In this study,the efects of diferent heat treatment process parameters on the microstructure and mechanical properties of Al-12Si-5Cu-1.1Mg-2.3Ni-0.3La alloy were explored.Research showed that eutectic Si underwent th...In this study,the efects of diferent heat treatment process parameters on the microstructure and mechanical properties of Al-12Si-5Cu-1.1Mg-2.3Ni-0.3La alloy were explored.Research showed that eutectic Si underwent three stages during solution treatment:difusing,spheroidization and coarsening.As the solution temperature and time increased,the size of eutectic Si showed a trend of frst decreasing and then increasing.Compared with the heat treatment time,the heat treatment temperature had a more signifcant efect on the mechanical properties.The coarsening of microstructure was the main reason for the deterioration of mechanical properties.The Al_(3)Ti and Al_(3)CuNiLa in the microstructure after aging can signifcantly improve the mechanical properties of the alloy.The Al_(11)La_(3) with secondary precipitation occurred in the La-rich phase.The addition of La inhibited the growth of coherent/semi-coherentθandβphases,which was very benefcial for the improvement of high-temperature strength.Under the optimal heat treatment process parameters of 500℃×4 h+190℃×4 h,the ultimate tensile strength(UTS)of the alloy reached 366.65 MPa.The high-temperature strength and elongation of the alloy reached 101.98 MPa and 13.77%at 350℃,respectively.展开更多
Ultrafast heating(UFH)at the rates of 10-300℃/s was employed as a new strategy to anneal a coldrolled 7 wt%Mn steel,followed by the immediate cooling.Severely deformed strain-induced martensite and lightly-deformed t...Ultrafast heating(UFH)at the rates of 10-300℃/s was employed as a new strategy to anneal a coldrolled 7 wt%Mn steel,followed by the immediate cooling.Severely deformed strain-induced martensite and lightly-deformed thermal martensite,both had been already enriched with C and Mn before,transformed to fine and coarse austenite grains during the UFH,leading to the bimodal size distribution.Compared with the long intercritical annealing(IA)process,the UFH processes produced larger fraction of RA grains(up to 37%)with a high density of dislocation,leading to the significant increase in yield strength by 270 MPa and the product of strength and elongation up to 55 GPa%due to the enormous work hardening capacity.Such a significant strengthening is first attributed to high density dislocations preserved after UFH and then to the microstructural refinement and the precipitation strengthening;whilst the sustainable work hardening is attributed to the successive TRIP effect during deformation,resulting from the large fraction of RA instantly formed with the bimodal size distribution during UFH.Moreover,the results on the microstructural characterization,thermodynamics calculation on the reverse transformation temperature and the kinetic simulations on the reverse transformation all suggest that the austenitization during UFH is displacive and involves the diffusion and partition of C.Therefore,we propose that it is a bainite-like transformation.展开更多
The microstructural changes of Fe83Si4B13 amorphous mother alloy during the heating process were investigated by Laser Scanning Confocal Microscopy （LSCM） ,and the phase transformation was determined by the Thermo-C...The microstructural changes of Fe83Si4B13 amorphous mother alloy during the heating process were investigated by Laser Scanning Confocal Microscopy （LSCM） ,and the phase transformation was determined by the Thermo-Calc calculations. The differences in the melting points measured by Differential Scanning Calorimetry （DSC） and LSCM, and those obtained by Thermo-Calc calculations were also discussed. It is found that the melting points measured by DSC and LSCM are relatively similar, whereas the onset and end of the melting temperatures calculated by Thermo-Calc software are higher than those measured by DSC and observed by LSCM.展开更多
Ground-state cooling of mesoscopic mechanical objects is still a major challenge in the unresolved-sideband regime.We present a frequency modulation(FM)scheme to achieve cooling of the mechanical resonator to its grou...Ground-state cooling of mesoscopic mechanical objects is still a major challenge in the unresolved-sideband regime.We present a frequency modulation(FM)scheme to achieve cooling of the mechanical resonator to its ground-state in a double-cavity optomechanical system containing a mechanical resonator.The mean phonon number is determined by numerically solving a set of differential equations derived from the quantum master equations.Due to efficient suppression of Stokes heating processes in the presence of FM,the ground-state cooling,indicated by numerical calculations,is significantly achievable,regardless of whether in the resolved-sideband regime or the unresolved-sideband regime.Furthermore,by choosing parameters reasonably,the improvement of the quantum cooling limit is found to be capable of being positively correlated with the modulation frequency.This method provides new insight into quantum manipulation and creates more possibilities for applications of quantum devices.展开更多
In-situ HVEM observation on phase transition of the YBa_2Cu_3O_(7-x) superconducting compound in pro- cess of heating was carried out,and high temperature X-ray diffraction analysis in air and X-ray diffraction phase ...In-situ HVEM observation on phase transition of the YBa_2Cu_3O_(7-x) superconducting compound in pro- cess of heating was carried out,and high temperature X-ray diffraction analysis in air and X-ray diffraction phase analysis for the sample treated in vacuum condition were made.The results showed that the temperature of phase transition is related to oxygen content in the sample and in general,is 100℃ to 120℃ lower in vacu- um condition than in air.At 320℃ to 350℃ twin bands begin to disappear,and some Cu_2O are formed on the surface of the sample and transit from orthorhombic YBa_2Cu_3O_(7-x) to arthorhombic Y_2BaCuO_5 compound. This transition was completed at about 500℃.Above 900℃,this compound consists of the Y_2BaCuO_5, BaCuO_2,Y_2O_3 and some other minor compounds.No phase transition was observed during cooling the sample.展开更多
Three-dimensional thermal a nalysis simulation of a horizontal zone refining system is conducted for germanimn semiconductor materials. The considered geometry includes a g＇ral）hite boat filled with germanium placed...Three-dimensional thermal a nalysis simulation of a horizontal zone refining system is conducted for germanimn semiconductor materials. The considered geometry includes a g＇ral）hite boat filled with germanium placed in a cylindrical quartz tube. A flow of Ar and H2 gas mixture is purged througll the tube. A narrow section of the, boat is assmned to be exposed to a constant heat rate produced b v an rf coil located outside the quartz tube. The results of this analysis provide essential information about various parameters such as the shape of tile molten zone, required power and temperature gradient in the system.展开更多
