The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification pro...The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification process of the Al—2Sc alloy controlled by a novel PMS using NdFeB permanent magnets under various rotation speeds(0,50,100 and 150 r/min).The simulated results reveal that the maximum electromagnetic force increases proportionally from 4.14 to 12.39 kN/m^(3)and the maximum tangential velocity increases from 0.13 to 0.36 m/s when the rotation speed of PMS enhances from 50 to 150 r/min in the ingot melt.Besides,the experimental results demonstrate that PMS can achieve a uniform distribution of blocky Al_(3)Sc precipitated phase in the longitudinal direction under the impact of a forced fluid flow.Moreover,increasing rotation speed of PMS is beneficial to refining aluminum grain size significantly and decreasing the texture intensity in the alloy.In addition,the Brinell hardness of Al-2Sc alloy is increased by 33%to 27.8 HB and the tensile strength is enhanced by 34%-128.2 MPa,due to the improved distribution of the strengthening Al_(3)SC phase and the grain refinement of Al matrix under the impact of PMS.This work provides an effective application of NdFeB permanent magnets in the metal cast field.展开更多
Mg alloys have the defects of low stiffness,low strength,and high coefficient of thermal expansion(CTE).The composites strategy and its architecture design are effective approaches to improve the comprehensive perform...Mg alloys have the defects of low stiffness,low strength,and high coefficient of thermal expansion(CTE).The composites strategy and its architecture design are effective approaches to improve the comprehensive performance of materials,but the processing difficulty,especially in ceramics forming,limits the control and innovation of material architecture.Here,combined with 3D printing and squeeze infiltration technology,two precisely controllable architectures of AZ91/Al_(2)O_(3)interpenetrating phase composites(IPC)with ceramic scaffold were prepared.The interface,properties and impact of different architecture on IPC performance were studied by experiments and finite element simulation.The metallurgical bonding of the interface was realized with the formation of MgAl_(2)O_(4)reaction layer.The IPC with 1 mm circular hole scaffold(1C-IPC)exhibited significantly improved elastic modulus of 164 GPa,high compressive strength of 680 MPa,and good CTE of 12.91×10^(-6)K^(−1),which were 3.64 times,1.98 times and 55%of the Mg matrix,respectively.Their elastic modulus,compressive strength,and CTE were superior to the vast majority of Mg alloys and Mg based composites.The reinforcement and matrix were bicontinuous and interpenetrating each other,which played a critical role in ensuring the potent strengthening effect of the Al_(2)O_(3)reinforcement by efficient load transfer.Under the same volume fraction of reinforcements,compared to IPC with 1 mm hexagonal hole scaffold(1H-IPC),the elastic modulus and compressive strength of 1C-IPC increased by 15%and 28%,respectively,which was due to the reduced stress concentration and more uniform stress distribution of 1C-IPC.It shows great potential of architecture design in improving the performance of composites.This study provides architectural design strategy and feasible preparation method for the development of high performance materials.展开更多
High-temperature experiments were carried out for the slag systems of“FeO”−SiO_(2)−CaO−Al_(2)O_(3)and“FeO”−SiO_(2)−CaO−MgO at 1200℃and p(O_(2))of 10^(−7)kPa.The equilibrated samples were quenched,and the phase co...High-temperature experiments were carried out for the slag systems of“FeO”−SiO_(2)−CaO−Al_(2)O_(3)and“FeO”−SiO_(2)−CaO−MgO at 1200℃and p(O_(2))of 10^(−7)kPa.The equilibrated samples were quenched,and the phase compositions were measured by electron probe microanalysis(EPMA).A series of pseudo-ternary and pseudo-binary phase diagrams are constructed to demonstrate their applications in copper smelting process and evaluation of the thermodynamic database.Spinel and tridymite are identified to be the major primary phases in the composition range related to the copper smelting slags.It is found that the operating window of the smelting slag is primarily determined by w_(Fe)/w_(SiO_(2))ratio in the slag.Both MgO and Al_(2)O_(3)in the slag reduce the operating window which requires extra fluxing agent to keep the slag to be fully liquid.Complex spinel solid solutions cause inaccurate predictions of the current thermodynamic database.展开更多
