EFFECT OF PREDEFORMATION RATE IN SIMA PROCESS ON THIXOTROPIC STRUCTURE OF AA2024 ALUMINIUM ALLOY

In this study, thixotropic microstructure produced in a wrought aa2024 alloy for the semi-solid forming was investigated by strain induced melt activated (sima) method. for this purpose, aa2024 alloy as extruded state were subjected to cold deformation at different rates, following heated to a semi-solid region, and cooled in water at room temperature. microstructure analysis was achieved by metallographic and quantitative methods. experimental results showed that spherical shaped thixotropic microstructures which required for semi-solid forming can be produced in aa2024 al alloy by sima process. with increasing cold deformation rate, the shape factor increases while the grain size decreased. for the production of thixotropic structure by sima process, cold deformation rate was determined to be necessary at least 20%, and there is no need to isothermal holding at semi-solid temperature for thixotropic structure transformation