The bulk TC17was subjected to the high energy shot peening(HESP)at the air pressures ranging from0.35to0.55MPa and processing durations ranging from15to60min.The microhardness(HV0.02)from topmost surface to matrix of ...The bulk TC17was subjected to the high energy shot peening(HESP)at the air pressures ranging from0.35to0.55MPa and processing durations ranging from15to60min.The microhardness(HV0.02)from topmost surface to matrix of the HESP processed TC17was measured,which generally decreases with the increase of depth from topmost surface to matrix and presents different variation with air pressure and processing duration at different depths.A fuzzy neural network(FNN)model was established to predict the surface layer microhardness of the HESP processed TC17,where the maximum and average difference between the measured and the predicted microhardness were respectively8.5%and3.2%.Applying the FNN model,the effects of the air pressure and processing duration on the microhardness at different depths were analyzed,revealing the significant interaction between the refined layer shelling and the continuous grain refinement.展开更多
The high temperature deformation behavior and microstructures evolution of TC17 alloy in the temperature range of 820°C - 930°C, strain rate range of 0.01 s-1 - 10 s-1 and height direction reduction of 20% -...The high temperature deformation behavior and microstructures evolution of TC17 alloy in the temperature range of 820°C - 930°C, strain rate range of 0.01 s-1 - 10 s-1 and height direction reduction of 20% - 80% have been studied by hot compressing testing. The microstructures of TC17 alloy were observed and analyzed using Olympus/PMG3 optical microscope. The flow stresses were correlated with strain rate and the temperature by the constitutive equation. The results show that the flow stress of TC17 alloy increase quickly with the strain, then decrease with a steady value. The deformation activation energy obtained in the α + β region for TC17 was 407 kJ/mol, and in the β region was 155 kJ/mol. It was also found that the degree of dynamic globularization of α phase increases with increasing strains, increasing temperature and decreasing strain rate in α + β region, the dynamic re-crystallization is obvious at low strain rate and dynamic recovery is obvious at high strain rate in β region.展开更多
1. Introduction The discovery of possible high T;super-conductivity at 35K in La-Ba-Cu-O systemsparked an intense study on the new classof cupric oxides by a few laboratoriesincluding the joint research group of highT...1. Introduction The discovery of possible high T;super-conductivity at 35K in La-Ba-Cu-O systemsparked an intense study on the new classof cupric oxides by a few laboratoriesincluding the joint research group of highT;superconductivity in the Institute ofPhysics, Academia Sinica. A few monthslater we not only confirmed the展开更多
On microscopic and microstructural levels, the relations between high Tc superconductivity and percolation have been discussed. On the microscopic level, the critical oxygen concentration in YBa2Cu3O7 with Tc around 9...On microscopic and microstructural levels, the relations between high Tc superconductivity and percolation have been discussed. On the microscopic level, the critical oxygen concentration in YBa2Cu3O7 with Tc around 90 K has been obtained in terms of percolation. On the microstruc(?)ural level, the percolation considerations have provided, usefully theoretical basis for materials design of metal/high-Tc superconducting phase ( nonmetal) composites.展开更多
The temperature dependent Fe Mossbauer and X-ray diffraction measurement on Bi-system 2:2:2:3 phase have been carried out from 77 K to 300 K. It was found that there are two anomalous behaviors of lattice vibrational ...The temperature dependent Fe Mossbauer and X-ray diffraction measurement on Bi-system 2:2:2:3 phase have been carried out from 77 K to 300 K. It was found that there are two anomalous behaviors of lattice vibrational modes near 125 K and 220 K. This phenomena of lattice softening above Tc is taken as a precursor effect of superconductivity.展开更多
The high temperature superconductor of CuBa2Ca2Cu3O8+δ(Cu-1223) was synthesized experimentally by solid-state reaction. There were many pa-rameters affecting the preparation technique such as oxygen flow, si...The high temperature superconductor of CuBa2Ca2Cu3O8+δ(Cu-1223) was synthesized experimentally by solid-state reaction. There were many pa-rameters affecting the preparation technique such as oxygen flow, sintering temperature, sintering time, and compacted pressure. The XRD-pattern exhibited a tetragonal phase for both Cu-1223, and Cu-1212. The resistivity measurement was considered the important experiment to show the predominant phase of superconductor if it was a high phase or low phase. The critical temperature (Tc) was about (128 K) for the high phase of Cu-1223, whereas the low phase of (Cu-1212) appeared at (Tc = 64 K). The correlation between the Miller indices and resistivity measurements was a good tool to predicate the expected mechanism of conductivity within the unit cell. It was clear that the arrangement of these planes was aligned in the a-c direction. That should make the motion of the charge to be simpler by a stepping plane toward c-axis.展开更多
