In this study, reheating of liquidus semi-continuous cast billets of 7075 Al alloy was carried out in a resistance furnace, and the temperature contrast of the outer and the center of the reheated billets was investig...In this study, reheating of liquidus semi-continuous cast billets of 7075 Al alloy was carried out in a resistance furnace, and the temperature contrast of the outer and the center of the reheated billets was investigated, then the reheating microstructures were investigated. Results show that: the difference of temperature between the outer and center is small and the difference of their microstructures are also small. During reheating at 576℃ the spheroidization of grains is significant after 5min and no rosettes are visible after 20min by optical microscopy. Similar observations were madeon materials reheated at 596℃, but the ripening process is faster. The grains growup to 30-60μm, fine enough for thixoforming.展开更多
Fine, equiaxed, non dendritic structure needed by semi solid processing was obtained by liquidus cast, i.e. 7075 wrought aluminum alloy cast from liquidus temperature. The microstructures after heat treatment at diffe...Fine, equiaxed, non dendritic structure needed by semi solid processing was obtained by liquidus cast, i.e. 7075 wrought aluminum alloy cast from liquidus temperature. The microstructures after heat treatment at different temperatures and time in the semi solid range were observed, and the compression deformation behavior at different temperatures (490～600 ℃) and strain rates (5×10 -3 ～5s -1 ) was investigated by means of Gleeble 1500 thermal mechanical simulator. The results show that the deformation resistance of the non dendritic structure attained by liquidus cast in semi solid is remarkably lower than that of conventional dendritic structure. The formability of non dendritic structure is better than that of dendritic structure.展开更多
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 single hot thermocouple technique （SHTT） and high temperature equilibrium technique were combined to investigate the phase diagram of the CaO-SiO2-5%MgO-20%AlzO3-TiO2 system. The 1300 ℃ to 1500 ℃ liquidus line...The single hot thermocouple technique （SHTT） and high temperature equilibrium technique were combined to investigate the phase diagram of the CaO-SiO2-5%MgO-20%AlzO3-TiO2 system. The 1300 ℃ to 1500 ℃ liquidus lines are calculated according to the thermodynamic equations based on the pseudo-melting temperatures measured by the single hot thermocouple technique. The phase equilibria relationships are experimentally determined at 1400 ℃ using the high temperature equilibria technique followed by X-ray fluorescence （XRF）, X-ray diffraction（XRD）, scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDX） analysis. The liquid phase（L）, melilite solid solution phase （（C2MSz,C2AS）ss）, diopside phase（CMS2） and perovskite phase （CaO·TiO2） are found. Coupled with the liquidus lines and equilibria results, the phase diagram is constructed for the specified region of the CaO-SiO2-5%MgO-20%Al2O3-TiO2 system.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
After the investigation on partial remelting of thixotropic magnesium serial alloys （ZK60） by near non-equilibrium liquidus casting （NNLC）, the primary solid grains of ZK60-2Ca alloy spheroidized notably during pa...After the investigation on partial remelting of thixotropic magnesium serial alloys （ZK60） by near non-equilibrium liquidus casting （NNLC）, the primary solid grains of ZK60-2Ca alloy spheroidized notably during partial remelting processing, however, coarsening and polygonization as occurred holding time prolonged. The refining and globularity of the thixotropic alloys are promoted after further alloyed by Y, RE, Nd and/or Ag, and the results vary with those addition. The remelting structure of ZK60-2Ca-1Y alloy is finer than its base alloy. And the effect of RE, especially Ag, on the refinement of microstrueture is notable, but Nd does nothing on it. There is little impact of remelting temperature fluctuation on partial remelted microstrueture as holding time in general. On the contrary, it is more sensitive at longer holding time. The quality thixotropic silver-contained alloy can be achieved by remelted partially at 600℃ for 10 min.展开更多
