The effect of dissolved niobium on the eutectoid transformation behavior in near-eutectoid high-carbon steels has been studied.Dissolved niobium is important in the eutectoid transformation behavior.It increases the e...The effect of dissolved niobium on the eutectoid transformation behavior in near-eutectoid high-carbon steels has been studied.Dissolved niobium is important in the eutectoid transformation behavior.It increases the eutectoid carbon content significantly(by^0.0477% per 0.00001% dissolved niobium),increases the hardenability of steel markedly,yields finer,more uniform,polygonal proeutectoid ferrite,induces a transition in morphology of eutectoid cementite from lamellar to somewhat spheroidal,and increases the misorientation angle of pearlite colonies from being focused near 0°to near 60°.展开更多
A new hot-dip galvanizing method was employed on hot-rolled low carbon steel.The effects of Al contents on microstructure,micro-hardness and corrosion resistance of Zn-Al alloy coatings were systematically investigate...A new hot-dip galvanizing method was employed on hot-rolled low carbon steel.The effects of Al contents on microstructure,micro-hardness and corrosion resistance of Zn-Al alloy coatings were systematically investigated.Phase composition,microstructure and element distribution in Zn-Al alloy coatings were analyzed using X-ray diffraction(XRD)and electron probe micro analysis(EPMA),respectively.It is found that Al content(0.6-6.0 wt.%)in galvanizing zinc affects surface quality and adhesion between coatings and matrix in the newly developed method.In addition,with increasing Al content,micro-hardness significantly increased due to the increase in Zn-Al eutectoid phases.Potentiodynamic polarization and electrochemical impedance spectroscopy(EIS)also revealed that increase in Al plays a noticeable role in improving the corrosion resistance of Zn-Al alloy coatings.展开更多
Understandings of the effect of hot deformation parameters close to the practical production line on grain refinement are crucial for enhancing both the strength and toughness of future rail steels.In this work,the au...Understandings of the effect of hot deformation parameters close to the practical production line on grain refinement are crucial for enhancing both the strength and toughness of future rail steels.In this work,the austenite dynamic recrystallization(DRX)behaviors of a eutectoid pearlite rail steel were studied using a thermo-mechanical simulator with hot deformation parameters frequently employed in rail production lines.The single-pass hot deformation results reveal that the prior austenite grain sizes(PAGSs)for samples with different deformation reductions decrease initially with an increase in deformation temperature.However,once the deformation temperature is beyond a certain threshold,the PAGSs start to increase.It can be attributed to the rise in DRX volume fraction and the increase of DRX grain with deformation temperature,respectively.Three-pass hot deformation results show that the accumulated strain generated in the first and second deformation passes can increase the extent of DRX.In the case of complete DRX,PAGS is predominantly determined by the deformation temperature of the final pass.It suggests a strategic approach during industrial production where part of the deformation reduction in low temperature range can be shifted to the medium temperature range to release rolling mill loads.展开更多
Mssbauer spectrum and three dimensional atom probes(3DAP) were combined to investigate the mechanism of cementite dissolution in a cold-drawn eutectoid steel at a true strain of 2.89.The experimental results suggest...Mssbauer spectrum and three dimensional atom probes(3DAP) were combined to investigate the mechanism of cementite dissolution in a cold-drawn eutectoid steel at a true strain of 2.89.The experimental results suggest that the dislocations play an important role in the dissolution of the cementite by sweeping across the nano-scaled cementite,and transferring carbon from cementite to ferrite inducing cementite decomposition.The mechanism of cementite dissolution in the steel is discussed in association with the investigation of nonstoichiometric cementite structure after heavy deformation.展开更多
