Processing and Microstructure of AZ61 Thin Strip Prepared by Twin Roll Casting

AZ61 thin strips with the thickness of 3-4 mm and width of 150 mm were prepared by a vertical twin roll caster( 250 mm×150 mm) and the effect of different nozzles and casting temperatures on microstructure and surface quality was examined.As the results,the cast strips prepared by B nozzle had less surface cracks than those by A nozzle.The number of the surface cracks of the strips increased with the decrease of the casting temperature.Microstructure of the AZ61 strips consisted of the first crystallized α-Mg and over saturated α-Mg matrix.When the casting process was the combination of the casting temperature of 630 ℃ and the B nozzle,microstructure of the cast strip was fine and uniform.While the casting temperature was between the solidus and the liquidus of AZ61,the coarse α-Mg dendrites existed locally in the AZ61 strips.