CRYSTAL MORPHOLOGIES AND THE PHASES IN THE Mg-6Zn-3Y ALLOY SOLIDIFIED UNDER SUPER-HIGH PRESSURE

The solidification microstructure of Mg-6Zn-3Y alloy under super-high pressure was investigated by SEM and EDS. The results show that solidification microstructure of Mg-6Zn-3Y alloy under super-high pressure (GPa level) could be evidently refined and was further refined with the increase of solidification pressure. Solubility of Zn in the alloy reached up to 1.64% under 4 GPa pressure which was increased by 44% than that under the atmosphere condition. Y is insoluble in the matrix, which resulted in a new phase riched in Y and granular phases which were dispersed in the matrix. The morphology of crystal changes follow: bulky branch crystal→superfine branch crystal→cellular crystal, and the growth of crystal changed from branch growth to cellular growth. KEY WORDS Mg-6Zn-3Y alloy, super-high pressure solidification, dendritic crystal, cellular crystal, phase component