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
As a part of the systematical investigation of the phase relationships of the Zn-Al base alloys,decomposi- tion of the supersaturated phase β_S in a eutectoid Zn-Al-Cu-Si alloy was studied by hardness testing,opti- c...As a part of the systematical investigation of the phase relationships of the Zn-Al base alloys,decomposi- tion of the supersaturated phase β_S in a eutectoid Zn-Al-Cu-Si alloy was studied by hardness testing,opti- cal,electron microscopy and X-ray diffraction.Com- pared to the monotectoid Zn-Al-Cu-Si alloy,a similar sequence of decomposition was found to consist of three stages of phase transformation,which were in accordance to various equilibrium reactions at the temperatures above the ageing temperatures.展开更多
A continuously cast eutectoid Zn-Al alloy was extruded at about 250℃ and the complex microstructures of three phases (α. ε and η'E) were observed in the extruded eutectoid Zn-Al alloy.The fcc Al-rich α phase ...A continuously cast eutectoid Zn-Al alloy was extruded at about 250℃ and the complex microstructures of three phases (α. ε and η'E) were observed in the extruded eutectoid Zn-Al alloy.The fcc Al-rich α phase appeared as isolated particles with clear boundaries instead of the α phase occurring with diffuse boundary within the dendrites of the as-cast structure. A new unstable phase η'E was determined to have hexagonal close packed crystal structure. The decomposed β's, phase comprised the matrix. The new phase η'E decompoeed and a four phase transformation α+ε T'+η occurred afterwards during the isothermal holding. The extruded alloy tended to be stable after these two phase transformations. The early shrinkage and the following increase in dimension were related to the decomposition of the new phase η'E and the four phase transformation.展开更多
Furnace cooling is a slow cooling process. It is of importance to study structural evolution and its effects on the properties of alloys during the furnace cooling. Decomposition of aluminium rich α phase in a furnac...Furnace cooling is a slow cooling process. It is of importance to study structural evolution and its effects on the properties of alloys during the furnace cooling. Decomposition of aluminium rich α phase in a furnace cooled eutectoid Zn-Al based alloy was studied by transmission electron microscopy. Two kinds of precipitates in the α phase were detected in the FCZA22 alloy during ageing at 170℃. One was the hcp transitional α＂ m phase which aooears as directional rods and the round precipitates. The other was the fcc α＇m phase. 〈101〉. The orientation relationship between the a phase and transitional phase α＇m was determined as （022）α＇m （fcc）//（022^-）α（fcc）, [1^-11]α＇m, （fcc）//[2^-33]α（fcc）. The non-equilibrium phase decomposition of the α phase is discussed in correlation with the equilibrium phase relationships.展开更多
The corrosion behavior of Mg-8Li-3Zn-Al alloy was investigated in neutral 3.5%NaCl aqueous solution by morphology observation and electrochemical tests.The weight loss method was to measure the corrosion rate.The elec...The corrosion behavior of Mg-8Li-3Zn-Al alloy was investigated in neutral 3.5%NaCl aqueous solution by morphology observation and electrochemical tests.The weight loss method was to measure the corrosion rate.The electrochemical results indicated that the corrosion resistance of Mg-8Li-3Zn-Al alloy in 3.5%NaCl solution is poorer than that in distilled water.The Cl-anion leads to the initiation and development of the corrosion pits.And the corrosion products are mainly Mg(OH)_(2).展开更多
The interaction between Zn-AI eutectic alloy and Al203p/6061AI composites in the vacuum furnace was investigated. Great attention has been paid to the elements diffusion, the microstructure and formation of the interf...The interaction between Zn-AI eutectic alloy and Al203p/6061AI composites in the vacuum furnace was investigated. Great attention has been paid to the elements diffusion, the microstructure and formation of the interface between Zn-AI eutectic alloy and Al2O3p/6061AI composites. Experimental results show that Zn-AI eutectic alloy has a good wetting ability to Al2O3p/6061 Al composites and the wetting angle decreases with increasing the temperature in vacuum. After the interaction, an interaction layer forms between Zn-AI alloy and Al2O3p/6061 Al composites. The phases in the interaction layer mainly consist of α-AI(Zn), Al2O3 and CuZn5 resulted from the diffusion of elements from the Zn-AI alloy. Several porosities distribute in the region near the interface of the Zn-AI alloy/interaction layer. The amount of shrinkage voids in the interacting layer is relevant to the penetration of Zn element into Al2O3p/6061Al composites which is a function of temperature. So it is necessary to lower heating temperature in order to limit the Zn penetration.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
