Ag/Ni Multilayers were prefabricated by Accumulative Roll-Bonding(ARB),with an average layer thickness ranging 20-100 nm.The Ag-45.8wt%Ni alloys were annealed under 31.2T high magnetic field to study its effect on mic...Ag/Ni Multilayers were prefabricated by Accumulative Roll-Bonding(ARB),with an average layer thickness ranging 20-100 nm.The Ag-45.8wt%Ni alloys were annealed under 31.2T high magnetic field to study its effect on microstructure and performance.31.2T high magnetic field significantly suppressed the coarsening of layer structure during annealing,the magnetic field parallel to the layer has a larger suppression effect.As the annealing temperature increased,the resistivity of Ag/Ni multilayers increased,and the hardness decreased.The case of perpendicular high magnetic field has the largest resistivity and the largest hardness,compared with the other two cases.The hysteresis loops shows that Ag-Ni has a hard ferromagnetic property.The case of parallel magnetic field has the largest coercivity about 90Gs.展开更多
The effect of electromagnetic stirring(EMS)on the distribution of Nb particles in solidified microstructure of a Cu-5wt%Nb alloy were studied.In this paper,we have Cu-5wt%Nb alloy remelted and solidified with or witho...The effect of electromagnetic stirring(EMS)on the distribution of Nb particles in solidified microstructure of a Cu-5wt%Nb alloy were studied.In this paper,we have Cu-5wt%Nb alloy remelted and solidified with or without electromagnetic stirring,to study the effect of EMS on the distribution of Nb phase and the hardness of ingots.The 300A/16Hz EMS has refined the mircostrucrure of Cu-5%Nb alloy,with smaller particles sizes and larger amounts,and is benefit to the homogenous distribution of particles.The fitted lognormal distribution of particles diameter that in case without or with EMS are compared,and the EMS case has the highest frequency percentage in the range of smaller size. EMS considerably increased the hardness of Cu-5%Nb alloy ingot.展开更多
The microstructure of ripening processed Cu-15%Cr alloys and deformed samples were examined under a 12T high magnetic field.The high magnetic field has accelerated the Ostwald Ripening process of Cr phase,the Cr-rich ...The microstructure of ripening processed Cu-15%Cr alloys and deformed samples were examined under a 12T high magnetic field.The high magnetic field has accelerated the Ostwald Ripening process of Cr phase,the Cr-rich particles in 12T HMF case are coarser compared with 0T case.The 12T high magnetic field increased the peak strength of Cu(111)crystal plane and Cr(110)crystal plane,and appeared to has an orientation effect.Compared with the 0T case, the 12T high magnetic field case decreased the tensile strength and hardness.展开更多
A simple but effective process to fabricate the bulk and practical Fe-Ga alloys at low fields is proposed just by applying a static magnetic field to their solidification process.We have introduced a static 1-T magnet...A simple but effective process to fabricate the bulk and practical Fe-Ga alloys at low fields is proposed just by applying a static magnetic field to their solidification process.We have introduced a static 1-T magnetic field to solidify the Fe-17%Ga alloys.The results indicate that the magnetostriction of a polycrystalline textured Fe-17%Ga alloy is increased about threefold by solidifying with a 1-T magnetic field compared to that without a magnetic field.This large magnetostiction could be attributed to the increasing volume fraction and the strong texture of the disordered α-Fe phases. The systematic analysis shows that they are originated from the undercooling and orientation effects induced by the imposed magnetic field during the solidification process.展开更多
Magnetic field has great impact on the second phase distribution in metal solidification process.In this paper, we have Cu-20wt%Nb alloy remelted and solidified with or without the imposition of magnetic field,to stud...Magnetic field has great impact on the second phase distribution in metal solidification process.In this paper, we have Cu-20wt%Nb alloy remelted and solidified with or without the imposition of magnetic field,to study the effect of magnetic field on the distribution of Nb phase and the properties of deformed wires.Magnetic field has an inhibiting effect on the ripening process of Nb particles,and is benefit to the prolongation of Nb-rich phase in deformed wires.Both the ultimate tensile strength and conductivity in 1 T case is larger than that in 0 T case.展开更多
The effects of different electromagnetic stirring currents on the microstructures of Cu-6%Ag alloys by applying electromagnetic stirring during solidification process are investigated experimentally.The results show t...The effects of different electromagnetic stirring currents on the microstructures of Cu-6%Ag alloys by applying electromagnetic stirring during solidification process are investigated experimentally.The results show that with increasing stirring current,the macro-microstructural grains of the Cu-Ag alloys are refined gradually and evenly distributed.The observation on the microstructure indicates that the primary Cu dendrites become shorter and thicker,and the secondary dendrites are underdeveloped with small-sized equiaxed dendrites with increasing current.Cu-6%Ag alloys solidified with electromagnetic stirring are drawn to the composite wires with different drawing ratios.The results show that their microstructures are refined along the drawing direction when the stirring current increases from 100 A to 200 A. As the current increases to 350 A,the microstructure is not changed obviously.Correspondingly,the tensile strength of Cu-6%Ag alloys increases and the conductivity reduces with increasing drawing rate.Cu-6%Ag alloys could get the better strength with stirring current of 200 A,which is consistent with the microstructural results.展开更多
