The microstructural evolution of pearlite during severe cold rolling in Fe-0.8C binary alloy and Fe-1Mn-0.8C ternary alloys was investigated by using SEM, TEM and XRD etc. The results show that the deformed pearlite c...The microstructural evolution of pearlite during severe cold rolling in Fe-0.8C binary alloy and Fe-1Mn-0.8C ternary alloys was investigated by using SEM, TEM and XRD etc. The results show that the deformed pearlite consists of irregularly bent lamella, coarse lamella with shear-band and fine lamella. As the rolling reduction increases, the proportion of fine lamella increases. The strong plastic deformation, amorphization and dissolution of cementite take place during the severe cold rolling. The maximum carbon content in ferrite reaches 0.15 mass% after 90% cold rolling.展开更多
The viscosities of liquid Fe-4.30C and Fe-4.30C-Ce alloys were measured by oscillating crucible viscometer. The results show that viscosity of Fe-4.30C alloy changes from 5.50 to 8.30 MPa·s when the liquid is coo...The viscosities of liquid Fe-4.30C and Fe-4.30C-Ce alloys were measured by oscillating crucible viscometer. The results show that viscosity of Fe-4.30C alloy changes from 5.50 to 8.30 MPa·s when the liquid is cooled from 1425 ℃ to the melting point. The abnormity of viscosity of Fe-4.30C alloy near the melting point is reasonable due to the formation of graphite. The addition of cerium especially with content higher than 0.21% causes an evidently decrease in viscosity for eutectic alloy resulting from increase of free volume and size decrease of atom cluster in the liquids. It can be concended that the existence of C-Ce compound contributes to the discontinuous of viscosity at 1340～1370 ℃ for the Fe-4.30C-Ce alloy by experinments with differential scanning calorimeter.展开更多
Based on the classic diffusion controlled nucleation and goth theory, the sympathatic nucleation- ledgewise growth mechanism of bainite was studied theoretically for low carbon Fe-C alloys. The rationality of the occu...Based on the classic diffusion controlled nucleation and goth theory, the sympathatic nucleation- ledgewise growth mechanism of bainite was studied theoretically for low carbon Fe-C alloys. The rationality of the occurrence of sympathetic nucleation on the terraces of ledges compating with lateral ledge growth and other sites nucleation was demonstrated by the present work quantita- tively The calculations indicated that low reaction temperatures and high carbon concentrations may favor the sympathetic nucleation, thus accounting for the formation of multilayer structures of bainite.展开更多
The growth of bainitic ferrite is a couple process of the shear transformation of Fe atoms with the diffusion of C atoms.The diffusion growth of the ferrite is impossible when the tempera- ture is below 400℃,and the ...The growth of bainitic ferrite is a couple process of the shear transformation of Fe atoms with the diffusion of C atoms.The diffusion growth of the ferrite is impossible when the tempera- ture is below 400℃,and the paraequilibrium shear growth may occur at the temperature be- low 550℃.This paraequilibrium shear growth model explains the overlap of the bainites created from two growth mechanisms at 400—550℃.展开更多
By using the melt spinning techniques, the Fe63Co32Gd5 alloy ribbons with 15-50 m in thickness and 3-7 mm in width were prepared at the wheel speeds of 15, 20, 25 and 35 m/s. The rapid solidification microstructures w...By using the melt spinning techniques, the Fe63Co32Gd5 alloy ribbons with 15-50 m in thickness and 3-7 mm in width were prepared at the wheel speeds of 15, 20, 25 and 35 m/s. The rapid solidification microstructures were characterized by three layers, the middle layer of which reaches 80% thickness and forms the column grain of(Fe,Co) solid with Gd solution. Grain refinement takes place with the increase of the wheel speed. And after 0.5 h heat treatment at 823 K, the ribbon thickness becomes larger and the middle layer of column grain is very orderly perpendicular to the ribbon plane. The coercivity of quenched and annealed Fe63Co32Gd5 ribbons both have the inflection point at the wheel speed of 20 m/s, and the tendency is declining. The heat treatment processing makes the coercivity become lower by improving the order of(Fe,Co)17Gd2 compound. The saturation magnetization of quenched ribbons increases with the enhancement of wheel speed, whereas that of annealed ones decreases firstly and then increases. The minimum coercivity is 5.30×103 A/m and the maximum saturation magnetization is 163.62 A·m2/kg, which is obtained in the conditions of the wheel speed of 35 m/s and 0.5 h heat treatment at the temperature of 823 K.展开更多
