Microstructural characteristics of an AZ91 matrix-glassy carbon particle composite

This paper presents the results of a microstructural investigation of a new type of ultralight glassy carbon particles (C_p)-AZ91 magnesium alloy matrix composite manufactured by the powder metallurgy method. Glassy Cp with unmodified surfaces and surfaces modified with SiO₂ amorphous nanocoating were used in the experiment. The composite microstructure, with an emphasis given on the interface, was characterized by scanning electron microscope (SEM), TEM, and HRTEM microscopy. Uniform distribution of the particles in the matrix and their good bonding with the metal matrix were observed. A continuous very thin MgO oxide layer containing needle-like Al ₂MgO₄ phase was detected at the glassy carbon-AZ91 interface. An increase of aluminum concentration at the interface as a result of Mg and Al diffusion into the SiO₂ nanolayer was observed in the case of particles modified with SiO₂. Crystalline phases containing carbon were not detected at the interface.