The warm compression tests were performed on the eutectoid steel to investigate the evolution of cementite morphology. Several processing parameters, such as temperature, strain rate and reduction, were changed to ana...The warm compression tests were performed on the eutectoid steel to investigate the evolution of cementite morphology. Several processing parameters, such as temperature, strain rate and reduction, were changed to analyze the effect of each parameter on spheroidization of cementite. The results showed that the warm compression promoted the fragmentize and the spheroidization of lamellar cementites. When the specimen was compressed with reduction of 50% at 700 ℃ and in the strain rate of 0.01 s-1, the excellent spheroidized cementite was obtained. The mechanism of fragmentation and spheroidization of lamellar cementites during compression was discussed by using transmission electron microscope. The formation of spheroidized cementite was related to the time of compression process. The fragmentize of lamellar cementites was due to the extension of sub-grain boundary in the cementite. The spheroidization of cementite depended on the diffusion of carbon atoms at the tip of bended and breakup cementite.展开更多
The paper presents in detail the effects of macroscopic graphite (Gr) particulates on the damping behavior of Zn-Al eutectoid alloy (Zn-Al). Macroscopic defects are graphite particulates with sizes of the order of a m...The paper presents in detail the effects of macroscopic graphite (Gr) particulates on the damping behavior of Zn-Al eutectoid alloy (Zn-Al). Macroscopic defects are graphite particulates with sizes of the order of a millimeter (0.5 mm and 1.0 mm). Macroscopic graphite particulate-reinforced Zn-Al eutectoid alloys were prepared by the air pressure infiltration process. The damping characterization was conducted on a multifunction internal friction apparatus (MFIFA). The internal friction (IF), as well as the relative dynamic modulus, was measured at different frequencies over the temperature range of 20 to 400°C. The damping capacity of the Zn-Al/Gr, with two different volume fractions of macroscopic graphite particulates, was compared with that of bulk Zn-Al eutectoid alloy. The damping capacity of the materials is shown to increase with increasing volume fraction of macroscopic graphite particulates. Two IF peaks were found in the IF-temperature curves. The first is a grain boundary peak, which is associated with the diffusive flux on a boundary between like phases, Al/Al. Its activation energy has been calculated to be 1.13±0.03 eV and the pre-exponential factor is 10?14 s in IF measurements. The second is a phase transition peak, which results from the transformation of Zn-Al eutectoid. In light of internal friction measurements and differential scanning calorimetry (DSC) experiments, its activation energy has been calculated to be 2.36±0.08 eV.展开更多
The influences of coiling temperature and cooling condition on structural transformation of the hot-rolled tertiary oxide scale formed under continuous cooling conditions were studied by thermal gravimetric analyzer. ...The influences of coiling temperature and cooling condition on structural transformation of the hot-rolled tertiary oxide scale formed under continuous cooling conditions were studied by thermal gravimetric analyzer. The fourth oxide scale formed under different conditions were classified and plotted. Because the oxide scale structure transformation is diffusion-controlled and the transformation law is similar to "C" curve, the eutectoid transformation nose temperature is 450 ℃. Under condition of low temperature and high cooling rate, ion diffusion behavior is restricted so that the eutectoid reaction is suppressed, resulting in that the fourth oxide scale is mainly made up of pre-eutectoid Fe304 and FeO without eu- tectoid products. From scale structure transition diagram, the eutectoid reaction process was affected by coiling temperature and cooling rate, leading to various scale structures.展开更多
Based on current theories of diffusion and creep cavity closure at high temperature, a theoretical analysis of phase transformation diffusion bonding for T8/T8 eutectoid steel is carried out. The diffusion bonding is ...Based on current theories of diffusion and creep cavity closure at high temperature, a theoretical analysis of phase transformation diffusion bonding for T8/T8 eutectoid steel is carried out. The diffusion bonding is mainly described as two-stage process: Ⅰ The interfacial cavity with shape change from diamond to cylinder.Ⅱ The radius of the cylindrical cavity are reduced and eliminated gradually. A new theoretical model is established for the process of transformation superplastic diffusion bonding (TSDB) on the basis of a theoretical model for isothermal superplastic diffusion. The model can predict the bonding quality which is affected by technological parameters, such as limit cycling temperature, the compressive stress, the numbers of thermal cycles and temperature cycling through the phase transformation in the thermal cycling and so on. Results show that the maximum temperature, the compressive stress, the numbers of thermal cycles and the rate of temperature changing speed in the thermal cycling have an important influence on TSDB process. Meanwhile, reasonable technological parameters chosen from theoretical analysis is in good agreement with those obtained from experimental results.展开更多