The effects of Co as a substituent for Ni on microstructure and electrochemical capacity of hydrogen storage alloys MI（NiCoMnAl）5.4 at -30- ＋80 ℃, in which the content of Co was 0, 1.31%, 2.63%, 3.94%, 5.25%, and ...The effects of Co as a substituent for Ni on microstructure and electrochemical capacity of hydrogen storage alloys MI（NiCoMnAl）5.4 at -30- ＋80 ℃, in which the content of Co was 0, 1.31%, 2.63%, 3.94%, 5.25%, and 6.56% （mass fraction）, respectively, were reported. All of the alloys were prepared by vacuum induction melting followed by melt-spinning. It is found that the electrochemical capacity of alloys at different temperature depends upon the compositions and preparation methods. The electrochemical capacity of alloys increases at higher temperature （40 - 80 ℃ ） and decreases at lower temperature （ - 30 - 0 ℃ ） with an increasing cobalt content. With an increasing temperature, melt-spinning is more favorable for improved capacity of the alloys than casting. Analyses of the charging/discharging potential curves illustrate that higher cobalt content and melt-spinning techniques are more effective to increase the capacity at higher temperature because of the higher hydrogen evolution potential. On the contrary, the capacity of alloys at lower temperature can be increased by decreasing cobalt content and casting, which is ascribed to higher hydrogen evolution potential and delayed hydrogen evolution reaction, as well as reduced potential drop in the charging/discharging process. XRD patterns confirm that all of the specimens present a single hexagonal CaCu5-type structure and an increased lattice parameters with increasing Co content. The FWHM of the main peak of melt-spun ribbons reduces because of more homogeneous composition and less lattice strain defects.展开更多
Seeking high-performance computing methods to solve the problem of a large amount of calculation,low calculation efficiency,and small simulation scale on the traditional single central processing unit (CPU) platform i...Seeking high-performance computing methods to solve the problem of a large amount of calculation,low calculation efficiency,and small simulation scale on the traditional single central processing unit (CPU) platform is of great value to the simulation study of micro-structure.In this study,based on the three-dimensional multi-phase-field model of KKSO coupling phase-field and solute field,the open computing language (OpenCL) + graphics processing unit (GPU) heterogeneous parallel computing technology is used to simulate the eutectoid growth of Fe-C alloy and the end growth process of pearlite under pure diffusion.The effects of initial supercooling and different diffusion coefficients on the growth morphology of lamellar pearlite were investigated.The results show that ferrite and cementite are perpendicular to the front of the solid-solid interface and are coupled and coordinated to grow,and there is no leading phase under the initial supercooling degree of 20 K.With the continuous increase of the initial supercooling degree (19 K-22 K),the morphology changes of the eutectoid layer are as follows:cementite stops growing → slice amplitude increases → regular symmetric growth → oblique growth → layer merge.With the increase of the diffusion coefficient from 3×10^(-13) m^(2)·s^(-1) to 15×10^(-13) m^(2)·s^(-1),the growth rate of the microstructure of the lamellar pearlite increases linearly,and there is no obvious change in the frontal appearance of the pearlite.展开更多
The effect of wheel speed on microstructures of Ti-48%Ni (mole fraction) melt-spun ribbons was investigated by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy. When the wheel sp...The effect of wheel speed on microstructures of Ti-48%Ni (mole fraction) melt-spun ribbons was investigated by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy. When the wheel speed is 26 and 42 m/s, the as-spun ribbons are completely crystallized to the Ti-Ni B2 phase. The Ti-rich plate precipitates lying on {100} planes are observed in the as-spun ribbon fabricated with a wheel speed of 26 m/s. The spherical Ti2Ni precipitates are observed at grain boundaries in the as-spun ribbons fabricated with a wheel speed of 42 m/s. Amorphous and B2 phases coexist in the as-spun ribbon fabricated with a wheel speed of 52 m/s. The uniformity of grain size in heat treated ribbons decreases with increasing wheel speed.展开更多
