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 their microstructure evolution and strengthening mechanism were explored. Results showed 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 were dissolved into the matrix, whereas the Mg₂Si phases were not. The subsequent multi-pass ECAP at different temperatures promoted the dynamic recrystallization and uniform distribution of the 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 SiC nanoparticles were mainly distributed at grain boundaries, which effectively prevented dislocation movement. The excellent comprehensive mechanical properties can be attributed to grain boundary strengthening and Orowan strengthening.