A high temperature equilibration experiment was carried out to investigate the effect of oxygen partial pres- sure on the phase equilibria and liquidus in CaO-Al2O3- FeOx system with the intermediate oxygen partial pr...A high temperature equilibration experiment was carried out to investigate the effect of oxygen partial pres- sure on the phase equilibria and liquidus in CaO-Al2O3- FeOx system with the intermediate oxygen partial pressures of 10.13 Pa and 1.01 × 10^-3 Pa. The equilibrated phases and their compositions of the quenched samples were analyzed by using SEM/EPMA （Scanning Electron Microscope/Electron Probe Micro Analysis） and XRD （X Ray Diffraction）. The phase equilibrium results include two cases, the two phase coexistence and the three-phase coexistence in the high Al2O3 region with oxygen partial pressure of either 10.13 Pa or 1.01 × 10^-3 Pa. Effects of oxygen partial pressure and temperature on the liquidus along the primary phase fields of CaO · Al2O3 and CaO · 2Al2O3 were nota hle. With the decrease of oxygen partial pressure, the liquid area expands and the liquidus of CaO · Al2O3 and CaO · 2Al2O3 primary fields moves to the Al2O3-FeOx region. On the other hand, the liquid area of CaO Al2O3-FeOx sys tem extends extremely to the high Al2O3 region with the temperature increasing from 1 400 to 1 500℃, especially at lower oxygen partial pressure. The present experiment results are in good agreement with the calculated ones by FactSage.展开更多
The liquidus of the ternary Ag-Cd-Si alloy system in the Ag-Cu rich region was determined by DTA. The ternary Ag-Cd-Si system was divided into two ternary systems Ag-Cu-Cuo.76Si0.24 and Ag-Cu0.76Si0.24-Si by the sec...The liquidus of the ternary Ag-Cd-Si alloy system in the Ag-Cu rich region was determined by DTA. The ternary Ag-Cd-Si system was divided into two ternary systems Ag-Cu-Cuo.76Si0.24 and Ag-Cu0.76Si0.24-Si by the section of Ag-Cu0.76 Si0.24.There is one ternary eutectic point for both the systems with the composition of 12. 5at. %Ag+71. 7at.%Cu+15.8at. %Si and 30at.% Ag+44.7at.%Cu+25.3at.%Sirespectivelg and the temperatures of the eutectic points are 740 and 705℃ respectively.展开更多
Liquidus projection usually refers to a two-dimensional projection of ternary liquidus univariant lines at constant pressure. The algorithms used in Pandat for the calculation of liquidus projection with isothermal li...Liquidus projection usually refers to a two-dimensional projection of ternary liquidus univariant lines at constant pressure. The algorithms used in Pandat for the calculation of liquidus projection with isothermal lines and invariant reaction equations in a ternary system are presented. These algorithms have been extended to multicomponent liquidus projections and have also been implemented in Pandat. Some examples on ternary and quaternary liquidus projections are presented.展开更多
The liquidus of ternary system NdCl_3-MgCl_2-LiCl has been determined by means of DTA.It was found that there are two surfaces corresponding to the primary crystallization of NdCl_3 and α-(MgCl_2,LiCl)respectively,an...The liquidus of ternary system NdCl_3-MgCl_2-LiCl has been determined by means of DTA.It was found that there are two surfaces corresponding to the primary crystallization of NdCl_3 and α-(MgCl_2,LiCl)respectively,and a univariant line related to the secondary crystallization with a minimum M(68.5 wt-% NdCl_3,2.7 wt-% MgCl_2,28.8 wt-% LiCl_2 441℃)in the system.展开更多
The diagram of system Au-Cu-Si was constructed from data of 9 internal sections by DTA in an atmosphere of dry N_2.The composition of ternary eutectic point melting at 337℃ lies in Au(74.7)-Cu(6.1)-Si(19.2) at.-%.The...The diagram of system Au-Cu-Si was constructed from data of 9 internal sections by DTA in an atmosphere of dry N_2.The composition of ternary eutectic point melting at 337℃ lies in Au(74.7)-Cu(6.1)-Si(19.2) at.-%.The liquidus of the 3 side-binary systems have been redetermined.展开更多
The diagram of Ag-Cu-Ge system was constructed from the investigation of 13 internal sec- tions by DTA heating as well as cooling curves in an atomsphere of dry N_2 . The phase dia- gram is subdivided into two pseudo-...The diagram of Ag-Cu-Ge system was constructed from the investigation of 13 internal sec- tions by DTA heating as well as cooling curves in an atomsphere of dry N_2 . The phase dia- gram is subdivided into two pseudo-ternary systems shown as Ag-Cu-Cu_3Ge and Ag-Cu_3Ge-Ge. Both systems belong to simple eutectic type. The ternary eutectic points lie in.' E_1, Ag(22.0)-Cu(58.8)-Ge(19.2), 632℃ and E_2 , Ag(44.3)-Cu(29.5)-Ge(26.2), 533℃. The three side binary systems were redetermined.展开更多