The eutectoid decomposition reaction that occurred in RECo5 phases(RE=Dy and Gd ) at low temperature was discussed and confirmed by X-ray powder diffraction(XRD), differential thermal analysis, and scanning electr...The eutectoid decomposition reaction that occurred in RECo5 phases(RE=Dy and Gd ) at low temperature was discussed and confirmed by X-ray powder diffraction(XRD), differential thermal analysis, and scanning electron microscopy.The decomposition temperature of the GdCo5 and DyCo5 were identified as 805.8 and 900 °C, respectively.The GdCo5 and DyCo5 phases could not be found in the isothermal section of Gd-Dy-Co ternary system at 800 K.Reasons for the absence of the RE2Co7 phase in the XRD patterns were discussed in detail.展开更多
Thermohydrogen treatment (THT) is an effective way to refine microstructure and improve the mechanical properties of the titanium alloys. In the current work, as-cast Ti-6.5Al-2Zr-Mo-V alloy was hydrogenated with di...Thermohydrogen treatment (THT) is an effective way to refine microstructure and improve the mechanical properties of the titanium alloys. In the current work, as-cast Ti-6.5Al-2Zr-Mo-V alloy was hydrogenated with different hydrogen contents and processed solution aging. Accordingly, the microstructure evolution and phase transformation were analyzed. Results show that during solution aging, eutectoid decomposition occurs and the product is a mixture of coarse primaryα, fine eutectoid product and undecomposed βH. The size of primary α is closely dependent on the hydrogen content, and large primary α can be obtained at medium hydrogen content. Further, the influence of hydrogen content on the growth of primary α phase was revealed. The primary α is much fine, and the eutectoid product is relatively homo- geneous with 0.984 wt% H. After THT, the ultimate strength is beyond 1,100 MPa that has increased by 23.15% compared with that in as-cast state.展开更多
This paper discusses the microstructure of nickel-aluminium bronzes con-taining(9-10)wt% Al and(0.1~5)wt% Ni,in which three eutectoids may exist.Themorphologies of α+γ<sub>2</sub> and α+β’<sub...This paper discusses the microstructure of nickel-aluminium bronzes con-taining(9-10)wt% Al and(0.1~5)wt% Ni,in which three eutectoids may exist.Themorphologies of α+γ<sub>2</sub> and α+β’<sub>2</sub> are similar but the latter is finer.In the α+β’<sub>2</sub>+γ<sub>2</sub>eutectoid structure β’<sub>2</sub> is mainly concentrated at the α/β boundaries,while γ<sub>2</sub> is distrib-uted inside prior B regions.Both K-S and N-W orientation relationships exist betweenα and β’<sub>2</sub>(or γ<sub>2</sub>)in alloys consisting of α+β’<sub>2</sub> or α+γ<sub>2</sub>.However,if the alloy consists ofα+β’<sub>2</sub>+γ<sub>2</sub> eutectoid,the lattices of β’<sub>2</sub> and γ<sub>2</sub> are parallel,both of them have the N-Worientation relationship with α.展开更多
The phenomenon of anisotropism in most rolled products necessitates that the rolling direction that enhances desirable mechanical property is established. In this paper, the comparative deep drawability of as-received...The phenomenon of anisotropism in most rolled products necessitates that the rolling direction that enhances desirable mechanical property is established. In this paper, the comparative deep drawability of as-received and annealed mild steel containing about 0.1%C was investigated. The flat steel sample was divided into two and classified as as-received and heat treated respectively. The heat treated sample was obtained by annealing at 950°C after been soaked for 5 hours and deep drawn at ambient temperatures (35°C - 42°C). From both samples, circular specimens were machine- blanked parallel to the rolling directions inclined at 0°, 45° and 90° respectively and were prepared for deep drawability test while rectangular specimens were prepared for tensile test. Both specimens, as-received and annealed were then sub- jected to tensile, cupping and microstructural analyses. Results show that the contribution to increased formability at 90° rolling direction seems to have come from the spheroid-like pearlite grains induced during annealing while the sta- bility of spread observed was achieved through a modest increase in strength. Thus, the resistance of annealed eutectoid steel to cupping is quite minimal at 90° to the rolling direction. The desirable drawability characteristics developed by the annealed eutectoid steel specimen are: cup-height, 30 mm maximum and ear, 6.4% maximum.展开更多