The energy and exergy performances of the corn straw and Silicon Carbide (SiC) in the microwave heating process are crucial to sufficiently utilize crop residues for mitigating environmental pollution, promoting waste...The energy and exergy performances of the corn straw and Silicon Carbide (SiC) in the microwave heating process are crucial to sufficiently utilize crop residues for mitigating environmental pollution, promoting waste value, and improving farmer incomes. In this study, the comprehensive energy and exergy performances (the absorbed energy, energy efficiency, absorbed exergy, and exergy efficiency) of the mass ratio (SiC to corn straw), microwave power, and reaction chamber volume were compared and analyzed. The effect of the mass ratio of SiC to corn straw on energy and exergy performances based on the experimental data was newly studied. Also, the parametric analysis of the microwave power and reaction chamber for the microwave heating process of corn straw assisted by SiC was conducted. The findings indicate that increasing the mass ratio of SiC to corn straw from 0 to 1 significantly improves performance metrics: final absorbed energy increased from 5466 J to 6195 J, energy efficiency from 9.1% to 20.7%, absorbed exergy from 1102 J to 1312 J, and exergy efficiency from 1.8% to 4.4%. Similarly, increasing microwave power from 400 W to 600 W enhanced final absorbed energy from 5752 J to 6195 J, energy efficiency from 11.1% to 20.7%, absorbed exergy from 1177 J to 1312 J, and exergy efficiency from 2.3% to 4.4%. Conversely, enlarging the reaction chamber from 100 mL to 300 mL resulted in decreases: final absorbed energy dropped from 5758 J to 5700 J, energy efficiency from 11.6% to 9.0%, absorbed exergy from 1122 J to 1118 J, and exergy efficiency from 2.3% to 1.8%. These results underscore the substantial influence of the mass ratio on energy and exergy performances, while indicating that the reaction chamber volume has a minimal impact on the performances.展开更多
The formation process and composition of the acrylonitrile/urea inclusion compounds （AN/UIC） with different aging times and AN/urea molar feed ratios are studied by differential scanning calorimetry （DSC） and X-ra...The formation process and composition of the acrylonitrile/urea inclusion compounds （AN/UIC） with different aging times and AN/urea molar feed ratios are studied by differential scanning calorimetry （DSC） and X-ray diffraction （XRD）. It is suggested that DSC can determine the vip/host ratio and the heat of decomposition. Meanwhile, the vip/host ratio and heat of decomposition are obtained, which are 1.17 and 5361.53 J/mol, respec- tively. It is suggested AN molecules included in urea canal lattice may be packed flat against each other. It is found that the formation of AN/UIC depends on the aging time. XRD results reveal that once AN molecules enter urea lattice, AN/UIC are formed, which possess the final structure. When AN molecules are sufficient, the length of AN molecular arrays in urea canals increases as aging time prolonging until urea tunnels are saturated by AN.展开更多
Dry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50--300 N at 400℃ by a pin-on-disc high temperature wear machine. The effect of heat treatment process on wear res...Dry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50--300 N at 400℃ by a pin-on-disc high temperature wear machine. The effect of heat treatment process on wear resistance was systematically studied in order to select heat treatment processes of the steel with high wear resistance. The morphology, structure and composition were analyzed using scanning electron microscopy （SEM）, X-ray diffraction （XRD） and energy dispersive spectroscopy （EDS） ; wear mechanism was also discussed. Tribo-oxide layer was found to form on worn surfaces to reduce wear under low loads, but appear inside the matrix to increase wear under high loads. The tribo-oxides were mainly consisted of Fe3O4 and Fe2O3, FeO only appeared under a high load. Oxidative mild wear, transition of mild-severe wear in oxidative wear and extrusive wear took turns to operate with increasing the load. The wear resistance strongly depended on the selection of heat treatment processes or microstructures. It was found that bainite presented a better wear resistance than martensite plus bainite duplex structure, martensite structure was of the poorest wear resistance. The wear resistance increased with increasing austenizing temperature in the range of 920 to 1 120 ℃, then decreased at up to 1 220 ℃. As for tempering temperature and microstructure, the wear resistance increased in following order： 700℃ （tempered sorbite）, 200 ℃ （tempered martensite）, 440 to 650 ℃ （tempered troostite）. An appropriate combination of hardness, toughness, microstructural thermal stability was re- quired for a good wear resistance in high-temperature wear. The optimized heat treatment process was suggested for the cast hot-forging steel to be austenized at 1020 to 1 120 ℃, quenched in oil, then tempered at 440 to 650℃ for 2 h.展开更多
In this study, a two-step heating process is introduced for transient liquid phase ( TLP) diffusion bonding fo r sound joints with T91 heat resistant steels. At first, a short-time higher temperature heating ...In this study, a two-step heating process is introduced for transient liquid phase ( TLP) diffusion bonding fo r sound joints with T91 heat resistant steels. At first, a short-time higher temperature heating step is addressed to melt the interlayer, followed by the second step to complete isothermal solidification at a low temperature. The most critical feature of our new method is producing a non-planar interface at the T9/ heat resistant steels joint. We propose a transitional liquid phase bonding of T91 heat resistant steels by this approach. Since joint microstructures have been studied, we tested the tensile strength to assess joint mechanical property. The result indicates that the solidified bond may contain a primary solid-solution, similar composition to the parent metal and free from precipitates. Joint tensile strength of the joint is not lower than parent materials. Joint bend's strengths are enhanced due to the higher metal-to-metal junction producing a non-planar bond lines. Nevertheless, the traditional transient liquid phase diffusion bonding produces planar ones. Bonding parameters of new process are 1 260 °C for 0. 5 min and 1 230 °C fo r 4 min.展开更多
