-b-poly（N-isopropylacrylamide） in aqueous solutions were investigated in detail by laser light scattering and TEM. By employing two separate heating protocols, step-by-step heating at 〈 5 K/step and one-step jump, to heat the sample from 15℃ to the selected temperature, we found that the heating rate only showed significant effect on the aggregates above the cloud point. The aggregate formed by step-by-step heating exhibited a much larger size and a broader size distribution than those formed by one-step jump heating. Moreover, neither of the aggregates were ideal micellar structures as indicated by the size and the Rg/Rh values. On the contrary, at temperatures below the cloud point where the block copolymer formed core-shelled micelles, the heating rate showed negligible effect on the size and size distribution of the micelles. Since the system underwent a phase separation above the cloud point, the heating rate effect could be reasonably explained by the phase separation mechanisms： the nucleation-and-growth mechanism in the metastable region and the spinodal decomposition mechanism in the unstable region.展开更多
The phase transformation from martensite to austenite during intercritical tempering with high heating rate in a low carbon martensitic stainless steel Fe-13%Cr-4%Ni-Mo has been investigated to clarify the microstruct...The phase transformation from martensite to austenite during intercritical tempering with high heating rate in a low carbon martensitic stainless steel Fe-13%Cr-4%Ni-Mo has been investigated to clarify the microstructure evolution in some regions of the weld joint heat affected zone （HAZ）. The experimental results indicate that the start and finish temperatures of the martensite to austenite transformation keep constant when the heating rate is higher than 10 K/s, and the transformation is much faster than nickel diffusion. The mechanism of the martensite to austenite transformation changes from diffusion to diffusionless during the intercritical tempering when the heating rate is higher than 10 K/s. The diffusionless transformation and higher As temperature render it difficult for any austenite to remain at room temperature during the intercritical tempering with high heating rate that occurs in the HAZ. Adding a proper intercritical tempering with low heating rate can induce some reversed austenite in the rapid heated sample.展开更多
In the framework of the finite element method (FEM), a prediction method for the heating rate and the skin friction on a body surface is presented by using the energy and momentum conservation equations respectively. ...In the framework of the finite element method (FEM), a prediction method for the heating rate and the skin friction on a body surface is presented by using the energy and momentum conservation equations respectively. Meanwhile, a brief analysis is made of the role the weighted functions play in the present work.展开更多
The effect of the heating rate on the nucleation of metallic glass in a rapid heating process starting from the glass transition temperature is investigated. The critical nucleus radius increases with the increase of ...The effect of the heating rate on the nucleation of metallic glass in a rapid heating process starting from the glass transition temperature is investigated. The critical nucleus radius increases with the increase of the temperature of the undercooling liquid. If the increment rate of the critical nucleus radius, owing to the heating process, is higher than the growth rate of the nuclei, the nuclei generated at the low temperature will become the embryos at the high temperature. This means that the high heating rate can make no nucleation happen in the heating process. In consideration of the interfacial energy, the growth rate of the nuclei increases with the increase of their size and the growth rate of the critical nucleus is zero. Thus, the lower heating rate can also make the nuclei decline partially. Finally, this theory is used to analyze the nucleation process during laser remelting metallic glass.展开更多
AlxOy films by DC reactive magnetron sputtering were annealed in air ambient at 500 ℃for 1 h with different heating rates of 5,15,and 25 ℃/min.Then heat treatments at 900 ℃ were carried out on these 500 ℃-annealed...AlxOy films by DC reactive magnetron sputtering were annealed in air ambient at 500 ℃for 1 h with different heating rates of 5,15,and 25 ℃/min.Then heat treatments at 900 ℃ were carried out on these 500 ℃-annealed films to simulate the high-temperature application environment.Effects of the annealing heating rate on structure and properties of both 500 ℃-annealed and 900 ℃-heated films were investigated systematically.It was found that distinct γ-Al2O3 crystallization was observed in the 900 ℃-heated films only when the annealing heating rates are 15 and 25 ℃/min.The 500 ℃-annealed film possessed the most compact surface morphology in the case of 25 ℃/min.The highest microhardness of both 500 ℃-annealed and 900℃-heated films were obtained when the annealing heating rate was 15 ℃/min.展开更多
