EBSD study of the microstructure and texture evolution in an Al–Si–Cu alloy processed by route A ECAP

Abstract

Microstructure and texture of an Al–Si–Cu alloy subjected to high-temperature equal channel angular pressing (ECAP) were evaluated by electron backscatter diffraction (EBSD). Besides, the inhomogeneity of the ECAP process was investigated in three different zones of ECAPed specimens (i.e., top, center, and bottom). The texture evaluation showed that by increasing the number of passes, the A∗1 and A∗2 components strengthen, and theB/B¯ component becomes stable. Excellent grain refinement was observed after the first pass due to the recrystallization through particle-stimulated nucleation (PSN) mechanism. After the fourth passes, the average size of primary silicon particles (PSPs) and eutectic silicon particles (ESPs) decreased to 26 μm (41%) and 2.8 μm (48%), respectively, compared to the as-cast specimen. The long strain path at the bottom of ECAP die led to significant refinement of the microstructure of the Al alloy, while, due to the high strain rate at the top of the die, the refinement of microstructure postponed. However, a remarkable fragmentation of PSPs has happened at the top of the ECAP die.