A 3-D mathematical model considering turbulence phenomena has been established based on a computational fluid dynamics technique, so called 3-D SOLA-VOF (Solution Algorithm-Volume of Fluid), to simulate the fluid flow...A 3-D mathematical model considering turbulence phenomena has been established based on a computational fluid dynamics technique, so called 3-D SOLA-VOF (Solution Algorithm-Volume of Fluid), to simulate the fluid flow of mold filling process of die casting. In addition, the mathematical model for simulating the heat transfer in die casting process has also been established. The computation program has been developed by the authors with the finite difference method (FDM) recently. As verification, the mold filling process of a S-shaped die casting has been simulated and the simulation results coincide with that of the benchmark test. Finally, as a practical application, the gating design of a motorcycle component was modified by the mold filling simulation and the dies design of another motorcycle component was optimized by the heat transfer simulation. All the optimized designs were verified by the production practice.展开更多
A number of dry bridges have been built to substitute for the roadbed on the Qinghai-Tibet Railway,China.The aim of this study was to investigate the exothermic process of cast-in-place (CIP) pile foundation of a dry ...A number of dry bridges have been built to substitute for the roadbed on the Qinghai-Tibet Railway,China.The aim of this study was to investigate the exothermic process of cast-in-place (CIP) pile foundation of a dry bridge and its harm to the stability of nearby frozen ground.We present 3D heat conduction functions of a concrete pile and of frozen ground with related boundaries.Our analysis is based on the theory of heat conduction and the exponent law describing the adiabatic temperature rise caused by hydration heat.Results under continuous and initial conditions were combined to establish a finite element model of a CIP pile-frozen ground system for a dry bridge under actual field conditions in cold regions.Numerical results indicated that the process could effectively simulate the exothermic process of CIP pile foundation.Thermal disturbance to frozen ground under a long dry bridge caused by the casting temperature and hydration heat of CIP piles was substantial and long-lasting.The simulated thermal analysis results agreed with field measurements and some significant rules relating to the problem were deduced and conclusions reached.展开更多
A T-Q diagram based on entransy theory is applied to graphically and quantitatively describe the irreversibility of the heat transfer processes.The hot and cold composite curves can be obtained in the T-Q diagram.The ...A T-Q diagram based on entransy theory is applied to graphically and quantitatively describe the irreversibility of the heat transfer processes.The hot and cold composite curves can be obtained in the T-Q diagram.The entransy recovery and entransy dissipation that are affected by temperature differences can be obtained through the shaded area under the composite curves.The method for setting the energy target of the HENs in T-Q diagram based on entransy theory is proposed.A case study of the diesel oil hydrogenation unit is used to illustrate the application of the method.The results show that three different heat transfer temperature differences is 10 K,15 K and 20 K,and the entransy recovery is 5.498×10~7k W·K,5.377×10~7k W·K,5.257×10~7k W·K,respectively.And the entransy transfer efficiency is 92.29%,91.63%,90.99%.Thus,the energy-saving potential of the HENs is obtained by setting the energy target based on the entransy transfer efficiency.展开更多
The process characteristics of heat treatment of aluminum alloy auto body sheet and the working principle of air cushion furnace were introduced.The process position and irreplaceable role of air cushion furnace in th...The process characteristics of heat treatment of aluminum alloy auto body sheet and the working principle of air cushion furnace were introduced.The process position and irreplaceable role of air cushion furnace in the aluminum alloy auto body sheet production was pointed out after the difficulty and key points in the whole production process of auto body sheet were studied.Then the development process of air cushion furnace line of aluminum alloy sheet was reviewed,summarized and divided to two stages.Based on the research of air cushion furnace,the key technology of it was analyzed,then the key points on process,equipment and control models of air cushion furnace for aluminum alloy auto body sheet in future were put forward.With the rapid development of automotive industry,there will be certainly a new upsurge of research and application of air cushion furnace for heat treatment of aluminum alloy auto body sheet.展开更多
An as-cast Al-Zn-Mg-Sc alloy was friction stir processed varying tool related parameters, yielding microstructures with different grain sizes （0.68, 1.8 and 5.5 μm）. Significant increases in room temperature ductil...An as-cast Al-Zn-Mg-Sc alloy was friction stir processed varying tool related parameters, yielding microstructures with different grain sizes （0.68, 1.8 and 5.5 μm）. Significant increases in room temperature ductility were obtained in these materials with reasonable enhancement in strength. It is demonstrated that the type of microstructure produced by friction stir processing （FSP） has a significant influence on the choice of post-FSP heat treatment design for achieving improved tensile properties. It is also found that the ultrafine grained FSP material could not achieve the desired high strength during the post-FSP heat treatment without grain coarsening, whereas the micro-grained FSP materials could reach such strength levels （〉560 MPa） under conventional age hardening heat treatment conditions.展开更多
Due to the deterioration of serious energy dilemma,energy-conservation and emission–reduction have been the strategic target in the past decades,thus people have identified the vital importance of higher energy effic...Due to the deterioration of serious energy dilemma,energy-conservation and emission–reduction have been the strategic target in the past decades,thus people have identified the vital importance of higher energy efficiency and the influence of lower carbon development.Since work exchange network is a significant part of energy recovery system,its optima design will have dramatically significant effect on energy consumption reduction in chemical process system.With an extension of the developed transshipment model in isothermal process,a novel step-wise methodology for synthesis of direct work exchange network(WEN)in adiabatic process involving heat integration is first proposed in this paper,where a nonlinear programming(NLP)model is formulated by regarding the minimum utility consumption as objective function and optimizing the initial WEN in accordance with the presented matching rules to get the optimized WEN configuration at first.Furthermore,we focus on the work exchange network synthesis with heat integration to attain the minimal total annual cost(TAC)with the introduction of heat-exchange equipment that is achieved by the following strategies in sequence:introducing heat-exchange equipment directly,adjusting the work quantity of the adjacent utility compressors or expanders,and approximating upper/lower pressure limits consequently to obtain considerable cost savings of expanders or compressors and work utility.Finally,a case taken from the literature is studied to illustrate the feasibility and effectiveness of the proposed method.展开更多