The microstructure of CosoNi22Ga28 ribbon with the L10 structure is examined. The band-like morphology is observed. These bands with the width in a range of 40-200 nm appear along the transverse direction of the ribbo...The microstructure of CosoNi22Ga28 ribbon with the L10 structure is examined. The band-like morphology is observed. These bands with the width in a range of 40-200 nm appear along the transverse direction of the ribbon. The giant magnetoimpedance （GMI） effect in this alloy is measured. The results show that Co5oNi22Ga28 exhibits a sharp peak of the GAI effect. The maximum GAH ratio up to 360% is detected. The GMI effect measured versus temperature shows large jumps of the magnetoimpedance amplitude at the reversal martensitic transformation temperature 240℃ and Curie temperature 375℃C respectively. The jump ratios of the magnetoimpedance amplitude examined at these temperatures are about 5 and 10, respectively.展开更多
Macrosegregation in Fe-0.8 wt pct C alloy solidifying with equiaxed morphology was numerically simulated. Based on a two-phase volumetric averaging approach, heat transfer, melt convection, composition distribution, n...Macrosegregation in Fe-0.8 wt pct C alloy solidifying with equiaxed morphology was numerically simulated. Based on a two-phase volumetric averaging approach, heat transfer, melt convection, composition distribution, nucleation and grain evolution on the system scale were described. A weak-coupling numerical procedure was designed to solve conservation equations. Simulations were conducted to study the effects of cooling rate and nuclei density on the macrosegregation pattern. The relative infliJence of thermal buoyancy- and solutal buoyancy-induced flows on macrosegregation was identified. Calculated results indicate that a higher cooling rate establishes a more homogeneous composition. More uniform solute distributions are formed with increasing nuclei density. In addition, it is noted that the direction of channel segregates depends on the relative strength of thermal and solutal buoyancy forces.展开更多
The liquid structure of Fe-4.30C and Fe-4.30C-0.21Ce alloys was studied by high temperature X-ray diffractometer. The results show that for Fe-C alloy the nearest neighbor distance of the eutectic alloy is 0.259-0.260...The liquid structure of Fe-4.30C and Fe-4.30C-0.21Ce alloys was studied by high temperature X-ray diffractometer. The results show that for Fe-C alloy the nearest neighbor distance of the eutectic alloy is 0.259-0.260 nm at the temperature range of 1200-1400℃, which increases to 0.269-0.271 nm with the addition of 0.21% (mass fraction) Ce in the Fe-C alloy at the same temperature range. There is a pre-peak at Q = 15.5 nm-1 on the original intensity curve and structure factor S(Q) of the liquid Fe-4.30C-0.21Ce alloy, which was caused by the Ce atoms in the C-Ce clusters. Combined with the shared face, the tetragonal structure can meet the requirement for the distance of Ce-Ce atoms. It also shows that the cluster size in the liquid Fe-4.30C-0.21Ce alloy increases with the decreasing temperature.展开更多
The electrical transport properties of (Ni0.8Nb0.2)100-xZrx (x = 30, 40 and 50) amorphous ribbons and hydrogen charged specimens were investigated. The amorphous ribbons indicated a negative coefficient in the tempera...The electrical transport properties of (Ni0.8Nb0.2)100-xZrx (x = 30, 40 and 50) amorphous ribbons and hydrogen charged specimens were investigated. The amorphous ribbons indicated a negative coefficient in the temperature dependence of their electrical resistivity as well as the typical transport properties of the amorphous alloys with comparatively high values of electrical resistivity, ρ. The normalized temperature coefficient of the resistivity (TCR ≡ 1/ρ300K·dρ/dT) tended to increase with increasing x in the temperature range of 100-300 K. These behaviors would suggest that the transport properties of the present amorphous ribbons were governed by temperature variation of the Debye-Waller factor, not by electron-phonon scattering. The hydrogen charged ribbons obtained by an electrochemical method also showed similar electrical resistivity behaviors as a function of the temperature. However, TCR of x = 40 with hydrogen charged ribbon, in which the amount of absorbed hydrogen was about 14 at%, increased about three times more than that of the pre-charged amorphous ribbon.展开更多
基金The financial support of the Iron and Alloy Institute of Japan is gratefully acknowledged.One of the authors(Wantang Fu)appreciates the support from the National Natural Science Foundation of China(No.50271061).
