坩堝比例和電磁頻率對半固態(tài)A356鋁合金漿料流動影響的研究

坩堝比例和電磁頻率對半固態(tài)A356鋁合金漿料流動影響的研究EFFECT OF CRUCIBLE RATIO AND ELECTROMAGNETIC FREQUENCY ON FLOW DURING FABRICATION OF SEMISOLID A356 ALUMINUM ALLOY SLURRY

采用數(shù)值模擬通過改變坩堝長短軸比例和電磁攪拌頻率研究半固態(tài)A356鋁合金漿料時的流動規(guī)律，以及不同坩堝長短軸比例對半固態(tài)A356鋁合金漿料初生相組織的影響。結果表明：坩堝長短軸比例越大，半固態(tài)A356鋁合金在短軸上所受的電磁力和流速呈先增大后減小的趨勢，在長軸上的半固態(tài)A356鋁合金所受的電磁力和流速呈先增后減再增的現(xiàn)象；頻率越高，短軸和長軸上的半固態(tài)A356鋁合金所受的電磁力差和流速差越明顯，因而可使得熔體流動時出現(xiàn)“加速-減速-加速”的循環(huán)運動現(xiàn)象。當電磁頻率和坩堝長短軸比例分別為30 Hz和1.1時，坩堝長軸和短軸上的流速分別為153.6 mm/s和143.2 mm/s，流速差最小，此時可制備出較優(yōu)的半固態(tài)A356鋁合金漿料。

A356 aluminum alloy has been widely used in semisolid processing because of its wide range of liquidus and solidus temperatures. The flow of the melt during solidification has a certain influence on the composition, distribution, phase morphology and crystal defects of the alloy in the solidification structure. The flow of melt is an important factor that influences the overall performance of the solidification process. The researchers use various external field to act on the melt to induce the melt flow. Electromagnetic stirring has the characteristics of no contact, no pollution, light oxidation, less gas content and easy to control stirring parameters. It is the most popular method to fabricate semisolid alloy slurry. The electromagnetic force of the electromagnetic field can be used to study the flow phenomena of the melt. Numerical simulation combined with experimental research can get better results. The effect of crucible ratio and electromagnetic frequency on flow during fabrication of semisolid A356 aluminum alloy slurry under electromagnetic stirring through numerical simulation as well as the influence of crucible ratio on the primary phase of semisolid A356 aluminum alloy slurry induced by electromagnetic field. The results show that the greater the crucible ratio, the electromagnetic force and flow velocity of the semisolid A356 aluminum alloy at the minor axis firstly increase and then decrease, and the electromagnetic force and flow velocity of the semisolid A356 aluminum alloy at the major axis increase first, then decrease and then increase. The higher the electromagnetic frequency, the electromagnetic force difference and the flow velocity difference of the semisolid A356 aluminum alloy at the minor axis and the major axis are apparent, so that occurs the phenomenon of "acceleration-deceleration-acceleration" in the melt flow. When the electromagnetic frequency and the crucible ratio are 30 Hz and 1.1 respectively, the flow velocity at the major axis and the minor axis of the crucible are 153.6 mm/s and 143.2 mm/s respectively, and the flow velocity difference is the smallest, a better semisolid A356 aluminum alloy slurry can be fabricated at this condition.

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