The corrosion behaviors of 1420 and 2195 Al-Li alloys under 308 and 490 MPa tensile stress respectively in neutral 3.5% NaCl solution were investigated using electrochemical impedance spectroscopy(EIS) and scanning el...The corrosion behaviors of 1420 and 2195 Al-Li alloys under 308 and 490 MPa tensile stress respectively in neutral 3.5% NaCl solution were investigated using electrochemical impedance spectroscopy(EIS) and scanning electron microscope(SEM). It is found that the unstressed 1420 alloy is featured with large and discrete pits, while general corrosion and localized corrosion including intergranular corrosion and pitting corrosion occur on the unstressed 2195 alloy. As stress is applied to 1420 alloy, the pit becomes denser and its size is decreased. While, for the stressed 2195 alloy, intergranular corrosion is greatly aggravated and severe general corrosion is developed from connected pits. The EIS analysis shows that more severe general corrosion and localized corrosion occur on the stressed 2195 Al-Li alloy than on 1420 Al-Li alloy. It is suggested that tensile stress has greater effect on the corrosion of 2195 Al-Li alloy than on 1420 Al-Li alloy.展开更多
True stress-true strain curve,microstructure and texture information were obtained to investigate the superplastic deformation behavior of 1420 Al-Li alloy sheets with initial elongated grains.From the true stress-tru...True stress-true strain curve,microstructure and texture information were obtained to investigate the superplastic deformation behavior of 1420 Al-Li alloy sheets with initial elongated grains.From the true stress-true curve,the stress increases with the increase of strain to 0.15,then dramatically decreases with the increase of strain to 0.80,and finally keeps almost a horizontal line.Meanwhile,initial elongated grains are gradually changed into equiaxed grains and the initial strong Brass {0 1 1} <2 1 1> and S {1 2 3} <6 3 4> orientations are turned into nearly random orientation with increasing strain.All these results suggest that dislocation activity is the dominant mechanism during the first stage,then dynamic recrystallization occurs,and grain rotation is expected as an accommodation for grain boundary sliding(GBS).At larger strains,grain boundary migration(GBM) becomes necessary to accommodate GBS.展开更多
In order to investigate the effects of Ce on mechanical anisotorpy of Al-Li alloys, the texture of 2090 AlLi alloy with different Ce content was determined using orientation distribution function technique, in which ...In order to investigate the effects of Ce on mechanical anisotorpy of Al-Li alloys, the texture of 2090 AlLi alloy with different Ce content was determined using orientation distribution function technique, in which the mechanical properties with different angles to rolling direction were measured. The effects of Ce on texture and mechanical properties of 2090 alloys were discussed. The results show that the type of main texture of 2090 alloys is {225} <554>. Ce will not change the type of main texture of the alloy, but make the distributiodn of main texture scattered. Ce can change the volume fractions of ideal texture components and will decrease the anisotropy of yield strength, hence the content of the texture components that enhance the anisotropy of yield strength can be reduced.展开更多
A nanostructured surface layer was fabricated on 1420 aluminum alloy by high-energy shot peening.Microstructures were characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM) and high-resolu...A nanostructured surface layer was fabricated on 1420 aluminum alloy by high-energy shot peening.Microstructures were characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM) and high-resolution electron microscope(HRTEM), and microhardness measurement was conducted along the depth from top surface layer to matrix of the sample peened for 30 min. The results show that a nanocrystalline layer about 20 μm in thickness is formed on the surface of the sample after high-energy shot peening, in which the grain size is changed from about 20 nm to 100 nm. In the surface layer of 20 -50 μm in depth, the microstructure consists of submicron grains. The surface nanocrystallization is accomplished by dislocation slip. The microhardness of the top surface nanostructured layer is enhanced obviously after high-energy shot peening(HESP) compared with that of the coarse-grained matrix.展开更多
Effect of trace rare earth Er addition on the aging behavior of 1420 alloys was studied using hardness testing. Precipitation behavior during aging was investigated by electron microscopy transmission. It is found tha...Effect of trace rare earth Er addition on the aging behavior of 1420 alloys was studied using hardness testing. Precipitation behavior during aging was investigated by electron microscopy transmission. It is found that small amounts of Er can modify the aging behavior of 1420 alloy, for example, improve the hardness and shift peak aging time. All those results may be attributed to the increase of diffusion coefficient of Li atom in the Al matrix added with Er. As a consequence, rate of nucleation and growth of δ′ (Al_3Li) was promoted; the Al_3Er particles act as preferential sites for the nucleation and growth of δ′, which in turn results in the presentation of more composite particles.展开更多