Phase transformation and microstructural change of an extruded eutectoid Zn-Al alloy Zn76Al22Cu2 (wt pct) were investigated during creep testing by using SEM and X-ray diffraction techniques. Creep induced decompositi...Phase transformation and microstructural change of an extruded eutectoid Zn-Al alloy Zn76Al22Cu2 (wt pct) were investigated during creep testing by using SEM and X-ray diffraction techniques. Creep induced decomposition of a metastable η'T phase and a four phase transformation, α+ ε →T' +η, occurred during the creep testing. Also a microstructural change was observed from a lamellar structure into a spheroidized structure in the rupture part of the extruded alloy. It provided evidence of creep induced phase transformations which occurred in ageing process. The mechanism of creep rupture of the extruded Zn-Al alloy was also discussed.展开更多
The Al-Zn eutectoid alloy has been widely known as a typical superplastic metallic material, where fine-grained microstructure is usually obtained by heat treatment. Recently, thermo-mechanical controlled process has ...The Al-Zn eutectoid alloy has been widely known as a typical superplastic metallic material, where fine-grained microstructure is usually obtained by heat treatment. Recently, thermo-mechanical controlled process has also been reported to provide a fine-grained microstructure. In the present study, Al-Zn alloy ingots of 20 mm in thickness were homogenized and hot-rolled to a thickness of 2 mm under three processes： 1） the specimen was air-cooled after homogenization and hot-rolled; 2） the specimen was water-quenched after homogenization and hot-rolled; 3） the specimen was immediately hot-rolled after homogenization. Microstructural observation showed that, in processes l and 3, lamellar microstructure was formed after homogenization, and became fragmented to fine-grained microstructure as the hot roiling process proceeded. In process 2, fine-grained microstructure without lamellar microstructure was attained throughout the hot-rolling process. A minimum grain size of 1.6 μm was obtained in process 3. Tensile tests at room temperature showed that the elongation to failure was the largest in process 3.展开更多
The nanostructural evolution and phase transformation of the films of a Zn-Al based alloy (Zn68Al10Cu22 in wt pct) have been studied by using X-ray diffraction and scanning electron microscopy. Nanostructural thin fil...The nanostructural evolution and phase transformation of the films of a Zn-Al based alloy (Zn68Al10Cu22 in wt pct) have been studied by using X-ray diffraction and scanning electron microscopy. Nanostructural thin films of the Zn-AI based alloy were produced by using an electron beam deposition technique. It was found that a nanocrystalline phase η'n had a strong preferred crystal orientation at (0002) crystal planes in the as-deposited films. During ageing at 220℃, the decomposition of nanophase η'n started with clustering to form Z-zones, and transitionai phase, which was accompanied by an eutectoid decomposition of the η'n phase: η'n β'eut T'. Decomposition, such as clustering and the formation of the Z-zones, and the transitionai phase etc. were observed in the nanophase β'eut. The formation and the decomposition of the transitionai phase of micrometers in size were involved in the decomposition of the main nanophase η'n. The mechanism of the Z-zones formation and the stability of nanophases were discussed.展开更多
The method of controlling separating anode and separating power source was used to perform orthogonal optimization for the parameters in electroplating Zn Al alloy.The electroplating Zn-Al alloy technology was decide...The method of controlling separating anode and separating power source was used to perform orthogonal optimization for the parameters in electroplating Zn Al alloy.The electroplating Zn-Al alloy technology was decided, in which the content of Al is about 12%-15% .展开更多
Both furnace cooled and as-cast eutectoid Zn-Al alloys were investigated under external tensile stress at 100℃. It was observed that the external tensile stress caused decomposition of two metastable phases η'T ...Both furnace cooled and as-cast eutectoid Zn-Al alloys were investigated under external tensile stress at 100℃. It was observed that the external tensile stress caused decomposition of two metastable phases η'T and η'S which derived from both original state of the alloy, and a phase transformation, αf +ε→T' +η， in both furnace cooled and as-cast eutectoid Zn-Al alloys. Also spheroidized structure formed partially during tensile testing. Superplasticity of the alloy has been discussed correlating with the phase transformations and microstructural changes.展开更多
