The fracture surface of the normalized steel 55SiMnMo was observed,under tensile device at- tached on the SEM,to be of ductile dimple feature on the bainite which is composed of lath ferrite and austenite platelet.The...The fracture surface of the normalized steel 55SiMnMo was observed,under tensile device at- tached on the SEM,to be of ductile dimple feature on the bainite which is composed of lath ferrite and austenite platelet.The dimple is essentially nucleated in the ferrite.Because the austenitic plastic deformation is remarkable during fracturing,the tear ridge of dimple is very sharp.展开更多
The transformation of upper bainite of normalized 55SiMnMo steel during tempering has been studied by optical microscopy,X-ray diffraction,transmission electron microscopy and differential scanning calorimetry.Ferrite...The transformation of upper bainite of normalized 55SiMnMo steel during tempering has been studied by optical microscopy,X-ray diffraction,transmission electron microscopy and differential scanning calorimetry.Ferrite plate surface is parallel to ferrite{110}and is the coherent interface for α and γ,the crystallographic relationship is(111)_γ,∥(011)_α.The small plate surface of Fe_3C precipitated during tempering is parallel to(100).The strengthening mechanism for carbon-rich austenite in normalized condition is primarily uniform solid so- lution hardening,however,in the tempered state,it is strengthened chiefly by non-uniform one.展开更多
Based on the analyses of hot-deformation mechanism of the steel,a new constitutive equation describing the flow stress of steels was derived.The flow stress data of steel 55SiMnVB have been determined at 900—1200℃,s...Based on the analyses of hot-deformation mechanism of the steel,a new constitutive equation describing the flow stress of steels was derived.The flow stress data of steel 55SiMnVB have been determined at 900—1200℃,strain rates of 1—100s^(-1)and true-strain of 0.08—0.8.An available evaluated formula on the flows tress has been obtained by means of non-linear regression.It can express clearly the physical process of hot-deformation.展开更多
The γ-ray radiation technique combined with hydrothermal crystallization was firstly used to prepare ultrafine metallic particles of An,Cu and Au-Cu alloy.Particle size for Au in average is about 10 nm.The morphologi...The γ-ray radiation technique combined with hydrothermal crystallization was firstly used to prepare ultrafine metallic particles of An,Cu and Au-Cu alloy.Particle size for Au in average is about 10 nm.The morphologies were observed by TEM.The nucleation mechanism of metal particles and their stability are discussed.展开更多
The rate equation of reaction between PbS and PbO is dα/dt=kx_(PbS)~3 x_(PbO)^(-2).A transition product, PbSO_4·2PbO,is found by X-ray diffraction analysis.The reaction mechanism was dis- cussed on the basis of ...The rate equation of reaction between PbS and PbO is dα/dt=kx_(PbS)~3 x_(PbO)^(-2).A transition product, PbSO_4·2PbO,is found by X-ray diffraction analysis.The reaction mechanism was dis- cussed on the basis of electron transfer.展开更多
Recently,a novel 718 superalloy with remarkable structural stability at 680℃has been designed and fabricated by CISRI(Central Iron and Steel Research Institute)etc.Phase identification of novel 718 alloy under the ab...Recently,a novel 718 superalloy with remarkable structural stability at 680℃has been designed and fabricated by CISRI(Central Iron and Steel Research Institute)etc.Phase identification of novel 718 alloy under the above-mentioned heat-treatment condition was performed using optical microscopy(OM),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).Results show that the novel 718 alloy has outstanding structural stability at 680℃.The novel 718alloy possess excellent structural stability and good mechanical properties,which is attributed to y-phase strengthening and also to the specific sandwich structure of theγ′+γ'strengthening phase.展开更多
