Microstructure and mechanical properties of stir cast ZX51/Al2O3p magnesium matrix composites

Magnesium matrix composites can overcome the limitations of magnesium and its alloys. This paper investigates the effect of adding Al2O3 microparticles on microstructure and mechanical response of ZX51 alloy-matrix composites. Stir casting process was chosen due largely to its low cost to fabricate the novel ZX51/Al2O3p composites. Scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffractometry were used in order to analyze the microstructure of as-cast composites. Tension, compression, and Brinell hardness tests were performed to determine mechanical properties of the composites. It was revealed that the microstructure of matrix alloy is composed of α-Mg grains and (α-Mg+Ca2Mg6Zn3) eutectic mixture distributed predominantly along grain boundaries. The addition of Al2O3p brought about a marked grain refinement and also introduced slight amounts of porosity. The results showed that with increasing volume percentage of Al2O3p, hardness and yield strength increase while tensile strength, compressive strength, and ductility decrease; in consequence, toughness decreases as well.