A rapid-heating method in the absence of electric/magnetic field was achieved by introducing a self-propagating-combustion （SHS） as heating source. The effect of heating rate on the alumina grain growth was explored...A rapid-heating method in the absence of electric/magnetic field was achieved by introducing a self-propagating-combustion （SHS） as heating source. The effect of heating rate on the alumina grain growth was explored based on this rapid-heating method. Comparing with the alumina prepared by two different heating ratios （greater than 1 000 ℃/min in SItS and about 50 ℃/min in common pressureless sintering furnace）, it was revealed that the rapid heating could promote the grain growth greatly without pressure during sintering. However, if a pressure was applied simultaneously, the grain growth would be almost completely restrained. Since these observations are quite different from the expectation, a new grain growth model was proposed.展开更多
The relation between the melting point of Portland cement raw meal and its heating rate have been studied. The raw meal was burnt at different heating rate ranging from 10 similar to 900 degrees C/min Dy the following...The relation between the melting point of Portland cement raw meal and its heating rate have been studied. The raw meal was burnt at different heating rate ranging from 10 similar to 900 degrees C/min Dy the following methods: (A) in electric resistance furnace; (B) in DTA-TG analyzer with infrared ray focused heating; (C) in high temperature microscope with electron stream heating. Based on thermal analysis theory and melt theory and the tests above, it is found that melting point T-m of cement raw meal decreases with the increased heating rate Phi during burning in the following relation: T-m=1280-0.107 empty set.展开更多
文摘Grain-oriented silicon steels were prepared at different heating rates during high temperature annealing,in which the evolution of magnetic properties,grain orientations and precipitates were studied.To illustrate the Zener factor,the diameter and number density of precipitates of interrupted testing samples were statistically calculated.The effect of precipitate ripening on the Goss texture and magnetic property was investigated.Data indicated that the trend of Zener factor was similar under different heating rates,first increasing and then decreasing,and that the precipitate maturing was greatly inhibited as the heating rate increased.Secondary recrystallization was developed at the temperature of 1010℃when a heating rate of 5℃/h was used,resulting in Goss,Brass and{110}<227>oriented grains growing abnormally and a magnetic induction intensity of 1.90T.Furthermore,increasing the heating rate to 20℃/h would inhibit the development of undesirable oriented grains and obtain a sharp Goss texture.However,when the heating rate was extremely fast,such as 40℃/h,poor secondary recrystallization was developed with many island grains,corresponding to a decrease in magnetic induction intensity to 1.87 T.At a suitable heating rate of 20℃/h,the sharpest Goss texture and the highest magnetic induction of 1.94 T with an onset secondary recrystallization temperature of 1020℃were found among the experimental variables in this study.The heating rate affected the initial temperature of secondary recrystallization by controlling the maturation of precipitates,leading to the deviation and dispersion of Goss texture,thereby reducing the magnetic properties.
基金Item Sponsored by National Natural Science Foundation of China (50874010 ,50802008) Program for New Century Excellent Talents in University of China (NCET-05-0101)
文摘The effects of heating rate （ranging from 50 to 300 ℃/s） during the final annealing process on microstructure evolution and magnetic properties of cold rolled non-oriented electrical steel were investigated. It was found that increasing heating rate increased the nucleation temperature and complete recrystallization temperature. At the same time, heating rate increasing could cause the substantially refined structures for the recrystallization grains and this grain refinement would decline when the heating rate was beyond 50 ℃/s. The recrystallization texture exhibited pronounced improvement with heating rate, such as the intensity decrease of 〈111〉//ND （normal direction） fiber and the intensity increase of { 110}%〈001〉 Goss texture component. The texture improvement and grain size refinement caused by heating rate increasing resulted in complicated variation of the magnetic properties. The magnetic induction （B50） keeps increasing while heating rate increases from 15 to 300 ℃/s which is due to the recrystallized texture optimization caused by rapid heating. The core losses （P1.5/50） decrease while heating rate increases from 15 to 100 ℃/s; however, the core losses would increase when heating rate is higher than 100 ℃/s, which is caused by the mean grain size refinement after rapid heating annealing. The results indicate that recrystallization texture and the magnetic properties of the non-oriented electrical steel can be improved definitely by rapid heating during the final annealing treatment.