The effect of austenite deformation on the pearlite microstructure of eutectoid steel w as investigated by hot uniaxial compression tests using a Gleeble 1500 thermo-mechanical simulator. The results show ed that the ...The effect of austenite deformation on the pearlite microstructure of eutectoid steel w as investigated by hot uniaxial compression tests using a Gleeble 1500 thermo-mechanical simulator. The results show ed that the deformation of the austenite phase accelerated the transformation of pearlite,leading to a smaller colony size and a smaller interlamellar space of pearlite; meanw hile,the orientation of pearlite lamellae became more heterogeneous,and the lamellar thickness decreased. Larger strain of austenite w as observed to accelerate the spheroidization process of carbides w ithin pearlite colonies.展开更多
Compounds [n-CnH2n+1N(CHs)3]2CoCl4(n=16, C46C3Co; n=18, C18C3Co) containing lipid-like bilayers embedded in a crystalline matrix exist in solid-solid phase transition. The low-temperature bilayer structures of th...Compounds [n-CnH2n+1N(CHs)3]2CoCl4(n=16, C46C3Co; n=18, C18C3Co) containing lipid-like bilayers embedded in a crystalline matrix exist in solid-solid phase transition. The low-temperature bilayer structures of the two compounds were organized by neutralizing CoCl24- with alkylammonium ions. Alkyl chains lay parallel to each other and slightly tilted with respect to the normal of the inorganic layers. The adjacent alkyl chains interacted with each other by van der Waals interaction. When the temperature increased, the two compounds underwent a reversible solid-solid phase transformation within 310-330 K. In such a case, the chains showed a large motional freedom, and a disordered phase appeared. The structures can alternatively be viewed as a double layer of alkylammonium ions between COCl24- sheets and be considered as crystalline models of lipid bilayers. The experimental subsolidus binary phase diagram of [n-C16H33N(CH3)3]2CoCl4-[n-C18H37N(CH3)3]2CoCl4 was constructed over the entire composition range by differential scanning calorimetry and X-ray diffraction technique. Experimental phase diagram indicates one stable intermediate phase [n-C16H33N(CH3)3][n-C18H37N(CH3)3]CoCl4 at wC16C3Co = 39.89% and two invariant three-phase equilibria, which shows two eutectoid temperatures: Te1 at (316±1) K for WC16C3Co=27.35% and Te2 at (313±1)K for Wc16c3co =59.76%. These three noticeable solid-solution ranges are a-phase at the left, β-phase at the right, and γ-phase in the middle of the phase diagram.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
文摘The effect of dissolved niobium on the eutectoid transformation behavior in near-eutectoid high-carbon steels has been studied.Dissolved niobium is important in the eutectoid transformation behavior.It increases the eutectoid carbon content significantly(by^0.0477% per 0.00001% dissolved niobium),increases the hardenability of steel markedly,yields finer,more uniform,polygonal proeutectoid ferrite,induces a transition in morphology of eutectoid cementite from lamellar to somewhat spheroidal,and increases the misorientation angle of pearlite colonies from being focused near 0°to near 60°.
基金the National Science and Technology Pillar Program of China (2011BAE13B04)National Natural Science Foundation of China(51204047and U1660117)Fundamental Research Funds for the Central Universi-ties of China(N130407004)for the financial support
文摘A new hot-dip galvanizing method was employed on hot-rolled low carbon steel.The effects of Al contents on microstructure,micro-hardness and corrosion resistance of Zn-Al alloy coatings were systematically investigated.Phase composition,microstructure and element distribution in Zn-Al alloy coatings were analyzed using X-ray diffraction(XRD)and electron probe micro analysis(EPMA),respectively.It is found that Al content(0.6-6.0 wt.%)in galvanizing zinc affects surface quality and adhesion between coatings and matrix in the newly developed method.In addition,with increasing Al content,micro-hardness significantly increased due to the increase in Zn-Al eutectoid phases.Potentiodynamic polarization and electrochemical impedance spectroscopy(EIS)also revealed that increase in Al plays a noticeable role in improving the corrosion resistance of Zn-Al alloy coatings.