The objective of this study is to predict grain size and heat transfer coefficient at the metal-die interface during high pressure die casting process and solidification of the magnesium alloy AM60. Multiple runs of t...The objective of this study is to predict grain size and heat transfer coefficient at the metal-die interface during high pressure die casting process and solidification of the magnesium alloy AM60. Multiple runs of the commercial casting simulation package, ProCASTTM, were used to model the mold filling and solidification events employing a range of interfacial heat transfer coefficient values. The simulation results were used to estimate the centerline cooling curve at various locations through the casting. The centerline cooling curves, together with the die temperature and the thermodynamic properties of the alloy, were then used as inputs to compute the solution to the Stefan problem of a moving phase boundary, thereby providing the through-thickness cooling curves at each chosen location of the casting, Finally, the local cooling rate was used to calculate the resulting grain size via previously established relationships. The effects of die temperature, filling time and heat transfer coefficient on the grain structure in skin region and core region were quantitatively characterized. It was observed that the grain size of skin region strongly depends on above three factors whereas the grain size of core region shows dependence on the interracial heat transfer coefficient and thickness of the samples. The grain size distribution from surface to center was estimated from the relationship between grain size and the predicted cooling rate. The prediction of grain size matches well with experimental results. A comparison of the predicted and experimentally determined grain size profiles enables the determination of the apparent interracial heat transfer coefficient for different locations.展开更多
Sealing quality strongly affects heat pipe performance, but few studies focus on the process of heat pipe sealing. Cold welding sealing technology based on a stamping process is applied for heat pipe sealing. The bond...Sealing quality strongly affects heat pipe performance, but few studies focus on the process of heat pipe sealing. Cold welding sealing technology based on a stamping process is applied for heat pipe sealing. The bonding mechanism of the cold welding sealing process （CWSP） is investigated and compared with the experimental results obtained from the bonding interface analysis. An orthogonal experiment is conducted to observe the effects of various parameters, including the sealing gap, sealing length, sealing diameter, and sealing velocity on bonding strength. A method with the utilization of saturated vapor pressure inside a copper tube is proposed to evaluate bonding strength. A corresponding finite element model is developed to investigate the effects of sealing gap and sealing velocity on plastic deformation during the cold welding process. Effects of various parameters on the bonding strength are determined and it is found that the sealing gap is the most critical factor and that the sealing velocity contributes the least effect. The best parameter combination （AIB3CID3, with a 0.5 mm sealing gap, 6 mm sealing length, 3.8 mm sealing diameter, and 50 mm/s sealing velocity） is derived within the experimental parameters. Plastic deformation results derived from the finite element model are consistent with those from the experiment. The instruction for the CWSP of heat pipes and the design of sealing dies of heat pipes are provided.展开更多
Recovering waste heat from industrial processes is bene ficial in order to reduce the primary energy demands and heat pumps can be used to this purpose.Absorption heat pumps are energy-saving and environment-friendly ...Recovering waste heat from industrial processes is bene ficial in order to reduce the primary energy demands and heat pumps can be used to this purpose.Absorption heat pumps are energy-saving and environment-friendly because use working fluids that do not cause ozone depletion and can reduce the global warming emissions.The hybrid heat pump processes combine the conventional vapor-compression and the absorption heat pump cycles.Studies about the simulations and modeling of hybrid heat pumps are few in literature.In this research a mathematical model for single effect absorption and hybrid heat pump is carried out with Chem Cad? 6.0.1.LiBr–H_2O is used as working fluid while electrolytic NRTL and electrolytes latent heat are used as thermodynamic model due to the better results.Binary parameters of activity coef ficients are regressed from experimental vapor pressure data while default constants are used for the solubility expressions.A design of heat pumps is developed and a new modeling of generator is analyzed.The coef ficient of performance of absorption heat pump and hybrid heat pump is equal to 0.7 and 0.83 respectively.For absorption heat pump a sensitivity analysis is carried out to evaluate the effect of temperature and pressure generator,the concentration of Li–Br solution on coef ficient of performance,cooling capacity and working fluid temperature.For hybrid heat pump,the different coef ficients of performance,the primary energy ratio,the generator heat,and the compressor power are analyzed for different values of compressor proportion.Results show that comparing the two systems the hybrid pump allows to save more primary energy,costs and carbon dioxide emissions with respect to absorption heat pump with the increasing of compressor proportion parameter.Future researches should focus on the construction of this heat pumps integrated in chemical processes as a biogas plant or trigeneration systems.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.U2241232,U2341253 and 52375317)the National Key R&D Program of China(No.2022YFB3404204).