By introducing aparameter of difference in ferrite formation temperature between binary Fe-C and multicomponent system,and referring to the thermodynamic model for Fe-C binary system,a simplified thermodynamic model f...By introducing aparameter of difference in ferrite formation temperature between binary Fe-C and multicomponent system,and referring to the thermodynamic model for Fe-C binary system,a simplified thermodynamic model for pro-eutectoid ferrite formation in Fe-ΣXiC multicomponent structural steels(Xi=Mn,Si,Mo,Cr,Ni or Ti,etc)was suggested.The comparison of the calculated Ae3 temperatures with the measured data of steels 42 shows that the relative standard deviation and root-mean-square(RMS)error between them are only 0.71% and 8.92 K,respectively.However,the deviations between the same measured data and the values calculated from the superelement model are as high as 1.86% and 23.83 K,respectively.It can be concluded that the simplified thermodynamic model for pro-eutectoid ferrite formation in multicomponent structural steels is acceptable and the calculated Ae3 temperatures are in good agreement with the experimental data.展开更多
Under 20～350 ℃ thermal cycling tensile condition,the as-cast Zn-5Al-RE alloy can realize transformation superplasticity. Rare-earths added into the alloy can make the strain rate and rupture elongation decrease,whil...Under 20～350 ℃ thermal cycling tensile condition,the as-cast Zn-5Al-RE alloy can realize transformation superplasticity. Rare-earths added into the alloy can make the strain rate and rupture elongation decrease,while the annealing treatment has an opposite effect. The longer the annealing time,the larger the strain rate and rupture elongation will be. The effect of rare earths on the thermal-cycling transformation superplasticity of Zn-5Al-RE alloy as-cast is two-faced: on the one side,rare earths can make the eutectic structure of Zn-5Al-RE alloy fine and thus benefits superplastic deformation. On the other side,rare earths make the diffusion velocity of Zn and Al decrease and postpone the diffusion coordination process,which will hinder the viscous flow of the interphase boundaries,enhance superplastic deformation stress,and make the strain rate and elongation decrease.展开更多
The influence of RE and Tion ZA-27 casting alloy was studied. The results show that RE and Ti refine microstructure of the alloy and improve its mechanical properties and wear-resistance, which make it possible to use...The influence of RE and Tion ZA-27 casting alloy was studied. The results show that RE and Ti refine microstructure of the alloy and improve its mechanical properties and wear-resistance, which make it possible to use ZA-27TiRE casting alloy in the field of artificial limb industry.展开更多
The stored energy and the energy release during SPD (superplastic deformation) of a Zn-5 Al alloy were studied. The alloy after rolling process gains more stored energy, and the as-rolled specimen can obtain maximum e...The stored energy and the energy release during SPD (superplastic deformation) of a Zn-5 Al alloy were studied. The alloy after rolling process gains more stored energy, and the as-rolled specimen can obtain maximum elongation and minimum flow stress without hot holding treatment before SPD. Experimental results show that stored energy release process is along with SPD process and is also an impetus to SPD. The as-rolled Zn-5Al alloy has 48 J/mol stored energy which was measured with DSC (differential scanning calorimeter) and conforms well to the calculated value. The as-rolled Zn-5Al alloy after SPD with an elongation of 2 500% releases 112 J/mol stored energy. Analysis shows that the strain rate is in direct ratio to the rate of stored energy release.展开更多
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.
文摘As a part of the systematical investigation of the phase relationships of the Zn-Al base alloys,decomposi- tion of the supersaturated phase β_S in a eutectoid Zn-Al-Cu-Si alloy was studied by hardness testing,opti- cal,electron microscopy and X-ray diffraction.Com- pared to the monotectoid Zn-Al-Cu-Si alloy,a similar sequence of decomposition was found to consist of three stages of phase transformation,which were in accordance to various equilibrium reactions at the temperatures above the ageing temperatures.
文摘A continuously cast eutectoid Zn-Al alloy was extruded at about 250℃ and the complex microstructures of three phases (α. ε and η'E) were observed in the extruded eutectoid Zn-Al alloy.The fcc Al-rich α phase appeared as isolated particles with clear boundaries instead of the α phase occurring with diffuse boundary within the dendrites of the as-cast structure. A new unstable phase η'E was determined to have hexagonal close packed crystal structure. The decomposed β's, phase comprised the matrix. The new phase η'E decompoeed and a four phase transformation α+ε T'+η occurred afterwards during the isothermal holding. The extruded alloy tended to be stable after these two phase transformations. The early shrinkage and the following increase in dimension were related to the decomposition of the new phase η'E and the four phase transformation.
