Effect of cerium(Ce)on creep strength and microstructure of 316LN austenitic stainless steel(316LN steel)at 700℃/150 MPa was investigated by scanning electron microscopy(SEM),scanning transmission electron microscopy...Effect of cerium(Ce)on creep strength and microstructure of 316LN austenitic stainless steel(316LN steel)at 700℃/150 MPa was investigated by scanning electron microscopy(SEM),scanning transmission electron microscopy(STEM)and thermodynamic calculations.Addition of 0.032 wt%Ce to 316LN steel results in a prominent increase in creep life from 313 to 556 h.Ce enriches in titanium nitride nanoparticles,increases slightly the activity and diffusion coefficient of Mo,and facilitates the formation of fine and dense intragranular Laves phase precipitates.Thus the creep strength is remarkably enhanced by Ce addition in 316LN steel through the intragranular Laves phase precipitation strengthening.It reveals a new insight into the improvement effect of rare earth(RE)elements such as Ce on creep strength of austenitic stainless steels,which inspired the design of RE-microalloying heat-resistant steels.展开更多
Effects of nucleation sites and diffusivity enhancement of chromium on reverted transformation of AISI 304 stainless steel during annealing process were investigated.Dynamics calculation revealed that the reverted tra...Effects of nucleation sites and diffusivity enhancement of chromium on reverted transformation of AISI 304 stainless steel during annealing process were investigated.Dynamics calculation revealed that the reverted transformation of strain-inducedα’-martensite→γaustenite could were closely associated with active nucleation sites and diffusivity enhancement of chromium in nanocrystallineα’-martensite.The experimental data and the results were in accordance with 2-grain austenite/α’-martensite junctions calculated theoretically,which could result from high chromium diffusion rate in nanocrystallineα’-martensite.In addition,low temperature is not conducive to reversed transformation,while high temperature and long annealing time will lead to inhomogeneous grain size distribution.展开更多
The influence of Ce addition on the solidification structure and σphase of super austenitic stainless steel S32654 was systematically investigated via microstructural characterization and thermodynamic calcula- tion....The influence of Ce addition on the solidification structure and σphase of super austenitic stainless steel S32654 was systematically investigated via microstructural characterization and thermodynamic calcula- tion. The results indicate that a small addition of Ce could modify MgO and MnS into Ce-bearing inclu- sions Ce_(2)O_(3)and Ce_(2)O_(2)S. Ce addition led to noticeable refinement of both the dendrite structure and σphase. The refinement mechanism could be attributed to the combined actions of effective Ce-bearing inclusions and solute Ce. Effective Ce-bearing inclusions could serve as heterogeneous nucleation cores of austenite as well as σphase, which provided a favorable prerequisite for their refinement. Solute Ce significantly enhanced the undercooling degree of the system, further promoting dendrite structure re- finement. Meanwhile, solute Ce improved the eutectic precipitation conditions of σphase and further promoted its nucleation, while the dendrite refinement limited its growth space. Finally, more fine and dispersed σphase particles formed in S32654 with Ce addition. The refinement of dendrite structure and σ phase will reduce the temperature and time required for high-temperature homogenization, which is beneficial to the hot working of this steel.展开更多
The internal oxide precipitates were supposed to be spherical in Wagner’s original theory,while the fol-lowing research demonstrated that this assumption is an exception rather than the truth,which caused deviations ...The internal oxide precipitates were supposed to be spherical in Wagner’s original theory,while the fol-lowing research demonstrated that this assumption is an exception rather than the truth,which caused deviations in the application of this theory.In this study,the internal oxide precipitates have a needle-like and a near-spherical morphology in a Fe-9Cr ferritic and a Fe-17Cr-9Ni austenitic steels after expo-sure to 600℃ deaerated steam for 600 h,respectively.The nano-to-atomic scale characterization shows that the morphology of the internal oxide precipitates is controlled by the structure of the interfaces be-tween the metal matrix and the internal oxide,while the interface structure is mainly affected by the crystallographic structure of the two phases and their orientation relationship.In addition,the internal oxide precipitation-induced volume expansion and the outward Fe diffusion-induced volume shrink oc-cur simultaneously during the oxidation process.The stress status in the internal oxidation zone(IOZ)is the competing result of the two factors,which could dynamically affect the high-temperature oxidation.The results obtained in this study suggest that there is potential to control the distribution,morphology,and interface structure of the internal oxide precipitates by selecting appropriate base metal and internal oxide-forming element,in order to obtain better high-temperature oxidation-resistant materials.展开更多
