| Semi-solid Metal Forming (SSF), which was called the new forming technology of metal materials in the 21th century, appears to offer significant advantages over conventional casting and forging. Specially, the SSF of aluminum alloy is necessary to auto industry and aviation industry. The presupposition of SSF of aluminum alloy is the production of non-dendritic semi-solid billet.On the basis of the reviewing the history and the evaluation of previous research works and the progress of semi-solid metal forming, following the development directions of SSF technology in developed countries, in the light of the present study status of the SSF in China, the effect of electromagnetic stirring (EMS) on the evolution of morphology and its mechanism, the production technology of non-dendritic aluminum alloy billet and the effect of heat treatment upon microstructure and mechanical properties of non-dendritic alloy have been studied.Using the water molding method, the movement of metal fluid under the given magnetic filed has been observed The effect of electromagnetic stirring on the flow of metal fluid, under cooling and melt thermal current have been discussed. The experimental results showed that the greater the intensity of electromagnetic field (namely the greater the intensity of EMS), the greater the ability of heat exchanger and the more favorable the alloy structure with the equiaxed grain. The experimental results also showed that the relationship between EMS and under cooling was complex. The decrease value ofalloy's under cooling is in direct proportion to the square of induced current. So, with increasing of EMS intensity, on the one hand, the EMS force is added and the grain is refined, on the other hand, the heat energy of system will increase, the under cooling will decrease, and the grain will be coarsened.The experimental results demonstrated again that under the conditions of continuous cooling and EMS action, with increasing stirring intensity and time and decreasing cooling rate, the structure of aluminum alloy primary phase particles will evolve along with initial dendritic fragment-dendritic growth- "rosette" -ripened rosette-spheroid. Accompanied with the effect of EMS, there are three phenomena in solidification process. First, the grain will be increase at double speed, second, a large scale "structure" builds by collision and coalescence of favorably oriented particles (namely primary phase coalescence), third, primary phase entraps the eutectic structure.The mixed mechanism forming non-dendritic structure was put forward which include three kinds of mechanism under conditions of EMS action, (a), remelting of the root of dendritic arm; (b). dendritic arm curve and merging growth; (c). violent fluid flow and equiaxed growth. Upon the effect of above mechanisms, the non-dendritic structure will be formed in solidification system at last.Based on above study, in order to popularize the SSF technology in our country, the semisolid ZL101A alloy billet with non-dentritic structure was prepared by direct-chill-cast(DC) combined with EMS method(DC-EMS method) using the equipment devised and made by ourselves. The effects of DC-EMS method technical parameters, such as pouring temperature, casting rate and cooling rate, on the structure of ZL101A alloy were studied. The optimum results showed that on thisexperiment condition, when pouring temperature is 650-670 C, casting rate is 8.4~9.6cm/rnin and second cooling water capacity is 1.0~2.0t/h, the optimum non-dendritic alloy billet can be obtained. A synthetic study of the effects of magnetic field intensity B and cooling rate (casting rate) V on the average size D and shape factor S of non-dendritic alloy showed:When the magnetic field intensity is about 0.08-0.09T and the cooling rate at liquid-solid two phases zone of ZL101A is less than 0.3 癈/s, the optimum non-dendritic structure can be obtained.After the optimization of DC-EMS method technical parameters, the production technology of semisolid alloy is formed, and the ZL101A bi...
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