EFFECTS OF PROCESSING PARAMETERS ON FLOW BEHAVIOR OF SEMI-SOLID AZ91 ALLOY AND APPLICATION OF CONTINUOUS CAST MAGNESIUM BILLETS

摘要

Semi-solid processing (SSP) is an emerging technology for near-net shape production of engineering components because many advantages are derived from the process. Although there has been a significant progress in the SSP of Al alloys, very limited information is available on the SSP of magnesium alloys. There are a number of parameters that affect the flow and solidification behavior of semi-solid slurries such as viscosity, casting pressure, geometry of the die, gate velocity, mold temperature, etc. In the present study, the effects of gate velocity and thickness on the mold filling behavior of the semi-solid AZ91 alloy were also investigated. Based on the results, a processing map, which can be applied to the high-pressure die casting (HPDC) of the semi-solid AZ91 alloy, was constructed to predict the flow behavior of semi-solid slurries. In this study, a continuous casting process has been developed for the production of magnesium billets for subsequent SSP. The process utilizes an electromagnetic stirring system in order to obtain the desired microstructure with an excellent degree of homogeneity in both microstructure and composition. Prototypes of an air conditioner cover and a telescope housing were produced using the SSP of the continuously cast AZ91 magnesium alloy billets.