Preparation of an Mg-Gd-Zn alloy semisolid slurry by low frequency electro-magnetic stirring

The effects of low frequency electromagnetic stirring (LFEMS) including applied voltage, rotational frequency and cooling rate on the microstructure of semisolid slurry of the Mg-2.5Gd-1Zn (at.%) alloy have been investigated. The applied voltage, rotational frequency and cooling rate all have a remarkable influence on the microstructures of the slurries. The LFEMS treatment leads to the morphology of primary Mg particles evolved from dendritic to non-dendritic. The increase of applied voltage leads to refined primary Mg particles, while the increase in rotational frequency makes the alpha-Mg particles initially refined and then coarsened. The decrease of cooling rate also leads to refinement of primary Mg particles. The optimal processing parameters for the fabrication of semisolid slurry are found to be: applied voltage 300-350 V, rotational frequency 15-20 Hz and cooling rate below 1.4 K/min. Under the optimized parameters, fine and spherical primary Mg particles were obtained, and the average particle size is refined from similar to 680 to similar to 150 mu m. (C) 2015 Elsevier Ltd. All rights reserved.