文摘The microstructural evolution of pearlite during severe cold rolling in Fe-0.8C binary alloy and Fe-1Mn-0.8C ternary alloys was investigated by using SEM, TEM and XRD etc. The results show that the deformed pearlite consists of irregularly bent lamella, coarse lamella with shear-band and fine lamella. As the rolling reduction increases, the proportion of fine lamella increases. The strong plastic deformation, amorphization and dissolution of cementite take place during the severe cold rolling. The maximum carbon content in ferrite reaches 0.15 mass% after 90% cold rolling.
文摘The viscosities of liquid Fe-4.30C and Fe-4.30C-Ce alloys were measured by oscillating crucible viscometer. The results show that viscosity of Fe-4.30C alloy changes from 5.50 to 8.30 MPa·s when the liquid is cooled from 1425 ℃ to the melting point. The abnormity of viscosity of Fe-4.30C alloy near the melting point is reasonable due to the formation of graphite. The addition of cerium especially with content higher than 0.21% causes an evidently decrease in viscosity for eutectic alloy resulting from increase of free volume and size decrease of atom cluster in the liquids. It can be concended that the existence of C-Ce compound contributes to the discontinuous of viscosity at 1340～1370 ℃ for the Fe-4.30C-Ce alloy by experinments with differential scanning calorimeter.
文摘Based on the classic diffusion controlled nucleation and goth theory, the sympathatic nucleation- ledgewise growth mechanism of bainite was studied theoretically for low carbon Fe-C alloys. The rationality of the occurrence of sympathetic nucleation on the terraces of ledges compating with lateral ledge growth and other sites nucleation was demonstrated by the present work quantita- tively The calculations indicated that low reaction temperatures and high carbon concentrations may favor the sympathetic nucleation, thus accounting for the formation of multilayer structures of bainite.
文摘The growth of bainitic ferrite is a couple process of the shear transformation of Fe atoms with the diffusion of C atoms.The diffusion growth of the ferrite is impossible when the tempera- ture is below 400℃,and the paraequilibrium shear growth may occur at the temperature be- low 550℃.This paraequilibrium shear growth model explains the overlap of the bainites created from two growth mechanisms at 400—550℃.
基金Projects(51271149,50901060)supported by the National Natural Science Foundation of ChinaProject(NPU-310201401007JCY01007)supported by the Nothwestern Polytechnical University(NPU)Foundations for Fundamental Research,ChinaProject(2012-0009451)supported by the National Research Foundation of Korea
文摘By using the melt spinning techniques, the Fe63Co32Gd5 alloy ribbons with 15-50 m in thickness and 3-7 mm in width were prepared at the wheel speeds of 15, 20, 25 and 35 m/s. The rapid solidification microstructures were characterized by three layers, the middle layer of which reaches 80% thickness and forms the column grain of(Fe,Co) solid with Gd solution. Grain refinement takes place with the increase of the wheel speed. And after 0.5 h heat treatment at 823 K, the ribbon thickness becomes larger and the middle layer of column grain is very orderly perpendicular to the ribbon plane. The coercivity of quenched and annealed Fe63Co32Gd5 ribbons both have the inflection point at the wheel speed of 20 m/s, and the tendency is declining. The heat treatment processing makes the coercivity become lower by improving the order of(Fe,Co)17Gd2 compound. The saturation magnetization of quenched ribbons increases with the enhancement of wheel speed, whereas that of annealed ones decreases firstly and then increases. The minimum coercivity is 5.30×103 A/m and the maximum saturation magnetization is 163.62 A·m2/kg, which is obtained in the conditions of the wheel speed of 35 m/s and 0.5 h heat treatment at the temperature of 823 K.
