Liquidus temperatures in the molten salt system Na3AlF6-K3AlF6-AlF3 of interest for aluminum electrolysis were determined by thermal analysis method. The results were presented and an empirical equation describing liq...Liquidus temperatures in the molten salt system Na3AlF6-K3AlF6-AlF3 of interest for aluminum electrolysis were determined by thermal analysis method. The results were presented and an empirical equation describing liquidus temperatures for primary crystallization was derived t=1003.5–0.081×A2.3159–5.87×B0.657–0.024×A2.22×B1.14+ 0.035×A2.17×B1.084, where t is the liquidus temperature in degree Celsius, A denotes the mass fraction of AlF3 in system Na3AlF6-K3AlF6- AlF3, and B denotes K3AlF6/(Na3AlF6+K3AlF6 ) in mass(%, the value was defined as KR in this paper). The composition limitations are 0w(AlF3)30%, and 0KR50%. The isothermal diagram of molten salt system Na3AlF6-K3AlF6-AlF3 was obtained in this composition limitation.展开更多
The liquidus temperature of the Fe-C-Mn-Si-Al alloy was investigated by using an improved differential thermal analysis method, which effectively tackles down the manganese evaporation in the course of differential th...The liquidus temperature of the Fe-C-Mn-Si-Al alloy was investigated by using an improved differential thermal analysis method, which effectively tackles down the manganese evaporation in the course of differential thermal analysis experiments for high-manganese twinning-induced plasticity (TWIP) steels at high temperature. It was found that the liquidus temperature is more strongly dependent on the silicon content than expected. By considering the high manganese content in the Fe-C-Mn-Si-Al TWIP steels, the effect of carbon content on the depression coefficient of manganese should not be ignored, which has considerable impact on the liquidus temperature. An equation was summarized to effectively predict the liquidus temperature for a wide range of high-manganese steels. Meanwhile, the prediction results of the equation are consistent with the experimental results, as well as those results acquired from ThermoCalc.展开更多
The liquidus and solidus temperatures of FeCrAl stainless steel were determined by differential scanning calorimetry(DSC) at different heating rates. They were also calculated by Thermo-calc software and empirical f...The liquidus and solidus temperatures of FeCrAl stainless steel were determined by differential scanning calorimetry(DSC) at different heating rates. They were also calculated by Thermo-calc software and empirical formulae separately. The accuracy of calculation results was assessed by comparison with the corresponding DSC results. The liquidus temperatures calculated by empirical formulae, which exhibited a maximum deviation of 8.6℃ were more accurate than those calculated using Thermo-calc, which exhibited a maximum deviation of 12.11℃. On the basis of Thermo-calc calculations performed under the Scheil model, the solidus temperature could be well determined from solid fraction(fS) vs. temperature(t) curves at fS = 0.99. Furthermore, a theoretical analysis to determine the solidus temperature with this method was also provided.展开更多
The glass-forming ability (GFA) of Nd70-xFe2oAl10Yx and Nd60-xFe30Al10Yx (0< x <15) alloys produced by Cu mold casting was investigated. Except Y=5 at. pct, bulk amorphous Nd70-xFe20Al10Yx alloys up to 2 mm in d...The glass-forming ability (GFA) of Nd70-xFe2oAl10Yx and Nd60-xFe30Al10Yx (0< x <15) alloys produced by Cu mold casting was investigated. Except Y=5 at. pct, bulk amorphous Nd70-xFe20Al10Yx alloys up to 2 mm in diameter were obtained. The GFA for Nd60-xFe30Al10Yx alloys, however, was found to decrease with increase of Y due to the increasing compositional deviation from the original eutectic point of Nd60Fe30Al10 alloy. The Nd60Fe20Al10Y10 and Nd60Fe30Al10 alloy exhibit the largest GFA and can be cast into bulk amorphous cylindrical specimens of 3 mm in diameter. The melting temperature or/and the reduced crystallization temperature is closely related to the GFA of Y-containing alloys. The bulk amorphous cylinder for the Nd55Fe20Al10Y15 alloy shows a distinct glass transition temperature and a wide supercooled liquid region before crystallization. The crystallization temperature, Tg, and the supercooled liquid region, TX, are 776 K and 58 K, respectively. The GFA and thermal stability of the Nd-Fe-AI-Y alloys were discussed.展开更多
Hot-rolled Fe-(0.75-2.20)Si (mass%) alloys were oxidized in dry air at 600-1200 ℃. The oxidation process was carried out by thermal gravimetric analysis (TGA). At 600- 1 150 ℃, oxidation gain curves were appro...Hot-rolled Fe-(0.75-2.20)Si (mass%) alloys were oxidized in dry air at 600-1200 ℃. The oxidation process was carried out by thermal gravimetric analysis (TGA). At 600- 1 150 ℃, oxidation gain curves were approximately parabolic. Electron probe mieroanalysis (EPMA) was applied to investigate cross-section morphology of oxide layer and element distribution across the layer. At lower temperature of 700 ℃, the oxide layer consisted of internal oxidation zone (IOZ), inner Si-rich layer (conglomerate of fayalite and magnetite) and outer hematite layer, while at higher temperature of 1200 ℃, fayalite and wustite were observed in external oxide scale. Liquidus temperature of fayalite was detected by differential scanning calorimetry (DSC). Through comparing the oxidation mass gain and parabolic rate constant of the alloys, it was found that oxidation resistance of Fe-Si alloy was enhanced by increasing Si content below 1 150 ℃ while increasing Si content of the alloy resulted in higher oxidation rate above 1150 ℃ owing to the liquid fayalite formation.展开更多
