The semi-solid slurry of a hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouting temperature and stirring power on the semi-solid slurry were inve...The semi-solid slurry of a hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouting temperature and stirring power on the semi-solid slurry were investigated. The results indicated that the semi-solid slurry to satisfy rheocasting can be manufactured by low superheat pouring and weak electromagnetic stirring. The pouring temperature （or superheat） and the stirring power remarkably affected the morphology of primary α-Al and the size of primary α-Al, and there is no obvious effect of stirring time on primary α-Al. Compared with the samples made by low superheat pouring with no stirring, the nucleation rate, particle morphology and grain size of primary α-Al in A356 were markedly improved by low superheat pouring and weak electromagnetic stirring. On the condition of weak electromagnetic stirring, the pouring temperature with low superheat can be suitably raised to reach the effectiveness obtained from the lower pouring temperature without stirring.展开更多
The effect of pouring temperature, electromagnetic stirring power and holding process on semi-solid A356 aluminum alloy slurry was investigated, then the slurry was squeeze-cast. The results show that when the pouring...The effect of pouring temperature, electromagnetic stirring power and holding process on semi-solid A356 aluminum alloy slurry was investigated, then the slurry was squeeze-cast. The results show that when the pouring temperatures are properly above the liquidus line, for example 630-650 ℃, the slurry with spherical primary α（Al） grains can be prepared under the stirring power of 1.27 kW. The slurry is then homogeneously held for a short time, and the primary α（Al） grains are further ripened and distributed evenly in the slurry. The results of the rheo-squeezed casting experiments show that the injection specific pressure has a great effect on the filling ability of the semi-solid A356 aluminum alloy slurry, and the higher the injection specific pressure is, the better the ability for the slurry to fill the mould cavity is. When the injection specific pressure is equal to or above 34 MPa, the whole and compact rheo-squeezed castings can be obtained. The microstructure of the castings indicates that the shape, size and numbers of the primary α（Al） grains in different parts of the castings are highly consistent. After being held at 535 ℃ for 5 h and then aged at 155 ℃ for 12 h, the ultimate strength of the rheo-squeezed castings can reach 300-320 MPa, the yield strength 230-255 MPa, and the elongation 11%-15%.展开更多
In this article, semi-solid AlSiTMg alloy slurry was prepared by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature and stirring power on the microstructure of the AISiTMg allo...In this article, semi-solid AlSiTMg alloy slurry was prepared by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature and stirring power on the microstructure of the AISiTMg alloy slurry were studied. The results showed that the semi-solid AISiTMg alloy slurry, 127 mm in diameter, could be prepared by using the low superheat pouring and weak electromagnetic stirring technology and this new technology could save energy and make the pouring process convenient. When the liquid AISiTMg alloy was poured at 650℃ or 630℃, the solidified micrastructure of the AISiTMg alloy slurry, prepared by weak electromagnetic stirring, was remarkably improved when compared with that of the slurry prepared without stirring. The primary α-Al grains appeared rosette-like or spherical. When the pouring temperature was decreased, the shape of the primary α-Al grains gradually changed from dendritic-like grains to spherical grains. When the pouring temperature was appropriately increased, that is, raised to a certain superheat, the pouring process became easier and an ideal spherical microstructure of the AISiTMg alloy slurry, prepared by weak electromagnetic stirring, could also be obtained. In this experiment, when the stirring power was 0.36 kW, the optimized pouring temperature parameter was 630 ℃. When the AISiTMg alloy slurry was prepared by low superheat pouring and weak electromagnetic stirring, the pouring temperature was 630℃. Increasing the stirring power appropriately could gain better spherical primary α-Al grains, but if the stirring power was increased to a certain value, the shape of the primary α-Al grains did not improve further. In this experiment, the optimized stirring power parameter was 0.36 kW.展开更多
In order to solve the problem of low signal-to-noise ratio（about 15 d B） in magnetic signal acquisition of banknotes, a new method of magnetic signal acquisition and processing is proposed taking RMB as an example. ...In order to solve the problem of low signal-to-noise ratio（about 15 d B） in magnetic signal acquisition of banknotes, a new method of magnetic signal acquisition and processing is proposed taking RMB as an example. In this method, weak signa detection is performed to reduce the noise accompanied with the signal. Seven orders of Chebyshev（Ⅰ） filter and the anti-jamming technology are used in the PCB layout, and grounding modes are introduced to reduce the noise of the amplitude waveform. The proposed method reduce the final output noise by 2/3 and the sig nal-to-noise ratio is increased to 24 d B. The experimental results show that the magnetic signal of RMB banknotes are acquired by the circuit stability, which provides an important guarantee for the improvements of the anti-counterfeit and discrimination for banknotes performance.展开更多
基金The project was financially supported by the Hi-tech Research and Development Program of China (No. G2002AA336080) and the National Natural Science Foundation of China (No. 50374012)
文摘The semi-solid slurry of a hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouting temperature and stirring power on the semi-solid slurry were investigated. The results indicated that the semi-solid slurry to satisfy rheocasting can be manufactured by low superheat pouring and weak electromagnetic stirring. The pouring temperature （or superheat） and the stirring power remarkably affected the morphology of primary α-Al and the size of primary α-Al, and there is no obvious effect of stirring time on primary α-Al. Compared with the samples made by low superheat pouring with no stirring, the nucleation rate, particle morphology and grain size of primary α-Al in A356 were markedly improved by low superheat pouring and weak electromagnetic stirring. On the condition of weak electromagnetic stirring, the pouring temperature with low superheat can be suitably raised to reach the effectiveness obtained from the lower pouring temperature without stirring.