基金Project(50401012) supported by the National Natural Science Foundation of China
文摘The corrosion behaviors of 1420 and 2195 Al-Li alloys under 308 and 490 MPa tensile stress respectively in neutral 3.5% NaCl solution were investigated using electrochemical impedance spectroscopy(EIS) and scanning electron microscope(SEM). It is found that the unstressed 1420 alloy is featured with large and discrete pits, while general corrosion and localized corrosion including intergranular corrosion and pitting corrosion occur on the unstressed 2195 alloy. As stress is applied to 1420 alloy, the pit becomes denser and its size is decreased. While, for the stressed 2195 alloy, intergranular corrosion is greatly aggravated and severe general corrosion is developed from connected pits. The EIS analysis shows that more severe general corrosion and localized corrosion occur on the stressed 2195 Al-Li alloy than on 1420 Al-Li alloy. It is suggested that tensile stress has greater effect on the corrosion of 2195 Al-Li alloy than on 1420 Al-Li alloy.
基金Project(2006DFA53250) supported by the International Science and Technology Cooperation Program of ChinaProject(2005CB623706) supported by the National Basic Research Program of China
文摘True stress-true strain curve,microstructure and texture information were obtained to investigate the superplastic deformation behavior of 1420 Al-Li alloy sheets with initial elongated grains.From the true stress-true curve,the stress increases with the increase of strain to 0.15,then dramatically decreases with the increase of strain to 0.80,and finally keeps almost a horizontal line.Meanwhile,initial elongated grains are gradually changed into equiaxed grains and the initial strong Brass {0 1 1} <2 1 1> and S {1 2 3} <6 3 4> orientations are turned into nearly random orientation with increasing strain.All these results suggest that dislocation activity is the dominant mechanism during the first stage,then dynamic recrystallization occurs,and grain rotation is expected as an accommodation for grain boundary sliding(GBS).At larger strains,grain boundary migration(GBM) becomes necessary to accommodate GBS.
基金the National Natural Science Foundation of China!58971071
文摘In order to investigate the effects of Ce on mechanical anisotorpy of Al-Li alloys, the texture of 2090 AlLi alloy with different Ce content was determined using orientation distribution function technique, in which the mechanical properties with different angles to rolling direction were measured. The effects of Ce on texture and mechanical properties of 2090 alloys were discussed. The results show that the type of main texture of 2090 alloys is {225} <554>. Ce will not change the type of main texture of the alloy, but make the distributiodn of main texture scattered. Ce can change the volume fractions of ideal texture components and will decrease the anisotropy of yield strength, hence the content of the texture components that enhance the anisotropy of yield strength can be reduced.
文摘A nanostructured surface layer was fabricated on 1420 aluminum alloy by high-energy shot peening.Microstructures were characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM) and high-resolution electron microscope(HRTEM), and microhardness measurement was conducted along the depth from top surface layer to matrix of the sample peened for 30 min. The results show that a nanocrystalline layer about 20 μm in thickness is formed on the surface of the sample after high-energy shot peening, in which the grain size is changed from about 20 nm to 100 nm. In the surface layer of 20 -50 μm in depth, the microstructure consists of submicron grains. The surface nanocrystallization is accomplished by dislocation slip. The microhardness of the top surface nanostructured layer is enhanced obviously after high-energy shot peening(HESP) compared with that of the coarse-grained matrix.
文摘Effect of trace rare earth Er addition on the aging behavior of 1420 alloys was studied using hardness testing. Precipitation behavior during aging was investigated by electron microscopy transmission. It is found that small amounts of Er can modify the aging behavior of 1420 alloy, for example, improve the hardness and shift peak aging time. All those results may be attributed to the increase of diffusion coefficient of Li atom in the Al matrix added with Er. As a consequence, rate of nucleation and growth of δ′ (Al_3Li) was promoted; the Al_3Er particles act as preferential sites for the nucleation and growth of δ′, which in turn results in the presentation of more composite particles.
