Microstructure and mechanical properties of an asymmetric twin-roll cast AZ31 magnesium alloy strip

► The strip of AZ31 alloy was fabricated by asymmetric twin-roll casting process. ► The microstructure and precipitation distribution in the strip were investigated. ► The mechanical properties of the strip was measured. The microstructure along the thickness of a strip produced by asymmetric twin-roll casting was found to be significantly inhomogeneous. There were many banded structures with flow form near the upper surface of the strip, whereas a fine dendritic structure dominated near the lower surface of the strip. Precipitates of Mg17Al12 and Al8Mn5 were dispersively distributed throughout the as-cast strip. Recrystallization of the strip during homogenization first occurred in the banded structures. After rolling and annealing, the strip consisted of fine grains measuring approximately 5μm in size. It was concluded that the shear strain caused by the difference in linear velocity between the surfaces of the upper and lower rolls resulted in the banded structures of the strip.