Continuous Casting of Magnesium Billets for Semi-Solid Processing

Abstract

Semi-solid processing is recognized as an attractive alternative method for the near net-shape production of engineering components. Although there has been a significant progress in semi-solid processing of aluminum alloys, very limited information is available on semi-solid processing of magnesium alloys, except for the thixomolding process. Continuous casting process has been utilized to produce the billets with the desirable cross-section at a reduced production cost for many metals, such as steel, copper and aluminum alloys. It has also been commercially utilized to produce the aluminum billets with non-dendritic microstructure for subsequent thixocasting process. However, continuous casting of magnesium billets for semi-solid processing has not yet been commercialized due to the difficulties involved in casting of magnesium alloys. In the present study, a continuous casting process has been developed for the production of the cylindrical billets of magnesium alloys for the subsequent thixocasting process. In order to obtain the desired non-dendritic microstructure with an excellent degree of homogeneity both in microstructure and composition, an electromagnetic stirring system has been utilized. A continuous casting process has been proven to be an efficient way to produce the high quality billets of magnesium alloys for semi-solid processing. A prototype air conditioner cover was produced using the continuously cast billets of AZ91 alloy.