Vertical section of Fe-18Cr-12Mn-0.04C-N system phase diagram varying with nitrogen content at 1×105 Pa was calculated using Thermo-Calc software and thermodynamic database.The morphology and crystallography info...Vertical section of Fe-18Cr-12Mn-0.04C-N system phase diagram varying with nitrogen content at 1×105 Pa was calculated using Thermo-Calc software and thermodynamic database.The morphology and crystallography information of precipitates in Fe-18Cr-12Mn-0.04C-0.48N high-nitrogen austenitic stainless steel during isothermal aging at 800 ℃ after austenization was investigated using optical microscopy(OM),and transmission electron microscopy(TEM) with energy distribution spectrum(EDS).The experimental results show that three precipitates,(Cr,Fe,Mn)2(N,C),(Cr,Fe,Mn)23(C,N)6 and σ phase exist in this steel,which is consistent with the thermodynamic calculation,indicating that thermodynamic calculation can provide instructions for alloy composition design,heat treatment and prediction of precipitation sequence in Fe-18Cr-12Mn-0.04C-N system.展开更多
Effects of compression deformation on the sigma-phase precipitation behavior of B-containing S31254 stainless steel after solution treatment were studied using the Gleeble compression test. The cold and hot processing...Effects of compression deformation on the sigma-phase precipitation behavior of B-containing S31254 stainless steel after solution treatment were studied using the Gleeble compression test. The cold and hot processing characteristics of B-containing S31254 stainless steel were evaluated, and the results show that the speed of compression deformation increased the precipitation rate of the sigma phase, and the location of precipitation extended from the austenite grain boundary to the original hot rolling deformation area. During cold deformation at room temperature, the precipitation rate increased when the deformation reached at 40%. Deformation at 950℃ affected precipitation more obviously. At 1074 ℃, when the deformation reached 20%, the precipitated phases started increasing, and above this deformation range, precipitation began decreasing. Also, at 1074℃ the deformation accelerated the precipitation of sigma phase;but with deformation, there was a change in critical temperature for the sigma-phase excursion. The precipitation position of the sigma phase is strongly related to the area of the original hot rolling deformation. With an increase in the deformation amount, precipitates in this region appeared as coarse-grained, skeletal, and network-like features.展开更多
The prediction of microstructure constituents and their morphologies is of great importance for the evaluation of material properties and design of advanced materials.There have been considerable efforts to model and ...The prediction of microstructure constituents and their morphologies is of great importance for the evaluation of material properties and design of advanced materials.There have been considerable efforts to model and simulate microstructure evolution using a wide spectrum of models and simulation approaches.This paper initially reviews the atomistic and mesoscale simulation approaches for microstructure evolution,emphasizing their advantages and disadvantages.Atomistic approaches,such as molecular dynamics,are restricted by the scale of the studied system because they are computationally expensive.Continuum mesoscale simulation approaches,such as phase field,cellular automata,and Monte Carlo,have inconsistent phenomenological equations,each of which only describes one aspect of microstructure evolution.To provide comprehensive insight into microstructure evolution,a unified model that is capable of equally evaluating the nucleation and growth processes is required.In this paper,a physics-based model is proposed that incorporates statistical mechanics,the energy conservation law,and the force equilibrium concept to include all aspects of microstructure evolution.A compatible simulation approach is also described to simulate microstructure evolution during thermomechanical treatments.Furthermore,the microstructure evolution of AISI 304 austenitic steel during isothermal heat treatment and fusion welding is simulated and discussed.The use of fundamental physical rules instead of phenomenological equations,together with the real spatial and temporal scales of the proposed model,facilitates the comparison of the simulation results with experimental results.To examine the accuracy of the proposed simulation approach,the isothermal heat treatment simulation results are compared with experimental data over a broad region of temperatures and time periods.展开更多
