The ribbons of melt-spun AZ91D
magnesium alloy with thickness of 4070 μm and length of 80100 mm were obtained by a single
roller apparatus. According to the grain morphology, the
rapid solidification microstructure of melt-spun magnesium alloy is roughly subdivided into three crystal zones through the thickness section: the fine equiaxed zone near the roller surface, the inner columnar zone and the outer equiaxed zone near the free surface. The X-ray analysis results indicate that the microstructure of the alloy is composed of the single phase α -Mg supersaturated solid solution and the eutectic reaction of L→α -Mg+β -Mg_(17)Al_(12) is suppressed due to rapid
Solidification. TEM analysis reveals that a little amount of β -Mg_(17)Al_(12) compound, which disperses inside the α -Mg grains and locates at the grain boundaries, is the product of precipitation from supersaturated α -Mg solid solution during cooling processes. Lots of dislocations and dislocation cells exist in α -Mg grains. With the increasing of roller velocity, the α -Mg grains become gradually finer and the inner columnar zone tends to elimination, and the density of dislocation inside the grains increases, and hence the strength and electrical resistivity of the alloy increase remarkably, while the elongation of the alloy decreases.