Metal Sm has been widely used in making Al–Sm magnet alloy materials. Conventional distillation technology to produce Sm has the disadvantages of low productivity, high costs, and pollution generation. The objective ...Metal Sm has been widely used in making Al–Sm magnet alloy materials. Conventional distillation technology to produce Sm has the disadvantages of low productivity, high costs, and pollution generation. The objective of this study was to develop a molten salt electrolyte system to produce Al–Sm alloy directly, with focus on the electrical conductivity and optimal operating conditions to minimize the energy consumption. The continuously varying cell constant(CVCC) technique was used to measure the conductivity for the Na3AlF6–AlF3–LiF–MgF2–Al2O3–Sm2O3electrolysis medium in the temperature range from 905 to 1055°C. The temperature(t) and the addition of Al2O3(W(Al2O3)), Sm2O3(W(Sm2O3)), and a combination of Al2O3and Sm2O3into the basic fluoride system were examined with respect to their effects on the conductivity(κ) and activation energy. The experimental results showed that the molten electrolyte conductivity increases with increasing temperature(t) and decreases with the addition of Al2O3or Sm2O3or both. We concluded that the optimal operation conditions for Al–Sm intermediate alloy production in the Na3AlF6–AlF3–LiF–MgF2–Al2O3–Sm2O3system are W(Al2O3) + W(Sm2O3) = 3wt%, W(Al2O3):W(Sm2O3) = 7:3, and a temperature of 965 to 995°C, which results in satisfactory conductivity, low fluoride evaporation losses, and low energy consumption.展开更多
The preparation techniques of Mg-mischmetal intermediate alloy and the effects of the mischmetal addition ranging from 0.45% to 1.04% on the microstructure and properties of AZ91D alloy prepared by die casting were in...The preparation techniques of Mg-mischmetal intermediate alloy and the effects of the mischmetal addition ranging from 0.45% to 1.04% on the microstructure and properties of AZ91D alloy prepared by die casting were investigated. The Mg-MM intermediate alloy was prepared by permanent mold casting and then was extruded into the bars. The microstructure and analytical studies were carried out using optical microscopy and differential scanning calorimetry (DSC). Testing results shows the Mg-MM intermediate alloy could melt easily down at die casting temperature of 680 ℃ that was lower than the melting point of lanthanum (918 ℃) and that of cerium (798 ℃). This was propitious to protection the alloy from the oxidation at high temperatures. Then magnesium alloy test bars were produced under conventional cold chamber die casting condition with addition of different weight of the Mg-MM intermediate alloy. Observation and analysis indicated that the microstructures of the alloy were refined and RE containing Al phase was formed with increasing RE addition. The data obtained by tensile tests showed that alloying with mischmetal improved the tensile property of the AZ91D magnesium die casting alloy at ambient temperature.展开更多
The standard heat treatment of cast nickel base superalloy K403 is the solid solution treatment of 1210℃/4h, air cooling. It is very difficult to meet the requirements of Aviation Standard HB5155, in which the stre...The standard heat treatment of cast nickel base superalloy K403 is the solid solution treatment of 1210℃/4h, air cooling. It is very difficult to meet the requirements of Aviation Standard HB5155, in which the stress rupture life at 750℃ and 645MPa is longer than 50h. The results showed that the intermediate temperature stress rupture properties impaired by treatment of 1210℃/4h were due to precipitation of too small γ′ phase(<0.2μm) in grains and absence of the secondary carbides at grain boundaries. Microstructure containing the intergranular M6C carbides with envelope of γ′ and the residual coarse γ′ was obtained by means of 1180℃/4h treatment, therefore the stress rupture life was obviously increased to meet the demand of HB5155. The effect of γ′ size was also discussed from the view point of deformation mechanism in this paper.展开更多
