Microstructure evolution and semi-solid deformation behavior of an A356 aluminum alloy processed by strain induced melt activated method

The effects of strain induced melt activated (SIMA) process parameters on the microstructure evolution of an A356 aluminum alloy have been investigated. It is concluded that a fine uniform globular microstructure may be obtained through heating the 45% pre-deformed specimen at 615 °C for 6 min. In addition, a model for microstructure evolution during SIMA process is proposed. This accounts for the mechanisms causing the microstructural changes in two successive steps of pre-deformation and heating. The present work also explores the semi-solid deformation behavior of the experimental alloy possessing different initial microstructures, including cast, rosette-like, globular and coarsened ones. The applied thixoforming process encompasses a set of isothermal hot compression tests in the semi-solid temperature range. The results indicate that the SIMA processed specimen with globular microstructure exhibits the lowest flow resistance during thixoforming process, followed by those with coarsened, rosette-like and cast microstructures. This has been justified considering the governing deformation mechanisms for different thixoformed microstructures.

► A proper globular microstructure was obtained after 45% strain and holding at 615 °C for 6 min.
► Ostwald ripening was the dominant coarsening mechanism for SIMA processed A356 alloy.
► A model for microstructure evolution of A356 aluminum alloy during SIMA was proposed.
► The effect of initial microstructure on the semi-solid deformation behavior was studied.