文摘Furnace cooling is a slow cooling process. It is of importance to study structural evolution and its effects on the properties of alloys during the furnace cooling. Decomposition of aluminium rich α phase in a furnace cooled eutectoid Zn-Al based alloy was studied by transmission electron microscopy. Two kinds of precipitates in the α phase were detected in the FCZA22 alloy during ageing at 170℃. One was the hcp transitional α＂ m phase which aooears as directional rods and the round precipitates. The other was the fcc α＇m phase. 〈101〉. The orientation relationship between the a phase and transitional phase α＇m was determined as （022）α＇m （fcc）//（022^-）α（fcc）, [1^-11]α＇m, （fcc）//[2^-33]α（fcc）. The non-equilibrium phase decomposition of the α phase is discussed in correlation with the equilibrium phase relationships.
基金This work was supported by the financial support of the National Natural Science Foundation of China(No.41276074)National Research Program of China(No.2014CB643304).
文摘The corrosion behavior of Mg-8Li-3Zn-Al alloy was investigated in neutral 3.5%NaCl aqueous solution by morphology observation and electrochemical tests.The weight loss method was to measure the corrosion rate.The electrochemical results indicated that the corrosion resistance of Mg-8Li-3Zn-Al alloy in 3.5%NaCl solution is poorer than that in distilled water.The Cl-anion leads to the initiation and development of the corrosion pits.And the corrosion products are mainly Mg(OH)_(2).
文摘The interaction between Zn-AI eutectic alloy and Al203p/6061AI composites in the vacuum furnace was investigated. Great attention has been paid to the elements diffusion, the microstructure and formation of the interface between Zn-AI eutectic alloy and Al2O3p/6061AI composites. Experimental results show that Zn-AI eutectic alloy has a good wetting ability to Al2O3p/6061 Al composites and the wetting angle decreases with increasing the temperature in vacuum. After the interaction, an interaction layer forms between Zn-AI alloy and Al2O3p/6061 Al composites. The phases in the interaction layer mainly consist of α-AI(Zn), Al2O3 and CuZn5 resulted from the diffusion of elements from the Zn-AI alloy. Several porosities distribute in the region near the interface of the Zn-AI alloy/interaction layer. The amount of shrinkage voids in the interacting layer is relevant to the penetration of Zn element into Al2O3p/6061Al composites which is a function of temperature. So it is necessary to lower heating temperature in order to limit the Zn penetration.
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Phase transformation and microstructural change of an extruded eutectoid Zn-Al alloy Zn76Al22Cu2 (wt pct) were investigated during creep testing by using SEM and X-ray diffraction techniques. Creep induced decomposition of a metastable η'T phase and a four phase transformation, α+ ε →T' +η, occurred during the creep testing. Also a microstructural change was observed from a lamellar structure into a spheroidized structure in the rupture part of the extruded alloy. It provided evidence of creep induced phase transformations which occurred in ageing process. The mechanism of creep rupture of the extruded Zn-Al alloy was also discussed.
文摘The Al-Zn eutectoid alloy has been widely known as a typical superplastic metallic material, where fine-grained microstructure is usually obtained by heat treatment. Recently, thermo-mechanical controlled process has also been reported to provide a fine-grained microstructure. In the present study, Al-Zn alloy ingots of 20 mm in thickness were homogenized and hot-rolled to a thickness of 2 mm under three processes： 1） the specimen was air-cooled after homogenization and hot-rolled; 2） the specimen was water-quenched after homogenization and hot-rolled; 3） the specimen was immediately hot-rolled after homogenization. Microstructural observation showed that, in processes l and 3, lamellar microstructure was formed after homogenization, and became fragmented to fine-grained microstructure as the hot roiling process proceeded. In process 2, fine-grained microstructure without lamellar microstructure was attained throughout the hot-rolling process. A minimum grain size of 1.6 μm was obtained in process 3. Tensile tests at room temperature showed that the elongation to failure was the largest in process 3.