基金financially supported by the National Natural Science Foundation of China(Nos.52293395 and 52293393)the Xiongan Science and Technology Innovation Talent Project of MOST,China(No.2022XACX0500)。
文摘Understandings of the effect of hot deformation parameters close to the practical production line on grain refinement are crucial for enhancing both the strength and toughness of future rail steels.In this work,the austenite dynamic recrystallization(DRX)behaviors of a eutectoid pearlite rail steel were studied using a thermo-mechanical simulator with hot deformation parameters frequently employed in rail production lines.The single-pass hot deformation results reveal that the prior austenite grain sizes(PAGSs)for samples with different deformation reductions decrease initially with an increase in deformation temperature.However,once the deformation temperature is beyond a certain threshold,the PAGSs start to increase.It can be attributed to the rise in DRX volume fraction and the increase of DRX grain with deformation temperature,respectively.Three-pass hot deformation results show that the accumulated strain generated in the first and second deformation passes can increase the extent of DRX.In the case of complete DRX,PAGS is predominantly determined by the deformation temperature of the final pass.It suggests a strategic approach during industrial production where part of the deformation reduction in low temperature range can be shifted to the medium temperature range to release rolling mill loads.
基金supported by the National Natural Science Foundation of China(No.50371057)
文摘Mssbauer spectrum and three dimensional atom probes(3DAP) were combined to investigate the mechanism of cementite dissolution in a cold-drawn eutectoid steel at a true strain of 2.89.The experimental results suggest that the dislocations play an important role in the dissolution of the cementite by sweeping across the nano-scaled cementite,and transferring carbon from cementite to ferrite inducing cementite decomposition.The mechanism of cementite dissolution in the steel is discussed in association with the investigation of nonstoichiometric cementite structure after heavy deformation.
基金Item Sponsored by National Natural Science Foundation of China(50271060)Natural Science Foundation of Hebei Province of China(503291)
文摘The warm compression tests were performed on the eutectoid steel to investigate the evolution of cementite morphology. Several processing parameters, such as temperature, strain rate and reduction, were changed to analyze the effect of each parameter on spheroidization of cementite. The results showed that the warm compression promoted the fragmentize and the spheroidization of lamellar cementites. When the specimen was compressed with reduction of 50% at 700 ℃ and in the strain rate of 0.01 s-1, the excellent spheroidized cementite was obtained. The mechanism of fragmentation and spheroidization of lamellar cementites during compression was discussed by using transmission electron microscope. The formation of spheroidized cementite was related to the time of compression process. The fragmentize of lamellar cementites was due to the extension of sub-grain boundary in the cementite. The spheroidization of cementite depended on the diffusion of carbon atoms at the tip of bended and breakup cementite.
基金Supported by the Natural Science Foundation of Jiangxi Province of China (Grant No.0550050)the Jiangxi Provincial Department of Education of China (Grant No.13-3-B-04)
文摘The paper presents in detail the effects of macroscopic graphite (Gr) particulates on the damping behavior of Zn-Al eutectoid alloy (Zn-Al). Macroscopic defects are graphite particulates with sizes of the order of a millimeter (0.5 mm and 1.0 mm). Macroscopic graphite particulate-reinforced Zn-Al eutectoid alloys were prepared by the air pressure infiltration process. The damping characterization was conducted on a multifunction internal friction apparatus (MFIFA). The internal friction (IF), as well as the relative dynamic modulus, was measured at different frequencies over the temperature range of 20 to 400°C. The damping capacity of the Zn-Al/Gr, with two different volume fractions of macroscopic graphite particulates, was compared with that of bulk Zn-Al eutectoid alloy. The damping capacity of the materials is shown to increase with increasing volume fraction of macroscopic graphite particulates. Two IF peaks were found in the IF-temperature curves. The first is a grain boundary peak, which is associated with the diffusive flux on a boundary between like phases, Al/Al. Its activation energy has been calculated to be 1.13±0.03 eV and the pre-exponential factor is 10?14 s in IF measurements. The second is a phase transition peak, which results from the transformation of Zn-Al eutectoid. In light of internal friction measurements and differential scanning calorimetry (DSC) experiments, its activation energy has been calculated to be 2.36±0.08 eV.