The development of high temperature phase change materials(PCMs)with great comprehensive performance is significant in the future thermal energy storage system.In this study,novel and durable Al-Si/Al_(2)O_(3)-Al N co...The development of high temperature phase change materials(PCMs)with great comprehensive performance is significant in the future thermal energy storage system.In this study,novel and durable Al-Si/Al_(2)O_(3)-Al N composite PCMs with controllable melting temperature were successfully synthesized by using pristine Al powder as raw material and tetraethyl orthosilicate as SiO_(2)source.The Al_(2)O_(3)shell and Al-Si alloy were in-situ produced via the substitution reaction between molten Al and SiO_(2).Importantly,the crack caused by the incomplete encapsulation of the Al_(2)O_(3)shell could repair itself by the nitridation reaction of internal molten Al and thereby forming a highly dense Al_(2)O_(3)-Al N composite shell.The produced dense Al_(2)O_(3)-Al N composite shell could significantly improve the thermal cycling stability of composite PCMs,and thus,the thermal storage density decrease of the Al-Si/Al_(2)O_(3)-Al N(59.8 J/g to77.7 J/g)was far less than that of the Al-Si/Al_(2)O_(3)(118.5 J/g)after 3000 thermal cycles.Moreover,the synthesized Al-Si/Al_(2)O_(3)-Al N still exhibited a controllable melting temperature(571.5-637.9℃),relatively high thermal storage density(105.6-150.7 J/g),great dimensional stability and structural stability after3000 thermal cycles.Hence,the synthesized Al-Si/Al_(2)O_(3)-Al N composite PCMs,as promising preferential thermal energy storage materials,can be stably used in the energy utilization efficiency improvement of various systems for more than 6 years.展开更多
Ultrafine particles prepared by evaporating pure Fe in CH4 atmosphere using arc-dischargeheating method, were found to consist of Fe-C solid solution, γ-Fe and Fe3C phases. EfFect of annealing temperature on phase tr...Ultrafine particles prepared by evaporating pure Fe in CH4 atmosphere using arc-dischargeheating method, were found to consist of Fe-C solid solution, γ-Fe and Fe3C phases. EfFect of annealing temperature on phase transformation and hyperfine interactions has been investigated by Mossbauer spectroscopy, X-ray diffraction (XRD), differential thermal analysis and thermogravimetry (DTA-TG), transmission electron microscopy (TEM), oxygen determination and vibrating sample magnetometer (VSM) measurements. It was observed that phase transformation of γ-Fe to α-Fe occurs during annealing in vacuum. The mechanism causing the change of hyperfine interactions with annealing temperature differs for Fe-C solution and interstitial compounds. DifFerence of hyperfine interactions of Fe-C solid solution in the starting sample and its annealed samples is ascribed to the improvement of activation of interstitial carbon atoms. Stress-relieving in structure of annealed Fe3C particle can result in a weak influence on hyperfine interactions. Parameters fitted to the Mossbauer spectra show the existence of superparamagnetism in all the samples. Absorbed and combined oxygen on particle surface of the starting sample were determined.展开更多
The phase equilibrium information of slag plays an important role in pyrometallurgical processes to obtain optimum fluxing conditions and operating temperatures.The smelting reduction of titanomagnetite and ilmenite o...The phase equilibrium information of slag plays an important role in pyrometallurgical processes to obtain optimum fluxing conditions and operating temperatures.The smelting reduction of titanomagnetite and ilmenite ores in an iron blast furnace(BF)can form Ti(C,N)particles,causing the increased viscosities of slag and hot metal.HIsmelt has been developed in recent years for ironmaking and does not need coke and sinter.The formation of Ti(C,N)in the HIsmelt process is avoided because the oxygen partial pressure in the process is higher than that in the BF.The smelting of TiO_(2)-containing ores in the HIsmelt process results in Al_(2)O_(3)-MgO-SiO_(2)-CaO-TiO_(2)slag.Phase equilibrium in this slag system has been investigated using equilibration,quenching,and electron probe microanalysis techniques.The experimental results were presented in two pseudo-binary sections,which represent the process of HIsmelt for the treatment of 100%titanomagnetite ore and mixed titanomagnetite+ilmenite ore(mass ratio of 2:1),respectively.The primary phases observed in the composition range investigated include pseudo-brookite M_(3)O_(5)(MgO·2TiO_(2)-Al_(2)O_(3)·TiO_(2)),spinel(MgO·Al_(2)O_(3)),perovskite CaTiO_(3),and rutile TiO_(2).The results show that the liquidus temperatures decrease in the TiO_(2)and M_(3)O_(5) primary phase fields and increase in the spinel and CaTiO_(3)primary phase fields with the increase in CaO concentration.The calculation of solid-phase fractions from the experimental data has been demonstrated.The effect of basicity on the liquidus temperatures of the slag has been discussed.The smelting of titanomagnetite plus ilmenite ores has significant advantages to obtain low-sulfur hot metal and high-TiO_(2)slag.Experimentally determined liquidus temperatures were compared with the FactSage predictions to evaluate the existing thermodynamic databases.展开更多