文摘The effects of Co as a substituent for Ni on microstructure and electrochemical capacity of hydrogen storage alloys MI（NiCoMnAl）5.4 at -30- ＋80 ℃, in which the content of Co was 0, 1.31%, 2.63%, 3.94%, 5.25%, and 6.56% （mass fraction）, respectively, were reported. All of the alloys were prepared by vacuum induction melting followed by melt-spinning. It is found that the electrochemical capacity of alloys at different temperature depends upon the compositions and preparation methods. The electrochemical capacity of alloys increases at higher temperature （40 - 80 ℃ ） and decreases at lower temperature （ - 30 - 0 ℃ ） with an increasing cobalt content. With an increasing temperature, melt-spinning is more favorable for improved capacity of the alloys than casting. Analyses of the charging/discharging potential curves illustrate that higher cobalt content and melt-spinning techniques are more effective to increase the capacity at higher temperature because of the higher hydrogen evolution potential. On the contrary, the capacity of alloys at lower temperature can be increased by decreasing cobalt content and casting, which is ascribed to higher hydrogen evolution potential and delayed hydrogen evolution reaction, as well as reduced potential drop in the charging/discharging process. XRD patterns confirm that all of the specimens present a single hexagonal CaCu5-type structure and an increased lattice parameters with increasing Co content. The FWHM of the main peak of melt-spun ribbons reduces because of more homogeneous composition and less lattice strain defects.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51661020,11504149 and 11364024)the Postdoctoral Science Foundation of China(Grant No.2014M560371)the Funds for Distinguished Young Scientists of Lanzhou University of Technology(Grant No.J201304)。
文摘Seeking high-performance computing methods to solve the problem of a large amount of calculation,low calculation efficiency,and small simulation scale on the traditional single central processing unit (CPU) platform is of great value to the simulation study of micro-structure.In this study,based on the three-dimensional multi-phase-field model of KKSO coupling phase-field and solute field,the open computing language (OpenCL) + graphics processing unit (GPU) heterogeneous parallel computing technology is used to simulate the eutectoid growth of Fe-C alloy and the end growth process of pearlite under pure diffusion.The effects of initial supercooling and different diffusion coefficients on the growth morphology of lamellar pearlite were investigated.The results show that ferrite and cementite are perpendicular to the front of the solid-solid interface and are coupled and coordinated to grow,and there is no leading phase under the initial supercooling degree of 20 K.With the continuous increase of the initial supercooling degree (19 K-22 K),the morphology changes of the eutectoid layer are as follows:cementite stops growing → slice amplitude increases → regular symmetric growth → oblique growth → layer merge.With the increase of the diffusion coefficient from 3×10^(-13) m^(2)·s^(-1) to 15×10^(-13) m^(2)·s^(-1),the growth rate of the microstructure of the lamellar pearlite increases linearly,and there is no obvious change in the frontal appearance of the pearlite.
文摘The effect of wheel speed on microstructures of Ti-48%Ni (mole fraction) melt-spun ribbons was investigated by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy. When the wheel speed is 26 and 42 m/s, the as-spun ribbons are completely crystallized to the Ti-Ni B2 phase. The Ti-rich plate precipitates lying on {100} planes are observed in the as-spun ribbon fabricated with a wheel speed of 26 m/s. The spherical Ti2Ni precipitates are observed at grain boundaries in the as-spun ribbons fabricated with a wheel speed of 42 m/s. Amorphous and B2 phases coexist in the as-spun ribbon fabricated with a wheel speed of 52 m/s. The uniformity of grain size in heat treated ribbons decreases with increasing wheel speed.