The first step in the production of tungsten is to enrich tungsten from two minerals wolframite((Fe,Mn)WO_(4))and scheelite(CaWO_(4))through the leaching process.The leaching residue usually contains a certain amount(...The first step in the production of tungsten is to enrich tungsten from two minerals wolframite((Fe,Mn)WO_(4))and scheelite(CaWO_(4))through the leaching process.The leaching residue usually contains a certain amount(2-5 wt%)of WO_(3) which is higher than that in the tungsten ore(generally less than 1 wt%).In addition,the leaching residue may also consist of other valuable elements such as Cu,Ta,Nb,Sn,Sc,Mn and Fe.Understanding the phases and their compositions present in the residue is one of the key steps for the efficient utilization.The typical residue sample is carefully analysed by electron probe X-ray microanalysis and X-ray fluorescence.A high-temperature process,which includes pre-reduction at 1000-1100℃and smelting reduction at 1450-1500℃,is proposed to efficiently recover the valuable elements.Experimental work and thermo-dynamic calculations confirmed that most of the valuable elements can be economically recovered with optimum conditions.展开更多
High manganese steels can damage the differential thermal analysis (DTA) instrument due to the manganese evaporation during high temperature experiments. After analyzing the relationship between residual oxygen and ...High manganese steels can damage the differential thermal analysis (DTA) instrument due to the manganese evaporation during high temperature experiments. After analyzing the relationship between residual oxygen and manganese evaporation, tanta- lum metal was employed to modify the crucible of DTA, and zirconium getter together with strict gas purification measures were applied to control the volatilization of manganese. By these modifications, problems of thermocouple damage and DTA instrument contamination were successfully resolved. Cobalt samples were adopted to calibrate the accuracy of DTA instruments under the same trial condition of high manganese steel samples, and the detection error was confirmed to be less than 1 ℃. Liquidus and soli- dus temperatures of high Mn steels were measured by improved DTA method. It was found that the liquidus temperatures of sam- ples tested by experiments increased linearly with the heating rates. To eliminate the effects of the heating rate, equilibrium liquidus temperature was determined by fitting the liquidus temperatures at different heating rates, and referred as real liquidus temperature. No clear relationship between solidus temperatures and heating rates was found, and the solidus temperature was finally set as the average value of several experimental data.展开更多
The application of Pr-Nd-Dy alloy in the field of high-performance Nd-Fe-B permanent magnet materials has great potential.The composition of the PrF_(3)-NdF_(3)-DyF_(3)-LiF(PND-LiF) electrolyte system used in the prod...The application of Pr-Nd-Dy alloy in the field of high-performance Nd-Fe-B permanent magnet materials has great potential.The composition of the PrF_(3)-NdF_(3)-DyF_(3)-LiF(PND-LiF) electrolyte system used in the production of Pr-Nd-Dy alloys,the distribution of F,Li,RE and other elements in the electrolyte and their occurrence state were studied in this paper.The effect of temperature and lithium fluoride addition on electrolyte conductivity was revealed using the continuous conductivity cell constant(CVCC) method.The thermal analysis method was used to study the influence of lithium fluoride addition on the electrolyte’s liquidus temperature and the optimal process conditions for the production of Pr-Nd-Dy alloy were determined.The results show that the overall distribution of praseodymium neodymium fluoride and lithium fluoride is uniform in the electrolyte and dysprosium fluoride is distributed between praseodymium-neodymium fluoride and lithium fluoride.Praseodymium-neodymium oxide is embedded in praseodymium neodymium fluoride in spotty pattern.The electrolyte’s conductivity is increased as the temperature and lithium fluoride addition are going up,while the liquidus temperature is going down with increasing lithium fluoride addition.The best electrolysis process conditions for the PND-LiF system to produce praseodymium neodymium dysprosium alloy are as follows:temperature1050℃ and 15.56 wt% PrF_(3)-62.22 wt% NdF_(3)-11.11 wt% DyF_(3)-11.11 wt% LiF.展开更多
基金Supported by the National Basic Research Program of China(No.2005CB623703)the National High-Tech Research and Development Program of China(No.2008AA030503)
文摘Liquidus temperatures in the molten salt system Na3AlF6-K3AlF6-AlF3 of interest for aluminum electrolysis were determined by thermal analysis method. The results were presented and an empirical equation describing liquidus temperatures for primary crystallization was derived t=1003.5–0.081×A2.3159–5.87×B0.657–0.024×A2.22×B1.14+ 0.035×A2.17×B1.084, where t is the liquidus temperature in degree Celsius, A denotes the mass fraction of AlF3 in system Na3AlF6-K3AlF6- AlF3, and B denotes K3AlF6/(Na3AlF6+K3AlF6 ) in mass(%, the value was defined as KR in this paper). The composition limitations are 0w(AlF3)30%, and 0KR50%. The isothermal diagram of molten salt system Na3AlF6-K3AlF6-AlF3 was obtained in this composition limitation.
