以AZ91D镁合金为试验材料,采用双螺旋半固态浆料制备装置,研究了在液相线附近施加不同搅拌速度时,镁合金熔体凝固过程中非枝晶组织的形成机理及演变特征。结果表明：搅拌温度为605℃,搅拌速度950 r/min时,坯料组织中初生α-Mg变得细小圆整,主要以球状晶为主,由于强烈的搅拌使得熔体内部温度场与浓度场均匀,有利于晶核生长成球状;搅拌温度为590℃时,在较低的搅拌速度下就可以观察到球状初生α-Mg晶粒,且随着搅拌速度的提高,组织中初生α-Mg数量增多,晶粒逐渐变得细小、圆整,主要由于搅拌速度的增大对球晶的生长起到了抑制作用。
Taking AZ91 D magnesium alloy as experimental material, formation of non-dendritic microstructure of the alloy melt near the liquidus during solidification process under different stirring speed was investigated by using a twin-screw rheomoulding device. The experimental results show that when the alloy melt is stirred at temperature of 605 ℃ with stirring speed of 950 r/min, the primary α-Mg particles become fine and nearly spherical. It is argued that intensive stirring makes the temperature field and concentration field uniform; which is beneficial to the growth of spherical nucleus. When stirring the alloy melt at 590 ℃ , the spherical primary α-Mg phase is observed under lower stirring speed. Moreover, the amount of primary α-Mg particles increase and become fine and spherical as stirring speed increases, mainly due to the inhibition of increasing stirring speed to the growth of spherical grains
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