Journal of Japan Institute of Light Metals

AZ91D magnesium alloy chips were coated with SiC powder using a binder, and injection molding was attempted using SiC powder coated magnesium chips as raw material. The metallurgical structure of the injection molded products showed uniform dispersion of SiC particles in the matrix, and there were no significant defects such as voids at the SiC particle-matrix interface. The hardness and 0.2% proof stress of the injection molded products tended to improve with increasing SiC content, while the elongation decreased with increasing SiC content. The Young's modulus of the injection molded products improved with increasing SiC content. It was confirmed that the specific bending rigidity of the injection molded products also improves due to the significant increase in the Young's modulus, although the addition of SiC leads to an increase in density.

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Cube specimens of AC4B aluminum alloy, Al-1%Mg, and Al-3%Mg were oxidized in air at 773 K for up to 25 h to investigate the influence of heat treatment time and Mg concentration. The original specimens and oxidation products were characterized by X-ray diffractometry, scanning electron microscopy, and X-ray photoelectron spectroscopy. SEM observation showed that the oxide scale grew thick and the surface of the oxide scale consisted of granular grain. Simultaneously, the tone color of the specimens became darker. The XRD and XPS analysis indicated that oxide scales mainly consist of MgO and MgAl₂O₄, and the top surface was covered with MgO. In addition, the ratio of MgAl₂O₄ on the surface of oxide scales tended to increase with heat treatment time. The XPS depth profile of Al-3%Mg alloy showed that oxide scale grew up to the thickness of 6μm. The thermodynamic calculations suggested that the most stable compound on the surface of specimens is MgAl₂O₄ and then the kinetic factor is strongly influenced by the surface oxidation of Mg-containing Al alloys.

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