Multi-wall carbon nanotubes(MWNTs)/SnO core/shell nanosturcture was synthesized by a simple solution-based method,in which SnCl2 was solved in distilled water containing dispersed MWNTs,then stired,filtered and washed...Multi-wall carbon nanotubes(MWNTs)/SnO core/shell nanosturcture was synthesized by a simple solution-based method,in which SnCl2 was solved in distilled water containing dispersed MWNTs,then stired,filtered and washed in ambient atmosphere,finally dryed in air at 90 ℃ for 6 h.The MWNTs/SnO core/shell nanostructure was characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM).It is found that surface defects of MWNTs are necessary for the deposition of SnO.The mechanism of the SnO nanocoating formation through the hydrolysis of SnCl2 in water(4SnCl_2+2H_2O-Sn_4(OH)2Cl_6+2HCl) was presented.展开更多
The relationship between the γ/(γ+δ) boundary temperature Tδ of austenitic steels and the equivalent weights of [Crl and [Ni] and the variation rule of the δ phase volume with the temperature are studied With th...The relationship between the γ/(γ+δ) boundary temperature Tδ of austenitic steels and the equivalent weights of [Crl and [Ni] and the variation rule of the δ phase volume with the temperature are studied With the aid of computer,the regressives expression derived from the experimental results are Tδ(℃) = T4 -21.2[Cr] +15.8[Ni]-223. Vδ(%)=0.715 exp 0.015(T-Tδ).展开更多
In this study, the precipitation behavior of a new austenitic heat-resistant steel （Fe-20Cr-30Ni-2Nb, in at%） was investigated. The effects of alloying addition of boron （B） and lanthanum （La） on the microstruct...In this study, the precipitation behavior of a new austenitic heat-resistant steel （Fe-20Cr-30Ni-2Nb, in at%） was investigated. The effects of alloying addition of boron （B） and lanthanum （La） on the microstructure of the austenitic steel were scrutinized using SEM, EPMA, TEM, and XRD. The results showed that the addition of B enhanced the precipitation of bar-type Laves phase. A small precipitate with high La concentration was observed at the grain boundary in the alloy without aging; similar precipitates without La also presented in region adjacent to the La single phase. This result indicates that La can exist independently and does not contribute to the formation of new compounds. However, in both B- and La-modified alloy, B appeared in the precipitate free zone. In the alloy containing both B and La, only Fe2Nb Laves- phase precipitates, as indicated by the XRD result.展开更多
The application of components often depends to a large extent on the properties of the surface layer.A novel process chain for the production of components with a hardened surface layer from metastable austenitic stee...The application of components often depends to a large extent on the properties of the surface layer.A novel process chain for the production of components with a hardened surface layer from metastable austenitic steel was presented.The investigated metastable austenitic AISI 347 steel was cold-drawn in solution annealed condition at cryogenic temperatures for pre-hardening,followed by post-hardening via cryogenic turning.The increase in hardness in both processes was due to strain hardening and deformation-induced phase transformation from y-austenite to^-martensite.Cryogenic turning experiments were carried out with solution annealed AISI 347 steel as well as with solution annealed and subsequently cold-drawn AISI 347 steel.The thermomechanical load of the workpiece surface layer during the turning process as well as the resulting surface morphology was characterized.The forces and temperatures were higher in turning the cold-drawn AISI 347 steel than turning the solution annealed AISI 347 steel.After cryogenic turning of the solution annealed material,deformation-induced phase transformation and a significant increase in hardness were detected in the near-surface layer.In contrast,no additional phase transformation was observed after cryogenic turning of the cold-drawn AISI 347 steel.The maximum hardness in the surface layer was similar,whereas the hardness in the core of the cold-drawn AISI 347 steel was higher compared to that in the solution annealed AISI 347 steel.展开更多
The precipitation behavior of different phases in a high-silicon stainless steel(6 wt%Si)during aging at 600–1050℃for24 h was investigated.The morphology,crystal structure and composition of various precipitates wer...The precipitation behavior of different phases in a high-silicon stainless steel(6 wt%Si)during aging at 600–1050℃for24 h was investigated.The morphology,crystal structure and composition of various precipitates were detailly characterized using optical microscopy,scanning electron microscopy and transmission electron microscopy.Four phases were mainly identified:χ-phase,M_6C carbides,σphase and a new type of fcc-phase.During aging at 600–900℃,the main precipitate was(Cr,Mo and Si)-richχ-phase which was directly precipitated fromγmatrix.Theχ-phase was calibrated as bcc structure with a lattice parameter of 8.90?.The peak temperature for the precipitation ofχ-phase was 800℃,and it was dissolved when aging at temperatures above 1000℃.Theσ-phase was observed only at 700℃and grew next toχ-phase.Above 700℃,a new fcc-phase was found to be precipitated along withχ-phase,with a space group of Fd3c and a lattice parameter of 12.56?.The M_6C carbides started to be precipitated at 700℃in the vicinity ofχ-phase.And its amount basically increased with the increasing of temperature.An orientation relationship between M_6C/γwas found:[100]c//[100]γ,(001)c//(001)γ,i.e.,the cube-on-cube relationship.