基金It is gratefully acknowledged that the work presented in this paper has been supported by the Chair of Ferrous Metallurgy, Montanuniversitat Leoben, National Natural Science Foundation of China (No. 51704083), Education Department Foundation of Guizhou Province of China (No. [20171118) and Research Foundation for Talents of Guizhou University (No. 201628). The author would like to thank Prof. Christian Bernhard, Prof. Johannes Schenk, Dr. Peter Presoly, Dr. Susanne Michelic, Bernd Lederhaas and Gerhard Wieser for their support of the research.
文摘The liquidus temperature of the Fe-C-Mn-Si-Al alloy was investigated by using an improved differential thermal analysis method, which effectively tackles down the manganese evaporation in the course of differential thermal analysis experiments for high-manganese twinning-induced plasticity (TWIP) steels at high temperature. It was found that the liquidus temperature is more strongly dependent on the silicon content than expected. By considering the high manganese content in the Fe-C-Mn-Si-Al TWIP steels, the effect of carbon content on the depression coefficient of manganese should not be ignored, which has considerable impact on the liquidus temperature. An equation was summarized to effectively predict the liquidus temperature for a wide range of high-manganese steels. Meanwhile, the prediction results of the equation are consistent with the experimental results, as well as those results acquired from ThermoCalc.
基金financially supported by the National Natural Science Foundation of China (No. 51374023)
文摘The liquidus and solidus temperatures of FeCrAl stainless steel were determined by differential scanning calorimetry(DSC) at different heating rates. They were also calculated by Thermo-calc software and empirical formulae separately. The accuracy of calculation results was assessed by comparison with the corresponding DSC results. The liquidus temperatures calculated by empirical formulae, which exhibited a maximum deviation of 8.6℃ were more accurate than those calculated using Thermo-calc, which exhibited a maximum deviation of 12.11℃. On the basis of Thermo-calc calculations performed under the Scheil model, the solidus temperature could be well determined from solid fraction(fS) vs. temperature(t) curves at fS = 0.99. Furthermore, a theoretical analysis to determine the solidus temperature with this method was also provided.
基金This work was performed with the support of the National Development Project for Basic Scientific Research of China under grant number G2000067201 as well as the fund for the best doctor dissertation .
文摘The glass-forming ability (GFA) of Nd70-xFe2oAl10Yx and Nd60-xFe30Al10Yx (0< x <15) alloys produced by Cu mold casting was investigated. Except Y=5 at. pct, bulk amorphous Nd70-xFe20Al10Yx alloys up to 2 mm in diameter were obtained. The GFA for Nd60-xFe30Al10Yx alloys, however, was found to decrease with increase of Y due to the increasing compositional deviation from the original eutectic point of Nd60Fe30Al10 alloy. The Nd60Fe20Al10Y10 and Nd60Fe30Al10 alloy exhibit the largest GFA and can be cast into bulk amorphous cylindrical specimens of 3 mm in diameter. The melting temperature or/and the reduced crystallization temperature is closely related to the GFA of Y-containing alloys. The bulk amorphous cylinder for the Nd55Fe20Al10Y15 alloy shows a distinct glass transition temperature and a wide supercooled liquid region before crystallization. The crystallization temperature, Tg, and the supercooled liquid region, TX, are 776 K and 58 K, respectively. The GFA and thermal stability of the Nd-Fe-AI-Y alloys were discussed.
