Microstructures of AZ91D alloy solidified during electromagnetic stirring
(School of Materials Science and Engineering,
University of Science and Technology Beijing, Beijing 100083, China)
University of Science and Technology Beijing, Beijing 100083, China)
Abstract: With the help of an electromagnetic stirring device self-made and alloy melt quenching technology, the effect of electromagnetic stirring parameters on the microstructures of semi-solid AZ91D alloy was mainly studied at the stirring frequency of 200Hz. The experimental results show that when the stirring power rises, the primary α-Mg rosettes in the semi-solid melt will bear stronger man-made temperature fluctuation and the root remelting effect of the dendritic arms is promoted so that the spherical primary α-Mg grains become much more and rounder. If the stirring frequency is 200Hz, the ideal semi-solid microstructure of AZ91D magnesium alloy can be obtained when the stirring power is increased to 6.0kW. If the stirring frequency is 200 Hz and the stirring power is 6.0kW, it is found that the lower cooling rate is favorable for the spherical primary α-Mg grains to be developed during the electromagnetic stirring stage. If the AZ91D magnesium alloy billet prepared during electromagnetic stirring at the stirring frequency of 200Hz and the stirring power of 6.0kW is reheated to the solidus and liquidus temperature region, the primary α-Mg grain’s shape will get more spherical, so it is very advantageous to the semi-solid thixoforming process.
Key words: AZ91D magnesium alloy; semi-solid; electromagnetic stirring; microstructure