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51871212)the National Key Research and Development Program of China(2020YFB2006800)+4 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDC04010400)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.Y2021060)the Key Project for the Application of Advances in Science and Technology of the Chinese Academy of Sciences(KFJ-HGZX-032)the Project for the Application of Advances in Science and Technology of the Chinese Academy of Sciences in Henan Province(2022203)the K.C.Wong Education Foundation。
文摘Effect of cerium(Ce)on creep strength and microstructure of 316LN austenitic stainless steel(316LN steel)at 700℃/150 MPa was investigated by scanning electron microscopy(SEM),scanning transmission electron microscopy(STEM)and thermodynamic calculations.Addition of 0.032 wt%Ce to 316LN steel results in a prominent increase in creep life from 313 to 556 h.Ce enriches in titanium nitride nanoparticles,increases slightly the activity and diffusion coefficient of Mo,and facilitates the formation of fine and dense intragranular Laves phase precipitates.Thus the creep strength is remarkably enhanced by Ce addition in 316LN steel through the intragranular Laves phase precipitation strengthening.It reveals a new insight into the improvement effect of rare earth(RE)elements such as Ce on creep strength of austenitic stainless steels,which inspired the design of RE-microalloying heat-resistant steels.
文摘Effects of nucleation sites and diffusivity enhancement of chromium on reverted transformation of AISI 304 stainless steel during annealing process were investigated.Dynamics calculation revealed that the reverted transformation of strain-inducedα’-martensite→γaustenite could were closely associated with active nucleation sites and diffusivity enhancement of chromium in nanocrystallineα’-martensite.The experimental data and the results were in accordance with 2-grain austenite/α’-martensite junctions calculated theoretically,which could result from high chromium diffusion rate in nanocrystallineα’-martensite.In addition,low temperature is not conducive to reversed transformation,while high temperature and long annealing time will lead to inhomogeneous grain size distribution.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. U1860204, 52004061)Talent Project of Revitalizing Liaoning (Grant No. XLYC1802101)+2 种基金Project funded by China Postdoctoral Science Foundation (Grant No. 2020M670777)Northeastern University Postdoctoral Funds (Grant No. 20200321)Fundamental Research Funds for the Central Universities (Grant No. N2125017)。
文摘The influence of Ce addition on the solidification structure and σphase of super austenitic stainless steel S32654 was systematically investigated via microstructural characterization and thermodynamic calcula- tion. The results indicate that a small addition of Ce could modify MgO and MnS into Ce-bearing inclu- sions Ce_(2)O_(3)and Ce_(2)O_(2)S. Ce addition led to noticeable refinement of both the dendrite structure and σphase. The refinement mechanism could be attributed to the combined actions of effective Ce-bearing inclusions and solute Ce. Effective Ce-bearing inclusions could serve as heterogeneous nucleation cores of austenite as well as σphase, which provided a favorable prerequisite for their refinement. Solute Ce significantly enhanced the undercooling degree of the system, further promoting dendrite structure re- finement. Meanwhile, solute Ce improved the eutectic precipitation conditions of σphase and further promoted its nucleation, while the dendrite refinement limited its growth space. Finally, more fine and dispersed σphase particles formed in S32654 with Ce addition. The refinement of dendrite structure and σ phase will reduce the temperature and time required for high-temperature homogenization, which is beneficial to the hot working of this steel.
基金This work was financially supported by National Key Re-search and Development Program of China(No.2018YFE0116200)Shanghai Pujiang Program(No.21PJ1406400)+1 种基金EPSRC(Nos.EP/K040375/1,EP/N010868/1,and EP/R009392/1)Prof.Lefu Zhang is acknowledged for providing the samples used in this study.In-strumental Analysis Center of SJTU is also gratefully acknowledged.The atom probe facilities at the University of Oxford are funded by the EPSRC(No.EP/M022803/1).