基金financially supported by the National Key Research and Development Program of China(No.2018YFB1106600)the National Natural Science Foundation of China(No.51672217)。
文摘The effect of heating rates during vacuum debinding on the microstructure and mechanical properties of alumina ceramics are discussed in this paper.The threedimensional(3D)-printed alumina ceramics examined in this study were found to have a layered structure,and interlayer spacing increased as the heating rate increased The pore diameter,shrinkage,flexural strength and hardness were found to decrease as the heating rate increased due to weak interfacial bonding between alumina particles Shrinkage was found to be much larger along the Z direction than along the X or Y directions due to the layer-bylayer forming mode during 3D printing.0.5°C·min-1is considered the optimum heating rate,yielding ceramics with interlayer spacing of 0.65 lm,shrinkage of 2.6%2.3%and 4.0%along the X,Y and Z directions,respectively,flexural strength of 27.5 MPa,hardness of29.8 GPa,Vickers hardness of HV 266.5,pore diameter of356.8 nm,bulk density of 2.5 g·cm-3,and open porosity of38.4%.The debinding procedure used in this study could be used to produce a high-quality ceramic which can be used for fabricating alumina ceramic cores.
基金The authors are grateful for the financial supports from the Science Challenge Project(TZ2018001)the State Key Laboratory of Advanced Metals and Materials University of Science and Technology Beijing,China(2019-Z02)+3 种基金the National Natural Science Foundation of China(52075272)the Key Laboratory of Impact and Safety Engineering,Ministry of Education,Ningbo University,China(CJ201912)the Ningbo Natural Science Foundation,China(2018A610174)the K.C.Wong Magna Fund from Ningbo University,China.
文摘The relationship among heating rate, mechanical properties, microstructure and texture of Al-Mg-Si-Cu alloy during solution treatment was investigated through tensile test, scanning electron microscope, X-ray diffractometer and EBSD technology. The experimental results reveal that there is a non-monotonic relationship among solution heating rate, mechanical properties, microstructure and texture. As the solution heating rate increases, the strength variations are dependent on the tensile direction;work hardening exponent n decreases first, and then increases;plastic strain ratio r increases first, and then decreases, and finally increases. The final microstructure and texture are also affected by heating rate. As heating rate increases, the microstructure transforms from elongated grain structure to equiaxed grain structure, and the average grain size decreases first, and then increases, and decreases finally. Although the texture components including CubeND{001}<310> and P{011}<122> orientations almost have no change with the increase of heating rate, the texture intensity and volume fraction decrease first, and then increase, and finally decrease. Both microstructure and texture evolutions are weakly affected by heating rate. Improving heating rate is not always favorable for the development of fine equiaxed grain structure, weak texture and high average r value, which may be related to the recrystallization behavior.
基金support from the National Natural Science Foundation of China(No.51701219)the Doctoral Scientific Research Foundation of Liaoning Province(No.20180540133)the Special Project on Information Technology of the Chinese Academy of Sciences(No.XXH13506–304)。
文摘The effects of heating rate on the alloy element partitioning and mechanical properties during the phase transformation ofα→βin Ti-6Al-4 V alloy under solution treatment have been investigated by the experiments and phase field simulations,which reveal the evolutions of microstructure and compositions at the non-equilibrium state and well verify the experimental results.The specific results indicate that the compositions measured through electron probe micro-analysis(EPMA)under a lower heating rate are close to the equilibrium ones corresponding to the solution temperature.Heating up to the target solution temperature,as the heating rate increases,the Al content decreases and V increases in the primaryα(α_(p))grain with a larger size,the volume fraction ofα_(p)increases and the composition gradient betweenα_(p)andβphases gets steeper.The interrelated relationship among the diffusion,compositions,solution temperature and free energy of the system has been discussed in detail.Moreover,increasing the heating rate(~20.0 K/min)may help to improve the mechanical properties of the alloy by mainly adjusting theα_(p)/β;volume fractions,α_(p)particle size and secondaryα(α_(p))size during the process of heating up to the solution temperature.These results may shed some light on the optimization of the knowledge-based heat treatment route.