A new process to refine the microstructure of α+βtvpe Ti alloys was developed by using hydrogen as a temporary alloying element.It involves hydrogenating the alloys below the hydrogenated β transus temperature abou...A new process to refine the microstructure of α+βtvpe Ti alloys was developed by using hydrogen as a temporary alloying element.It involves hydrogenating the alloys below the hydrogenated β transus temperature about 0-40 K,air cooling to room temperature and then dehydrogenating at 948 K.Ti-6AI-4V and Ti-5AI-2.5Fe alloys treated hy this new process show much refined microstructures,and the yield strength,ultimate strength as well as the elongation increase 8—15,5—13 and 7—14% respectively展开更多
Based on theoretical analysis about local strain,strain rate and dissolving rate at crack tip, the corrosion fatigue crack growth rate of steels ZG20SiMn and SM50B-Zc in fresh water and 3.5% NaCl solution were measure...Based on theoretical analysis about local strain,strain rate and dissolving rate at crack tip, the corrosion fatigue crack growth rate of steels ZG20SiMn and SM50B-Zc in fresh water and 3.5% NaCl solution were measured experimentally,and the PH and electrode potential within crack were also measured continuously along with crack propagating.It showed that the increase of crack growth rate,caused by both decreasing frequency and raising stress ratio,was mainly accelerated by hydrogen embrittlement.展开更多
A model is established to analyze three-dimensional fluid flow and heat transfer in TICweld pools with full penetration.It considers the deformation of the molten pool surfaceat the condition of full penetrated workpi...A model is established to analyze three-dimensional fluid flow and heat transfer in TICweld pools with full penetration.It considers the deformation of the molten pool surfaceat the condition of full penetrated workpieees,takes the are pressure as the drivingforce of the pool surface deformation,and determines the surface configuration of weldpool based on the dynamic balance of arc pressure,pool gravity and surface tension atdeformed weld pool surface. The SIMPLER algorithm is used to calculate the fluid flowfield and temperature distribution in TIG weld pools of stainless steel workpieces.TIGwelding experiments are made to verify the validity of the model.It shows the calculatedresults by the model are in good agreement with experimental measurements. professor,Dept of Welding Engineering,Harbin Institute of Technology,Harbin 150006,China展开更多
Effect of laser scanning speed on phase constitution,microstructure,microhardness and wear resistance of laser-cladding hard facing alloy Stellite 12 has been investigated by means of a cross-flow-type CO_2 laser of 1...Effect of laser scanning speed on phase constitution,microstructure,microhardness and wear resistance of laser-cladding hard facing alloy Stellite 12 has been investigated by means of a cross-flow-type CO_2 laser of 1.5 kW.The laser-cladding layer on the alloy consists of ma- trix phase of suppersaturated solid solution γ(Co,Cr)and complex hexagonal carbide M_7C_3.Under certain condition,at higher laser scanning speed,the suppersaturated solubility of elements increases in γ(Co,Cr),and the precipitation of the complex carbtde M_7C_3 de- creases,so the microhardness increases and the wear resistance decreases.But at slower laser scanning speed,more complex carbide M_7C_3 may precipitate,and the wear resistance may be improved.Therefore,it is believed that the principal factor in improving wear resistance is the precipitation of carbide M_7C_3,while increment of microhardness is the suppersaturated solu- bility of elements in matrix phase γ(Co,Cr).展开更多
The environment-sensitive fracture behaviour of 0Cr18Ni9Ti austenitic stainless steel in boiling 42% MgCl_2 under the specific load of low frequency and high mean stress was inves- tigated from the relations and diffe...The environment-sensitive fracture behaviour of 0Cr18Ni9Ti austenitic stainless steel in boiling 42% MgCl_2 under the specific load of low frequency and high mean stress was inves- tigated from the relations and differences of crack growth rates and fractographs between stress corrosion fatigue and stress corrosion cracking.The interaction between stress corro- sion cracking and corrosion fatigue was also studied from fracture characteristics with empha- sis on the effects of applied potential on the interaction.展开更多
