Microstructure and Mechanical Properties of AZ31 Magnesium Alloy Strip Produced by Twin Roll Casting

摘要

Twin roll casting has been used to produce AZ31 magnesium alloy strip. The size of the cast strip is 5 mm thick and 250 mm wide. The microstructure of the as-cast AZ31 alloy strip consists of columnar zones from the surface to mid-thickness region and equiaxed zone in the mid-thickness region. The secondary dendrite arm spacing varies from 5.0 to 6.5 mu m through the thickness and width of the strip and is much smaller than 34 mu m of AZ31 alloy DC ingot used for the comparison. In temperature ranging from room temperature to 400 deg C, tensile strength and elongation of the as-cast strip are higher and smaller than those of DC ingot, respectively. Elongation is evidently improved by homogenization treatment and becomes more than that of DC ingot. Such an improvement of elongation is though to be caused by homogenization of segregation of Al and Zn atoms in the dendrite cell boundaries.