基金Project(2006AA03Z115) supported by the National Hi-tech Research and Development Program of ChinaProject(2006CB605203) supported by the National Basic Research Program of ChinaProject(50774007) supported by the National Natural Science Foundation of China
文摘The effect of pouring temperature, electromagnetic stirring power and holding process on semi-solid A356 aluminum alloy slurry was investigated, then the slurry was squeeze-cast. The results show that when the pouring temperatures are properly above the liquidus line, for example 630-650 ℃, the slurry with spherical primary α（Al） grains can be prepared under the stirring power of 1.27 kW. The slurry is then homogeneously held for a short time, and the primary α（Al） grains are further ripened and distributed evenly in the slurry. The results of the rheo-squeezed casting experiments show that the injection specific pressure has a great effect on the filling ability of the semi-solid A356 aluminum alloy slurry, and the higher the injection specific pressure is, the better the ability for the slurry to fill the mould cavity is. When the injection specific pressure is equal to or above 34 MPa, the whole and compact rheo-squeezed castings can be obtained. The microstructure of the castings indicates that the shape, size and numbers of the primary α（Al） grains in different parts of the castings are highly consistent. After being held at 535 ℃ for 5 h and then aged at 155 ℃ for 12 h, the ultimate strength of the rheo-squeezed castings can reach 300-320 MPa, the yield strength 230-255 MPa, and the elongation 11%-15%.
文摘In this article, semi-solid AlSiTMg alloy slurry was prepared by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature and stirring power on the microstructure of the AISiTMg alloy slurry were studied. The results showed that the semi-solid AISiTMg alloy slurry, 127 mm in diameter, could be prepared by using the low superheat pouring and weak electromagnetic stirring technology and this new technology could save energy and make the pouring process convenient. When the liquid AISiTMg alloy was poured at 650℃ or 630℃, the solidified micrastructure of the AISiTMg alloy slurry, prepared by weak electromagnetic stirring, was remarkably improved when compared with that of the slurry prepared without stirring. The primary α-Al grains appeared rosette-like or spherical. When the pouring temperature was decreased, the shape of the primary α-Al grains gradually changed from dendritic-like grains to spherical grains. When the pouring temperature was appropriately increased, that is, raised to a certain superheat, the pouring process became easier and an ideal spherical microstructure of the AISiTMg alloy slurry, prepared by weak electromagnetic stirring, could also be obtained. In this experiment, when the stirring power was 0.36 kW, the optimized pouring temperature parameter was 630 ℃. When the AISiTMg alloy slurry was prepared by low superheat pouring and weak electromagnetic stirring, the pouring temperature was 630℃. Increasing the stirring power appropriately could gain better spherical primary α-Al grains, but if the stirring power was increased to a certain value, the shape of the primary α-Al grains did not improve further. In this experiment, the optimized stirring power parameter was 0.36 kW.
基金Supported by the project of image recognition and control system in class A machine(HT201403)
文摘In order to solve the problem of low signal-to-noise ratio（about 15 d B） in magnetic signal acquisition of banknotes, a new method of magnetic signal acquisition and processing is proposed taking RMB as an example. In this method, weak signa detection is performed to reduce the noise accompanied with the signal. Seven orders of Chebyshev（Ⅰ） filter and the anti-jamming technology are used in the PCB layout, and grounding modes are introduced to reduce the noise of the amplitude waveform. The proposed method reduce the final output noise by 2/3 and the sig nal-to-noise ratio is increased to 24 d B. The experimental results show that the magnetic signal of RMB banknotes are acquired by the circuit stability, which provides an important guarantee for the improvements of the anti-counterfeit and discrimination for banknotes performance.
