Developing a heterostructured SiCp/AZ91 composite with enhanced mechanical properties by multipass equal channel angular pressing and single-pass high-reduction rolling

Abstract

In this study, multipass equal channel angular pressing (ECAP) and single-pass high-reduction rolling (SPHRR) were used to create a heterostructured SiC particle (SiCp) reinforced AZ91 magnesium matrix (SiCp/AZ91) composite. The microstructure evolution and mechanical properties of the composite were then investigated. Results showed that the SiCp particles exhibited excellent dispersion, and a heterogeneous microstructure comprising minute β-Al₁₂Mg₁₇ phases and a high proportion of fine grains was developed in the matrix of the composite after ECAP and SPHRR. The area fraction of fine grains (＜5 μm) was determined to be 68.4%, and the area fraction of coarse grains (≥5 μm) accounted for 31.6%. A significant increase was observed in the ultimate tensile strength, reaching 426 MPa, and the yield tensile strength, reaching 372 MPa. Additionally, a ductility of 6.8% was achieved in the heterostructured composite. The heterogeneous grain structure was generated under the coeffect of micro SiCp particles and dispersed β-Mg₁₇Al₁₂ precipitates, resulting in inhomogeneous recrystallization and impeding the grain growth. The results of this study offered a new method to develop a heterogeneous grain structure that optimized the ductility and strength of magnesium matrix composites.