According to the misfitting dislocation theory,a method of theoretical calculation was devel- oped for the specific energy of the semicoherent interface between microalloy carbonitrides and austenite matrix.The calcul...According to the misfitting dislocation theory,a method of theoretical calculation was devel- oped for the specific energy of the semicoherent interface between microalloy carbonitrides and austenite matrix.The calculating formulae were derived and the results were satisfactorily applied on the research works.展开更多
A high temperature embrittlement occures in Fe-15Cr-4AI and Fe-20Cr-4Al alloys treated over 1000 C.It is caused mainly by 475℃ brittleness during cooling.When a secondary treatment at 500℃ was conducted,the 475℃ br...A high temperature embrittlement occures in Fe-15Cr-4AI and Fe-20Cr-4Al alloys treated over 1000 C.It is caused mainly by 475℃ brittleness during cooling.When a secondary treatment at 500℃ was conducted,the 475℃ brittleness developed very rapidly.After only 15 rain of the treating,little plasticity was remained for all samples pretreuted at the temper- atures over 1000℃ and cooled in water.However,no 475℃ brittleness was generated when pretreating temperature was below 1000℃,Addition of Yttrium can inhibit not only grain growth,but also 475℃ brittleness.For the alloys with 0.2—0.4 wt-%Y,after treating at 800—1300℃,the plasticity did not decrease and the properties of furnace cooled samples were not lower than those of water cooled samples.展开更多
The mathematical models of the kinetics of the layer growth at different ion nitriding condi- tions of armco iron.steels 45,40Cr,42CrMo and 38CrMoAl have been established.Based on these models the expression of nitrog...The mathematical models of the kinetics of the layer growth at different ion nitriding condi- tions of armco iron.steels 45,40Cr,42CrMo and 38CrMoAl have been established.Based on these models the expression of nitrogen concentration profile of ion nitrided layers have been deduced with profile simulating method.They are C_=C_(min)^+(P_4)/(ξ_1-x)+(P_5)/(ξ_(10)~2)(ξ_1-x)~2 C_(γ′)=C_(min)^(γ′)+(P_1)/(ξ_(21))(ξ_2-x)+(P_2)/(ξ_(21)~2)(ξ_2-x)~2 C_α=C_(min)~α+(C_(33))/(C_(33))/(ξ_(32))(ξ_3-x)~3 Using these models,the kinetics of layer growth and the nitrogen concentration profile of ion nitrided layers were sinulated on Apple-Ⅱ computer.Results show that the simulated curves coincide quite well with the experimental data.展开更多
The solidification microstructure and phase composition of Ni-base superalloy FGH95 pow- der with different mesh size have been investigated.The structure transition was found from dendrite in major into cellular stru...The solidification microstructure and phase composition of Ni-base superalloy FGH95 pow- der with different mesh size have been investigated.The structure transition was found from dendrite in major into cellular structure as the powder size reduces and the cooling rate in- creases.The predominant phase was identified as MC-type carbide,with different morphologies,which may be related to their composition and the condition of solidification.Minor phases,such as boride,Laves and primary γ' are also present as ac- companiments of the carbide.展开更多
A series of single bcc,bcc plus fcc duplex and single fcc microcrystalline coatings of 1Cr18Ni9Ti stainless steel were prepared by using sputtering technique.The resistance against pitting corrosion was studied by mea...A series of single bcc,bcc plus fcc duplex and single fcc microcrystalline coatings of 1Cr18Ni9Ti stainless steel were prepared by using sputtering technique.The resistance against pitting corrosion was studied by measurements of pitting corrosion potentials and electrochemical noise during initiation of corrosion pits.The results show that the sputtered coatings with single bcc phase or single fcc structure are more resistant to pitting corrosion than those with bcc plus fcc duplex phase structure.展开更多