The diagram of Ag-Cu-Bi system was constructed from the investigation of 12 internal sec- tions by DTA heating as well as cooling curves in an atmosphere of dry N_2.The composi- tion of ternary eutectic point melting ...The diagram of Ag-Cu-Bi system was constructed from the investigation of 12 internal sec- tions by DTA heating as well as cooling curves in an atmosphere of dry N_2.The composi- tion of ternary eutectic point melting at 258℃ lies in Ag(5.0)-Cu(0.5)-Bi(94.5) at.-%.The liquiduses of Ag-Cu,Ag-Bi and Cu-Bi binaries were reinvestigated.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
Many investigations have revealed that transition of melt structure can effectively influence the final solidification microstructures. In this study, ultrasonic treatment was applied to AI-20%Si melt and Sr-modified ...Many investigations have revealed that transition of melt structure can effectively influence the final solidification microstructures. In this study, ultrasonic treatment was applied to AI-20%Si melt and Sr-modified AI-20%Si melt at 720 ℃ （i.e. above liquidus of about 690℃） for 60 s, and then the melt was quickly quenched to room temperature. Experimental results show that ultrasonic treatment can refine the primary Si phase and a-AI of AI-20%Si alloy; strontium can make the morphology of Si phase spheroidized and refined as Sr addition changes the faceted growth characteristic of Si phase; however, the refinement effect of ultrasonic treatment on the primary Si phase and α-AI is weakened by Sr addition.展开更多
The effect of solid-solution-treatment on the semisolid microstructure of Zn-22Al with developed dendrites was investigated. Forming Zn-22Al products by semisolid metal processing offers significant advantages, such a...The effect of solid-solution-treatment on the semisolid microstructure of Zn-22Al with developed dendrites was investigated. Forming Zn-22Al products by semisolid metal processing offers significant advantages, such as reductions in macro-segregation, porosity and forming costs. Thermal and rnicrostructural analyses of the formed Zn-22Al alloy were performed by differential scanning calorimetry, scanning electron microscopy and optical microscopy. The changes in the microstructures and phase transformation in response to various solid- solution-treatments were analysed. In this study, as-cast samples were held isothermally at 330 ℃ for 0.5- 5 h and then partially remelted at a semisolid temperature of 438 ℃ for 1 h to produce a solid-globular grain structure in a liquid matrix. A non-dendritic semisolid microstructure could not be obtained when the traditionally cast Zn 22Al alloy with developed dendrites was subjected directly to partial remelting. After solid-solution-treatment at 330 ℃, the black interdendritic eutectics were dissolved, and the dendritic structures gradually transformed into uniform β structures when the treatment time was increased. The coarsened and merged dendrites were separated as a result of penetration by the liquid phase and melting of the residual eutectic at sites along the former grain boundaries. The microstructure of the solid-solution- treated sample transformed into a small globular structure; the best shape factor of 0.9, corresponding to a particle size of 40 ± 16 μm, is achieved when the sample was treated for 3 h followed by direct partial remelting into its semisolid zone.展开更多
Nd-F species in NdF3-LiF melts were studied using cryoscopic method.Liquidus temperatures of melts of various compositions were determined by differential thermal analysis(DTA).Based on the different model calculation...Nd-F species in NdF3-LiF melts were studied using cryoscopic method.Liquidus temperatures of melts of various compositions were determined by differential thermal analysis(DTA).Based on the different model calculations,NdF4- was identified as the most likely Nd-F entity in the melts in which the mole fraction of NdF3 was lower than 20%,considering only one single Nd species in the melt,and which was formed in accordance with Temkin model or Flood model.Then,activities of different components in the melts were researched.The results show that activity of LiF decreases,and that of NdF3 increases with increasing the mole fraction of NdF3.The value of activity coefficient of NdF3 is higher than 1,and that of LiF is lower than 1.展开更多