文摘The alloy was reheated to 580℃ for tempering at rates of 2 , 5 , 10 , 20 , and 40℃ / s , respectively , after quenching.The amount , distribution , and stability of reversed austenite were investigated by X-ray diffraction ( XRD ) and electron back scatter diffraction ( EBSD ) .The microstructure and cryogenic impact energy were studied by scanning electron microscope ( SEM ), transmission electron microscope ( TEM ) and Charpy V-notch ( CVN ) tests.The results showed that when the sample was heated at 10℃ / s , the volume fraction of reversed austenite exhibited maximum of 8% ; the reversed austenite was uniform along all kinds of boundaries ; the reversed austenite contained higher concentration of carbon which enabled it to be more stable.The cryogenic toughness of the alloy was greatly improved when heated at 10℃ / s , as the fracture surface observation showed that it mainly fractured in ductile rupture mode , which was consistent with the results of cryogenic impact energy.
基金the National Natural Science Foundation of China(No.50945018)
文摘This study introduces a novel method of electric field sintering for preparing NdFeB magnets. NdFeB alloy compacts were all sintered by electric fields for 8 min at 1000~C with different preset heating rates. The characteristics of electric field sintering and the effects of heating rate on the sintering densification of NdFeB alloys were also studied. It is found that electric field sintering is a new non-pressure rapid sintering method for preparing NdFeB magnets with fine grains at a relatively lower sintering temperature and in a shorter sintering time. Using this method, the sintering temperature and process of the compacts can be controlled accurately. When the preset heating rate in- creasing from 5 to 2000~C/s the densification of NdFeB sintered compacts gradHally improves. As the preset heating rate is 2000C/s, Nd-rich phases are small, dispersed and uniformly distributed in the sintered compact, and the magnet has a better microstructure than that made by conventional vacuum sintering. Also, the maximum energy product of the sintered magnet reaches 95% of conventionally vacuum sintered magnets.
文摘Oxide scale formation on a C-steel surface has been investigated using linear heating rates ranging from 0.1℃/min to 10℃/min at high temperatures. The studies on the oxide scale formation at high temperature (650℃) at slower heating rate (0.1℃/min) shows that the kinetic regime is linear. X-ray diffraction measurements revealed that the scale constituents are significantly influenced by the heating rate. The adherence of the scale was improved by using slower heating rate (0.1℃/min-≤650℃), while above such degree the scale was susceptible to cracking and flaking out of the alloy surface. In fact, the development of oxide growth stresses can cause considerable scale cracking. As well, variation of the crystallite sizes under the aforementioned conditions might affect the scale stacking to the alloy surface. The secondary electron detector images of the oxide scale shows that the scale was imperfectly smooth and there were a number of voids and defects in the scale skin, especially at fast heating rate. This observation could be attributed to defects of the as-received alloy. In general, slower heating rate reduced the defects of the scale and improved its adherence.
基金Projects(10872221,50621403)supported by the National Natural Science Foundation of China
文摘Effects of temperature and heating rate on the mechanical properties of the tensile specimens of magnesium alloy AZ31 were experimentally investigated using a Gleeble-1500 thermo-mechanical material testing system.The metallurgraphs of the fracture section of the specimens were also experimentally observed and analyzed for exploring their failure mechanism under different temperatures and heating rates.The results show that the higher the temperature,the lower the ultimate strength of the specimens.And the higher the heating rate,the higher the ultimate strength of the specimens.The high temperatures and high heating rates will induce microvoids in the specimens which make the specimens failure under relatively low loads.
文摘The release characteristics of CH_(4),H_(2),CO and CO_(2) from iron coke hot briquette(ICHB)during carbonization were studied.The results show that compared with briquette without iron ore,Fe_(3)O_(4) can inhibit the release rate of H2 and promote the production of CO and CO_(2).In addition,when the heating rate increases from 3 to 7℃/min,the release rates of CH4 and H2 increase,while the release rates of CO and CO_(2) first increase and then decrease.The carbonization process of ICHB was segmented,and corresponding kinetic analysis was carried out.The results show that the activation energy of StageⅡand StageⅣis higher in the carbonization process of ICHB,and the active pyrolysis of coal and the reduction of iron ore occur in these two stages.In addition,the effect of heating rate on the kinetic parameters of ICHB carbonization process was investigated.It was found that when the heating rate increased,the reaction activation energy of StageⅣdecreased first and then increased,which was consistent with the release law of CO and CO_(2).The analysis showed that the increase in heating rate leads to more reactions at higher temperatures,resulting in an increase in the release rate of some gases.In addition,thermal hysteresis can also cause some processes to fail to fully react at the end of heating.It is also found that the apparent activation energy and preexponential factor have kinetic compensation effect during the car-bonization of ICHB.
