In order to study the effect of dynamic recrystallization on the metal flow behavior during thermal deformation,the elevated temperature compression experiments of CuCrZr alloy and 35CrMo steel are carried out using G...In order to study the effect of dynamic recrystallization on the metal flow behavior during thermal deformation,the elevated temperature compression experiments of CuCrZr alloy and 35CrMo steel are carried out using Gleeble-3810 thermal simulator.It is proved that the samples underwent obvious dynamic recrystallization behavior during thermal deformation by microstructure observation of deformed specimens.The size of recrystallized grains increases as the temperature improved and the strain rate decreased.Meanwhile,the net softening rate caused by dynamic recrystallization is determined based on the stress-dislocation relationship.It can be found that the value of net softening rate increases quadratically as the Z parameter decreases,and the dynamic recrystallization net softening rate of CuCrZr alloy and 35CrMo steel are calculated to be 21.9%and 29.8%,respectively.Based on the dynamic recrystallization softening effect proposed,the novel elevated temperature flow constitutive models of two different alloys are proposed,and the related parameters are well defined and solved in detail.The predicted values of the obtained models are agreed well with the experimental values.展开更多
The significance of this paper lies in the application of bending-upsetting 35CrMo steel in train crack-shaft. The hot deforming tests of 35CrMo steel have been done on the Gleeble-1500 testing machine with the deform...The significance of this paper lies in the application of bending-upsetting 35CrMo steel in train crack-shaft. The hot deforming tests of 35CrMo steel have been done on the Gleeble-1500 testing machine with the deformation temperature at the range of 900癈-1250癈, a strain strain of 0.05 s-1, 0.5 s-1, 1.0 s-1 and compress degree of 15%-80%. Through respectively analyzing and studying the microstructure of the specimen and getting the data from the testing, the results obtained are as follows: the model of flow stress and the stress-strain relationship of material hot deformation, the model of dynamic and static re-crystallization and the correlative references of hot forming parameters and changes of microstructure. The hot deforming stress-strain curses and relevantly re-crystallized micro-structure of 35CrMo steel are drawn at the deformation temperature of 1250 and the strain rate of 1.0 s. Through analyzing and regressive calculating the grain size of the deformation specimen of 35CrMo steel at different locations under the large-deformation and high-temperature conditions, the hot-deforming model of grain calculation is verified. The experimental results and the model of grain calculation can provide scientific basis for analyzing the hot deformation processes and controlling quality.展开更多
Multilayer hard coatings of TiC/Ti(C,N)/TiN on 35 CrMo steel substrates were deposited by a chemical vapor deposition system(CVD).X-ray diffraction(XRD),scanning electron microscopy(SEM),and energy dispersive X-ray sp...Multilayer hard coatings of TiC/Ti(C,N)/TiN on 35 CrMo steel substrates were deposited by a chemical vapor deposition system(CVD).X-ray diffraction(XRD),scanning electron microscopy(SEM),and energy dispersive X-ray spectrometer(EDX)were used to analyze phase composition,morphology,and chemical composition of the coatings.The mechanical,corrosion,and wear properties of the produced coatings were primarily examined.The results indicate that multilayer coatings are consisted of TiC,Ti(C0.2N0.8),and TiN.The coatings surface is dense,and the thickness is about 11μm.The adhesion between coatings and steel substrate was characterized by critical load(Lc)and is found to be about 70 N.The microhardness of the multilayer coatings is HV 2400,which is about 5 times as that of the 35 CrMo steel substrate.The corrosion current of the coated sample is 4.368×10^(-5)A·cm^(-2),which decreases by one order of magnitude compared with the uncoated one(1.324×10^(-4)A·cm^(-2)).Friction and wear tests show that the TiC/Ti(C,N)/TiN coatings with high hardness adhere well to the 35 CrMo substrate and display good wear resistance and low friction coefficient under non-lubricated friction test at room temperature.展开更多
Observation under high resolution electron microscope shows that the continuous bombing of high speed ions produces a great amount of vacant site defects.The assembly of vacancies forms vacant dish,and the collapase o...Observation under high resolution electron microscope shows that the continuous bombing of high speed ions produces a great amount of vacant site defects.The assembly of vacancies forms vacant dish,and the collapase of vacant dish forms stacking fault tetrahedrons and oth- er crystal defects.The interfaces between phase ε(Fe_(2-3)N)and phase γ'(Fe_4N)are smooth, straight and coherent,and they have the orientation relationships of(11)//(0001)and [110]/[110] .展开更多