基金Item Sponsored by National Natural Science Foundation of China(51204047)National High Technology Research and Development Program of China(2011BAE13B04)Fundamental Research Funds for the Central Universities of China(N130407004)
文摘The influences of coiling temperature and cooling condition on structural transformation of the hot-rolled tertiary oxide scale formed under continuous cooling conditions were studied by thermal gravimetric analyzer. The fourth oxide scale formed under different conditions were classified and plotted. Because the oxide scale structure transformation is diffusion-controlled and the transformation law is similar to "C" curve, the eutectoid transformation nose temperature is 450 ℃. Under condition of low temperature and high cooling rate, ion diffusion behavior is restricted so that the eutectoid reaction is suppressed, resulting in that the fourth oxide scale is mainly made up of pre-eutectoid Fe304 and FeO without eu- tectoid products. From scale structure transition diagram, the eutectoid reaction process was affected by coiling temperature and cooling rate, leading to various scale structures.
文摘Based on current theories of diffusion and creep cavity closure at high temperature, a theoretical analysis of phase transformation diffusion bonding for T8/T8 eutectoid steel is carried out. The diffusion bonding is mainly described as two-stage process: Ⅰ The interfacial cavity with shape change from diamond to cylinder.Ⅱ The radius of the cylindrical cavity are reduced and eliminated gradually. A new theoretical model is established for the process of transformation superplastic diffusion bonding (TSDB) on the basis of a theoretical model for isothermal superplastic diffusion. The model can predict the bonding quality which is affected by technological parameters, such as limit cycling temperature, the compressive stress, the numbers of thermal cycles and temperature cycling through the phase transformation in the thermal cycling and so on. Results show that the maximum temperature, the compressive stress, the numbers of thermal cycles and the rate of temperature changing speed in the thermal cycling have an important influence on TSDB process. Meanwhile, reasonable technological parameters chosen from theoretical analysis is in good agreement with those obtained from experimental results.
基金supported by the National Natural Science Foundation of China (50471108)the Natural Science Foundation of Guangxi (0448022, 0540009, 0640040)Key Project of Guangxi University for Nationality (2007, 2008)
文摘The eutectoid decomposition reaction that occurred in RECo5 phases(RE=Dy and Gd ) at low temperature was discussed and confirmed by X-ray powder diffraction(XRD), differential thermal analysis, and scanning electron microscopy.The decomposition temperature of the GdCo5 and DyCo5 were identified as 805.8 and 900 °C, respectively.The GdCo5 and DyCo5 phases could not be found in the isothermal section of Gd-Dy-Co ternary system at 800 K.Reasons for the absence of the RE2Co7 phase in the XRD patterns were discussed in detail.
文摘Thermohydrogen treatment (THT) is an effective way to refine microstructure and improve the mechanical properties of the titanium alloys. In the current work, as-cast Ti-6.5Al-2Zr-Mo-V alloy was hydrogenated with different hydrogen contents and processed solution aging. Accordingly, the microstructure evolution and phase transformation were analyzed. Results show that during solution aging, eutectoid decomposition occurs and the product is a mixture of coarse primaryα, fine eutectoid product and undecomposed βH. The size of primary α is closely dependent on the hydrogen content, and large primary α can be obtained at medium hydrogen content. Further, the influence of hydrogen content on the growth of primary α phase was revealed. The primary α is much fine, and the eutectoid product is relatively homo- geneous with 0.984 wt% H. After THT, the ultimate strength is beyond 1,100 MPa that has increased by 23.15% compared with that in as-cast state.
