Microstructure Evolutions of Rapidly-Solidified and Conventionally-Cast Mg<SUB>97</SUB>Zn<SUB>1</SUB>Y<SUB>2</SUB> Alloys

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Microstructure evolutions of rapidly-solidified (RS) ribbon and conventionally cast bulk Mg-1 at%Zn-2 at%Y alloys have been studied by transmission electron microscopy (TEM), particularly focusing on formation process and phase stability of the long-period structures. It is found that there are significant differences in microstructural evolutions between the RS ribbon and the cast-bulk alloys, in terms of thermal stability of the long-period phases at temperatures higher than 673 K. For both the as-quench ribbon and the as-cast bulk specimens, 18R-type long-period phase is dominantly observed at grain boundaries. After annealing at temperatures higher than 673 K, the long-period phases at grain boundaries in the RS ribbon almost disappear to form Mg<SUB>24</SUB>Y<SUB>5</SUB> and Mg<SUB>3</SUB>Zn<SUB>3</SUB>Y<SUB>2</SUB> compounds within the grain interiors, while the long-period phases remained stable in the cast-bulk alloy even at temperatures higher than 673 K.



    MATERIALS TRANSACTIONS 49(5), 990-994, 2008

    The Japan Institute of Metals and Materials


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