基金Project(2019zzts525)supported by the Fundamental Research Funds for the Central Universities,ChinaProjects(U1837207,U1637601)supported by the National Natural Science Foundation of China
文摘In order to study the effect of dynamic recrystallization on the metal flow behavior during thermal deformation,the elevated temperature compression experiments of CuCrZr alloy and 35CrMo steel are carried out using Gleeble-3810 thermal simulator.It is proved that the samples underwent obvious dynamic recrystallization behavior during thermal deformation by microstructure observation of deformed specimens.The size of recrystallized grains increases as the temperature improved and the strain rate decreased.Meanwhile,the net softening rate caused by dynamic recrystallization is determined based on the stress-dislocation relationship.It can be found that the value of net softening rate increases quadratically as the Z parameter decreases,and the dynamic recrystallization net softening rate of CuCrZr alloy and 35CrMo steel are calculated to be 21.9%and 29.8%,respectively.Based on the dynamic recrystallization softening effect proposed,the novel elevated temperature flow constitutive models of two different alloys are proposed,and the related parameters are well defined and solved in detail.The predicted values of the obtained models are agreed well with the experimental values.
文摘The significance of this paper lies in the application of bending-upsetting 35CrMo steel in train crack-shaft. The hot deforming tests of 35CrMo steel have been done on the Gleeble-1500 testing machine with the deformation temperature at the range of 900癈-1250癈, a strain strain of 0.05 s-1, 0.5 s-1, 1.0 s-1 and compress degree of 15%-80%. Through respectively analyzing and studying the microstructure of the specimen and getting the data from the testing, the results obtained are as follows: the model of flow stress and the stress-strain relationship of material hot deformation, the model of dynamic and static re-crystallization and the correlative references of hot forming parameters and changes of microstructure. The hot deforming stress-strain curses and relevantly re-crystallized micro-structure of 35CrMo steel are drawn at the deformation temperature of 1250 and the strain rate of 1.0 s. Through analyzing and regressive calculating the grain size of the deformation specimen of 35CrMo steel at different locations under the large-deformation and high-temperature conditions, the hot-deforming model of grain calculation is verified. The experimental results and the model of grain calculation can provide scientific basis for analyzing the hot deformation processes and controlling quality.
基金the National High Technology Research and Development Program of China(No.2007AA09Z202)the Foundation of Sichuan Educational Committee(No.2012ZB164)。
文摘Multilayer hard coatings of TiC/Ti(C,N)/TiN on 35 CrMo steel substrates were deposited by a chemical vapor deposition system(CVD).X-ray diffraction(XRD),scanning electron microscopy(SEM),and energy dispersive X-ray spectrometer(EDX)were used to analyze phase composition,morphology,and chemical composition of the coatings.The mechanical,corrosion,and wear properties of the produced coatings were primarily examined.The results indicate that multilayer coatings are consisted of TiC,Ti(C0.2N0.8),and TiN.The coatings surface is dense,and the thickness is about 11μm.The adhesion between coatings and steel substrate was characterized by critical load(Lc)and is found to be about 70 N.The microhardness of the multilayer coatings is HV 2400,which is about 5 times as that of the 35 CrMo steel substrate.The corrosion current of the coated sample is 4.368×10^(-5)A·cm^(-2),which decreases by one order of magnitude compared with the uncoated one(1.324×10^(-4)A·cm^(-2)).Friction and wear tests show that the TiC/Ti(C,N)/TiN coatings with high hardness adhere well to the 35 CrMo substrate and display good wear resistance and low friction coefficient under non-lubricated friction test at room temperature.
文摘Observation under high resolution electron microscope shows that the continuous bombing of high speed ions produces a great amount of vacant site defects.The assembly of vacancies forms vacant dish,and the collapase of vacant dish forms stacking fault tetrahedrons and oth- er crystal defects.The interfaces between phase ε(Fe_(2-3)N)and phase γ'(Fe_4N)are smooth, straight and coherent,and they have the orientation relationships of(11)//(0001)and [110]/[110] .
