Microstructure Evolution and Mechanical Behaviors of SiCp/CNTs Hybrid Reinforced Al-Si-Cu-Mg Composite by Semi-solid Stir Casting

In this study, Al -Si -Cu -Mg composites reinforced with Silicon carbide (SiC) particles and/or Carbon nanotubes (CNTs) were fabricated using semi -solid stirring casting technology (SSC). The aim of the study was to investigate the influence of SiC and/or CNTs on the mechanical properties, microstructural evolution, and deformation mechanisms of the Al -Si -Cu -Mg alloy. The findings indicated that the presence of SiC/CNTs in the composite had a significant effect on refining the alpha-Al phase and altering its grain orientation. Additionally, the results obtained from EBSD and TEM revealed that the microstructure of the Al-Si-Cu-Mg-SiC/CNTs hybrid composite (HAMC) underwent dynamic recrystallization (DRX) and static recrystallization (SRX), resulting in a fine equiaxed recrystallized structure. This process also led to the formation of high -angle grain boundaries (HAGBs) through dislocation rearrangement. The SiC particles were evenly distributed within the matrix, ensuring good interface bonding between SiC and alpha-Al phases. Moreover, the CNTs reacted with the matrix, resulting in the in -situ formation of the Al 4 C 3 phase at the interface. The addition of SiC/CNTs significantly increased the tensile strength of HAMC at 25 degrees C and 250 degrees C, from 319MPa and 178MPa to 438MPa and 331MPa. Examination of the fracture surface of the hybrid composite unveiled that void formation occurred primarily at the regions surrounding the matrix-particle interface.