The morphological evolution of Fe-rich phases in the Alalloy has been investigated with various contents of Fe,Mn,and Cr.The results show that coarse Chinese script Fe-rich phases appear in the alloy with 0.6 wt%Fe co...The morphological evolution of Fe-rich phases in the Alalloy has been investigated with various contents of Fe,Mn,and Cr.The results show that coarse Chinese script Fe-rich phases appear in the alloy with 0.6 wt%Fe combined with trace Mn,while the blocky Fe-rich phases appear combined with trace Cr.Under the coexistence of trace Mn and Cr,a large number of fine Chinese script Fe-rich phases could be visible in the low iron-bearing AlSi_9Cu_3-alloy（0.60 wt%）.At high Fe level（1.30 wt%）,numerous Fe-rich phases with hexagonal morphologies are observed with the trace Cr,while fish-bone and pentagonal morphologies of Fe-rich phases could be simultaneously observed with the addition of both Mn and Cr.The results reveal that the trace Mn and Cr promote the morphological evolution of Fe-rich phases.The morphology evolution mechanism of Fe-rich phases has been discussed by using the atom radius and electronegativity differences of Fe,Mn,and Cr.展开更多
To explore the approaches of combined toughening and strengthening of the Al_3Ti-based L1_2 intermetallic alloys, multiphase Al_3Ti alloys formed by combining with reinforcement or by second phase precipitation are be...To explore the approaches of combined toughening and strengthening of the Al_3Ti-based L1_2 intermetallic alloys, multiphase Al_3Ti alloys formed by combining with reinforcement or by second phase precipitation are being studied. The interface reactions between Al_(66)Fe_9Ti_(25)matrix and SiC reinforcement were investigated. It is determined that SiC is chemically incompatible with the Al_(66)Fe_9Ti_(25)matrix, Al_2O_3 barrier coating on SiC by sol-gel process was developed to minimize the interfacial reactions. On the other hand, a new type of Al_3Ti-based alloy having a L1_2 matrix with second phase precipitation has been developed. The quaternary alloys based on Al_(66)Fe_9Ti_(25)and modified with Nb additions, consist of a L1_2 matrix and D0_(22) second phase in the annealed state ,but the second phase can be dissolved by solution treatment and precipitated during high temperature aging.展开更多
The ordering of the α-Fe(Si) crystallization phase in annealed Fe73.5Cu1Mo3Si13.5B9 alloy has been studied using XRD method. The α-Fe(Si) phase in Fe73.5Cu1Mo3Si13.5B9 alloy annealed at 460℃ for 1 h consists of th...The ordering of the α-Fe(Si) crystallization phase in annealed Fe73.5Cu1Mo3Si13.5B9 alloy has been studied using XRD method. The α-Fe(Si) phase in Fe73.5Cu1Mo3Si13.5B9 alloy annealed at 460℃ for 1 h consists of the DO3-type ordered region with spherical shape and disordered region. The size of DO3 ordered region increases with the annealing temperature. When the annealing temperature is 560℃, the size of the ordered region in the α-Fe(Si) grain is 14.0nm,which is nearly as large as that of the α-Fe(Si) grain (14.2 nm) and the degree of order of the α-Fe(Si) phase is about 0.78. When Fe73.5Cu1 Mo3Si13.5B9 amorphous alloy is annealed at 520℃， with the increment of the annealing time, the shape of the DO3 ordered region in the α-Fe(Si) phase is spheroidal at the beginning of the annealing and becomes spherical and has asize of 12.8 nm when the annealing time is 60 min. In addition, the DO3 superlattice lines of the α-Fe(Si) phase will vanish if Fe73.5Cu1Mo3Si13.5 B9 amorphous alloy is annealed for 1 h at 750℃.展开更多
