电磁搅拌参数对半固态AZ91D镁合金组织的影响

Effect of Electromagnetic Stirring Parameters on the Microstructures of Semi-Solid AZ91D Alloy

利用自制的电磁搅拌装置和淬火技术,主要研究了电磁搅拌频率为50Hz下的搅拌参数对连续冷却条件下AZ91D镁合金组织的影响规律.在本试验条件下,当电磁搅拌频率小于50 Hz时,随着电磁搅拌频率的升高,半固态AZ91D镁合金浆料或坯料组织中的球状初生α-Mg越来越多,其形态更加圆整、分布更趋均匀;当电磁搅拌频率达到或高于50 Hz时,半固态AZ91D镁合金浆料或坯料的组织比较理想.当电磁搅拌功率增大时,半固态AZ91D镁合金熔体中的蔷薇状初生α-Mg会受到更加强烈的附加温度起伏,促使蔷薇状初生α-Mg枝晶臂根部的熔断,形成越来越多的球状初生α-Mg,而且初生α-Mg越来越圆整.在电磁搅拌制备半固态AZ91D镁合金浆料或坯料时,较低的冷却速率有利获得较理想的半固态组织.

With the help of a self-developed electromagnetic stirring device and alloy melt quenching technology,the effects of stirring parameters on the microstructure of AZ91D Mg alloy during continuously cooling process were investigated at the condition of the electromagnetic frequency of 50Hz.The results reveal that the spheroidal primary α-Mg phase in the semi-solid AZ91D slurry or billet is continuously increased with the stirring frequency increase,and become more round and more homogeneous distribution when the electromagnetic frequency is lower than 50 Hz.The desirable microstructure in semi-solid Mg slurry or billets can be prepared with the electromagnetic frequency up to or over 50 Hz.With the increase of the electromagnetic stirring power,the rosette-like primary α-Mg phase in the semi-solid alloy melt can be intensely subjected to the man-made temperature fluctuation to result in the root remelting effects of the dendritic arm,which forms more and more spheroidal primary α-Mg phase,and the phase become more and more round.Low cooling rate can be beneficial to forming desirable semi-solid microstructure of the Mg alloy by electromagnetic stirring method.