Specimens cut from the cold-rolled commercially pure （CP） Ti sheet were treated by high density electropulsing （the maximum current density 7.22 kA/mm2, pulse period 110 las）. The deformation behaviors of the CP T...Specimens cut from the cold-rolled commercially pure （CP） Ti sheet were treated by high density electropulsing （the maximum current density 7.22 kA/mm2, pulse period 110 las）. The deformation behaviors of the CP Ti specimens at different states were determined by the uniaxial tensile test. The microstructure morphologies were observed by the optical microscopy. The results show that the electropulsing induced formation of f＇me equal-axial grains and lamellar microstructures, which leads to the strength of the electropulsed CP Ti higher than that of the conventional annealed CP Ti. After electropulsing, the tensile strength and yield strength are increased by 100 MPa. And the electropulsed CP Ti has a good plasticity. The experimental results demonstrate that the electropulsing provides an effective approach to enhance the strength of cold-rolled CP Ti sheet and retain the required high ductility.展开更多
The effects of rare earth Ce on the microstructure and mechanical properties of impure copper containing Pb were investigated using OM,SEM,EPMA,TEM and tensile testing.TEM and EDS analysis reveal that spherical CePb3 ...The effects of rare earth Ce on the microstructure and mechanical properties of impure copper containing Pb were investigated using OM,SEM,EPMA,TEM and tensile testing.TEM and EDS analysis reveal that spherical CePb3 particles form after Ce addition.CePb3 particles,with average size of^3.6μm,homogenously distribute in the Cu matrix.Due to small lattice misfit(~4.62%)with Cu matrix,CePb3 particles can act as effective nucleation sites beneficial to the grain refinement.Pb at grain boundaries seriously deteriorates the mechanical properties of Cu.The tensile strength and the elongation of Cu-0.1 Pb are decreased by 43.1%and 56.7%compared with those of pure copper,respectively.Ce can purify grain boundaries,cause the precipitation of CePb3 particles and refine grain sizes,which contribute to significant improvement of the mechanical properties of Cu.Compared with Cu-0.1Pb,the tensile strength(179 MPa)and the elongation(38.5%)of Cu-0.1Pb-0.3Ce are increased by 117.6%and 151.6%,respectively.展开更多
Some investigations have been carried out on hot tears in the A713 cast alloy, which is one of the long freezing range alloys, with objective to minimize/prevent hot tears. Experiments were conducted by varying pourin...Some investigations have been carried out on hot tears in the A713 cast alloy, which is one of the long freezing range alloys, with objective to minimize/prevent hot tears. Experiments were conducted by varying pouring temperatures at 700, 750, and 780 ℃ on the alloy with the addition of grain refiners like Al-2.5Ti-0.5C and Al-3.5Ti-1.5C. It was found that hot tearing was minimized by the addition of Al-3.5Ti-1.5C grain refiner, but grain refinement alone could not prevent hot tearing in A713 cast alloy. This has contradicted the findings of some earlier researchers. Experiments conducted on hot tearing with the addition of iron were found to be interesting. It was found that grain refinement along with iron addition to the A713 alloy has reduced the inter-dendritic separation so that interlocking could take place along the grain boundaries. Thus, iron, which comes as an impurity in commercial aluminum, can prevent hot tearing of A713 alloy.展开更多
Two aluminum alloys,Al-8Zn and Al-6Bi-8Zn were subjected to equal channel angular pressing(ECAP)up to5passes at room temperature.The microstructural evolution and the grain refinement behavior of these alloys were sys...Two aluminum alloys,Al-8Zn and Al-6Bi-8Zn were subjected to equal channel angular pressing(ECAP)up to5passes at room temperature.The microstructural evolution and the grain refinement behavior of these alloys were systematically studied by electron backscatter diffraction(EBSD).After5passes of ECAP,ultrafine grained microstructures formed in both alloys.However,the grain structure in the Al-6Bi-8Zn alloy is much finer than that of Al-8Zn alloy,showing that the soft Bi particles have a strong influence on enhancing the grain refinement during ECAP.The strengths of the ECAP-processed materials were measured by hardness test and it showed that after5passes of ECAP,the hardness of the Al-6Bi-8Zn alloy was higher than that of the Al-8Zn alloy.The effects of soft Bi particles on the deformation behavior during ECAP and the final strength of the Al-6Bi-8Zn alloy were discussed.展开更多
In current research,the interactive effects of different parameters such as melt overheating temperature,the location of gating system and incorporation of the grain refiner in bar and micro-powder form on the mechani...In current research,the interactive effects of different parameters such as melt overheating temperature,the location of gating system and incorporation of the grain refiner in bar and micro-powder form on the mechanical and structural characteristics of commercially pure aluminium are examined.Results show that increasing the melt temperature as well as employing a gating system with higher heat transfer rate increases the ultimate tensile strength(UTS)of the pure aluminium by 7%.Also,the introduction of 2wt%Al–5Ti–1B grain refiner in bar form into the overheated melt enhances the UTS values by two times,while incorporating 2wt%Al–5Ti–1B grain refiner in micro-powder form leads to achieving 32%higher UTS compared to the samples with grain refiner in the bar form due to the elimination of Al3Ti brittle phase,as confirmed by XRD patterns and SEM fracture surface images.展开更多