The AA5052 aluminum alloy is widely used in automobile and aerospace manufacturing,and with the development of light-weight alloys,it is required that these materials exhibit better mechanical properties.Previous stud...The AA5052 aluminum alloy is widely used in automobile and aerospace manufacturing,and with the development of light-weight alloys,it is required that these materials exhibit better mechanical properties.Previous studies have demonstrated that the addition of Sc to aluminum alloys can improve both the microstructure and properties of the alloys.In this study,the effect of Sc on the Fe-rich phase and properties of the AA5052 aluminum alloy was studied by adding 0%,0.05%,0.2%,and 0.3%Sc.The results show that with the increase of Sc,the coarse needle-like Fe-rich phase gradually transforms into Chinese-script and then nearly spherical particles,reduce the size of Fe-rich phase,and refine the grain with increase of high angle grain boundaries(HAGBs).These microstructure changes enhance the strength of the AA5052 alloy through Sc addition.The ductility of the alloy is obviously improved because the addition of a lower amount of Sc changes the morphology of Fe-rich phase from needle-like into a Chinese-script,and it is subsequently reduced as a result of significant increase in HAGBs with increasing Sc content.展开更多
Al_(2)O_(3)and Ga_(2)O_(3)exhibit numerous crystal phases with distinct stabilities and materialproperties.However,the phase transitions among thosematerialsare typicallyundesirable in industrial applications,making i...Al_(2)O_(3)and Ga_(2)O_(3)exhibit numerous crystal phases with distinct stabilities and materialproperties.However,the phase transitions among thosematerialsare typicallyundesirable in industrial applications,making it imperative to elucidate the transition mechanisms between these phases.The configurational similarities between Al_(2)O_(3)and Ga_(2)O_(3)allow for the replication of phase transition pathways between these materials.In this study,we investigate the potential phase transition pathway of alumina from the 0-phase to the α-phase using stochastic surface walking global optimization based on global neural network potentials,while extending an existing Ga_(2)O_(3)phase transition path.Through this exploration,we identify a novel single-atom migration pseudomartensitic mechanism,which combines martensitic transformation with single-atom diffusion.This discovery offers valuable insights for experimental endeavors aimed at stabilizing alumina in transitional phases.展开更多
The effects of ternary solutes Ti, Co, V, Cr, Ta, W and Mo on the D03 phase 5tability of Fe3Alintermetallics are investigated by tight-binding linear Muffin-tin orbitaI method. The predictedsite preference5 of these e...The effects of ternary solutes Ti, Co, V, Cr, Ta, W and Mo on the D03 phase 5tability of Fe3Alintermetallics are investigated by tight-binding linear Muffin-tin orbitaI method. The predictedsite preference5 of these elements in Fe3AI are in agreement with the experimental observations.The calculated Iocal magnetic moment of Fe3AI is identical to the experimentaI. ln addition, itis found that the D03 phase stability of Fe3AI doped with Ti, V, Co and Cr depends on 'energygap- of energy band near Fermi level. while the D03 phase stability of Fe3AI doped with Ta, Wand Mo may be affected by Madelung energy.展开更多
The microstructure and the stability of Fe_73.5Cu_1Nb_3Si_13.5B_9 alloy at different stages of phase transformation were investigated through the observation of X-ray difraction and transmission electron microscopy an...The microstructure and the stability of Fe_73.5Cu_1Nb_3Si_13.5B_9 alloy at different stages of phase transformation were investigated through the observation of X-ray difraction and transmission electron microscopy and the measurement of magnetic aftereffect (MAE). It was found that the dependence of the volume fraction of amorphous phase and the MAE in the samples annealed from 450 to 700℃ on the annealing temperature is similar.展开更多
In order to explore synthetic method of pure sodium pyroxene,the pure chemical reagents of Na2CO3,Fe（OH）3 and H2SiO3were used as raw materials,and the possible solid phase reactions for Na2CO3-Fe（OH）3-H2SiO3system...In order to explore synthetic method of pure sodium pyroxene,the pure chemical reagents of Na2CO3,Fe（OH）3 and H2SiO3were used as raw materials,and the possible solid phase reactions for Na2CO3-Fe（OH）3-H2SiO3system in heating process had been studied by means of differential thermal analysis（DTA）and X-ray diffraction（XRD）. The influencing factors of sodium pyroxene（NaFeSi2O6）synthetic reaction,such as sintering temperature and holding time,had also been studied.The results show that sodium pyroxene can be largely synthesized at 737℃;it is helpful for synthesis of sodium pyroxene to increase sintering temperature appropriately,and the best temperature should be controlled at 900℃or so,because it will melt and decompose at temperatures higher than 900℃.In those influencing factors of sodium pyroxene synthesis the most important is temperature.The results will be helpful for providing pure NaFeSi2O6for further research on the formation of SFCA for NaFeSi2O6-KAlSi2O3-CaO-Fe2O3-CaF2 system in the sintering process of Bayan-obo iron ore.展开更多