文摘This paper discusses the microstructure of nickel-aluminium bronzes con-taining(9-10)wt% Al and(0.1~5)wt% Ni,in which three eutectoids may exist.Themorphologies of α+γ<sub>2</sub> and α+β’<sub>2</sub> are similar but the latter is finer.In the α+β’<sub>2</sub>+γ<sub>2</sub>eutectoid structure β’<sub>2</sub> is mainly concentrated at the α/β boundaries,while γ<sub>2</sub> is distrib-uted inside prior B regions.Both K-S and N-W orientation relationships exist betweenα and β’<sub>2</sub>(or γ<sub>2</sub>)in alloys consisting of α+β’<sub>2</sub> or α+γ<sub>2</sub>.However,if the alloy consists ofα+β’<sub>2</sub>+γ<sub>2</sub> eutectoid,the lattices of β’<sub>2</sub> and γ<sub>2</sub> are parallel,both of them have the N-Worientation relationship with α.
文摘The phenomenon of anisotropism in most rolled products necessitates that the rolling direction that enhances desirable mechanical property is established. In this paper, the comparative deep drawability of as-received and annealed mild steel containing about 0.1%C was investigated. The flat steel sample was divided into two and classified as as-received and heat treated respectively. The heat treated sample was obtained by annealing at 950°C after been soaked for 5 hours and deep drawn at ambient temperatures (35°C - 42°C). From both samples, circular specimens were machine- blanked parallel to the rolling directions inclined at 0°, 45° and 90° respectively and were prepared for deep drawability test while rectangular specimens were prepared for tensile test. Both specimens, as-received and annealed were then sub- jected to tensile, cupping and microstructural analyses. Results show that the contribution to increased formability at 90° rolling direction seems to have come from the spheroid-like pearlite grains induced during annealing while the sta- bility of spread observed was achieved through a modest increase in strength. Thus, the resistance of annealed eutectoid steel to cupping is quite minimal at 90° to the rolling direction. The desirable drawability characteristics developed by the annealed eutectoid steel specimen are: cup-height, 30 mm maximum and ear, 6.4% maximum.
文摘The effect of austenite deformation on the pearlite microstructure of eutectoid steel w as investigated by hot uniaxial compression tests using a Gleeble 1500 thermo-mechanical simulator. The results show ed that the deformation of the austenite phase accelerated the transformation of pearlite,leading to a smaller colony size and a smaller interlamellar space of pearlite; meanw hile,the orientation of pearlite lamellae became more heterogeneous,and the lamellar thickness decreased. Larger strain of austenite w as observed to accelerate the spheroidization process of carbides w ithin pearlite colonies.
基金Supported by the National Natural Science Foundation of China(Nos.21473048, 21246006), the Natural Science Foundation of Hcbci Province, China(No.B2012205034) and the Science Foundation of Hebci Normal University, China(Nos.L2011K04, L2013B07).
文摘Compounds [n-CnH2n+1N(CHs)3]2CoCl4(n=16, C46C3Co; n=18, C18C3Co) containing lipid-like bilayers embedded in a crystalline matrix exist in solid-solid phase transition. The low-temperature bilayer structures of the two compounds were organized by neutralizing CoCl24- with alkylammonium ions. Alkyl chains lay parallel to each other and slightly tilted with respect to the normal of the inorganic layers. The adjacent alkyl chains interacted with each other by van der Waals interaction. When the temperature increased, the two compounds underwent a reversible solid-solid phase transformation within 310-330 K. In such a case, the chains showed a large motional freedom, and a disordered phase appeared. The structures can alternatively be viewed as a double layer of alkylammonium ions between COCl24- sheets and be considered as crystalline models of lipid bilayers. The experimental subsolidus binary phase diagram of [n-C16H33N(CH3)3]2CoCl4-[n-C18H37N(CH3)3]2CoCl4 was constructed over the entire composition range by differential scanning calorimetry and X-ray diffraction technique. Experimental phase diagram indicates one stable intermediate phase [n-C16H33N(CH3)3][n-C18H37N(CH3)3]CoCl4 at wC16C3Co = 39.89% and two invariant three-phase equilibria, which shows two eutectoid temperatures: Te1 at (316±1) K for WC16C3Co=27.35% and Te2 at (313±1)K for Wc16c3co =59.76%. These three noticeable solid-solution ranges are a-phase at the left, β-phase at the right, and γ-phase in the middle of the phase diagram.
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.