电磁搅拌法制备的半固态2A50合金的显微组织演变Microstructural evolution of semisolid 2A50 alloy prepared by electromagnetic stirring

分析搅拌电流和搅拌频率等工艺参数对电磁搅拌法(EMS)制备的2A50铝合金半固态坯料显微组织的影响，并研究不同工艺参数制备的2A50半固态坯料二次重熔后的显微组织演变过程。结果表明，随着搅拌电流及搅拌频率的增大，半固态 2A50合金的显微组织由树枝晶转变为越来越细小均匀的近球状晶，且二次重熔后的球状晶粒也越来越圆整。搅拌参数为30 A和30 Hz时，二次重熔后的半固态2A50合金的球状晶粒平均尺寸约为80 μm，形状因子约为0.76，进一步增加搅拌电流或者搅拌频率，显微组织没有明显的改善。二次重熔过程中半固态2A50合金平均晶粒尺寸随着保温时间的延长而逐渐增大，Ostwald粗化机制促进了晶粒的球化程度的增加。最终获得半固态2A50合金的晶粒粗化速率为547 μm³？s^-1。

The effects of stirring current and stirring frequency on the microstructural evolution of semisolid 2A50 alloy prepared by electromagnetic stirring (EMS) were analyzed, and microstructure evolution of semisolid 2A50 alloy prepared by different technological parameters after partial remelting were investigated. The results show that with increasing the stirring current and frequency, the microstructures of semisolid 2A50 alloy evolve from coarse dendrites to fine and quasi-globular solid particles. Moreover, after partial remelting, these microstructures become more spherical with increasing the stirring current and stirring frequency. As the stirring parameters are 30 A and 30 Hz, the average particle size is about 80 μm and the shape factor is about 0.76. Further increasing the stirring current and frequency makes no obvious improvements of microstructure. Besides, average particle size constantly increases with prolonging the holding time because that Ostwald ripening can improve the degree of spheroidization. The current coarsening rate constant of semisolid 2A50 alloy is 547 μm³？s^–1 at 590℃.

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