The crack tip stress-strain fields of the elastic-plastic cracked specimens have been analyzed using finite element calculations.The crack initiation and steady propagation behaviours have also been investigated by me...The crack tip stress-strain fields of the elastic-plastic cracked specimens have been analyzed using finite element calculations.The crack initiation and steady propagation behaviours have also been investigated by means of slip line pattern etching technique and mechanical tests. The results show that there are HRR near field and distant field in the crack tip region,and the later depends on the specimen configuration.The crack initiation behaviour is controlled by a single parameter J.In contrast,the steady crack propagation is affected by the distant strain field and can not be described by single parameter only.展开更多
Strong, tough, and almost fully dense C fiber reinforced celsian matrix composites have been fabricated by impregnation of the fiber tows with the matrix slurry, winding on a drum, drying, stacking the prepreg tapes i...Strong, tough, and almost fully dense C fiber reinforced celsian matrix composites have been fabricated by impregnation of the fiber tows with the matrix slurry, winding on a drum, drying, stacking the prepreg tapes in the desired orientation, and hot pressing. The monoclinic celsian phase in the matrix was produced in situ, during hot pressing, from amphosous BAS. The unidirectional composites having ≈20 vol% of fibers exhibited graceful failure with extensive fiber pullout in three point bend tests at room temperature. Values of ultimate flexural strength and fracture toughness were 379MPa and 8 3MPa·m 1/2 , respectively.展开更多
It is verified that stainless steel AISI 321 is in the active anodic dissolution state in 0.5 mol/L HCll+0.5 mol/L NaCl solution at 55℃.The SCC of the steel in the solution can not be reasonably explained by passive ...It is verified that stainless steel AISI 321 is in the active anodic dissolution state in 0.5 mol/L HCll+0.5 mol/L NaCl solution at 55℃.The SCC of the steel in the solution can not be reasonably explained by passive film rupture-nepasivation theory and by hydrogen embrittlement theory.There are evidences that the fracture stress at the tip of the cracks is reduced by anodic dissolution due to its role in relieving strain hardening layer at crack tip.展开更多
文摘The fracture surface of the normalized steel 55SiMnMo was observed,under tensile device at- tached on the SEM,to be of ductile dimple feature on the bainite which is composed of lath ferrite and austenite platelet.The dimple is essentially nucleated in the ferrite.Because the austenitic plastic deformation is remarkable during fracturing,the tear ridge of dimple is very sharp.
文摘The transformation of upper bainite of normalized 55SiMnMo steel during tempering has been studied by optical microscopy,X-ray diffraction,transmission electron microscopy and differential scanning calorimetry.Ferrite plate surface is parallel to ferrite{110}and is the coherent interface for α and γ,the crystallographic relationship is(111)_γ,∥(011)_α.The small plate surface of Fe_3C precipitated during tempering is parallel to(100).The strengthening mechanism for carbon-rich austenite in normalized condition is primarily uniform solid so- lution hardening,however,in the tempered state,it is strengthened chiefly by non-uniform one.
文摘Based on the analyses of hot-deformation mechanism of the steel,a new constitutive equation describing the flow stress of steels was derived.The flow stress data of steel 55SiMnVB have been determined at 900—1200℃,strain rates of 1—100s^(-1)and true-strain of 0.08—0.8.An available evaluated formula on the flows tress has been obtained by means of non-linear regression.It can express clearly the physical process of hot-deformation.
文摘The γ-ray radiation technique combined with hydrothermal crystallization was firstly used to prepare ultrafine metallic particles of An,Cu and Au-Cu alloy.Particle size for Au in average is about 10 nm.The morphologies were observed by TEM.The nucleation mechanism of metal particles and their stability are discussed.
文摘The rate equation of reaction between PbS and PbO is dα/dt=kx_(PbS)~3 x_(PbO)^(-2).A transition product, PbSO_4·2PbO,is found by X-ray diffraction analysis.The reaction mechanism was dis- cussed on the basis of electron transfer.
基金This work was supported by the National High Technical Reasearch and Development Programme of China(No.2002AA305208)China Postdoctoral Science Foundation(No.2005037323).