A TTT diagram for th ie precipitation formed at some intermediate temperatures through cooling from high lemperalure parenl phase in a Cu-27 27Zn-3.73Al allay is established by means of dilatormetric measurement.The m...A TTT diagram for th ie precipitation formed at some intermediate temperatures through cooling from high lemperalure parenl phase in a Cu-27 27Zn-3.73Al allay is established by means of dilatormetric measurement.The morphology and structure of transformation products formed at some intermediate tem peratures isothermally through cooling from high temperature parent phase and up-quenching from DO_(3) parent phase are studied by metallographic.X-ray and electron microscopy analyses.Three regions in the two separate C curves are obtained according to different morphology of precipitate:rod-like a,plate-like bainite and a rods,and bainite plates.Prolonged aging makes bainite plate change gradually into a whose lattice parameters are no different from that of a formed equilibriumly from parent phase.The structure is almost orthorhombic long period structure for bainites formed from B_(2) and DO_(3) parent phase,but monoclinic for martensite from DO_(3).They correspond to the overlapping and separating of(1210)and(2010)diffraction peaks respectively,showing the lower degree of ordering in bainite.展开更多
For the purpose of improving the defects of the conventional friction welding method, the new friction welding technology has been examined. That is, the aim of the study is producing the joint of dissimilar materials...For the purpose of improving the defects of the conventional friction welding method, the new friction welding technology has been examined. That is, the aim of the study is producing the joint of dissimilar materials evaluated to be difficult for friction welding and non-round shape joints. In this process, after the intermediate material generates the independent friction heat on every side of the specimens, it is removed instantaneously and upset process begins to weld the specimens for a joint. In this study, similar joint of A2017 aluminum alloy and one of S45C steel were examined. On the other hand, thermal elastic-plastic stress analysis by the finite element method was carried out using ANSYS mechanical.展开更多
Understanding the corrosion behavior of high entropy alloys(HEAs)after intermediate temperature fatigue is critical to prevent their catastrophic failures from the reduction of corrosion resistance.Here,we investigate...Understanding the corrosion behavior of high entropy alloys(HEAs)after intermediate temperature fatigue is critical to prevent their catastrophic failures from the reduction of corrosion resistance.Here,we investigated the corrosion behavior of CrMnFeCoNi HEA after 500℃ fatigue test with strain amplitudes of 0.2%and 0.5%.The intermediate temperature fatigue induced two types of precipitates,which were determined as Cr-richσphase and NiMn-rich L10 phase.Higher strain amplitude not only promoted precipitates generations but also spread the nucleation sites from intergranular to both intergranular and intragranular.Furthermore,we found that the deterioration in corrosion resistance of the alloy was derived from the increase of precipitates,which destroyed the stability of the passive film.The above results revealed that intermediate temperature fatigue impaired the stabilization of the solid solution state and subsequent corrosion resistance of CrMnFeCoNi HEA,where the higher strain amplitude led to more precipitates and more severe corrosion.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 51564015 and 51674126)the Graduate Student Innovation Special Fund of Jiangxi Province (YC2015-B064)+2 种基金the Science and Technology Research Project of Jiangxi Department of Education (GJJ150664)the Outstanding Doctoral Dissertation Project Fund of JXUST (YB2016007)the Scientific Research Fund of JXUST (NSFJ2014-G09)
文摘Metal Sm has been widely used in making Al–Sm magnet alloy materials. Conventional distillation technology to produce Sm has the disadvantages of low productivity, high costs, and pollution generation. The objective of this study was to develop a molten salt electrolyte system to produce Al–Sm alloy directly, with focus on the electrical conductivity and optimal operating conditions to minimize the energy consumption. The continuously varying cell constant(CVCC) technique was used to measure the conductivity for the Na3AlF6–AlF3–LiF–MgF2–Al2O3–Sm2O3electrolysis medium in the temperature range from 905 to 1055°C. The temperature(t) and the addition of Al2O3(W(Al2O3)), Sm2O3(W(Sm2O3)), and a combination of Al2O3and Sm2O3into the basic fluoride system were examined with respect to their effects on the conductivity(κ) and activation energy. The experimental results showed that the molten electrolyte conductivity increases with increasing temperature(t) and decreases with the addition of Al2O3or Sm2O3or both. We concluded that the optimal operation conditions for Al–Sm intermediate alloy production in the Na3AlF6–AlF3–LiF–MgF2–Al2O3–Sm2O3system are W(Al2O3) + W(Sm2O3) = 3wt%, W(Al2O3):W(Sm2O3) = 7:3, and a temperature of 965 to 995°C, which results in satisfactory conductivity, low fluoride evaporation losses, and low energy consumption.
