| In order to enhance the mechanics performance of semi-solid AZ91 alloy products, especially toughness index-coefficient of elongation, arming at the characteristic of high Al content of liquid phase of semi-solid AZ91magnesium alloy, in this text the close component of the magnesium alloy has been simulated, the change law of solidification structures were analysed and researched when rare-earth element of Nd and Ce were added. The emphasis is to research the solidification characteristic of eutectic component Mg-Al alloy, analyse the mode of crystallization and grow shape of the primaryα-phase and eutecticβ-phase, in order to control the crystallization shape and size ofβ-phase. The result indicates that :(1)Rare earth Nd and Ce additions have remarkable modification actions on eutectic component Mg-Al alloy, mainly including: improving the amount and the grain number of primaryα-phase in the solidification structures of eutectic component Mg-Al alloy, many high Al content primaryα-phase appearing, reduceing the amount of eutectic structures.(2)The adding amount of Nd and Ce and the modification time have apparent effects on as-cast microstructures of eutectic component Mg-Al alloy.With the increasing of the adding amount of alterative, the modification effects become better firstly, and then become worse. When 0.4mass% Nd or 0.6mass% Ce was added, the modification effects were the best, the amount and the grain number of primaryα-phase were enhanced obviously .The modification effects will become more better with the prolonging of modification time.(3)With Nd and Ce added, rod-like compound Mg-Al-Nd and Mg-Al-Ce were found in microstructures of eutectic component Mg-Al alloy.(4)After 1.0%wt Nd and Ce were added to eutectic component Mg-Al alloy, with increasing of model's cooling speed,the primaryα-phase will be refined, and develop from two-folded dendrite to single high Al content dendriticα-phase; the eutectic structures become dense for the reduce of lamellar spacing.
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