基金Project supported by the Natural Science Foundation of Hunan Province(2024JJ4056)the Key Project of Guangxi Zhuang Autonomous Region(AB22080089)the Government of Chongzuo,Guangxi Zhuang Autonomous Region(FA20210716)。
文摘The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification process of the Al—2Sc alloy controlled by a novel PMS using NdFeB permanent magnets under various rotation speeds(0,50,100 and 150 r/min).The simulated results reveal that the maximum electromagnetic force increases proportionally from 4.14 to 12.39 kN/m^(3)and the maximum tangential velocity increases from 0.13 to 0.36 m/s when the rotation speed of PMS enhances from 50 to 150 r/min in the ingot melt.Besides,the experimental results demonstrate that PMS can achieve a uniform distribution of blocky Al_(3)Sc precipitated phase in the longitudinal direction under the impact of a forced fluid flow.Moreover,increasing rotation speed of PMS is beneficial to refining aluminum grain size significantly and decreasing the texture intensity in the alloy.In addition,the Brinell hardness of Al-2Sc alloy is increased by 33%to 27.8 HB and the tensile strength is enhanced by 34%-128.2 MPa,due to the improved distribution of the strengthening Al_(3)SC phase and the grain refinement of Al matrix under the impact of PMS.This work provides an effective application of NdFeB permanent magnets in the metal cast field.
基金supported by the National Key Research and Development Program of China(No.2022YFB3708400)the National Natural Science Foundation of China(No.52305158)+1 种基金the Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001)the Science Innovation Foundation of Shanghai Academy of Spaceflight Technology(No.USCAST2021-18).
文摘Mg alloys have the defects of low stiffness,low strength,and high coefficient of thermal expansion(CTE).The composites strategy and its architecture design are effective approaches to improve the comprehensive performance of materials,but the processing difficulty,especially in ceramics forming,limits the control and innovation of material architecture.Here,combined with 3D printing and squeeze infiltration technology,two precisely controllable architectures of AZ91/Al_(2)O_(3)interpenetrating phase composites(IPC)with ceramic scaffold were prepared.The interface,properties and impact of different architecture on IPC performance were studied by experiments and finite element simulation.The metallurgical bonding of the interface was realized with the formation of MgAl_(2)O_(4)reaction layer.The IPC with 1 mm circular hole scaffold(1C-IPC)exhibited significantly improved elastic modulus of 164 GPa,high compressive strength of 680 MPa,and good CTE of 12.91×10^(-6)K^(−1),which were 3.64 times,1.98 times and 55%of the Mg matrix,respectively.Their elastic modulus,compressive strength,and CTE were superior to the vast majority of Mg alloys and Mg based composites.The reinforcement and matrix were bicontinuous and interpenetrating each other,which played a critical role in ensuring the potent strengthening effect of the Al_(2)O_(3)reinforcement by efficient load transfer.Under the same volume fraction of reinforcements,compared to IPC with 1 mm hexagonal hole scaffold(1H-IPC),the elastic modulus and compressive strength of 1C-IPC increased by 15%and 28%,respectively,which was due to the reduced stress concentration and more uniform stress distribution of 1C-IPC.It shows great potential of architecture design in improving the performance of composites.This study provides architectural design strategy and feasible preparation method for the development of high performance materials.
文摘High-temperature experiments were carried out for the slag systems of“FeO”−SiO_(2)−CaO−Al_(2)O_(3)and“FeO”−SiO_(2)−CaO−MgO at 1200℃and p(O_(2))of 10^(−7)kPa.The equilibrated samples were quenched,and the phase compositions were measured by electron probe microanalysis(EPMA).A series of pseudo-ternary and pseudo-binary phase diagrams are constructed to demonstrate their applications in copper smelting process and evaluation of the thermodynamic database.Spinel and tridymite are identified to be the major primary phases in the composition range related to the copper smelting slags.It is found that the operating window of the smelting slag is primarily determined by w_(Fe)/w_(SiO_(2))ratio in the slag.Both MgO and Al_(2)O_(3)in the slag reduce the operating window which requires extra fluxing agent to keep the slag to be fully liquid.Complex spinel solid solutions cause inaccurate predictions of the current thermodynamic database.