Fine particles are difficult to fluidize due to strong interparticle attraction.An attempt has been made to study the bed expansion of silica gel(dp=25μm) powder in presence of an acoustic field.A 135 mm diameter flu...Fine particles are difficult to fluidize due to strong interparticle attraction.An attempt has been made to study the bed expansion of silica gel(dp=25μm) powder in presence of an acoustic field.A 135 mm diameter fluidized bed activated by an acoustic field with sound intensity up to 145 dB and frequency from 90 Hz to 170 Hz was studied.The effects of sound pressure level,sound frequency and particle loading on the bed expansion were investigated.Experimental results showed that,bed expansion was good in presence of acoustic field of particular frequency.In addition,it was observed that in presence of acoustic field the bed collapses slowly.展开更多
A consistent association has been observed between leukocyte telomere length(LTL)and atherosclerosis,but the mechanisms underlying these associations are still not well understood.Premature biology aging was evident i...A consistent association has been observed between leukocyte telomere length(LTL)and atherosclerosis,but the mechanisms underlying these associations are still not well understood.Premature biology aging was evident in atherosclerotic plaques,characterized by reduced cell proliferation,irreversible growth arrest and apoptosis,and telomere attrition.As atherosclerosis is a state of chronic low-grade inflammation and increased oxidative stress,shortened LTL in patients with atherosclerosis might stem from the two sources,one is an accelerated rate in hematopoietic stem cells(HSCs)replication to replace leukocytes consumed in the inflammatory process,and another is the increase in the loss of telomere repeats per replication.Thus,diminished HSC reserves at birth and age-dependent telomere attrition afterward are mirrored in shortened LTL during the adulthood.In addition,the inter-individual variation of LTL in the general population can be partly explained by genetic factors regulating telomere maintenance and the rate of HSCs replication.Atherosclerosis is an aging-related disease,and practically all humans develop atherosclerosis if they live long enough.Here we overview the potential roles of LTL dynamics in the imbalance between injurious oxidative stress/inflammation and endothelial repair during the pathogenesis of age-related atherosclerosis,and discuss the possibility that preventing accelerated cellular senescence is a potential target in prevention of atherosclerosis.展开更多
基金Project (50875061) supported by the National Natural Science Foundation of China
文摘Specimens cut from the cold-rolled commercially pure （CP） Ti sheet were treated by high density electropulsing （the maximum current density 7.22 kA/mm2, pulse period 110 las）. The deformation behaviors of the CP Ti specimens at different states were determined by the uniaxial tensile test. The microstructure morphologies were observed by the optical microscopy. The results show that the electropulsing induced formation of f＇me equal-axial grains and lamellar microstructures, which leads to the strength of the electropulsed CP Ti higher than that of the conventional annealed CP Ti. After electropulsing, the tensile strength and yield strength are increased by 100 MPa. And the electropulsed CP Ti has a good plasticity. The experimental results demonstrate that the electropulsing provides an effective approach to enhance the strength of cold-rolled CP Ti sheet and retain the required high ductility.
基金Projects(ZR2018MEE005,ZR2018MEE016)supported by the Natural Science Foundation of Shandong Province,ChinaProject(J18KA059)supported by the Higher Educational Science and Technology Program of Shandong Province,ChinaProject(HJ16B01)supported by the Doctoral Fund of Yantai University,China。
文摘The effects of rare earth Ce on the microstructure and mechanical properties of impure copper containing Pb were investigated using OM,SEM,EPMA,TEM and tensile testing.TEM and EDS analysis reveal that spherical CePb3 particles form after Ce addition.CePb3 particles,with average size of^3.6μm,homogenously distribute in the Cu matrix.Due to small lattice misfit(~4.62%)with Cu matrix,CePb3 particles can act as effective nucleation sites beneficial to the grain refinement.Pb at grain boundaries seriously deteriorates the mechanical properties of Cu.The tensile strength and the elongation of Cu-0.1 Pb are decreased by 43.1%and 56.7%compared with those of pure copper,respectively.Ce can purify grain boundaries,cause the precipitation of CePb3 particles and refine grain sizes,which contribute to significant improvement of the mechanical properties of Cu.Compared with Cu-0.1Pb,the tensile strength(179 MPa)and the elongation(38.5%)of Cu-0.1Pb-0.3Ce are increased by 117.6%and 151.6%,respectively.