The effect of rotary electromagnetic stirring(EMS)on the Cu grain size and Fe dendrites is investigated in this paper,in order to get a Cu-Fe alloy ingot with good quality.The macro-and micro-structures are observed b...The effect of rotary electromagnetic stirring(EMS)on the Cu grain size and Fe dendrites is investigated in this paper,in order to get a Cu-Fe alloy ingot with good quality.The macro-and micro-structures are observed by Leica-DMR optical microscope.The solidification structures of Cu-2 and 8wt.%Fe consist with finer equiaxed grains. The Cu grain size is most sensitive to the Fe content.EMS can't effectively improve the grain size for the Cu-Fe alloy. For ingot cooled without EMS,there are also many large Fe-rich particles distribute in the Cu-matrix,beside the Fe dendrites,because of the existence of metastable miscibility gap in the undercooled liquid state.And the Fe-rich phases are not found in the ingots with EMS,indicating the EMS can affect the undercooling of the liquid and further restrain the liquid phase separation.Under the EMS,the Fe dendrites break up into many smaller Fe fragments.And the size of Fe fragments decreases with the increasing stirring current.展开更多
Due to its excellent creep rupture strength and low cost,superalloy GH2984 has becoming a promising material to be used as heat exchanger in the prospective 700 oC fossil power plant.The mechanical strength,which is a...Due to its excellent creep rupture strength and low cost,superalloy GH2984 has becoming a promising material to be used as heat exchanger in the prospective 700 oC fossil power plant.The mechanical strength,which is a particularly important indicator for the superalloy,strongly depends on the grain size and crabide distribution.In current study,we have investigated the influence of a rotating magnetic field(RMF)on the solidified microstructures and tensile properties of superalloy GH2984.RMF has been applied to provide a forced convection within the solidifying melt.The melt stirring by a sufficiently high magnetic field provides homogeneous grain size and elements distribution in the sample volume.Meanwhile,yield strength is found to be effectively enhanced for the sample solidified under magnetic field.The result has demonstrated that the RMF method on the melt solidification process shows a promising perspective for refining the grains and promoting the mechanical strength of superalloy GH2984.展开更多
The microstructure evolution of Cu dendrites in Cu-6%Ag alloys by modified unidirectional solidification under a static magnetic field has been investigated experimentally and quantitatively.The results show that the ...The microstructure evolution of Cu dendrites in Cu-6%Ag alloys by modified unidirectional solidification under a static magnetic field has been investigated experimentally and quantitatively.The results show that the proeutectic Cu dendrites are finer when they are closer to the water-cooling copper mould and the unidirectional effect is more obvious,which is attributed to the higher solidification velocity.The quantitative analysis of the microstructure indicates that with increasing external magnetic flux density,the primary arms of the proeutectic Cu dendrites are refined and along a given direction.The analysis indicates that it is both the thermoelectromagnetic convection effect by the external magnetic field and the branch effect of the dendrites.展开更多
基金Item Sponsored by the National Natural Science Foundation of China[No.50901019]the Wuhan National High Magnetic Field Center[No.WHMFCKF2011007]+4 种基金the National Natural Science Foundation of China[No.51004038]the Fundamental Research Funds for the Central Universities[No.N100409009]National High-tech R&D Program of China[No.2007AA03Z519]China Postdoctoral Science Foundation[No.20100471458]the 111 Project of China(No.B07015)
文摘Ag/Ni Multilayers were prefabricated by Accumulative Roll-Bonding(ARB),with an average layer thickness ranging 20-100 nm.The Ag-45.8wt%Ni alloys were annealed under 31.2T high magnetic field to study its effect on microstructure and performance.31.2T high magnetic field significantly suppressed the coarsening of layer structure during annealing,the magnetic field parallel to the layer has a larger suppression effect.As the annealing temperature increased,the resistivity of Ag/Ni multilayers increased,and the hardness decreased.The case of perpendicular high magnetic field has the largest resistivity and the largest hardness,compared with the other two cases.The hysteresis loops shows that Ag-Ni has a hard ferromagnetic property.The case of parallel magnetic field has the largest coercivity about 90Gs.