文摘Recently,a novel 718 superalloy with remarkable structural stability at 680℃has been designed and fabricated by CISRI(Central Iron and Steel Research Institute)etc.Phase identification of novel 718 alloy under the above-mentioned heat-treatment condition was performed using optical microscopy(OM),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).Results show that the novel 718 alloy has outstanding structural stability at 680℃.The novel 718alloy possess excellent structural stability and good mechanical properties,which is attributed to y-phase strengthening and also to the specific sandwich structure of theγ′+γ'strengthening phase.
文摘A new process to refine the microstructure of α+βtvpe Ti alloys was developed by using hydrogen as a temporary alloying element.It involves hydrogenating the alloys below the hydrogenated β transus temperature about 0-40 K,air cooling to room temperature and then dehydrogenating at 948 K.Ti-6AI-4V and Ti-5AI-2.5Fe alloys treated hy this new process show much refined microstructures,and the yield strength,ultimate strength as well as the elongation increase 8—15,5—13 and 7—14% respectively
文摘Based on theoretical analysis about local strain,strain rate and dissolving rate at crack tip, the corrosion fatigue crack growth rate of steels ZG20SiMn and SM50B-Zc in fresh water and 3.5% NaCl solution were measured experimentally,and the PH and electrode potential within crack were also measured continuously along with crack propagating.It showed that the increase of crack growth rate,caused by both decreasing frequency and raising stress ratio,was mainly accelerated by hydrogen embrittlement.
基金The research work was surpported by the National Natural Science Foundation of China.
文摘A model is established to analyze three-dimensional fluid flow and heat transfer in TICweld pools with full penetration.It considers the deformation of the molten pool surfaceat the condition of full penetrated workpieees,takes the are pressure as the drivingforce of the pool surface deformation,and determines the surface configuration of weldpool based on the dynamic balance of arc pressure,pool gravity and surface tension atdeformed weld pool surface. The SIMPLER algorithm is used to calculate the fluid flowfield and temperature distribution in TIG weld pools of stainless steel workpieces.TIGwelding experiments are made to verify the validity of the model.It shows the calculatedresults by the model are in good agreement with experimental measurements. professor,Dept of Welding Engineering,Harbin Institute of Technology,Harbin 150006,China
文摘Effect of laser scanning speed on phase constitution,microstructure,microhardness and wear resistance of laser-cladding hard facing alloy Stellite 12 has been investigated by means of a cross-flow-type CO_2 laser of 1.5 kW.The laser-cladding layer on the alloy consists of ma- trix phase of suppersaturated solid solution γ(Co,Cr)and complex hexagonal carbide M_7C_3.Under certain condition,at higher laser scanning speed,the suppersaturated solubility of elements increases in γ(Co,Cr),and the precipitation of the complex carbtde M_7C_3 de- creases,so the microhardness increases and the wear resistance decreases.But at slower laser scanning speed,more complex carbide M_7C_3 may precipitate,and the wear resistance may be improved.Therefore,it is believed that the principal factor in improving wear resistance is the precipitation of carbide M_7C_3,while increment of microhardness is the suppersaturated solu- bility of elements in matrix phase γ(Co,Cr).
文摘The environment-sensitive fracture behaviour of 0Cr18Ni9Ti austenitic stainless steel in boiling 42% MgCl_2 under the specific load of low frequency and high mean stress was inves- tigated from the relations and differences of crack growth rates and fractographs between stress corrosion fatigue and stress corrosion cracking.The interaction between stress corro- sion cracking and corrosion fatigue was also studied from fracture characteristics with empha- sis on the effects of applied potential on the interaction.
文摘According to the misfitting dislocation theory,a method of theoretical calculation was devel- oped for the specific energy of the semicoherent interface between microalloy carbonitrides and austenite matrix.The calculating formulae were derived and the results were satisfactorily applied on the research works.