Experimental studies on phase equilibria and liquidus temperature in the PbO-ZnO-CaO-SiO2-＂Fe2O3＂ system,with the mass ratios of CaO/SiO2=1-1.6 and Fe/SiO2= 1.3-1.7,and 40% PbO and 8% ZnO,were carried out between 12...Experimental studies on phase equilibria and liquidus temperature in the PbO-ZnO-CaO-SiO2-＂Fe2O3＂ system,with the mass ratios of CaO/SiO2=1-1.6 and Fe/SiO2= 1.3-1.7,and 40% PbO and 8% ZnO,were carried out between 1273 and 1573 K.Slags were equilibrated at 1273 to 1573 K and cooled rapidly by quenching.The XRD and SEM-EDS results showed that the slag compositions are in the franklinite primary phase field.Calcium and lead silicates are formed between 1373 and 1473 K.The Ca/Pb silicate and magnetoplumbite phases are partially formed by an incongruent reaction.The experimental and thermodynamical results showed that the liquidus increased by increasing CaO/SiO2 mass ratio and decreasing Fe/SiO2 mass ratio.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
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
基金The National Natural Science Foundation of China (Grants No. 59974009) is greatly acknowledged for their financial support.
文摘In this study, reheating of liquidus semi-continuous cast billets of 7075 Al alloy was carried out in a resistance furnace, and the temperature contrast of the outer and the center of the reheated billets was investigated, then the reheating microstructures were investigated. Results show that: the difference of temperature between the outer and center is small and the difference of their microstructures are also small. During reheating at 576℃ the spheroidization of grains is significant after 5min and no rosettes are visible after 20min by optical microscopy. Similar observations were madeon materials reheated at 596℃, but the ripening process is faster. The grains growup to 30-60μm, fine enough for thixoforming.
文摘Fine, equiaxed, non dendritic structure needed by semi solid processing was obtained by liquidus cast, i.e. 7075 wrought aluminum alloy cast from liquidus temperature. The microstructures after heat treatment at different temperatures and time in the semi solid range were observed, and the compression deformation behavior at different temperatures (490～600 ℃) and strain rates (5×10 -3 ～5s -1 ) was investigated by means of Gleeble 1500 thermal mechanical simulator. The results show that the deformation resistance of the non dendritic structure attained by liquidus cast in semi solid is remarkably lower than that of conventional dendritic structure. The formability of non dendritic structure is better than that of dendritic structure.
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Projects(51104039,51374059,51304042)supported by the National Natural Science Foundation of ChinaProject(L2013114)supported by Scientific Research Fund of Liaoning Provincial Education Department,China+1 种基金Project(2012221013)supported by Programs of Liaoning Province for Science and Technology Development,ChinaProject(N130602002)supported by the Fundamental Research Funds for the Central Universities China
文摘The single hot thermocouple technique （SHTT） and high temperature equilibrium technique were combined to investigate the phase diagram of the CaO-SiO2-5%MgO-20%AlzO3-TiO2 system. The 1300 ℃ to 1500 ℃ liquidus lines are calculated according to the thermodynamic equations based on the pseudo-melting temperatures measured by the single hot thermocouple technique. The phase equilibria relationships are experimentally determined at 1400 ℃ using the high temperature equilibria technique followed by X-ray fluorescence （XRF）, X-ray diffraction（XRD）, scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDX） analysis. The liquid phase（L）, melilite solid solution phase （（C2MSz,C2AS）ss）, diopside phase（CMS2） and perovskite phase （CaO·TiO2） are found. Coupled with the liquidus lines and equilibria results, the phase diagram is constructed for the specified region of the CaO-SiO2-5%MgO-20%Al2O3-TiO2 system.
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.
文摘After the investigation on partial remelting of thixotropic magnesium serial alloys （ZK60） by near non-equilibrium liquidus casting （NNLC）, the primary solid grains of ZK60-2Ca alloy spheroidized notably during partial remelting processing, however, coarsening and polygonization as occurred holding time prolonged. The refining and globularity of the thixotropic alloys are promoted after further alloyed by Y, RE, Nd and/or Ag, and the results vary with those addition. The remelting structure of ZK60-2Ca-1Y alloy is finer than its base alloy. And the effect of RE, especially Ag, on the refinement of microstrueture is notable, but Nd does nothing on it. There is little impact of remelting temperature fluctuation on partial remelted microstrueture as holding time in general. On the contrary, it is more sensitive at longer holding time. The quality thixotropic silver-contained alloy can be achieved by remelted partially at 600℃ for 10 min.
