A comprehensive investigation on the effect of SiCp on microstructure and mechanical properties of Mg-5Sb-based hybrid composites

Microstructural development, strengthening mechanisms, and mechanical properties of the newly developed Mg-5Sb-xSiCp (x = 0, 1, 3, and 5) composites were studied in both as-cast and extruded states. The microstructures of composites were composed of alpha-Mg, in-situ Mg3Sb2, and SiCp phases. The cooling curves display that Mg3Sb2 intermetallics form as the primary phase. During solidification, the SiCp acts as heterogeneous sites for both alpha-Mg and intermetallics formation. The increase in SiCp content (from 0 % to 5 %) modified the as-cast grain size from 827 mu m to 411 mu m with the improvement of yield strength (YS) (74-97 MPa). Also, the SiC addition to as-cast facilitates the formation of a randomized texture and a significant reduction in intensity from 13.121 mrd to 6.301 mrd for SiC-Free and 5 wt% added MMCs, respectively. Grain refining and recrystallization are characterized by electron backscatter diffraction (EBSD) analysis. Grain refinement via SiCp and hot extrusion leads to substantial structural refinement, resulting in a decrease in grain size from about 411 mu m down to 3.92 mu m for MMC with 5 wt% of SiC. Consequently, the best combination of the ultimate tensile strength (UTS) (similar to 244 MPa) and total elongation (similar to 8.9 %) was obtained for the hot extruded composite containing 3 wt% SiCp. The prevailing strengthening mechanisms are supposed to be particle strengthening mechanism in the as-cast condition and coefficient of thermal expansion (CTE), Orowan, and Hall-Petch mechanisms in the as-extruded condition. Obviously, adding SiCp and employing hot working lead to significant increase in ultimate compressive strength (from 180 MPa to 321 MPa for 5 wt%).