Particle Size and Particle Percentage Effect of AZ61/SiCp Magnesium Matrix Micro- and Nano-Composites on Their Mechanical Properties Due to Extrusion and Subsequent Annealing

Magnesium metal matrix composites (Mg MMCs) possess relatively more favorable mechanical properties than Mg alloys because they add reinforcements, such as small particles, short fibers, or continuous fibers, into the matrix. This study investigated the influence of adding different sizes and percentages of silicon carbide particles (SiCp) for manufacturing AZ61/SiCp Mg alloy composite extrusion plates on the mechanical properties of SiCp. We also examined the impact and discussed the evolution of microstructures, changes of material strength, ductility, formability, and other mechanical properties caused by a subsequent annealing treatment after plate extrusion. The results showed that the mechanical properties of plates can be improved by adding reinforcement particles. The effects of grain refinement were as follows: the smaller the size of the reinforcement particles, the greater the enhancement of mechanical properties. Among them, the AZ61/1 wt % SiCp/50 nm MMC plate had relatively excellent mechanical properties. Specifically, the ultimate tensile strength, yielding strength, ductility, hardness, and grain size of the plate were 331 MPa, 136.4 MPa, 43.1%, 62 HV, and 3.3 μm, respectively. Compared with SiCp-free Mg MMC plates, these properties of the AZ61/1 wt % SiCp/50 nm MMC plate were enhanced (or refined) by 6.4%, 3.4%, 83.4%, 2%, and 13.2%, respectively; by contrast, formability decreased by 9.1%.