基金Item Sponsored by National High-tech Research and Development Program of China(2011BAE13B04)National Natural Science Foundation of China(51204047,51204053)
文摘Hot-rolled Fe-(0.75-2.20)Si (mass%) alloys were oxidized in dry air at 600-1200 ℃. The oxidation process was carried out by thermal gravimetric analysis (TGA). At 600- 1 150 ℃, oxidation gain curves were approximately parabolic. Electron probe mieroanalysis (EPMA) was applied to investigate cross-section morphology of oxide layer and element distribution across the layer. At lower temperature of 700 ℃, the oxide layer consisted of internal oxidation zone (IOZ), inner Si-rich layer (conglomerate of fayalite and magnetite) and outer hematite layer, while at higher temperature of 1200 ℃, fayalite and wustite were observed in external oxide scale. Liquidus temperature of fayalite was detected by differential scanning calorimetry (DSC). Through comparing the oxidation mass gain and parabolic rate constant of the alloys, it was found that oxidation resistance of Fe-Si alloy was enhanced by increasing Si content below 1 150 ℃ while increasing Si content of the alloy resulted in higher oxidation rate above 1150 ℃ owing to the liquid fayalite formation.
文摘The first step in the production of tungsten is to enrich tungsten from two minerals wolframite((Fe,Mn)WO_(4))and scheelite(CaWO_(4))through the leaching process.The leaching residue usually contains a certain amount(2-5 wt%)of WO_(3) which is higher than that in the tungsten ore(generally less than 1 wt%).In addition,the leaching residue may also consist of other valuable elements such as Cu,Ta,Nb,Sn,Sc,Mn and Fe.Understanding the phases and their compositions present in the residue is one of the key steps for the efficient utilization.The typical residue sample is carefully analysed by electron probe X-ray microanalysis and X-ray fluorescence.A high-temperature process,which includes pre-reduction at 1000-1100℃and smelting reduction at 1450-1500℃,is proposed to efficiently recover the valuable elements.Experimental work and thermo-dynamic calculations confirmed that most of the valuable elements can be economically recovered with optimum conditions.
基金Sponsored by National Natural Science Foundation of China(51374023)
文摘High manganese steels can damage the differential thermal analysis (DTA) instrument due to the manganese evaporation during high temperature experiments. After analyzing the relationship between residual oxygen and manganese evaporation, tanta- lum metal was employed to modify the crucible of DTA, and zirconium getter together with strict gas purification measures were applied to control the volatilization of manganese. By these modifications, problems of thermocouple damage and DTA instrument contamination were successfully resolved. Cobalt samples were adopted to calibrate the accuracy of DTA instruments under the same trial condition of high manganese steel samples, and the detection error was confirmed to be less than 1 ℃. Liquidus and soli- dus temperatures of high Mn steels were measured by improved DTA method. It was found that the liquidus temperatures of sam- ples tested by experiments increased linearly with the heating rates. To eliminate the effects of the heating rate, equilibrium liquidus temperature was determined by fitting the liquidus temperatures at different heating rates, and referred as real liquidus temperature. No clear relationship between solidus temperatures and heating rates was found, and the solidus temperature was finally set as the average value of several experimental data.
基金Project supported by the National Key Research and Development Program of China(2019YFC1908403)。
文摘The application of Pr-Nd-Dy alloy in the field of high-performance Nd-Fe-B permanent magnet materials has great potential.The composition of the PrF_(3)-NdF_(3)-DyF_(3)-LiF(PND-LiF) electrolyte system used in the production of Pr-Nd-Dy alloys,the distribution of F,Li,RE and other elements in the electrolyte and their occurrence state were studied in this paper.The effect of temperature and lithium fluoride addition on electrolyte conductivity was revealed using the continuous conductivity cell constant(CVCC) method.The thermal analysis method was used to study the influence of lithium fluoride addition on the electrolyte’s liquidus temperature and the optimal process conditions for the production of Pr-Nd-Dy alloy were determined.The results show that the overall distribution of praseodymium neodymium fluoride and lithium fluoride is uniform in the electrolyte and dysprosium fluoride is distributed between praseodymium-neodymium fluoride and lithium fluoride.Praseodymium-neodymium oxide is embedded in praseodymium neodymium fluoride in spotty pattern.The electrolyte’s conductivity is increased as the temperature and lithium fluoride addition are going up,while the liquidus temperature is going down with increasing lithium fluoride addition.The best electrolysis process conditions for the PND-LiF system to produce praseodymium neodymium dysprosium alloy are as follows:temperature1050℃ and 15.56 wt% PrF_(3)-62.22 wt% NdF_(3)-11.11 wt% DyF_(3)-11.11 wt% LiF.