電磁攪拌法制備的半固態(tài)2A50合金的顯微組織演變Microstructural evolution of semisolid 2A50 alloy prepared by electromagnetic stirring

分析攪拌電流和攪拌頻率等工藝參數(shù)對電磁攪拌法(EMS)制備的2A50鋁合金半固態(tài)坯料顯微組織的影響，并研究不同工藝參數(shù)制備的2A50半固態(tài)坯料二次重熔后的顯微組織演變過程。結(jié)果表明，隨著攪拌電流及攪拌頻率的增大，半固態(tài) 2A50合金的顯微組織由樹枝晶轉(zhuǎn)變?yōu)樵絹碓郊?xì)小均勻的近球狀晶，且二次重熔后的球狀晶粒也越來越圓整。攪拌參數(shù)為30 A和30 Hz時，二次重熔后的半固態(tài)2A50合金的球狀晶粒平均尺寸約為80 μm，形狀因子約為0.76，進(jìn)一步增加攪拌電流或者攪拌頻率，顯微組織沒有明顯的改善。二次重熔過程中半固態(tài)2A50合金平均晶粒尺寸隨著保溫時間的延長而逐漸增大，Ostwald粗化機(jī)制促進(jìn)了晶粒的球化程度的增加。最終獲得半固態(tài)2A50合金的晶粒粗化速率為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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