文摘In this study,the efects of diferent heat treatment process parameters on the microstructure and mechanical properties of Al-12Si-5Cu-1.1Mg-2.3Ni-0.3La alloy were explored.Research showed that eutectic Si underwent three stages during solution treatment:difusing,spheroidization and coarsening.As the solution temperature and time increased,the size of eutectic Si showed a trend of frst decreasing and then increasing.Compared with the heat treatment time,the heat treatment temperature had a more signifcant efect on the mechanical properties.The coarsening of microstructure was the main reason for the deterioration of mechanical properties.The Al_(3)Ti and Al_(3)CuNiLa in the microstructure after aging can signifcantly improve the mechanical properties of the alloy.The Al_(11)La_(3) with secondary precipitation occurred in the La-rich phase.The addition of La inhibited the growth of coherent/semi-coherentθandβphases,which was very benefcial for the improvement of high-temperature strength.Under the optimal heat treatment process parameters of 500℃×4 h+190℃×4 h,the ultimate tensile strength(UTS)of the alloy reached 366.65 MPa.The high-temperature strength and elongation of the alloy reached 101.98 MPa and 13.77%at 350℃,respectively.
基金financial support from National Natural Science Foundation of China[Nos.51831002 and 51861135302]the Fundamental Research Funds for the Central Universities(No.FRF-TP-18-002C2)。
文摘Ultrafast heating(UFH)at the rates of 10-300℃/s was employed as a new strategy to anneal a coldrolled 7 wt%Mn steel,followed by the immediate cooling.Severely deformed strain-induced martensite and lightly-deformed thermal martensite,both had been already enriched with C and Mn before,transformed to fine and coarse austenite grains during the UFH,leading to the bimodal size distribution.Compared with the long intercritical annealing(IA)process,the UFH processes produced larger fraction of RA grains(up to 37%)with a high density of dislocation,leading to the significant increase in yield strength by 270 MPa and the product of strength and elongation up to 55 GPa%due to the enormous work hardening capacity.Such a significant strengthening is first attributed to high density dislocations preserved after UFH and then to the microstructural refinement and the precipitation strengthening;whilst the sustainable work hardening is attributed to the successive TRIP effect during deformation,resulting from the large fraction of RA instantly formed with the bimodal size distribution during UFH.Moreover,the results on the microstructural characterization,thermodynamics calculation on the reverse transformation temperature and the kinetic simulations on the reverse transformation all suggest that the austenitization during UFH is displacive and involves the diffusion and partition of C.Therefore,we propose that it is a bainite-like transformation.
基金The financial support for this study by National Natural Science Foundation of China(No.30960242)National Basic Research Program of China(973 program)(No.2012CB720805)Training Project of Young Scientists of Jiangxi Province(Stars of Jing gang)is gratefully acknowledged.
文摘The microstructural changes of Fe83Si4B13 amorphous mother alloy during the heating process were investigated by Laser Scanning Confocal Microscopy （LSCM） ,and the phase transformation was determined by the Thermo-Calc calculations. The differences in the melting points measured by Differential Scanning Calorimetry （DSC） and LSCM, and those obtained by Thermo-Calc calculations were also discussed. It is found that the melting points measured by DSC and LSCM are relatively similar, whereas the onset and end of the melting temperatures calculated by Thermo-Calc software are higher than those measured by DSC and observed by LSCM.
基金supported by the National Natural Science Foundation of China(Grant No.62061028)the Foundation for Distinguished Young Scientists of Jiangxi Province(Grant No.20162BCB23009)+2 种基金the Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics(Grant No.KF202010)the Interdisciplinary Innovation Fund of Nanchang University(Grant No.9166-27060003-YB12)the Open Research Fund Program of Key Laboratory of Opto-Electronic Information Acquisition and Manipulation of Ministry of Education(Grant No.OEIAM202004)。
文摘Ground-state cooling of mesoscopic mechanical objects is still a major challenge in the unresolved-sideband regime.We present a frequency modulation(FM)scheme to achieve cooling of the mechanical resonator to its ground-state in a double-cavity optomechanical system containing a mechanical resonator.The mean phonon number is determined by numerically solving a set of differential equations derived from the quantum master equations.Due to efficient suppression of Stokes heating processes in the presence of FM,the ground-state cooling,indicated by numerical calculations,is significantly achievable,regardless of whether in the resolved-sideband regime or the unresolved-sideband regime.Furthermore,by choosing parameters reasonably,the improvement of the quantum cooling limit is found to be capable of being positively correlated with the modulation frequency.This method provides new insight into quantum manipulation and creates more possibilities for applications of quantum devices.