基金the National Key Technology R&D Program for the 11th Five-Year Plan(2006BAE04B01 ,2006BAE04B04) the National Basic Research Program ("973") of China (2007CB613705)
文摘The preparation techniques of Mg-mischmetal intermediate alloy and the effects of the mischmetal addition ranging from 0.45% to 1.04% on the microstructure and properties of AZ91D alloy prepared by die casting were investigated. The Mg-MM intermediate alloy was prepared by permanent mold casting and then was extruded into the bars. The microstructure and analytical studies were carried out using optical microscopy and differential scanning calorimetry (DSC). Testing results shows the Mg-MM intermediate alloy could melt easily down at die casting temperature of 680 ℃ that was lower than the melting point of lanthanum (918 ℃) and that of cerium (798 ℃). This was propitious to protection the alloy from the oxidation at high temperatures. Then magnesium alloy test bars were produced under conventional cold chamber die casting condition with addition of different weight of the Mg-MM intermediate alloy. Observation and analysis indicated that the microstructures of the alloy were refined and RE containing Al phase was formed with increasing RE addition. The data obtained by tensile tests showed that alloying with mischmetal improved the tensile property of the AZ91D magnesium die casting alloy at ambient temperature.
文摘The standard heat treatment of cast nickel base superalloy K403 is the solid solution treatment of 1210℃/4h, air cooling. It is very difficult to meet the requirements of Aviation Standard HB5155, in which the stress rupture life at 750℃ and 645MPa is longer than 50h. The results showed that the intermediate temperature stress rupture properties impaired by treatment of 1210℃/4h were due to precipitation of too small γ′ phase(<0.2μm) in grains and absence of the secondary carbides at grain boundaries. Microstructure containing the intergranular M6C carbides with envelope of γ′ and the residual coarse γ′ was obtained by means of 1180℃/4h treatment, therefore the stress rupture life was obviously increased to meet the demand of HB5155. The effect of γ′ size was also discussed from the view point of deformation mechanism in this paper.
基金supported by the National Natural Science Foundation
文摘A TTT diagram for th ie precipitation formed at some intermediate temperatures through cooling from high lemperalure parenl phase in a Cu-27 27Zn-3.73Al allay is established by means of dilatormetric measurement.The morphology and structure of transformation products formed at some intermediate tem peratures isothermally through cooling from high temperature parent phase and up-quenching from DO_(3) parent phase are studied by metallographic.X-ray and electron microscopy analyses.Three regions in the two separate C curves are obtained according to different morphology of precipitate:rod-like a,plate-like bainite and a rods,and bainite plates.Prolonged aging makes bainite plate change gradually into a whose lattice parameters are no different from that of a formed equilibriumly from parent phase.The structure is almost orthorhombic long period structure for bainites formed from B_(2) and DO_(3) parent phase,but monoclinic for martensite from DO_(3).They correspond to the overlapping and separating of(1210)and(2010)diffraction peaks respectively,showing the lower degree of ordering in bainite.
文摘For the purpose of improving the defects of the conventional friction welding method, the new friction welding technology has been examined. That is, the aim of the study is producing the joint of dissimilar materials evaluated to be difficult for friction welding and non-round shape joints. In this process, after the intermediate material generates the independent friction heat on every side of the specimens, it is removed instantaneously and upset process begins to weld the specimens for a joint. In this study, similar joint of A2017 aluminum alloy and one of S45C steel were examined. On the other hand, thermal elastic-plastic stress analysis by the finite element method was carried out using ANSYS mechanical.
基金the National Natural Science Foundation of China(Nos.52201072,12204143 and 52101013)the Natural Science Foundation of Hebei Province(No.E2020202009)+3 种基金the Technology Project of Hebei Education Department(No.QN2020150)the China Postdoctoral Science Foundation(No.2020M680843)the Central Funds Guiding the Local Science and Technology Development of Hebei Province(No.226Z1001G)the Central Funds Guiding the Local Science and Technology Development of Hebei Province(No.226Z1012G).
文摘Understanding the corrosion behavior of high entropy alloys(HEAs)after intermediate temperature fatigue is critical to prevent their catastrophic failures from the reduction of corrosion resistance.Here,we investigated the corrosion behavior of CrMnFeCoNi HEA after 500℃ fatigue test with strain amplitudes of 0.2%and 0.5%.The intermediate temperature fatigue induced two types of precipitates,which were determined as Cr-richσphase and NiMn-rich L10 phase.Higher strain amplitude not only promoted precipitates generations but also spread the nucleation sites from intergranular to both intergranular and intragranular.Furthermore,we found that the deterioration in corrosion resistance of the alloy was derived from the increase of precipitates,which destroyed the stability of the passive film.The above results revealed that intermediate temperature fatigue impaired the stabilization of the solid solution state and subsequent corrosion resistance of CrMnFeCoNi HEA,where the higher strain amplitude led to more precipitates and more severe corrosion.