文摘The internal oxide precipitates were supposed to be spherical in Wagner’s original theory,while the fol-lowing research demonstrated that this assumption is an exception rather than the truth,which caused deviations in the application of this theory.In this study,the internal oxide precipitates have a needle-like and a near-spherical morphology in a Fe-9Cr ferritic and a Fe-17Cr-9Ni austenitic steels after expo-sure to 600℃ deaerated steam for 600 h,respectively.The nano-to-atomic scale characterization shows that the morphology of the internal oxide precipitates is controlled by the structure of the interfaces be-tween the metal matrix and the internal oxide,while the interface structure is mainly affected by the crystallographic structure of the two phases and their orientation relationship.In addition,the internal oxide precipitation-induced volume expansion and the outward Fe diffusion-induced volume shrink oc-cur simultaneously during the oxidation process.The stress status in the internal oxidation zone(IOZ)is the competing result of the two factors,which could dynamically affect the high-temperature oxidation.The results obtained in this study suggest that there is potential to control the distribution,morphology,and interface structure of the internal oxide precipitates by selecting appropriate base metal and internal oxide-forming element,in order to obtain better high-temperature oxidation-resistant materials.
基金This work is financially supported by Key Program of the National Natural Science Foundation of China( No50534010)National Program on Key Basic Research Project ( No2004CB619103)
文摘Vertical section of Fe-18Cr-12Mn-0.04C-N system phase diagram varying with nitrogen content at 1×105 Pa was calculated using Thermo-Calc software and thermodynamic database.The morphology and crystallography information of precipitates in Fe-18Cr-12Mn-0.04C-0.48N high-nitrogen austenitic stainless steel during isothermal aging at 800 ℃ after austenization was investigated using optical microscopy(OM),and transmission electron microscopy(TEM) with energy distribution spectrum(EDS).The experimental results show that three precipitates,(Cr,Fe,Mn)2(N,C),(Cr,Fe,Mn)23(C,N)6 and σ phase exist in this steel,which is consistent with the thermodynamic calculation,indicating that thermodynamic calculation can provide instructions for alloy composition design,heat treatment and prediction of precipitation sequence in Fe-18Cr-12Mn-0.04C-N system.
基金The present work was financially supported by National Natural Science Foundation of China (Grant No. 51371123)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 2013140211003)+1 种基金Shanxi Natural Science Foundation Project (Grant Nos. 2014011002-1, 201601D202033, 201601D202034)Innovation Project for Graduate Education of Shanxi province (Grant No. 2016JD20).
文摘Effects of compression deformation on the sigma-phase precipitation behavior of B-containing S31254 stainless steel after solution treatment were studied using the Gleeble compression test. The cold and hot processing characteristics of B-containing S31254 stainless steel were evaluated, and the results show that the speed of compression deformation increased the precipitation rate of the sigma phase, and the location of precipitation extended from the austenite grain boundary to the original hot rolling deformation area. During cold deformation at room temperature, the precipitation rate increased when the deformation reached at 40%. Deformation at 950℃ affected precipitation more obviously. At 1074 ℃, when the deformation reached 20%, the precipitated phases started increasing, and above this deformation range, precipitation began decreasing. Also, at 1074℃ the deformation accelerated the precipitation of sigma phase;but with deformation, there was a change in critical temperature for the sigma-phase excursion. The precipitation position of the sigma phase is strongly related to the area of the original hot rolling deformation. With an increase in the deformation amount, precipitates in this region appeared as coarse-grained, skeletal, and network-like features.
文摘The prediction of microstructure constituents and their morphologies is of great importance for the evaluation of material properties and design of advanced materials.There have been considerable efforts to model and simulate microstructure evolution using a wide spectrum of models and simulation approaches.This paper initially reviews the atomistic and mesoscale simulation approaches for microstructure evolution,emphasizing their advantages and disadvantages.Atomistic approaches,such as molecular dynamics,are restricted by the scale of the studied system because they are computationally expensive.Continuum mesoscale simulation approaches,such as phase field,cellular automata,and Monte Carlo,have inconsistent phenomenological equations,each of which only describes one aspect of microstructure evolution.To provide comprehensive insight into microstructure evolution,a unified model that is capable of equally evaluating the nucleation and growth processes is required.In this paper,a physics-based model is proposed that incorporates statistical mechanics,the energy conservation law,and the force equilibrium concept to include all aspects of microstructure evolution.A compatible simulation approach is also described to simulate microstructure evolution during thermomechanical treatments.Furthermore,the microstructure evolution of AISI 304 austenitic steel during isothermal heat treatment and fusion welding is simulated and discussed.The use of fundamental physical rules instead of phenomenological equations,together with the real spatial and temporal scales of the proposed model,facilitates the comparison of the simulation results with experimental results.To examine the accuracy of the proposed simulation approach,the isothermal heat treatment simulation results are compared with experimental data over a broad region of temperatures and time periods.