文摘In-situ HVEM observation on phase transition of the YBa_2Cu_3O_(7-x) superconducting compound in pro- cess of heating was carried out,and high temperature X-ray diffraction analysis in air and X-ray diffraction phase analysis for the sample treated in vacuum condition were made.The results showed that the temperature of phase transition is related to oxygen content in the sample and in general,is 100℃ to 120℃ lower in vacu- um condition than in air.At 320℃ to 350℃ twin bands begin to disappear,and some Cu_2O are formed on the surface of the sample and transit from orthorhombic YBa_2Cu_3O_(7-x) to arthorhombic Y_2BaCuO_5 compound. This transition was completed at about 500℃.Above 900℃,this compound consists of the Y_2BaCuO_5, BaCuO_2,Y_2O_3 and some other minor compounds.No phase transition was observed during cooling the sample.
文摘Three-dimensional thermal a nalysis simulation of a horizontal zone refining system is conducted for germanimn semiconductor materials. The considered geometry includes a g＇ral）hite boat filled with germanium placed in a cylindrical quartz tube. A flow of Ar and H2 gas mixture is purged througll the tube. A narrow section of the, boat is assmned to be exposed to a constant heat rate produced b v an rf coil located outside the quartz tube. The results of this analysis provide essential information about various parameters such as the shape of tile molten zone, required power and temperature gradient in the system.
基金supports from the National Natural Science Foundation of China (52076049)Heilongjiang Province “Double First-class” Discipline Collaborative Innovation Achievement Project (LJGXCG2023-080)+1 种基金Heilongjiang Provincial Key R&D Program (2023ZX02C05)Heilongjiang Provincial Key R&D Program “Unveiling the Leader” Project (2023ZXJ02C04).
文摘The energy and exergy performances of the corn straw and Silicon Carbide (SiC) in the microwave heating process are crucial to sufficiently utilize crop residues for mitigating environmental pollution, promoting waste value, and improving farmer incomes. In this study, the comprehensive energy and exergy performances (the absorbed energy, energy efficiency, absorbed exergy, and exergy efficiency) of the mass ratio (SiC to corn straw), microwave power, and reaction chamber volume were compared and analyzed. The effect of the mass ratio of SiC to corn straw on energy and exergy performances based on the experimental data was newly studied. Also, the parametric analysis of the microwave power and reaction chamber for the microwave heating process of corn straw assisted by SiC was conducted. The findings indicate that increasing the mass ratio of SiC to corn straw from 0 to 1 significantly improves performance metrics: final absorbed energy increased from 5466 J to 6195 J, energy efficiency from 9.1% to 20.7%, absorbed exergy from 1102 J to 1312 J, and exergy efficiency from 1.8% to 4.4%. Similarly, increasing microwave power from 400 W to 600 W enhanced final absorbed energy from 5752 J to 6195 J, energy efficiency from 11.1% to 20.7%, absorbed exergy from 1177 J to 1312 J, and exergy efficiency from 2.3% to 4.4%. Conversely, enlarging the reaction chamber from 100 mL to 300 mL resulted in decreases: final absorbed energy dropped from 5758 J to 5700 J, energy efficiency from 11.6% to 9.0%, absorbed exergy from 1122 J to 1118 J, and exergy efficiency from 2.3% to 1.8%. These results underscore the substantial influence of the mass ratio on energy and exergy performances, while indicating that the reaction chamber volume has a minimal impact on the performances.
文摘The formation process and composition of the acrylonitrile/urea inclusion compounds （AN/UIC） with different aging times and AN/urea molar feed ratios are studied by differential scanning calorimetry （DSC） and X-ray diffraction （XRD）. It is suggested that DSC can determine the vip/host ratio and the heat of decomposition. Meanwhile, the vip/host ratio and heat of decomposition are obtained, which are 1.17 and 5361.53 J/mol, respec- tively. It is suggested AN molecules included in urea canal lattice may be packed flat against each other. It is found that the formation of AN/UIC depends on the aging time. XRD results reveal that once AN molecules enter urea lattice, AN/UIC are formed, which possess the final structure. When AN molecules are sufficient, the length of AN molecular arrays in urea canals increases as aging time prolonging until urea tunnels are saturated by AN.
基金Item Sponsored by National Nature Science Foundation of China(51071078)
文摘Dry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50--300 N at 400℃ by a pin-on-disc high temperature wear machine. The effect of heat treatment process on wear resistance was systematically studied in order to select heat treatment processes of the steel with high wear resistance. The morphology, structure and composition were analyzed using scanning electron microscopy （SEM）, X-ray diffraction （XRD） and energy dispersive spectroscopy （EDS） ; wear mechanism was also discussed. Tribo-oxide layer was found to form on worn surfaces to reduce wear under low loads, but appear inside the matrix to increase wear under high loads. The tribo-oxides were mainly consisted of Fe3O4 and Fe2O3, FeO only appeared under a high load. Oxidative mild wear, transition of mild-severe wear in oxidative wear and extrusive wear took turns to operate with increasing the load. The wear resistance strongly depended on the selection of heat treatment processes or microstructures. It was found that bainite presented a better wear resistance than martensite plus bainite duplex structure, martensite structure was of the poorest wear resistance. The wear resistance increased with increasing austenizing temperature in the range of 920 to 1 120 ℃, then decreased at up to 1 220 ℃. As for tempering temperature and microstructure, the wear resistance increased in following order： 700℃ （tempered sorbite）, 200 ℃ （tempered martensite）, 440 to 650 ℃ （tempered troostite）. An appropriate combination of hardness, toughness, microstructural thermal stability was re- quired for a good wear resistance in high-temperature wear. The optimized heat treatment process was suggested for the cast hot-forging steel to be austenized at 1020 to 1 120 ℃, quenched in oil, then tempered at 440 to 650℃ for 2 h.
