电磁搅拌方式和稀土对半固态A356合金凝固组织的影响

通过双向电磁搅拌和稀土元素制备了半固态A356铝合金浆料.利用OM、XRD和SEM研究磁场频率30 Hz搅拌12 s时，无稀土、单一稀土0.5 %Ce（质量分数，下同）、混合稀土0.3 %La+0.2 %Yb以及电磁搅拌方式(单向连续搅拌、双向连续搅拌、双向间歇搅拌)对初生相形貌的影响.结果表明:在控制稀土等同总百分含量下，混合稀土对凝固组织优化程度大于单一稀土和无稀土，初生相平均等积圆直径和形状因子达到36.4 μm、0.82；在此基础上进一步对熔体施加不同搅拌方式处理，试验发现双向连续搅拌作用液态熔体形成了强烈的紊流和惯性冲击，加快了凝固体系的质量传输热量传递，晶粒尺寸和形貌相较于单向连续搅拌、双向间歇搅拌更加细小圆整. 

Effect of electromagnetic stirring way and rare earth on solidification structure of semi-solid A356 alloy

The slurry of semi-solid A356 aluminum alloy was prepared by the mode of two-way electromagnetic stirring, combined with rare earth elements. The effects on its morphology of primary phase were investigated in the way that no rare earth, single rare earth 0.5 %Ce(mass fraction, similarly hereinafter) and mixed rare earth 0.3 %La+0.2 % Yb were applied to be stirred for 12 s in electromagnetic stirring modes (one-way continuous stirring, two-way continuous stirring, and two-way intermittent stirring) in the magnetic field with a frequency of 30 Hz by the ways of OM, XRD and SEM. The results indicate that when the total percentagecontent of RE is the same, mixed RE is better than the other two in optimizing the solidification microstructure of the alloy with the average of the equal-area-circle diameter and shape factor of the primary phase reaching 36.4 um and 0.82.On the basis of this, the melt was treated with different mixing methods. This experiment shows that the strong turbulence and inertial impact are formed by two-way continuous stirring, andthen accelerate the mass and heat transfer in the solidifying system, in which the size and morphology of grainsaremore finer and round compared to one-way continuous stirring and two-way intermittent stirring.