Partially stabilized zirconia ceramics were sintered using fine powder of ZrO 2 3mol%Y 2O 3 prepared by the chemical co precipitation method.The tetragonal to monoclinic phase transformation in ZrO 2 ceramics ...Partially stabilized zirconia ceramics were sintered using fine powder of ZrO 2 3mol%Y 2O 3 prepared by the chemical co precipitation method.The tetragonal to monoclinic phase transformation in ZrO 2 ceramics during the aging in boiling water and the effect of an applied stress of 100MPa were mainly investigated.The degradation of ZrO 2 ceramics is considered to be caused by the reaction between Y 2O 3 and H 2O,which leads to a decreasing in the stability of tetragonal phase of ZrO 2.It is found that the tensile stress improves the driving force of the phase transformation and accelerates the degradation while the compressive stress has no obvious effect on the degradation.展开更多
This study aims at the experimental analysis of the transformation induced plasticity (TRIP) phenomenon. Experiments are conducted in which martensite is allowed to grow under the influence of a series of externally...This study aims at the experimental analysis of the transformation induced plasticity (TRIP) phenomenon. Experiments are conducted in which martensite is allowed to grow under the influence of a series of externally applied stresses. The magnitude of the applied stresses is less than 67% of the yield strength of austenite σγ (Ts). Since there is no obvious difference between the transformation plasticity under tension and the compression for the lower applied stresses, only compressive stresses are applied. The results confirm that the transformation plasticity is proportional to the applied stress if the latter does not exceed 67 % of σγ (Ts). The TRiP-strain, the kinetics, and their dependence on the applied stresses are studied. The comparison between calculated results and experimental results shows that the model accurately describes the phenomenon.展开更多
To investigate the influence of stress alone on the stray field signals of ferromagnetic materials,the static tensile tests of 0.45%C steel and 45CrNiMoVA steel flat-shaped specimens were performed on an MTS810 hydrau...To investigate the influence of stress alone on the stray field signals of ferromagnetic materials,the static tensile tests of 0.45%C steel and 45CrNiMoVA steel flat-shaped specimens were performed on an MTS810 hydraulic testing machine. Hp(y) signals,the normal component of spontaneous stray field,were measured during the testing process by an EMS-2003 metal magnetic memory diagnostic apparatus cooperated with a non-magnetic electric control displacement instrument. Fracture and microstructure were observed by a scanning electronic microscope and a transmission electron microscope,respectively. The relationships between axial applied stress or residual stress measured by X-ray diffraction method and Hp(y) were analyzed. The results indicate that some regular pattern of the magnetic curve is displayed only between applied stress and stray field signals. The magnetic ordering process stops due to dislocation pinning magnetic domain structure,and Hp(y) value unvaried nearly with applied load increasing in the plastic deformation stage.展开更多
The two-dimensional diffusion of interstitial hydrogen atoms in zirconium in a non-uniform stress field was simulated using the phase-field method. The interaction between hydrogen interstitials and the stress field w...The two-dimensional diffusion of interstitial hydrogen atoms in zirconium in a non-uniform stress field was simulated using the phase-field method. The interaction between hydrogen interstitials and the stress field was described by Khachaturyan's elastic theory. The Cahn-Hilliard diffusion equation was then solved by an explicit finite difference method. The result shows that hydrogen atoms diffuse to the high-tensile hydrostatic region near the tip of the notch. The content of hydrogen near the tip of the notch increases by 13%, while the stress distribution caused by hydrogen interstitials around the notch is modified by only 0.7%.展开更多
The effects of surface state and applied stress on the stress corrosion cracking (SCC) behaviors of thermally treated (TT) Alloy 690 in 10 wt% NaOH solution with 100 mg/L litharge at 330 ℃ were investigated using...The effects of surface state and applied stress on the stress corrosion cracking (SCC) behaviors of thermally treated (TT) Alloy 690 in 10 wt% NaOH solution with 100 mg/L litharge at 330 ℃ were investigated using C-ring samples with four kinds of surface states and two different stress levels. Sample outer surfaces of the first three kinds were ground to 400 grit (ground), shot-peened (SP) and electro-polished (EP) and the last one was used as the as-received state. Two samples of every kind were stressed to 100% and 200% yield stress of Alloy 690TT, respectively. The results showed that the oxide film consisted of three layers whereas continuous layer rich in Cr was not found. The poor adhesive ability indicated that the oxide film could not protect the matrix from further corrosion. Lead was found in the oxide film and the oxides at the crack paths and accelerated the dissolution of thermodynamically unstable Cr in these locations and also in the matrix. The crack initiation and propagation on Alloy 690TT were effectively retarded by SP and EP treatments but were enhanced by grinding treatment, compared with the cracks on the as-received surface. The cracking severity was also enhanced by increasing the externally applied stress. The accelerated dissolution of Cr and the local tensile stress concentration in the near-surface layer caused by cold-working and higher applied stress reduced the SCC-resistance of Alloy 690TT in the studied solution.展开更多
The formation and evolution of deformation texture in polycrystalline materials are studied by phase-field dynamic model. In addition, the driving force of texture evolution is also discussed. In this model, grains wi...The formation and evolution of deformation texture in polycrystalline materials are studied by phase-field dynamic model. In addition, the driving force of texture evolution is also discussed. In this model, grains with different orientation are defined by a set of continuous non-conserved order parameter fields. Simulation results show that grains with preferred orientation grow at the expense of those with unfavorable orientations. It is more important that, elastic potentia evolution of texture whether the polycrystalline system rather than elastic energy plays a crucial role in the s subjected to uniaxial stress or shear stress.展开更多
文摘Partially stabilized zirconia ceramics were sintered using fine powder of ZrO 2 3mol%Y 2O 3 prepared by the chemical co precipitation method.The tetragonal to monoclinic phase transformation in ZrO 2 ceramics during the aging in boiling water and the effect of an applied stress of 100MPa were mainly investigated.The degradation of ZrO 2 ceramics is considered to be caused by the reaction between Y 2O 3 and H 2O,which leads to a decreasing in the stability of tetragonal phase of ZrO 2.It is found that the tensile stress improves the driving force of the phase transformation and accelerates the degradation while the compressive stress has no obvious effect on the degradation.