文摘Some investigations have been carried out on hot tears in the A713 cast alloy, which is one of the long freezing range alloys, with objective to minimize/prevent hot tears. Experiments were conducted by varying pouring temperatures at 700, 750, and 780 ℃ on the alloy with the addition of grain refiners like Al-2.5Ti-0.5C and Al-3.5Ti-1.5C. It was found that hot tearing was minimized by the addition of Al-3.5Ti-1.5C grain refiner, but grain refinement alone could not prevent hot tearing in A713 cast alloy. This has contradicted the findings of some earlier researchers. Experiments conducted on hot tearing with the addition of iron were found to be interesting. It was found that grain refinement along with iron addition to the A713 alloy has reduced the inter-dendritic separation so that interlocking could take place along the grain boundaries. Thus, iron, which comes as an impurity in commercial aluminum, can prevent hot tearing of A713 alloy.
基金Project(10407002)supported by Research Council of NorwayProject(201406080011)supported by China Scholarship Council
文摘Two aluminum alloys,Al-8Zn and Al-6Bi-8Zn were subjected to equal channel angular pressing(ECAP)up to5passes at room temperature.The microstructural evolution and the grain refinement behavior of these alloys were systematically studied by electron backscatter diffraction(EBSD).After5passes of ECAP,ultrafine grained microstructures formed in both alloys.However,the grain structure in the Al-6Bi-8Zn alloy is much finer than that of Al-8Zn alloy,showing that the soft Bi particles have a strong influence on enhancing the grain refinement during ECAP.The strengths of the ECAP-processed materials were measured by hardness test and it showed that after5passes of ECAP,the hardness of the Al-6Bi-8Zn alloy was higher than that of the Al-8Zn alloy.The effects of soft Bi particles on the deformation behavior during ECAP and the final strength of the Al-6Bi-8Zn alloy were discussed.
文摘In current research,the interactive effects of different parameters such as melt overheating temperature,the location of gating system and incorporation of the grain refiner in bar and micro-powder form on the mechanical and structural characteristics of commercially pure aluminium are examined.Results show that increasing the melt temperature as well as employing a gating system with higher heat transfer rate increases the ultimate tensile strength(UTS)of the pure aluminium by 7%.Also,the introduction of 2wt%Al–5Ti–1B grain refiner in bar form into the overheated melt enhances the UTS values by two times,while incorporating 2wt%Al–5Ti–1B grain refiner in micro-powder form leads to achieving 32%higher UTS compared to the samples with grain refiner in the bar form due to the elimination of Al3Ti brittle phase,as confirmed by XRD patterns and SEM fracture surface images.
文摘Fine particles are difficult to fluidize due to strong interparticle attraction.An attempt has been made to study the bed expansion of silica gel(dp=25μm) powder in presence of an acoustic field.A 135 mm diameter fluidized bed activated by an acoustic field with sound intensity up to 145 dB and frequency from 90 Hz to 170 Hz was studied.The effects of sound pressure level,sound frequency and particle loading on the bed expansion were investigated.Experimental results showed that,bed expansion was good in presence of acoustic field of particular frequency.In addition,it was observed that in presence of acoustic field the bed collapses slowly.
文摘A consistent association has been observed between leukocyte telomere length(LTL)and atherosclerosis,but the mechanisms underlying these associations are still not well understood.Premature biology aging was evident in atherosclerotic plaques,characterized by reduced cell proliferation,irreversible growth arrest and apoptosis,and telomere attrition.As atherosclerosis is a state of chronic low-grade inflammation and increased oxidative stress,shortened LTL in patients with atherosclerosis might stem from the two sources,one is an accelerated rate in hematopoietic stem cells(HSCs)replication to replace leukocytes consumed in the inflammatory process,and another is the increase in the loss of telomere repeats per replication.Thus,diminished HSC reserves at birth and age-dependent telomere attrition afterward are mirrored in shortened LTL during the adulthood.In addition,the inter-individual variation of LTL in the general population can be partly explained by genetic factors regulating telomere maintenance and the rate of HSCs replication.Atherosclerosis is an aging-related disease,and practically all humans develop atherosclerosis if they live long enough.Here we overview the potential roles of LTL dynamics in the imbalance between injurious oxidative stress/inflammation and endothelial repair during the pathogenesis of age-related atherosclerosis,and discuss the possibility that preventing accelerated cellular senescence is a potential target in prevention of atherosclerosis.