文摘The influence of heating rate on double reversible transformation in CuZnAlMnNi shape memory alloy was investigated by differential scanning calorimetry. It was found that rapid heating inhibits X -->M transformation but is favorable to the reverse martensite transformation, giving rise to the approach of the two transformation peaks. With the decrease of heating rate, the two transformation peaks separate gradually.
基金supported by the National Natural Science Foundation of China(Grant Nos.40875084and40705012)the National Key Technologies R&D Program of China(Grant No.2008BAC40B00)
文摘The latitude-altitude distributions of radiative fluxes and heating rates are investigated by utilizing CloudSat satellite data over China during summer. The Tibetan Plateau causes the downward shortwave fluxes of the lower atmosphere over central China to be smaller than the fluxes over southern and northern China by generating more clouds. The existence of a larger quantity of clouds over central China reflects a greater amount of solar radiation back into space. The vertical gradients of upward shortwave radiative fluxes in the atmosphere below 8 km are greater than those above 8 km. The latitudinal-altitude distributions of downward longwave radiative fluxes show a slantwise decreasing trend from low latitudes to high latitudes that gradually weaken in the downward direction. The upward longwave radiative fluxes also weaken in the upward direction but with larger gradients. The maximum heating rates by solar radiation and cooling rates by longwave infrared radiation are located over 28 40°N at 7 8 km mean sea level (MSL), and they are larger than the rates in the northern and southern regions. The heating and cooling rates match well both vertically and geographically.
基金Funded by the National Natural Science Foundation of China(Nos.51175210 and 51175211)
文摘We investigated the effects of heating rate on the process parameters of superplastic forming for Zr55Cu30Al10Ni5 by differential scanning calorimetry. The continuous heating and isothermal annealing analyses suggested that the temperatures of glass transition and onset crystallization are heating rate-dependent in the supercooled liquid region. Then, the time-temperature-transformation diagram under different heating rates indicates that increasing the heating rate can lead to an increase of the incubation time at the same anneal temperature in the supercooled liquid region. Based on the Arrhenius relationship, we discovered that the incubation time increases by 1.08-1.11 times with double increase of the heating rate at the same anneal temperature, and then verified it by the data of literatures and the experimental results. The obtained curve of the max available incubation time reveals that the incubation time at a certain anneal temperature in the supercooled liquid region is not infinite, and will increase with increasing heating rate until this temperature shifts out of the supercooled liquid region because of exceeding critical heating rate. It is concluded that heating rate must be an important processing parameter of superplastic forming for Zr55Cu30Al10Ni5.
基金supported by the National Natural Science Foundation of China(No.20504001)
文摘The effects of heating rate on the aggregate behavior of poly（ethylene oxide）-b-poly（N-isopropylacrylamide） in aqueous solutions were investigated in detail by laser light scattering and TEM. By employing two separate heating protocols, step-by-step heating at 〈 5 K/step and one-step jump, to heat the sample from 15℃ to the selected temperature, we found that the heating rate only showed significant effect on the aggregates above the cloud point. The aggregate formed by step-by-step heating exhibited a much larger size and a broader size distribution than those formed by one-step jump heating. Moreover, neither of the aggregates were ideal micellar structures as indicated by the size and the Rg/Rh values. On the contrary, at temperatures below the cloud point where the block copolymer formed core-shelled micelles, the heating rate showed negligible effect on the size and size distribution of the micelles. Since the system underwent a phase separation above the cloud point, the heating rate effect could be reasonably explained by the phase separation mechanisms： the nucleation-and-growth mechanism in the metastable region and the spinodal decomposition mechanism in the unstable region.