基金Item Sponsored by Hi-Tech Research and Development Program of China (2001AA332020)
文摘This study aims at the experimental analysis of the transformation induced plasticity (TRIP) phenomenon. Experiments are conducted in which martensite is allowed to grow under the influence of a series of externally applied stresses. The magnitude of the applied stresses is less than 67% of the yield strength of austenite σγ (Ts). Since there is no obvious difference between the transformation plasticity under tension and the compression for the lower applied stresses, only compressive stresses are applied. The results confirm that the transformation plasticity is proportional to the applied stress if the latter does not exceed 67 % of σγ (Ts). The TRiP-strain, the kinetics, and their dependence on the applied stresses are studied. The comparison between calculated results and experimental results shows that the model accurately describes the phenomenon.
基金the National Natural Science Foundation of China (No 50235030 and No 50505052)
文摘To investigate the influence of stress alone on the stray field signals of ferromagnetic materials,the static tensile tests of 0.45%C steel and 45CrNiMoVA steel flat-shaped specimens were performed on an MTS810 hydraulic testing machine. Hp(y) signals,the normal component of spontaneous stray field,were measured during the testing process by an EMS-2003 metal magnetic memory diagnostic apparatus cooperated with a non-magnetic electric control displacement instrument. Fracture and microstructure were observed by a scanning electronic microscope and a transmission electron microscope,respectively. The relationships between axial applied stress or residual stress measured by X-ray diffraction method and Hp(y) were analyzed. The results indicate that some regular pattern of the magnetic curve is displayed only between applied stress and stray field signals. The magnetic ordering process stops due to dislocation pinning magnetic domain structure,and Hp(y) value unvaried nearly with applied load increasing in the plastic deformation stage.
基金This work was financially supported by the National Natural Science Foundation of China (No.50428101), the Research GrantsCouncil of Hong Kong (B-Q471), the Hong Kong Polytechnic University (G-V851), and the U.S. National Science Foundation (DMR96-33719)
文摘The two-dimensional diffusion of interstitial hydrogen atoms in zirconium in a non-uniform stress field was simulated using the phase-field method. The interaction between hydrogen interstitials and the stress field was described by Khachaturyan's elastic theory. The Cahn-Hilliard diffusion equation was then solved by an explicit finite difference method. The result shows that hydrogen atoms diffuse to the high-tensile hydrostatic region near the tip of the notch. The content of hydrogen near the tip of the notch increases by 13%, while the stress distribution caused by hydrogen interstitials around the notch is modified by only 0.7%.
基金supported by the National Science and Technology Major Project(No. 20112x06004–009)the National Natural Science Foundation of China (No. 51025104)
文摘The effects of surface state and applied stress on the stress corrosion cracking (SCC) behaviors of thermally treated (TT) Alloy 690 in 10 wt% NaOH solution with 100 mg/L litharge at 330 ℃ were investigated using C-ring samples with four kinds of surface states and two different stress levels. Sample outer surfaces of the first three kinds were ground to 400 grit (ground), shot-peened (SP) and electro-polished (EP) and the last one was used as the as-received state. Two samples of every kind were stressed to 100% and 200% yield stress of Alloy 690TT, respectively. The results showed that the oxide film consisted of three layers whereas continuous layer rich in Cr was not found. The poor adhesive ability indicated that the oxide film could not protect the matrix from further corrosion. Lead was found in the oxide film and the oxides at the crack paths and accelerated the dissolution of thermodynamically unstable Cr in these locations and also in the matrix. The crack initiation and propagation on Alloy 690TT were effectively retarded by SP and EP treatments but were enhanced by grinding treatment, compared with the cracks on the as-received surface. The cracking severity was also enhanced by increasing the externally applied stress. The accelerated dissolution of Cr and the local tensile stress concentration in the near-surface layer caused by cold-working and higher applied stress reduced the SCC-resistance of Alloy 690TT in the studied solution.
基金the National Natural Science Foundation of China (Grant Nos.51174168,51274167)NPU Foundation for Fundamental Research (Grant No.JC20120222)
文摘The formation and evolution of deformation texture in polycrystalline materials are studied by phase-field dynamic model. In addition, the driving force of texture evolution is also discussed. In this model, grains with different orientation are defined by a set of continuous non-conserved order parameter fields. Simulation results show that grains with preferred orientation grow at the expense of those with unfavorable orientations. It is more important that, elastic potentia evolution of texture whether the polycrystalline system rather than elastic energy plays a crucial role in the s subjected to uniaxial stress or shear stress.