基金financially supported by the National Natural Science Foundation of China(No.51771158)the Development and Reform Commission of Shenzhen Municipality(No.ZX20190229)。
文摘The development of high temperature phase change materials(PCMs)with great comprehensive performance is significant in the future thermal energy storage system.In this study,novel and durable Al-Si/Al_(2)O_(3)-Al N composite PCMs with controllable melting temperature were successfully synthesized by using pristine Al powder as raw material and tetraethyl orthosilicate as SiO_(2)source.The Al_(2)O_(3)shell and Al-Si alloy were in-situ produced via the substitution reaction between molten Al and SiO_(2).Importantly,the crack caused by the incomplete encapsulation of the Al_(2)O_(3)shell could repair itself by the nitridation reaction of internal molten Al and thereby forming a highly dense Al_(2)O_(3)-Al N composite shell.The produced dense Al_(2)O_(3)-Al N composite shell could significantly improve the thermal cycling stability of composite PCMs,and thus,the thermal storage density decrease of the Al-Si/Al_(2)O_(3)-Al N(59.8 J/g to77.7 J/g)was far less than that of the Al-Si/Al_(2)O_(3)(118.5 J/g)after 3000 thermal cycles.Moreover,the synthesized Al-Si/Al_(2)O_(3)-Al N still exhibited a controllable melting temperature(571.5-637.9℃),relatively high thermal storage density(105.6-150.7 J/g),great dimensional stability and structural stability after3000 thermal cycles.Hence,the synthesized Al-Si/Al_(2)O_(3)-Al N composite PCMs,as promising preferential thermal energy storage materials,can be stably used in the energy utilization efficiency improvement of various systems for more than 6 years.
文摘Ultrafine particles prepared by evaporating pure Fe in CH4 atmosphere using arc-dischargeheating method, were found to consist of Fe-C solid solution, γ-Fe and Fe3C phases. EfFect of annealing temperature on phase transformation and hyperfine interactions has been investigated by Mossbauer spectroscopy, X-ray diffraction (XRD), differential thermal analysis and thermogravimetry (DTA-TG), transmission electron microscopy (TEM), oxygen determination and vibrating sample magnetometer (VSM) measurements. It was observed that phase transformation of γ-Fe to α-Fe occurs during annealing in vacuum. The mechanism causing the change of hyperfine interactions with annealing temperature differs for Fe-C solution and interstitial compounds. DifFerence of hyperfine interactions of Fe-C solid solution in the starting sample and its annealed samples is ascribed to the improvement of activation of interstitial carbon atoms. Stress-relieving in structure of annealed Fe3C particle can result in a weak influence on hyperfine interactions. Parameters fitted to the Mossbauer spectra show the existence of superparamagnetism in all the samples. Absorbed and combined oxygen on particle surface of the starting sample were determined.
文摘The phase equilibrium information of slag plays an important role in pyrometallurgical processes to obtain optimum fluxing conditions and operating temperatures.The smelting reduction of titanomagnetite and ilmenite ores in an iron blast furnace(BF)can form Ti(C,N)particles,causing the increased viscosities of slag and hot metal.HIsmelt has been developed in recent years for ironmaking and does not need coke and sinter.The formation of Ti(C,N)in the HIsmelt process is avoided because the oxygen partial pressure in the process is higher than that in the BF.The smelting of TiO_(2)-containing ores in the HIsmelt process results in Al_(2)O_(3)-MgO-SiO_(2)-CaO-TiO_(2)slag.Phase equilibrium in this slag system has been investigated using equilibration,quenching,and electron probe microanalysis techniques.The experimental results were presented in two pseudo-binary sections,which represent the process of HIsmelt for the treatment of 100%titanomagnetite ore and mixed titanomagnetite+ilmenite ore(mass ratio of 2:1),respectively.The primary phases observed in the composition range investigated include pseudo-brookite M_(3)O_(5)(MgO·2TiO_(2)-Al_(2)O_(3)·TiO_(2)),spinel(MgO·Al_(2)O_(3)),perovskite CaTiO_(3),and rutile TiO_(2).The results show that the liquidus temperatures decrease in the TiO_(2)and M_(3)O_(5) primary phase fields and increase in the spinel and CaTiO_(3)primary phase fields with the increase in CaO concentration.The calculation of solid-phase fractions from the experimental data has been demonstrated.The effect of basicity on the liquidus temperatures of the slag has been discussed.The smelting of titanomagnetite plus ilmenite ores has significant advantages to obtain low-sulfur hot metal and high-TiO_(2)slag.Experimentally determined liquidus temperatures were compared with the FactSage predictions to evaluate the existing thermodynamic databases.
