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Grain refinement of AZCa912 alloys solidified by an optimized electromagnetic stirring technique
Ist Teil von
Journal of materials processing technology, 2016-09, Vol.235, p.114-120
Ort / Verlag
Elsevier B.V
Erscheinungsjahr
2016
Link zum Volltext
Quelle
Elsevier ScienceDirect Journals Complete
Beschreibungen/Notizen
The electromagnetic torque produced on a metallic cylinder was measured as a function of output frequency of a three-phase inverter when the cylinder was placed in a three-phase induction stator. The results were analyzed by considering the characteristics of the induction coil at different alternating current frequencies. An optimal frequency existed at which the momentum, i.e., the electromagnetic torque, reached a maximum and then began to decrease with further increase in frequency. At an optimal frequency of 250Hz, an Mg-9wt%Al-1wt%Zn-2wt%Ca (AZCa912) magnesium alloy was solidified in the rotating magnetic field, in which electromagnetic stirring could be applied to the crystallizing melt. Alternate clockwise and counterclockwise electromagnetic stirring was imposed during solidification. Solidified structures were characterized as a function of reverse imposition time. Compared with the structure observed in an as-cast alloy, microstructures became finer when electromagnetic stirring was imposed. The mechanism of the grain refinement and counterclockwise imposition time-dependent microstructure development was discussed with a consideration of differences in electrical resistivity of the solid and liquid in the mushy zone during solidification.