基金Item Sponsored by the National Natural Science Foundation of China[No.50901019]the Fundamental Research Funds for the Central Universities[No.N100409009]+4 种基金the Wuhan National High Magnetic Field Center[No.WHMFCKF2011007]China Postdoctoral Science Foundation[No.20100471458]the National Natural Science Foundation of China[No.51004038]National High-tech R&D Program of China[No.2007AA03Z519]the 111 Project of China(No.B07015)
文摘The effect of electromagnetic stirring(EMS)on the distribution of Nb particles in solidified microstructure of a Cu-5wt%Nb alloy were studied.In this paper,we have Cu-5wt%Nb alloy remelted and solidified with or without electromagnetic stirring,to study the effect of EMS on the distribution of Nb phase and the hardness of ingots.The 300A/16Hz EMS has refined the mircostrucrure of Cu-5%Nb alloy,with smaller particles sizes and larger amounts,and is benefit to the homogenous distribution of particles.The fitted lognormal distribution of particles diameter that in case without or with EMS are compared,and the EMS case has the highest frequency percentage in the range of smaller size. EMS considerably increased the hardness of Cu-5%Nb alloy ingot.
基金Item Sponsored by National Natural Science Foundation of China(No.50901019)China Postdoctoral Science Foundation(No.20100471458)+4 种基金Fundamental Research Funds for the Central Universities(No.N100409009)Wuhan National High Magnetic Field Center(No.WHMFCKF2011007)National Natural Science Foundation of China(No.51004038)National High-tech R&D Program of China(No.2007AA03Z519)the 111 Project of China(No.B07015)
文摘The microstructure of ripening processed Cu-15%Cr alloys and deformed samples were examined under a 12T high magnetic field.The high magnetic field has accelerated the Ostwald Ripening process of Cr phase,the Cr-rich particles in 12T HMF case are coarser compared with 0T case.The 12T high magnetic field increased the peak strength of Cu(111)crystal plane and Cr(110)crystal plane,and appeared to has an orientation effect.Compared with the 0T case, the 12T high magnetic field case decreased the tensile strength and hardness.
基金Item Sponsored by the Fundamental Research Funds for the Central Universities[No.N090309002]the National Natural Science Foundation of China[No.51004038 and No.50901019]+2 种基金Wuhan National High Magnetic Field Center (Grant No.WHMFCKF2011007) National High Technology Research and Development Program of China (No.2007AA03Z519) the 111 Project of China (No.B07015)
文摘A simple but effective process to fabricate the bulk and practical Fe-Ga alloys at low fields is proposed just by applying a static magnetic field to their solidification process.We have introduced a static 1-T magnetic field to solidify the Fe-17%Ga alloys.The results indicate that the magnetostriction of a polycrystalline textured Fe-17%Ga alloy is increased about threefold by solidifying with a 1-T magnetic field compared to that without a magnetic field.This large magnetostiction could be attributed to the increasing volume fraction and the strong texture of the disordered α-Fe phases. The systematic analysis shows that they are originated from the undercooling and orientation effects induced by the imposed magnetic field during the solidification process.
基金Item Sponsored by the National Natural Science Foundation of China[No.50901019]the Fundamental Research Funds for the Central Universities[No.N100409009]+4 种基金the Wuhan National High Magnetic Field Center[No.WHMFCKF201107]China Postdoctoral Science Foundation[No.20100471458]the National Natural Science Foundation of China[No.51004038]National High-tech R&D Program of China[No.2007AA03Z519]the 111 Project of China (No.B07015)
文摘Magnetic field has great impact on the second phase distribution in metal solidification process.In this paper, we have Cu-20wt%Nb alloy remelted and solidified with or without the imposition of magnetic field,to study the effect of magnetic field on the distribution of Nb phase and the properties of deformed wires.Magnetic field has an inhibiting effect on the ripening process of Nb particles,and is benefit to the prolongation of Nb-rich phase in deformed wires.Both the ultimate tensile strength and conductivity in 1 T case is larger than that in 0 T case.