基金the financial support from the National Science Foundation of China(No.51201167)the Youth Innovation Promotion Association Chinese Academy of Sciences and National Science and Technology Major Project(No.2011ZX06004-016)
文摘The phase transformation from martensite to austenite during intercritical tempering with high heating rate in a low carbon martensitic stainless steel Fe-13%Cr-4%Ni-Mo has been investigated to clarify the microstructure evolution in some regions of the weld joint heat affected zone （HAZ）. The experimental results indicate that the start and finish temperatures of the martensite to austenite transformation keep constant when the heating rate is higher than 10 K/s, and the transformation is much faster than nickel diffusion. The mechanism of the martensite to austenite transformation changes from diffusion to diffusionless during the intercritical tempering when the heating rate is higher than 10 K/s. The diffusionless transformation and higher As temperature render it difficult for any austenite to remain at room temperature during the intercritical tempering with high heating rate that occurs in the HAZ. Adding a proper intercritical tempering with low heating rate can induce some reversed austenite in the rapid heated sample.
基金The project supported by the National Natural Science Foundation of China (19889210)
文摘In the framework of the finite element method (FEM), a prediction method for the heating rate and the skin friction on a body surface is presented by using the energy and momentum conservation equations respectively. Meanwhile, a brief analysis is made of the role the weighted functions play in the present work.
基金Project supported by the National Natural Science Foundation of China(Grant No.50971102)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20116102110016)+1 种基金the National Basic Research Program of China(Grant No.2011CB610402)the Fund of the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University,China(Grant No.SKLSP201306)
文摘The effect of the heating rate on the nucleation of metallic glass in a rapid heating process starting from the glass transition temperature is investigated. The critical nucleus radius increases with the increase of the temperature of the undercooling liquid. If the increment rate of the critical nucleus radius, owing to the heating process, is higher than the growth rate of the nuclei, the nuclei generated at the low temperature will become the embryos at the high temperature. This means that the high heating rate can make no nucleation happen in the heating process. In consideration of the interfacial energy, the growth rate of the nuclei increases with the increase of their size and the growth rate of the critical nucleus is zero. Thus, the lower heating rate can also make the nuclei decline partially. Finally, this theory is used to analyze the nucleation process during laser remelting metallic glass.
文摘AlxOy films by DC reactive magnetron sputtering were annealed in air ambient at 500 ℃for 1 h with different heating rates of 5,15,and 25 ℃/min.Then heat treatments at 900 ℃ were carried out on these 500 ℃-annealed films to simulate the high-temperature application environment.Effects of the annealing heating rate on structure and properties of both 500 ℃-annealed and 900 ℃-heated films were investigated systematically.It was found that distinct γ-Al2O3 crystallization was observed in the 900 ℃-heated films only when the annealing heating rates are 15 and 25 ℃/min.The 500 ℃-annealed film possessed the most compact surface morphology in the case of 25 ℃/min.The highest microhardness of both 500 ℃-annealed and 900℃-heated films were obtained when the annealing heating rate was 15 ℃/min.
基金Funded by the National Natural Science Foundation of China(No.U12301013)the State Ministry of Science and Technology Innovation Fund(No.0102010DFA52240)
文摘A rapid-heating method in the absence of electric/magnetic field was achieved by introducing a self-propagating-combustion （SHS） as heating source. The effect of heating rate on the alumina grain growth was explored based on this rapid-heating method. Comparing with the alumina prepared by two different heating ratios （greater than 1 000 ℃/min in SItS and about 50 ℃/min in common pressureless sintering furnace）, it was revealed that the rapid heating could promote the grain growth greatly without pressure during sintering. However, if a pressure was applied simultaneously, the grain growth would be almost completely restrained. Since these observations are quite different from the expectation, a new grain growth model was proposed.
文摘The relation between the melting point of Portland cement raw meal and its heating rate have been studied. The raw meal was burnt at different heating rate ranging from 10 similar to 900 degrees C/min Dy the following methods: (A) in electric resistance furnace; (B) in DTA-TG analyzer with infrared ray focused heating; (C) in high temperature microscope with electron stream heating. Based on thermal analysis theory and melt theory and the tests above, it is found that melting point T-m of cement raw meal decreases with the increased heating rate Phi during burning in the following relation: T-m=1280-0.107 empty set.
