Effect of Microstructure on the Mechanical Properties of Magnesium Composites Containing Dispersed Alumina Particles Prepared Using an MM/SPS Process

Abstract

Magnesium composites containing 0–20 vol% Al₂O₃ particles were produced via mechanical milling (MM) followed by spark plasma sintering (SPS), and the effect of the microstructure on their mechanical properties was investigated. Microstructural observation of the MM powders and SPS compacts was achieved using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM)/energy dispersive X-ray spectroscopy (EDS). The mechanical properties of the MM powders and SPS compacts were evaluated on the basis of the results of the Vickers hardness test. SEM micrographs indicated that Al₂O₃ fine particles were dispersed in the Mg composites with 10 and 20 vol% Al₂O₃. The hardness values for the MM powder and the SPS compact containing 10 vol% Al₂O₃ were nearly the same owing to their similar microstructures. However, the hardness of the SPS compact was higher than that of the MM powder for the Mg composite with 20 vol% Al₂O₃. TEM/EDS and XRD analyses revealed that the needle-like Mg₁₇Al₁₂ and equiaxed nano MgO particles formed in the Mg matrix with 20 vol% Al₂O₃ during the SPS process. The increase in hardness of the SPS compact compared to that of the MM powder is attributed to strengthening resulting from the formation of the Mg₁₇Al₁₂ and MgO phases.