基金Item Sponsored by the National Natural Science Foundation of China[No.51004038 and No.50901019]the Fundamental Research Funds for the Central Universities[No.N090309002]+2 种基金Wuhan National High Magnetic Field Center (Grant No.WHMFCKF2011007) National High Technology Research and Development Program of China (No.2007AA03Z519) the 111 Project of China (No.B07015)
文摘The effects of different electromagnetic stirring currents on the microstructures of Cu-6%Ag alloys by applying electromagnetic stirring during solidification process are investigated experimentally.The results show that with increasing stirring current,the macro-microstructural grains of the Cu-Ag alloys are refined gradually and evenly distributed.The observation on the microstructure indicates that the primary Cu dendrites become shorter and thicker,and the secondary dendrites are underdeveloped with small-sized equiaxed dendrites with increasing current.Cu-6%Ag alloys solidified with electromagnetic stirring are drawn to the composite wires with different drawing ratios.The results show that their microstructures are refined along the drawing direction when the stirring current increases from 100 A to 200 A. As the current increases to 350 A,the microstructure is not changed obviously.Correspondingly,the tensile strength of Cu-6%Ag alloys increases and the conductivity reduces with increasing drawing rate.Cu-6%Ag alloys could get the better strength with stirring current of 200 A,which is consistent with the microstructural results.
基金Item Sponsored by National High Technology Research and Development Program of China (Grant No.2007AA03Z519) the National Natural Science Foundation of China (Grant No.51004038 and No.50901019) +1 种基金the Fundamental Research Funds for the Central Universities (Grant No.N100609004) the 111 Project of China (Grant No.B07015)
文摘The effect of rotary electromagnetic stirring(EMS)on the Cu grain size and Fe dendrites is investigated in this paper,in order to get a Cu-Fe alloy ingot with good quality.The macro-and micro-structures are observed by Leica-DMR optical microscope.The solidification structures of Cu-2 and 8wt.%Fe consist with finer equiaxed grains. The Cu grain size is most sensitive to the Fe content.EMS can't effectively improve the grain size for the Cu-Fe alloy. For ingot cooled without EMS,there are also many large Fe-rich particles distribute in the Cu-matrix,beside the Fe dendrites,because of the existence of metastable miscibility gap in the undercooled liquid state.And the Fe-rich phases are not found in the ingots with EMS,indicating the EMS can affect the undercooling of the liquid and further restrain the liquid phase separation.Under the EMS,the Fe dendrites break up into many smaller Fe fragments.And the size of Fe fragments decreases with the increasing stirring current.
基金Item Sponsored by National Natural Science Foundation of China[Nos.51104047 and 50834009]the Doctoral Fund of Ministry of Education of China[No.20100042120001]+1 种基金the Fundamental Research Funds for the Central Universities under Grants[Nos.N090309001 and N090109001]the 111 Project of China[No.B07015]
文摘Due to its excellent creep rupture strength and low cost,superalloy GH2984 has becoming a promising material to be used as heat exchanger in the prospective 700 oC fossil power plant.The mechanical strength,which is a particularly important indicator for the superalloy,strongly depends on the grain size and crabide distribution.In current study,we have investigated the influence of a rotating magnetic field(RMF)on the solidified microstructures and tensile properties of superalloy GH2984.RMF has been applied to provide a forced convection within the solidifying melt.The melt stirring by a sufficiently high magnetic field provides homogeneous grain size and elements distribution in the sample volume.Meanwhile,yield strength is found to be effectively enhanced for the sample solidified under magnetic field.The result has demonstrated that the RMF method on the melt solidification process shows a promising perspective for refining the grains and promoting the mechanical strength of superalloy GH2984.
基金Item Sponsored by the National Natural Science Foundation of China[No.51004038 and No.50901019]the Fundamental Research Funds for the Central Universities[No.N090309002]+2 种基金Wuhan National High Magnetic Field Center (Grant No.WHMFCKF2011007) National High Technology Research and Development Program of China (No.2007AA03Z519) the 111 Project of China (No.B07015)
文摘The microstructure evolution of Cu dendrites in Cu-6%Ag alloys by modified unidirectional solidification under a static magnetic field has been investigated experimentally and quantitatively.The results show that the proeutectic Cu dendrites are finer when they are closer to the water-cooling copper mould and the unidirectional effect is more obvious,which is attributed to the higher solidification velocity.The quantitative analysis of the microstructure indicates that with increasing external magnetic flux density,the primary arms of the proeutectic Cu dendrites are refined and along a given direction.The analysis indicates that it is both the thermoelectromagnetic convection effect by the external magnetic field and the branch effect of the dendrites.