基金supported by the National Key Research and Development Plan (Nos. 2017YFB1103701, 2016YFB0701201, 2016YFB0701203)the National Natural Science Foundation of China (Nos. 51671101, 51464034, 51761037)+3 种基金the Natural Science Foundation of Jiangxi Province (Nos. 20161ACB21003, 20162BCB23013, and 20172BCB22002)the Scientific Research Foundation of the Education Department of Jiangxi Province (No. GJJ150010)the Innovative Funding for Graduate Students in Nanchang University (No. cx2016089)the Funding of Key Laboratory of Superlight Materials & Surface Technology (Harbin Engineering University), Ministry of Education
文摘The morphological evolution of Fe-rich phases in the Alalloy has been investigated with various contents of Fe,Mn,and Cr.The results show that coarse Chinese script Fe-rich phases appear in the alloy with 0.6 wt%Fe combined with trace Mn,while the blocky Fe-rich phases appear combined with trace Cr.Under the coexistence of trace Mn and Cr,a large number of fine Chinese script Fe-rich phases could be visible in the low iron-bearing AlSi_9Cu_3-alloy（0.60 wt%）.At high Fe level（1.30 wt%）,numerous Fe-rich phases with hexagonal morphologies are observed with the trace Cr,while fish-bone and pentagonal morphologies of Fe-rich phases could be simultaneously observed with the addition of both Mn and Cr.The results reveal that the trace Mn and Cr promote the morphological evolution of Fe-rich phases.The morphology evolution mechanism of Fe-rich phases has been discussed by using the atom radius and electronegativity differences of Fe,Mn,and Cr.
文摘To explore the approaches of combined toughening and strengthening of the Al_3Ti-based L1_2 intermetallic alloys, multiphase Al_3Ti alloys formed by combining with reinforcement or by second phase precipitation are being studied. The interface reactions between Al_(66)Fe_9Ti_(25)matrix and SiC reinforcement were investigated. It is determined that SiC is chemically incompatible with the Al_(66)Fe_9Ti_(25)matrix, Al_2O_3 barrier coating on SiC by sol-gel process was developed to minimize the interfacial reactions. On the other hand, a new type of Al_3Ti-based alloy having a L1_2 matrix with second phase precipitation has been developed. The quaternary alloys based on Al_(66)Fe_9Ti_(25)and modified with Nb additions, consist of a L1_2 matrix and D0_(22) second phase in the annealed state ,but the second phase can be dissolved by solution treatment and precipitated during high temperature aging.
文摘The ordering of the α-Fe(Si) crystallization phase in annealed Fe73.5Cu1Mo3Si13.5B9 alloy has been studied using XRD method. The α-Fe(Si) phase in Fe73.5Cu1Mo3Si13.5B9 alloy annealed at 460℃ for 1 h consists of the DO3-type ordered region with spherical shape and disordered region. The size of DO3 ordered region increases with the annealing temperature. When the annealing temperature is 560℃, the size of the ordered region in the α-Fe(Si) grain is 14.0nm,which is nearly as large as that of the α-Fe(Si) grain (14.2 nm) and the degree of order of the α-Fe(Si) phase is about 0.78. When Fe73.5Cu1 Mo3Si13.5B9 amorphous alloy is annealed at 520℃， with the increment of the annealing time, the shape of the DO3 ordered region in the α-Fe(Si) phase is spheroidal at the beginning of the annealing and becomes spherical and has asize of 12.8 nm when the annealing time is 60 min. In addition, the DO3 superlattice lines of the α-Fe(Si) phase will vanish if Fe73.5Cu1Mo3Si13.5 B9 amorphous alloy is annealed for 1 h at 750℃.
基金supported by the Key Research&Development Program of Yunnan Province(Grant numbers 202103AA080017,202203AE140011).