基金Item Sponsored by National Natural Science Foundation of China(50974034,51074039)
文摘A high temperature equilibration experiment was carried out to investigate the effect of oxygen partial pres- sure on the phase equilibria and liquidus in CaO-Al2O3- FeOx system with the intermediate oxygen partial pressures of 10.13 Pa and 1.01 × 10^-3 Pa. The equilibrated phases and their compositions of the quenched samples were analyzed by using SEM/EPMA （Scanning Electron Microscope/Electron Probe Micro Analysis） and XRD （X Ray Diffraction）. The phase equilibrium results include two cases, the two phase coexistence and the three-phase coexistence in the high Al2O3 region with oxygen partial pressure of either 10.13 Pa or 1.01 × 10^-3 Pa. Effects of oxygen partial pressure and temperature on the liquidus along the primary phase fields of CaO · Al2O3 and CaO · 2Al2O3 were nota hle. With the decrease of oxygen partial pressure, the liquid area expands and the liquidus of CaO · Al2O3 and CaO · 2Al2O3 primary fields moves to the Al2O3-FeOx region. On the other hand, the liquid area of CaO Al2O3-FeOx sys tem extends extremely to the high Al2O3 region with the temperature increasing from 1 400 to 1 500℃, especially at lower oxygen partial pressure. The present experiment results are in good agreement with the calculated ones by FactSage.
文摘The liquidus of the ternary Ag-Cd-Si alloy system in the Ag-Cu rich region was determined by DTA. The ternary Ag-Cd-Si system was divided into two ternary systems Ag-Cu-Cuo.76Si0.24 and Ag-Cu0.76Si0.24-Si by the section of Ag-Cu0.76 Si0.24.There is one ternary eutectic point for both the systems with the composition of 12. 5at. %Ag+71. 7at.%Cu+15.8at. %Si and 30at.% Ag+44.7at.%Cu+25.3at.%Sirespectivelg and the temperatures of the eutectic points are 740 and 705℃ respectively.
文摘Liquidus projection usually refers to a two-dimensional projection of ternary liquidus univariant lines at constant pressure. The algorithms used in Pandat for the calculation of liquidus projection with isothermal lines and invariant reaction equations in a ternary system are presented. These algorithms have been extended to multicomponent liquidus projections and have also been implemented in Pandat. Some examples on ternary and quaternary liquidus projections are presented.
文摘The liquidus of ternary system NdCl_3-MgCl_2-LiCl has been determined by means of DTA.It was found that there are two surfaces corresponding to the primary crystallization of NdCl_3 and α-(MgCl_2,LiCl)respectively,and a univariant line related to the secondary crystallization with a minimum M(68.5 wt-% NdCl_3,2.7 wt-% MgCl_2,28.8 wt-% LiCl_2 441℃)in the system.
文摘The diagram of system Au-Cu-Si was constructed from data of 9 internal sections by DTA in an atmosphere of dry N_2.The composition of ternary eutectic point melting at 337℃ lies in Au(74.7)-Cu(6.1)-Si(19.2) at.-%.The liquidus of the 3 side-binary systems have been redetermined.
文摘The diagram of Ag-Cu-Ge system was constructed from the investigation of 13 internal sec- tions by DTA heating as well as cooling curves in an atomsphere of dry N_2 . The phase dia- gram is subdivided into two pseudo-ternary systems shown as Ag-Cu-Cu_3Ge and Ag-Cu_3Ge-Ge. Both systems belong to simple eutectic type. The ternary eutectic points lie in.' E_1, Ag(22.0)-Cu(58.8)-Ge(19.2), 632℃ and E_2 , Ag(44.3)-Cu(29.5)-Ge(26.2), 533℃. The three side binary systems were redetermined.
