High strength Mg–Zn–Y alloys reinforced synergistically by Nano-SiCp and long period stacking ordered structure

In present study, high strength nano-SiCp/Mg₉₈Zn_0.8Y_1.2 composites with low SiCp content reinforced synergistically by nano-SiCp and long period stacking order (LPSO) phase have been successfully fabricated. The magnesium matrix composites (MMCs) were designed with four nano-SiCp contents (0.5, 1.0, 1.5 and 2.0 vol%). The microstructures of MMCs were significantly refined by the stimulating dynamic recrystallization effect of nano-SiCp. TEM observations indicated that numerous nano-SiCps were dispersed inside α-Mg and LPSO grains, showing a relationship with dislocations, while some were distributed along grain boundaries. The microhardness and strength of MMC increased as the SiCp content increased from 0 vol% to 1.0 vol%, but they decreased when the SiCp content increased from 1.0 vol% to 2.0 vol%. The plasticity of the MMC decreased as the SiCp content increased. The 1.0 vol% nano-SiCp MMC extruded at 330 °C exhibited excellent mechanical properties with a tensile yield strength (TYS) of 441 MPa, an ultimate tensile strength (UTS) of 464 MPa and a plastic elongation (PE) of 3.2%. Besides traditional enhanced factors, including the coefficients of thermal expansion mismatch, Orowan strengthening and grain refinement, novel synergistically strengthening of nano-SiCp and LPSO structure was the other important strengthening mechanism. During MMCs deformation, the LPSO strengthening phases were strengthened by nano-SiCps which would work as obstacles by hindering the motion of LPSO structures.