基金supported by the Natural Science Foundation of Henan Province(Grant No.152107000047)
文摘In this study, a two-step heating process is introduced for transient liquid phase ( TLP) diffusion bonding fo r sound joints with T91 heat resistant steels. At first, a short-time higher temperature heating step is addressed to melt the interlayer, followed by the second step to complete isothermal solidification at a low temperature. The most critical feature of our new method is producing a non-planar interface at the T9/ heat resistant steels joint. We propose a transitional liquid phase bonding of T91 heat resistant steels by this approach. Since joint microstructures have been studied, we tested the tensile strength to assess joint mechanical property. The result indicates that the solidified bond may contain a primary solid-solution, similar composition to the parent metal and free from precipitates. Joint tensile strength of the joint is not lower than parent materials. Joint bend's strengths are enhanced due to the higher metal-to-metal junction producing a non-planar bond lines. Nevertheless, the traditional transient liquid phase diffusion bonding produces planar ones. Bonding parameters of new process are 1 260 °C for 0. 5 min and 1 230 °C fo r 4 min.
文摘A 3-D mathematical model considering turbulence phenomena has been established based on a computational fluid dynamics technique, so called 3-D SOLA-VOF (Solution Algorithm-Volume of Fluid), to simulate the fluid flow of mold filling process of die casting. In addition, the mathematical model for simulating the heat transfer in die casting process has also been established. The computation program has been developed by the authors with the finite difference method (FDM) recently. As verification, the mold filling process of a S-shaped die casting has been simulated and the simulation results coincide with that of the benchmark test. Finally, as a practical application, the gating design of a motorcycle component was modified by the mold filling simulation and the dies design of another motorcycle component was optimized by the heat transfer simulation. All the optimized designs were verified by the production practice.
基金Project supported by the National Natural Science Foundation of China (No.50678076)the Opening Foundation of the State Key Laboratory of Frozen Soil Engineering (No.SKLFSE200603),China
文摘A number of dry bridges have been built to substitute for the roadbed on the Qinghai-Tibet Railway,China.The aim of this study was to investigate the exothermic process of cast-in-place (CIP) pile foundation of a dry bridge and its harm to the stability of nearby frozen ground.We present 3D heat conduction functions of a concrete pile and of frozen ground with related boundaries.Our analysis is based on the theory of heat conduction and the exponent law describing the adiabatic temperature rise caused by hydration heat.Results under continuous and initial conditions were combined to establish a finite element model of a CIP pile-frozen ground system for a dry bridge under actual field conditions in cold regions.Numerical results indicated that the process could effectively simulate the exothermic process of CIP pile foundation.Thermal disturbance to frozen ground under a long dry bridge caused by the casting temperature and hydration heat of CIP piles was substantial and long-lasting.The simulated thermal analysis results agreed with field measurements and some significant rules relating to the problem were deduced and conclusions reached.
基金Supported by the National Natural Science Foundation of China(21406124)
文摘A T-Q diagram based on entransy theory is applied to graphically and quantitatively describe the irreversibility of the heat transfer processes.The hot and cold composite curves can be obtained in the T-Q diagram.The entransy recovery and entransy dissipation that are affected by temperature differences can be obtained through the shaded area under the composite curves.The method for setting the energy target of the HENs in T-Q diagram based on entransy theory is proposed.A case study of the diesel oil hydrogenation unit is used to illustrate the application of the method.The results show that three different heat transfer temperature differences is 10 K,15 K and 20 K,and the entransy recovery is 5.498×10~7k W·K,5.377×10~7k W·K,5.257×10~7k W·K,respectively.And the entransy transfer efficiency is 92.29%,91.63%,90.99%.Thus,the energy-saving potential of the HENs is obtained by setting the energy target based on the entransy transfer efficiency.
文摘The process characteristics of heat treatment of aluminum alloy auto body sheet and the working principle of air cushion furnace were introduced.The process position and irreplaceable role of air cushion furnace in the aluminum alloy auto body sheet production was pointed out after the difficulty and key points in the whole production process of auto body sheet were studied.Then the development process of air cushion furnace line of aluminum alloy sheet was reviewed,summarized and divided to two stages.Based on the research of air cushion furnace,the key technology of it was analyzed,then the key points on process,equipment and control models of air cushion furnace for aluminum alloy auto body sheet in future were put forward.With the rapid development of automotive industry,there will be certainly a new upsurge of research and application of air cushion furnace for heat treatment of aluminum alloy auto body sheet.
文摘An as-cast Al-Zn-Mg-Sc alloy was friction stir processed varying tool related parameters, yielding microstructures with different grain sizes （0.68, 1.8 and 5.5 μm）. Significant increases in room temperature ductility were obtained in these materials with reasonable enhancement in strength. It is demonstrated that the type of microstructure produced by friction stir processing （FSP） has a significant influence on the choice of post-FSP heat treatment design for achieving improved tensile properties. It is also found that the ultrafine grained FSP material could not achieve the desired high strength during the post-FSP heat treatment without grain coarsening, whereas the micro-grained FSP materials could reach such strength levels （〉560 MPa） under conventional age hardening heat treatment conditions.