文摘The diagram of Ag-Cu-Bi system was constructed from the investigation of 12 internal sec- tions by DTA heating as well as cooling curves in an atmosphere of dry N_2.The composi- tion of ternary eutectic point melting at 258℃ lies in Ag(5.0)-Cu(0.5)-Bi(94.5) at.-%.The liquiduses of Ag-Cu,Ag-Bi and Cu-Bi binaries were reinvestigated.
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financially supported by the National Natural Science Foundation of China under contract No.50874022
文摘Many investigations have revealed that transition of melt structure can effectively influence the final solidification microstructures. In this study, ultrasonic treatment was applied to AI-20%Si melt and Sr-modified AI-20%Si melt at 720 ℃ （i.e. above liquidus of about 690℃） for 60 s, and then the melt was quickly quenched to room temperature. Experimental results show that ultrasonic treatment can refine the primary Si phase and a-AI of AI-20%Si alloy; strontium can make the morphology of Si phase spheroidized and refined as Sr addition changes the faceted growth characteristic of Si phase; however, the refinement effect of ultrasonic treatment on the primary Si phase and α-AI is weakened by Sr addition.
基金the Ministry of Science, Technology and Innovation(MOSTI)Malaysia for sponsoring this study under Grant 03-0 1-02-SF0047
文摘The effect of solid-solution-treatment on the semisolid microstructure of Zn-22Al with developed dendrites was investigated. Forming Zn-22Al products by semisolid metal processing offers significant advantages, such as reductions in macro-segregation, porosity and forming costs. Thermal and rnicrostructural analyses of the formed Zn-22Al alloy were performed by differential scanning calorimetry, scanning electron microscopy and optical microscopy. The changes in the microstructures and phase transformation in response to various solid- solution-treatments were analysed. In this study, as-cast samples were held isothermally at 330 ℃ for 0.5- 5 h and then partially remelted at a semisolid temperature of 438 ℃ for 1 h to produce a solid-globular grain structure in a liquid matrix. A non-dendritic semisolid microstructure could not be obtained when the traditionally cast Zn 22Al alloy with developed dendrites was subjected directly to partial remelting. After solid-solution-treatment at 330 ℃, the black interdendritic eutectics were dissolved, and the dendritic structures gradually transformed into uniform β structures when the treatment time was increased. The coarsened and merged dendrites were separated as a result of penetration by the liquid phase and melting of the residual eutectic at sites along the former grain boundaries. The microstructure of the solid-solution- treated sample transformed into a small globular structure; the best shape factor of 0.9, corresponding to a particle size of 40 ± 16 μm, is achieved when the sample was treated for 3 h followed by direct partial remelting into its semisolid zone.
基金Project(51004034)supported by the National Natural Science Foundation of ChinaProject(N090302009)supported by the Fundamental Research Funds for the Central Universities,China
文摘Nd-F species in NdF3-LiF melts were studied using cryoscopic method.Liquidus temperatures of melts of various compositions were determined by differential thermal analysis(DTA).Based on the different model calculations,NdF4- was identified as the most likely Nd-F entity in the melts in which the mole fraction of NdF3 was lower than 20%,considering only one single Nd species in the melt,and which was formed in accordance with Temkin model or Flood model.Then,activities of different components in the melts were researched.The results show that activity of LiF decreases,and that of NdF3 increases with increasing the mole fraction of NdF3.The value of activity coefficient of NdF3 is higher than 1,and that of LiF is lower than 1.
文摘Experimental studies on phase equilibria and liquidus temperature in the PbO-ZnO-CaO-SiO2-＂Fe2O3＂ system,with the mass ratios of CaO/SiO2=1-1.6 and Fe/SiO2= 1.3-1.7,and 40% PbO and 8% ZnO,were carried out between 1273 and 1573 K.Slags were equilibrated at 1273 to 1573 K and cooled rapidly by quenching.The XRD and SEM-EDS results showed that the slag compositions are in the franklinite primary phase field.Calcium and lead silicates are formed between 1373 and 1473 K.The Ca/Pb silicate and magnetoplumbite phases are partially formed by an incongruent reaction.The experimental and thermodynamical results showed that the liquidus increased by increasing CaO/SiO2 mass ratio and decreasing Fe/SiO2 mass ratio.
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.
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.