文摘The AA5052 aluminum alloy is widely used in automobile and aerospace manufacturing,and with the development of light-weight alloys,it is required that these materials exhibit better mechanical properties.Previous studies have demonstrated that the addition of Sc to aluminum alloys can improve both the microstructure and properties of the alloys.In this study,the effect of Sc on the Fe-rich phase and properties of the AA5052 aluminum alloy was studied by adding 0%,0.05%,0.2%,and 0.3%Sc.The results show that with the increase of Sc,the coarse needle-like Fe-rich phase gradually transforms into Chinese-script and then nearly spherical particles,reduce the size of Fe-rich phase,and refine the grain with increase of high angle grain boundaries(HAGBs).These microstructure changes enhance the strength of the AA5052 alloy through Sc addition.The ductility of the alloy is obviously improved because the addition of a lower amount of Sc changes the morphology of Fe-rich phase from needle-like into a Chinese-script,and it is subsequently reduced as a result of significant increase in HAGBs with increasing Sc content.
基金supported by the National Natural Science Foundation of China(No.12188101,No.22122301,No.22033003,No.91745201,No.91945301,No.92145302,and No.92061112)the Fundamental Research Funds for the Central Universities(20720220011)+1 种基金the National Key Research and Devel-opment Program of China(2018YF A0208600)the Tencent Foundation for XPLORER PRIZE.
文摘Al_(2)O_(3)and Ga_(2)O_(3)exhibit numerous crystal phases with distinct stabilities and materialproperties.However,the phase transitions among thosematerialsare typicallyundesirable in industrial applications,making it imperative to elucidate the transition mechanisms between these phases.The configurational similarities between Al_(2)O_(3)and Ga_(2)O_(3)allow for the replication of phase transition pathways between these materials.In this study,we investigate the potential phase transition pathway of alumina from the 0-phase to the α-phase using stochastic surface walking global optimization based on global neural network potentials,while extending an existing Ga_(2)O_(3)phase transition path.Through this exploration,we identify a novel single-atom migration pseudomartensitic mechanism,which combines martensitic transformation with single-atom diffusion.This discovery offers valuable insights for experimental endeavors aimed at stabilizing alumina in transitional phases.
文摘The effects of ternary solutes Ti, Co, V, Cr, Ta, W and Mo on the D03 phase 5tability of Fe3Alintermetallics are investigated by tight-binding linear Muffin-tin orbitaI method. The predictedsite preference5 of these elements in Fe3AI are in agreement with the experimental observations.The calculated Iocal magnetic moment of Fe3AI is identical to the experimentaI. ln addition, itis found that the D03 phase stability of Fe3AI doped with Ti, V, Co and Cr depends on 'energygap- of energy band near Fermi level. while the D03 phase stability of Fe3AI doped with Ta, Wand Mo may be affected by Madelung energy.
基金National Natural &ience Foundation of China!(No. 59671020).
文摘The microstructure and the stability of Fe_73.5Cu_1Nb_3Si_13.5B_9 alloy at different stages of phase transformation were investigated through the observation of X-ray difraction and transmission electron microscopy and the measurement of magnetic aftereffect (MAE). It was found that the dependence of the volume fraction of amorphous phase and the MAE in the samples annealed from 450 to 700℃ on the annealing temperature is similar.
基金Item Sponsored by National Natural Science Foundation of China (50944049)
文摘In order to explore synthetic method of pure sodium pyroxene,the pure chemical reagents of Na2CO3,Fe（OH）3 and H2SiO3were used as raw materials,and the possible solid phase reactions for Na2CO3-Fe（OH）3-H2SiO3system in heating process had been studied by means of differential thermal analysis（DTA）and X-ray diffraction（XRD）. The influencing factors of sodium pyroxene（NaFeSi2O6）synthetic reaction,such as sintering temperature and holding time,had also been studied.The results show that sodium pyroxene can be largely synthesized at 737℃;it is helpful for synthesis of sodium pyroxene to increase sintering temperature appropriately,and the best temperature should be controlled at 900℃or so,because it will melt and decompose at temperatures higher than 900℃.In those influencing factors of sodium pyroxene synthesis the most important is temperature.The results will be helpful for providing pure NaFeSi2O6for further research on the formation of SFCA for NaFeSi2O6-KAlSi2O3-CaO-Fe2O3-CaF2 system in the sintering process of Bayan-obo iron ore.