文摘A high temperature embrittlement occures in Fe-15Cr-4AI and Fe-20Cr-4Al alloys treated over 1000 C.It is caused mainly by 475℃ brittleness during cooling.When a secondary treatment at 500℃ was conducted,the 475℃ brittleness developed very rapidly.After only 15 rain of the treating,little plasticity was remained for all samples pretreuted at the temper- atures over 1000℃ and cooled in water.However,no 475℃ brittleness was generated when pretreating temperature was below 1000℃,Addition of Yttrium can inhibit not only grain growth,but also 475℃ brittleness.For the alloys with 0.2—0.4 wt-%Y,after treating at 800—1300℃,the plasticity did not decrease and the properties of furnace cooled samples were not lower than those of water cooled samples.
文摘The mathematical models of the kinetics of the layer growth at different ion nitriding condi- tions of armco iron.steels 45,40Cr,42CrMo and 38CrMoAl have been established.Based on these models the expression of nitrogen concentration profile of ion nitrided layers have been deduced with profile simulating method.They are C_=C_(min)^+(P_4)/(ξ_1-x)+(P_5)/(ξ_(10)~2)(ξ_1-x)~2 C_(γ′)=C_(min)^(γ′)+(P_1)/(ξ_(21))(ξ_2-x)+(P_2)/(ξ_(21)~2)(ξ_2-x)~2 C_α=C_(min)~α+(C_(33))/(C_(33))/(ξ_(32))(ξ_3-x)~3 Using these models,the kinetics of layer growth and the nitrogen concentration profile of ion nitrided layers were sinulated on Apple-Ⅱ computer.Results show that the simulated curves coincide quite well with the experimental data.
文摘The solidification microstructure and phase composition of Ni-base superalloy FGH95 pow- der with different mesh size have been investigated.The structure transition was found from dendrite in major into cellular structure as the powder size reduces and the cooling rate in- creases.The predominant phase was identified as MC-type carbide,with different morphologies,which may be related to their composition and the condition of solidification.Minor phases,such as boride,Laves and primary γ' are also present as ac- companiments of the carbide.
文摘A series of single bcc,bcc plus fcc duplex and single fcc microcrystalline coatings of 1Cr18Ni9Ti stainless steel were prepared by using sputtering technique.The resistance against pitting corrosion was studied by measurements of pitting corrosion potentials and electrochemical noise during initiation of corrosion pits.The results show that the sputtered coatings with single bcc phase or single fcc structure are more resistant to pitting corrosion than those with bcc plus fcc duplex phase structure.
文摘The crack tip stress-strain fields of the elastic-plastic cracked specimens have been analyzed using finite element calculations.The crack initiation and steady propagation behaviours have also been investigated by means of slip line pattern etching technique and mechanical tests. The results show that there are HRR near field and distant field in the crack tip region,and the later depends on the specimen configuration.The crack initiation behaviour is controlled by a single parameter J.In contrast,the steady crack propagation is affected by the distant strain field and can not be described by single parameter only.
文摘Strong, tough, and almost fully dense C fiber reinforced celsian matrix composites have been fabricated by impregnation of the fiber tows with the matrix slurry, winding on a drum, drying, stacking the prepreg tapes in the desired orientation, and hot pressing. The monoclinic celsian phase in the matrix was produced in situ, during hot pressing, from amphosous BAS. The unidirectional composites having ≈20 vol% of fibers exhibited graceful failure with extensive fiber pullout in three point bend tests at room temperature. Values of ultimate flexural strength and fracture toughness were 379MPa and 8 3MPa·m 1/2 , respectively.
文摘It is verified that stainless steel AISI 321 is in the active anodic dissolution state in 0.5 mol/L HCll+0.5 mol/L NaCl solution at 55℃.The SCC of the steel in the solution can not be reasonably explained by passive film rupture-nepasivation theory and by hydrogen embrittlement theory.There are evidences that the fracture stress at the tip of the cracks is reduced by anodic dissolution due to its role in relieving strain hardening layer at crack tip.
