The effect of electropulse on the solidification structure of commercially pure aluminium was studied. The orthogonal array L9 was used to determine the effect of three process parameters of electropulse modification ...The effect of electropulse on the solidification structure of commercially pure aluminium was studied. The orthogonal array L9 was used to determine the effect of three process parameters of electropulse modification （EPM）, which were pulse current intensity, pulse frequency, and treating time. For each factor, three levels were chosen to cover the experimental region. According to the experimental results, the solidification structure of commercially pure aluminium was modified from large grains with columnar crystals to finer grains with equiaxed crystals, by allowing the electropulse to act on liquid aluminium. However, the solidification structures could be refined differently at different EPM parameters. Certain EPM parameters should be selected to get the optimum solidification structure. Among the three parameters, pulse frequency was the most important factor influencing the solidification structure, the secondary factor was current intensity, and treating time was the third one. The optimum parameters were the pulse frequency of 5 Hz, the current intensity of 68 A, and the treating time of l0 s.展开更多
The aim of this paper was to address the effect of laser shock processing (LSP) on the microstructure of ultrafine-grained commercially pure aluminium which was produced through severe cold rolling and annealing. The ...The aim of this paper was to address the effect of laser shock processing (LSP) on the microstructure of ultrafine-grained commercially pure aluminium which was produced through severe cold rolling and annealing. The microstructure characteristics of ultrafine-grained commercially pure aluminium were experimentally investigated by TEM during ultra-high strain rate loading. The results show that microstructure was obviously refined due to ultra-high plastic strain induced by a single pass LSP impacts. The grain sizes decrease from 0.6 μm after severe cold rolling and annealing to 0.3 μm at the center of the laser shock wave after a single pass LSP. There is a distinct increase in the dislocation density at the edge of the laser shock wave. These experiments have guide meaning to the practical engineering applications of LSP technique.展开更多
A 2-D numerical model was developed to predict the shape of weld pool in stationary GTA welding of commercial pure aluminium, without considering fluid flow in the weld pool. A Gaussian current density and heat input ...A 2-D numerical model was developed to predict the shape of weld pool in stationary GTA welding of commercial pure aluminium, without considering fluid flow in the weld pool. A Gaussian current density and heat input distribution on the surface of the workpiece were considered. The parameters of Gaussian distribution were modified by comparing calculated results with experimental ones. It was found that these distribution parameters are fimctions of applied current and arc length. Effects of arc length, applied current and welding time on the geometry of the weld pool were investigated. To check the validity of the model, a series of experiments were also conducted. In general, the agreement between calculated overall shape of the weld pool and the experimental one was acceptable, especially in low applied currents. Therefore, it can be concluded that in pure aluminium, the heat conduction is dominant mechanism of heat transfer in the weld pool.展开更多
基金the National Natural Science Foundation of China (No.30160186).
文摘The effect of electropulse on the solidification structure of commercially pure aluminium was studied. The orthogonal array L9 was used to determine the effect of three process parameters of electropulse modification （EPM）, which were pulse current intensity, pulse frequency, and treating time. For each factor, three levels were chosen to cover the experimental region. According to the experimental results, the solidification structure of commercially pure aluminium was modified from large grains with columnar crystals to finer grains with equiaxed crystals, by allowing the electropulse to act on liquid aluminium. However, the solidification structures could be refined differently at different EPM parameters. Certain EPM parameters should be selected to get the optimum solidification structure. Among the three parameters, pulse frequency was the most important factor influencing the solidification structure, the secondary factor was current intensity, and treating time was the third one. The optimum parameters were the pulse frequency of 5 Hz, the current intensity of 68 A, and the treating time of l0 s.
基金National Nature Science Foundation of China (50801021)
文摘The aim of this paper was to address the effect of laser shock processing (LSP) on the microstructure of ultrafine-grained commercially pure aluminium which was produced through severe cold rolling and annealing. The microstructure characteristics of ultrafine-grained commercially pure aluminium were experimentally investigated by TEM during ultra-high strain rate loading. The results show that microstructure was obviously refined due to ultra-high plastic strain induced by a single pass LSP impacts. The grain sizes decrease from 0.6 μm after severe cold rolling and annealing to 0.3 μm at the center of the laser shock wave after a single pass LSP. There is a distinct increase in the dislocation density at the edge of the laser shock wave. These experiments have guide meaning to the practical engineering applications of LSP technique.
文摘A 2-D numerical model was developed to predict the shape of weld pool in stationary GTA welding of commercial pure aluminium, without considering fluid flow in the weld pool. A Gaussian current density and heat input distribution on the surface of the workpiece were considered. The parameters of Gaussian distribution were modified by comparing calculated results with experimental ones. It was found that these distribution parameters are fimctions of applied current and arc length. Effects of arc length, applied current and welding time on the geometry of the weld pool were investigated. To check the validity of the model, a series of experiments were also conducted. In general, the agreement between calculated overall shape of the weld pool and the experimental one was acceptable, especially in low applied currents. Therefore, it can be concluded that in pure aluminium, the heat conduction is dominant mechanism of heat transfer in the weld pool.
基金supported by the National Natural Science Foundation of China (No. 52171119)the Natural Science Foundation of Jiangsu Province, China (No. BK20201308)。
