Recrystallization behavior of ECAPed A356 alloy at semi-solid reheating temperature

The microstructural evolution of A356 aluminum alloy during reheating was investigated. In this study, thermomechanical treatment (TMT) method was carried out to produce feed stock for semi-solid forming by using equal channel angular pressing (ECAP) in solid state at ambient temperature. In TMT processes, globular microstructure is obtained by a deformation-recrystallization technique followed by partial re-melting. This work is an attempt to study in detail, the mechanism of the formation of globular microstructure of severely deformed Al-7% Si alloy by ECAP during reheating process by using scanning electron microscope (SEM) provided with an electron back scatter detection (EBSD) observation as well as recrystallization kinetics. The results indicated that equal channel angular pressing followed by reheating was an effective method to produce semi-solid ingot for thixoforming. According to the kinetics calculation and experimental results presented in this paper, recrystallization kinetics, which is mainly depended on the intrinsic material properties, amount of strain and heating rate, plays an important role on the grain size of the semi-solid microstructure.