| The microstructural characteristics and decomposition behaviour of rapidly solidified Mg-Nd-X(X=Al, Si) alloys have been investigated by using a detailed transmission electron microscopy. Rapid solidification of Mg-8Nd, Mg-8Nd-1Al and Mg-8Nd-1Si produces various types of solidification microstructure depending upon the alloy composition, i.e. fine Mg₃Nd precipitates and α-Mg in as-melt-spun Mg-8Nd, α-Mg cellular structure with secondary solidification phase particles at cell boundaries in as-melt-spun Mg-8Nd-1Al and supersaturated α-Mg grains with fine particles at the grain boundaries in as-melt-spun Mg-8Nd-1Si. Annealing of as-rapidly solidified Mg-8Nd and Mg-8Nd-1Si up to 300℃ results in coarsening of Mg₃Nd precipitates. However, no significant change occurs in Mg-8Nd-1Al with annealing up to 300℃. With annealing at 400℃, the pre-existing phase decomposes forming new phases stable at 400℃, i.e. a fcc phase(a=5.4Å) in Mg-8Nd, a fcc phase(a=8.0Å, Al₂Nd) in Mg-8Nd-1Al and Mg_9Nd in Mg-8Nd-1Si. |
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