基金Project (51475375) supported by the National Natural Science Foundation of China
文摘The bulk TC17was subjected to the high energy shot peening(HESP)at the air pressures ranging from0.35to0.55MPa and processing durations ranging from15to60min.The microhardness(HV0.02)from topmost surface to matrix of the HESP processed TC17was measured,which generally decreases with the increase of depth from topmost surface to matrix and presents different variation with air pressure and processing duration at different depths.A fuzzy neural network(FNN)model was established to predict the surface layer microhardness of the HESP processed TC17,where the maximum and average difference between the measured and the predicted microhardness were respectively8.5%and3.2%.Applying the FNN model,the effects of the air pressure and processing duration on the microhardness at different depths were analyzed,revealing the significant interaction between the refined layer shelling and the continuous grain refinement.
文摘The high temperature deformation behavior and microstructures evolution of TC17 alloy in the temperature range of 820°C - 930°C, strain rate range of 0.01 s-1 - 10 s-1 and height direction reduction of 20% - 80% have been studied by hot compressing testing. The microstructures of TC17 alloy were observed and analyzed using Olympus/PMG3 optical microscope. The flow stresses were correlated with strain rate and the temperature by the constitutive equation. The results show that the flow stress of TC17 alloy increase quickly with the strain, then decrease with a steady value. The deformation activation energy obtained in the α + β region for TC17 was 407 kJ/mol, and in the β region was 155 kJ/mol. It was also found that the degree of dynamic globularization of α phase increases with increasing strains, increasing temperature and decreasing strain rate in α + β region, the dynamic re-crystallization is obvious at low strain rate and dynamic recovery is obvious at high strain rate in β region.
文摘1. Introduction The discovery of possible high T;super-conductivity at 35K in La-Ba-Cu-O systemsparked an intense study on the new classof cupric oxides by a few laboratoriesincluding the joint research group of highT;superconductivity in the Institute ofPhysics, Academia Sinica. A few monthslater we not only confirmed the
基金This work was in part supported by the National‘863’Plan
文摘On microscopic and microstructural levels, the relations between high Tc superconductivity and percolation have been discussed. On the microscopic level, the critical oxygen concentration in YBa2Cu3O7 with Tc around 90 K has been obtained in terms of percolation. On the microstruc(?)ural level, the percolation considerations have provided, usefully theoretical basis for materials design of metal/high-Tc superconducting phase ( nonmetal) composites.
文摘The temperature dependent Fe Mossbauer and X-ray diffraction measurement on Bi-system 2:2:2:3 phase have been carried out from 77 K to 300 K. It was found that there are two anomalous behaviors of lattice vibrational modes near 125 K and 220 K. This phenomena of lattice softening above Tc is taken as a precursor effect of superconductivity.
文摘The high temperature superconductor of CuBa2Ca2Cu3O8+δ(Cu-1223) was synthesized experimentally by solid-state reaction. There were many pa-rameters affecting the preparation technique such as oxygen flow, sintering temperature, sintering time, and compacted pressure. The XRD-pattern exhibited a tetragonal phase for both Cu-1223, and Cu-1212. The resistivity measurement was considered the important experiment to show the predominant phase of superconductor if it was a high phase or low phase. The critical temperature (Tc) was about (128 K) for the high phase of Cu-1223, whereas the low phase of (Cu-1212) appeared at (Tc = 64 K). The correlation between the Miller indices and resistivity measurements was a good tool to predicate the expected mechanism of conductivity within the unit cell. It was clear that the arrangement of these planes was aligned in the a-c direction. That should make the motion of the charge to be simpler by a stepping plane toward c-axis.
