Microstructure evolution and mechanical properties of Mg-9Al-1Si-1SiC composites processed by multi-pass equal-channel angular pressing at various temperatures

In this study, Mg-9Al-1Si-1SiC (wt%) composites were processed by multi-pass equal-channel angular pressing (ECAP) at various temperatures, and the microstructure evolution and strengthening mechanism were explored. The results indicate that the as-cast microstructure was composed of an α-Mg matrix, discontinuous Mg₁₇Al₁₂ phase, and Chinese script-shaped Mg₂Si phase. After solution treatment, almost all of the Mg₁₇Al₁₂ phases are dissolved into the matrix, while the Mg₂Si phases are not. The subsequent multi-pass ECAP at different temperatures results in more complete dynamic recrystallization and uniform distribution of Mg₁₇Al₁₂ precipitates when compared with the multi-pass ECAP at a constant temperature. A large number of precipitates can effectively improve the nucleation ratio of recrystallization through a particle-stimulated nucleation mechanism. In addition, the nano-scale SiC particles are mainly distributed at grain boundaries, which can effectively prevent dislocation movement. The excellent comprehensive mechanical properties are mainly attributed to grain boundary strengthening and Orowan strengthening.