基金This work is financially supported by the National Science Foundation of China ( No 50602011)the Science Foundation of Heilongjiang Province ( No E200517) ]
文摘Multi-wall carbon nanotubes(MWNTs)/SnO core/shell nanosturcture was synthesized by a simple solution-based method,in which SnCl2 was solved in distilled water containing dispersed MWNTs,then stired,filtered and washed in ambient atmosphere,finally dryed in air at 90 ℃ for 6 h.The MWNTs/SnO core/shell nanostructure was characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM).It is found that surface defects of MWNTs are necessary for the deposition of SnO.The mechanism of the SnO nanocoating formation through the hydrolysis of SnCl2 in water(4SnCl_2+2H_2O-Sn_4(OH)2Cl_6+2HCl) was presented.
文摘The relationship between the γ/(γ+δ) boundary temperature Tδ of austenitic steels and the equivalent weights of [Crl and [Ni] and the variation rule of the δ phase volume with the temperature are studied With the aid of computer,the regressives expression derived from the experimental results are Tδ(℃) = T4 -21.2[Cr] +15.8[Ni]-223. Vδ(%)=0.715 exp 0.015(T-Tδ).
文摘In this study, the precipitation behavior of a new austenitic heat-resistant steel （Fe-20Cr-30Ni-2Nb, in at%） was investigated. The effects of alloying addition of boron （B） and lanthanum （La） on the microstructure of the austenitic steel were scrutinized using SEM, EPMA, TEM, and XRD. The results showed that the addition of B enhanced the precipitation of bar-type Laves phase. A small precipitate with high La concentration was observed at the grain boundary in the alloy without aging; similar precipitates without La also presented in region adjacent to the La single phase. This result indicates that La can exist independently and does not contribute to the formation of new compounds. However, in both B- and La-modified alloy, B appeared in the precipitate free zone. In the alloy containing both B and La, only Fe2Nb Laves- phase precipitates, as indicated by the XRD result.
文摘The application of components often depends to a large extent on the properties of the surface layer.A novel process chain for the production of components with a hardened surface layer from metastable austenitic steel was presented.The investigated metastable austenitic AISI 347 steel was cold-drawn in solution annealed condition at cryogenic temperatures for pre-hardening,followed by post-hardening via cryogenic turning.The increase in hardness in both processes was due to strain hardening and deformation-induced phase transformation from y-austenite to^-martensite.Cryogenic turning experiments were carried out with solution annealed AISI 347 steel as well as with solution annealed and subsequently cold-drawn AISI 347 steel.The thermomechanical load of the workpiece surface layer during the turning process as well as the resulting surface morphology was characterized.The forces and temperatures were higher in turning the cold-drawn AISI 347 steel than turning the solution annealed AISI 347 steel.After cryogenic turning of the solution annealed material,deformation-induced phase transformation and a significant increase in hardness were detected in the near-surface layer.In contrast,no additional phase transformation was observed after cryogenic turning of the cold-drawn AISI 347 steel.The maximum hardness in the surface layer was similar,whereas the hardness in the core of the cold-drawn AISI 347 steel was higher compared to that in the solution annealed AISI 347 steel.
文摘The precipitation behavior of different phases in a high-silicon stainless steel(6 wt%Si)during aging at 600–1050℃for24 h was investigated.The morphology,crystal structure and composition of various precipitates were detailly characterized using optical microscopy,scanning electron microscopy and transmission electron microscopy.Four phases were mainly identified:χ-phase,M_6C carbides,σphase and a new type of fcc-phase.During aging at 600–900℃,the main precipitate was(Cr,Mo and Si)-richχ-phase which was directly precipitated fromγmatrix.Theχ-phase was calibrated as bcc structure with a lattice parameter of 8.90?.The peak temperature for the precipitation ofχ-phase was 800℃,and it was dissolved when aging at temperatures above 1000℃.Theσ-phase was observed only at 700℃and grew next toχ-phase.Above 700℃,a new fcc-phase was found to be precipitated along withχ-phase,with a space group of Fd3c and a lattice parameter of 12.56?.The M_6C carbides started to be precipitated at 700℃in the vicinity ofχ-phase.And its amount basically increased with the increasing of temperature.An orientation relationship between M_6C/γwas found:[100]c//[100]γ,(001)c//(001)γ,i.e.,the cube-on-cube relationship.