文摘The nanostructural evolution and phase transformation of the films of a Zn-Al based alloy (Zn68Al10Cu22 in wt pct) have been studied by using X-ray diffraction and scanning electron microscopy. Nanostructural thin films of the Zn-AI based alloy were produced by using an electron beam deposition technique. It was found that a nanocrystalline phase η'n had a strong preferred crystal orientation at (0002) crystal planes in the as-deposited films. During ageing at 220℃, the decomposition of nanophase η'n started with clustering to form Z-zones, and transitionai phase, which was accompanied by an eutectoid decomposition of the η'n phase: η'n β'eut T'. Decomposition, such as clustering and the formation of the Z-zones, and the transitionai phase etc. were observed in the nanophase β'eut. The formation and the decomposition of the transitionai phase of micrometers in size were involved in the decomposition of the main nanophase η'n. The mechanism of the Z-zones formation and the stability of nanophases were discussed.
文摘The method of controlling separating anode and separating power source was used to perform orthogonal optimization for the parameters in electroplating Zn Al alloy.The electroplating Zn-Al alloy technology was decided, in which the content of Al is about 12%-15% .
文摘Both furnace cooled and as-cast eutectoid Zn-Al alloys were investigated under external tensile stress at 100℃. It was observed that the external tensile stress caused decomposition of two metastable phases η'T and η'S which derived from both original state of the alloy, and a phase transformation, αf +ε→T' +η， in both furnace cooled and as-cast eutectoid Zn-Al alloys. Also spheroidized structure formed partially during tensile testing. Superplasticity of the alloy has been discussed correlating with the phase transformations and microstructural changes.
基金supported by the Guangdong Academy of Sciences,China(No.2021GDASYL-20210102002)the Foundation Strengthening Program,China(No.2019-JCJQ-ZD-142-00)the Hebei Province Graduate Innovation Funding Project,China(No.CXZZBS2022032).
基金Item Sponsored by National Natural Science Foundation of China(50075053)
文摘By introducing aparameter of difference in ferrite formation temperature between binary Fe-C and multicomponent system,and referring to the thermodynamic model for Fe-C binary system,a simplified thermodynamic model for pro-eutectoid ferrite formation in Fe-ΣXiC multicomponent structural steels(Xi=Mn,Si,Mo,Cr,Ni or Ti,etc)was suggested.The comparison of the calculated Ae3 temperatures with the measured data of steels 42 shows that the relative standard deviation and root-mean-square(RMS)error between them are only 0.71% and 8.92 K,respectively.However,the deviations between the same measured data and the values calculated from the superelement model are as high as 1.86% and 23.83 K,respectively.It can be concluded that the simplified thermodynamic model for pro-eutectoid ferrite formation in multicomponent structural steels is acceptable and the calculated Ae3 temperatures are in good agreement with the experimental data.
文摘Under 20～350 ℃ thermal cycling tensile condition,the as-cast Zn-5Al-RE alloy can realize transformation superplasticity. Rare-earths added into the alloy can make the strain rate and rupture elongation decrease,while the annealing treatment has an opposite effect. The longer the annealing time,the larger the strain rate and rupture elongation will be. The effect of rare earths on the thermal-cycling transformation superplasticity of Zn-5Al-RE alloy as-cast is two-faced: on the one side,rare earths can make the eutectic structure of Zn-5Al-RE alloy fine and thus benefits superplastic deformation. On the other side,rare earths make the diffusion velocity of Zn and Al decrease and postpone the diffusion coordination process,which will hinder the viscous flow of the interphase boundaries,enhance superplastic deformation stress,and make the strain rate and elongation decrease.
文摘The influence of RE and Tion ZA-27 casting alloy was studied. The results show that RE and Ti refine microstructure of the alloy and improve its mechanical properties and wear-resistance, which make it possible to use ZA-27TiRE casting alloy in the field of artificial limb industry.
基金This work is financially supported by the National Natural Science Foundation of China (Nos. 59871025 and 59871031).
文摘The stored energy and the energy release during SPD (superplastic deformation) of a Zn-5 Al alloy were studied. The alloy after rolling process gains more stored energy, and the as-rolled specimen can obtain maximum elongation and minimum flow stress without hot holding treatment before SPD. Experimental results show that stored energy release process is along with SPD process and is also an impetus to SPD. The as-rolled Zn-5Al alloy has 48 J/mol stored energy which was measured with DSC (differential scanning calorimeter) and conforms well to the calculated value. The as-rolled Zn-5Al alloy after SPD with an elongation of 2 500% releases 112 J/mol stored energy. Analysis shows that the strain rate is in direct ratio to the rate of stored energy release.