基金Supported by the National High Technology Research and Development Programme of China under Grant No 2003AA327010, and the National Natural Science Foundation of China under Grant No 60271028.
文摘The microstructure of CosoNi22Ga28 ribbon with the L10 structure is examined. The band-like morphology is observed. These bands with the width in a range of 40-200 nm appear along the transverse direction of the ribbon. The giant magnetoimpedance （GMI） effect in this alloy is measured. The results show that Co5oNi22Ga28 exhibits a sharp peak of the GAI effect. The maximum GAH ratio up to 360% is detected. The GMI effect measured versus temperature shows large jumps of the magnetoimpedance amplitude at the reversal martensitic transformation temperature 240℃ and Curie temperature 375℃C respectively. The jump ratios of the magnetoimpedance amplitude examined at these temperatures are about 5 and 10, respectively.
基金support from the Innovative Scientific-Research Project of Institute of Metal Research,CAS under grant No.KGCXZ-YW-206the Post-Doctor Foundation for China undergrant No.20080431162the Foundation of Harbin University of Science and Technology,China under grant No.20081526
文摘Macrosegregation in Fe-0.8 wt pct C alloy solidifying with equiaxed morphology was numerically simulated. Based on a two-phase volumetric averaging approach, heat transfer, melt convection, composition distribution, nucleation and grain evolution on the system scale were described. A weak-coupling numerical procedure was designed to solve conservation equations. Simulations were conducted to study the effects of cooling rate and nuclei density on the macrosegregation pattern. The relative infliJence of thermal buoyancy- and solutal buoyancy-induced flows on macrosegregation was identified. Calculated results indicate that a higher cooling rate establishes a more homogeneous composition. More uniform solute distributions are formed with increasing nuclei density. In addition, it is noted that the direction of channel segregates depends on the relative strength of thermal and solutal buoyancy forces.
基金This work was supported by the National Natural Science Foundation of China (No.59871025).
文摘The liquid structure of Fe-4.30C and Fe-4.30C-0.21Ce alloys was studied by high temperature X-ray diffractometer. The results show that for Fe-C alloy the nearest neighbor distance of the eutectic alloy is 0.259-0.260 nm at the temperature range of 1200-1400℃, which increases to 0.269-0.271 nm with the addition of 0.21% (mass fraction) Ce in the Fe-C alloy at the same temperature range. There is a pre-peak at Q = 15.5 nm-1 on the original intensity curve and structure factor S(Q) of the liquid Fe-4.30C-0.21Ce alloy, which was caused by the Ce atoms in the C-Ce clusters. Combined with the shared face, the tetragonal structure can meet the requirement for the distance of Ce-Ce atoms. It also shows that the cluster size in the liquid Fe-4.30C-0.21Ce alloy increases with the decreasing temperature.
文摘The electrical transport properties of (Ni0.8Nb0.2)100-xZrx (x = 30, 40 and 50) amorphous ribbons and hydrogen charged specimens were investigated. The amorphous ribbons indicated a negative coefficient in the temperature dependence of their electrical resistivity as well as the typical transport properties of the amorphous alloys with comparatively high values of electrical resistivity, ρ. The normalized temperature coefficient of the resistivity (TCR ≡ 1/ρ300K·dρ/dT) tended to increase with increasing x in the temperature range of 100-300 K. These behaviors would suggest that the transport properties of the present amorphous ribbons were governed by temperature variation of the Debye-Waller factor, not by electron-phonon scattering. The hydrogen charged ribbons obtained by an electrochemical method also showed similar electrical resistivity behaviors as a function of the temperature. However, TCR of x = 40 with hydrogen charged ribbon, in which the amount of absorbed hydrogen was about 14 at%, increased about three times more than that of the pre-charged amorphous ribbon.