基金Supported by the National Natural Science Foundation of China(21576036,21406026)
文摘Due to the deterioration of serious energy dilemma,energy-conservation and emission–reduction have been the strategic target in the past decades,thus people have identified the vital importance of higher energy efficiency and the influence of lower carbon development.Since work exchange network is a significant part of energy recovery system,its optima design will have dramatically significant effect on energy consumption reduction in chemical process system.With an extension of the developed transshipment model in isothermal process,a novel step-wise methodology for synthesis of direct work exchange network(WEN)in adiabatic process involving heat integration is first proposed in this paper,where a nonlinear programming(NLP)model is formulated by regarding the minimum utility consumption as objective function and optimizing the initial WEN in accordance with the presented matching rules to get the optimized WEN configuration at first.Furthermore,we focus on the work exchange network synthesis with heat integration to attain the minimal total annual cost(TAC)with the introduction of heat-exchange equipment that is achieved by the following strategies in sequence:introducing heat-exchange equipment directly,adjusting the work quantity of the adjacent utility compressors or expanders,and approximating upper/lower pressure limits consequently to obtain considerable cost savings of expanders or compressors and work utility.Finally,a case taken from the literature is studied to illustrate the feasibility and effectiveness of the proposed method.
基金jointly supported by Canadian Network for Research and Innovation in Machining TechnologyNatural Sciences and Engineering Research Council of Canada-Automotive Partnership Canada programNRCan’s Office of Energy R&D through the Program on Energy R&D
文摘The objective of this study is to predict grain size and heat transfer coefficient at the metal-die interface during high pressure die casting process and solidification of the magnesium alloy AM60. Multiple runs of the commercial casting simulation package, ProCASTTM, were used to model the mold filling and solidification events employing a range of interfacial heat transfer coefficient values. The simulation results were used to estimate the centerline cooling curve at various locations through the casting. The centerline cooling curves, together with the die temperature and the thermodynamic properties of the alloy, were then used as inputs to compute the solution to the Stefan problem of a moving phase boundary, thereby providing the through-thickness cooling curves at each chosen location of the casting, Finally, the local cooling rate was used to calculate the resulting grain size via previously established relationships. The effects of die temperature, filling time and heat transfer coefficient on the grain structure in skin region and core region were quantitatively characterized. It was observed that the grain size of skin region strongly depends on above three factors whereas the grain size of core region shows dependence on the interracial heat transfer coefficient and thickness of the samples. The grain size distribution from surface to center was estimated from the relationship between grain size and the predicted cooling rate. The prediction of grain size matches well with experimental results. A comparison of the predicted and experimentally determined grain size profiles enables the determination of the apparent interracial heat transfer coefficient for different locations.
基金Supported by National Natural Science Foundation of China(Grant Nos.51175186,51675185)Guangdong Provincial Natural Science Foundation of China(Grant No.S2013020012757)EU project PIIF-GA-2012-332304(Grant No.ESR332304)
文摘Sealing quality strongly affects heat pipe performance, but few studies focus on the process of heat pipe sealing. Cold welding sealing technology based on a stamping process is applied for heat pipe sealing. The bonding mechanism of the cold welding sealing process （CWSP） is investigated and compared with the experimental results obtained from the bonding interface analysis. An orthogonal experiment is conducted to observe the effects of various parameters, including the sealing gap, sealing length, sealing diameter, and sealing velocity on bonding strength. A method with the utilization of saturated vapor pressure inside a copper tube is proposed to evaluate bonding strength. A corresponding finite element model is developed to investigate the effects of sealing gap and sealing velocity on plastic deformation during the cold welding process. Effects of various parameters on the bonding strength are determined and it is found that the sealing gap is the most critical factor and that the sealing velocity contributes the least effect. The best parameter combination （AIB3CID3, with a 0.5 mm sealing gap, 6 mm sealing length, 3.8 mm sealing diameter, and 50 mm/s sealing velocity） is derived within the experimental parameters. Plastic deformation results derived from the finite element model are consistent with those from the experiment. The instruction for the CWSP of heat pipes and the design of sealing dies of heat pipes are provided.
文摘Recovering waste heat from industrial processes is bene ficial in order to reduce the primary energy demands and heat pumps can be used to this purpose.Absorption heat pumps are energy-saving and environment-friendly because use working fluids that do not cause ozone depletion and can reduce the global warming emissions.The hybrid heat pump processes combine the conventional vapor-compression and the absorption heat pump cycles.Studies about the simulations and modeling of hybrid heat pumps are few in literature.In this research a mathematical model for single effect absorption and hybrid heat pump is carried out with Chem Cad? 6.0.1.LiBr–H_2O is used as working fluid while electrolytic NRTL and electrolytes latent heat are used as thermodynamic model due to the better results.Binary parameters of activity coef ficients are regressed from experimental vapor pressure data while default constants are used for the solubility expressions.A design of heat pumps is developed and a new modeling of generator is analyzed.The coef ficient of performance of absorption heat pump and hybrid heat pump is equal to 0.7 and 0.83 respectively.For absorption heat pump a sensitivity analysis is carried out to evaluate the effect of temperature and pressure generator,the concentration of Li–Br solution on coef ficient of performance,cooling capacity and working fluid temperature.For hybrid heat pump,the different coef ficients of performance,the primary energy ratio,the generator heat,and the compressor power are analyzed for different values of compressor proportion.Results show that comparing the two systems the hybrid pump allows to save more primary energy,costs and carbon dioxide emissions with respect to absorption heat pump with the increasing of compressor proportion parameter.Future researches should focus on the construction of this heat pumps integrated in chemical processes as a biogas plant or trigeneration systems.
